Now i have been doing some math this morning to try and do some figuring. of hp and tq and quarter mile times and such. And then i was thinking- you know that 197hp Oreif said he was getting at the wheels? Then he claimed it was like 220 at the eninge HP to start with a dyno and all... with 197hp to the wheels would he not be getting more like 246-247hp at the engine with the thought that 20% of the power is gone with an auto trans? because going with numbers that 220 to the enigne equals 197 to the wheels means that 1.12hp (rounded up from 1.1167XXXXX) to the wheels equals 1hp to the eninge. And with going with the 20% loss rule that means 1.25 rwhp = 1 ehp.
So did i screw up here. or am i missing some sort of factor. Or did Oreif screw up here? Or does the fiero just really put it to the wheels really well here?
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10:10 AM
PFF
System Bot
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
well, not sure myself. but, I would guess to say that he only had the chassis dyno (power at wheels) and the 220 was extracted from that. and since everyone goes so nuts about HP claims, he went conservative on the adjusted HP to keep from getting all kinds of crap.
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10:40 AM
Formula88 Member
Posts: 53788 From: Raleigh NC Registered: Jan 2001
So you would agree that he probably had 247ish HP at the enigne then? accodring to his 1/4 mi time as well that come closer as well. You need at least 237.62Hp to make a 14.2 second pass in the 1/4 mi. He claimed a 14.2 second pass. He cold have not made his total best time based on driver and other conditions to make that pass. At 14.018 seconds would be closer to 247ish HP (at engine) not the time that he actually made which is assuming that he weighed in at 2700 pounds.
Is this just me or does anyone else see fault in this somewhere?
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11:32 AM
Unsafe At Any Speed Member
Posts: 2299 From: Cheyenne, WY Registered: Feb 2003
It doesn't matter what his engine was putting out, it matters what made it to the ground when talking about the quarter mile time. FYI- there's more to track times than horsepower and weight.
First the facts, My carb'd 3.4L was Engine Dyno'd at 223hp. The transaxle was dyno'd with a 200hp reference engine and had a 34hp loss (17% loss) Then the car was assembled/built and was put on a Chassis dyno and everything was tuned together. Original baseline on dyno was 189 rwhp once the tuning was finished It had 197 rwhp. (8 hp gain after tuning.) The best 1/4 mile run was at 14.267 @ 94.3mph. So based on the facts: My trans used 34hp to drive it. So after tuning I had a calculated 231hp at the crank.
It takes XXX amout of power to drive a transmisssion. If it calculates out to say 17% loss on a 200hp reference engine it would be a 34hp loss so it would have 166 rwhp to the wheels. If the same trans was used with a 300hp engine I would have 266 rwhp to the wheels. A transaxle will require the same power to drive it regardless how much power the engine has.
------------------ Happiness isn't around the corner... Happiness IS the corner. ZZ4 Powered !!
[This message has been edited by Oreif (edited 02-21-2006).]
So each transmition has its own Hp loss rating? for the 125c it is 34hp or so then?
OK if that be true (which i am going to assume you are correct- as you usually are and do tell the truth which btw is much appriated) then do we do the power it required to turn not only the 125c but other trannies? More specific?
So each transmition has its own Hp loss rating? for the 125c it is 34hp or so then?
OK if that be true (which i am going to assume you are correct- as you usually are and do tell the truth which btw is much appriated) then do we do the power it required to turn not only the 125c but other trannies? More specific?
No, You cannot say that each TH125 uses 34 hp. The reason being is that each trans is different. My TH125 had heavy-duty clutch packs, a shift kit, and a street/strip torque converter which was just fresh from a rebuild. The losses of an auto trans depends on the torque converter, fluid pressure, condition of the clutch packs, and mileage/wear on the trans. On a manual trans, the frictional losses by the gearing, wear, and condition/pressure of the clutch make the difference.
You could use 34hp as a reference/average for a transaxle as the loss. But in order to get exact numbers, A trans dyno would be the way to get real numbers. I don't have any data on other transaxles.
i would agree that 34hp is more of an averaged thing. There is no absolute answer to anything anymore. We do not know just beyond cars or mechanical objects the exact nature of what they will turn out to be by jsut speculation. There is an average on the other hand. I mean we can't even tell the speed of light anymore from my other studies there has been some sunstantial proof that the speed of light it self has been slowing down for ever since its first existance. And if you know anything about physics that means that the expansion of the universe yes does expand will get to the point where it is done more or less "Growing" and then will wait out the fate of the rest of the universe the stars will lose their light and then we will all not exist. YEAH depression.....
Anyhow. does anyone else know anythign about the other trannies then?
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02:10 PM
rwright Member
Posts: 68 From: Hurricane, WV Registered: Jan 2006
A transaxle will require the same power to drive it regardless how much power the engine has.
That's not true.
A transaxle will absorb some constant amount of power (ie, there will be a minimum amount of power required to drive it), and in addition to that it will absorb a percentage of the engine's output.
In your case since your baseline for transaxle loss came from an engine with similar power as yours, you are probably very close in assuming a 34hp loss when installed in your car.
A transaxle will absorb some constant amount of power (ie, there will be a minimum amount of power required to drive it), and in addition to that it will absorb a percentage of the engine's output.
In your case since your baseline for transaxle loss came from an engine with similar power as yours, you are probably very close in assuming a 34hp loss when installed in your car.
No it is true. Here are some examples: Example 1: Most of the people who have dyno’d a Fiero with a 2.8L and a manual trans run on average about 117-119 rwhp. Taking an average of 118 rwhp. Assuming the 2.8L is 140 hp that is about a 22hp loss. (Or about 16%.) Now I and another member both have ZZ4 V-8’s with a manual trans and we both have dyno’s running 309 rwhp. The ZZ4 is rated at 355hp under ideal conditions. (they are tested with tuned headers, 3” pipes, and flow masters.) Obviously in a Fiero with the smaller diameter exhaust pipes and exhaust manifolds this will lower the HP. So going by the 16% my engine should have 368 hp. That is not the case. My engine has more like around 330hp using exhaust manifolds instead of tuned headers and 2.5” pipes instead of 3” pipes.
Example 2: Refer to dyno graph below. According to the dyno (NOTE: same car, same trans, same dyno) He made 176 rwhp as the baseline, (blue graph on posted dyno) After the mods he made 322 rwhp. (red graph on posted dyno) Which means if the 1995 stock crank hp was 210 (assumed by the engines factory rating) and with the mods he gained 146 rwhp, He will have 356 hp at the crank. So stock his engine was 210 hp/ 210 torque, after adding the 10.5 psi of boost and an intercooler his engine is now 356hp / 393 torque. Losses thru the driveline are not a percentage but rather power used/required. Going by the dyno data posted, It takes approximately 34 hp to drive the 4T60e trans in his car. (210 - 176 = 34)
1.) 322 rwhp minus the baseline of 176 rwhp = 146 rwhp difference. (all his mods gave him a 146 hp increase.) 2.) The stock rated crank hp is 210 add 146hp gain = 356 hp. 3.) Take the rated crank hp of 210 and subtract the rwhp of 176 = 34 hp used by the trans. 4.) Take the calculated crank hp of 356 from line # 2 and minus the 34 hp used by the trans = 322 rwhp. (which is what the dyno shows!)
So how do you explain the data above?
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04:14 PM
Doug Chase Member
Posts: 1487 From: Seattle area, Washington State, USA Registered: Sep 2001
My engine has more like around 330hp using exhaust manifolds instead of tuned headers and 2.5" pipes instead of 3" pipes.
Where does this 330hp number come from? Did you put this one on an engine dyno like you did your V6? Because without knowing where the 330hp comes from, or even the exact conditions where GM came up with 355hp, then everything is just conjecture.
Let's look at transaxle power loss from a few different logical perspectives.
1 Let's say the manual transmission in example 1 takes 22hp to turn. If you grabbed the input shaft by hand could you turn the transmission? Yes. Does your arm makes 22hp? No. (Well, mine doesn't, I don't know about yours). Therefore the transmission can't have a constant loss of 22hp or you wouldn't be able to turn it.
2 Gears slide when they mesh. The more force you apply to the gears the more friction there is between them and the more energy (power) they absorb. Angle cut gears slide even more, plus they make thrust loads, so they absorb more power than straight cut gears. Transmissions have gears in them. They're arranged a lot differently in manual vs. automatic, but they're there.
3 Let's say that you're cruising along a flat freeway at 60mph. The engine is putting out, say, 30hp to keep the car going this speed. Now you start climbing a hill and the hill gets so steep that you have to go full throttle to maintain this speed. Your engine is now putting out 200hp. Is the fluid in your transmission hotter, cooler, or the same temperature that it was when cruising on flat ground? It's hotter. Anybody who has towed in a vehicle with a transmission temperature gauge can verify this. The energy to heat this fluid is power that is coming out of the engine and not making it to the wheels. It's absorbed by the transaxle and dissipated as heat. More power in = more power dissipated as heat.
Your example 2 is circular logic. You say that 210 - 176 = 34 Then you say that because (210+146) - (176+146) = 34 then the transmission has a constant loss. In other words, you're making the assumption that transmission loss is constant in step 2 when you add the 146hp increase (measured at the wheels) to the stock power of 210hp (measured at the crank). The reality is that we don't know the hp increase at the crank. We have too many variables to be able to solve this equation. The only way to do it would be to do engine and chassis dyno runs before and after.
I remember reading some article about this in CarCraft or other car magazine and they did some tests and the power loss was not a constant. I need to find that one on my pile of mags...
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09:21 PM
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
Where does this 330hp number come from? Did you put this one on an engine dyno like you did your V6? Because without knowing where the 330hp comes from, or even the exact conditions where GM came up with 355hp, then everything is just conjecture.
No the V-8 has not gone on an engine dyno. The 330 is calculated and may be conjecture, but if we go by the "16% rule" then my engine would have 368 hp at the crank. There is no way the engine is going to gain 13hp with exhaust manifolds instead of headers and smaller diameter pipes. Not to mention that the GM rating is under "ideal" conditions, so generally the engine will have less power because it isn't running at the same ideal conditions. I have chassis dyno'd it at 309 rwhp, so what does your calculation say I have at the crank with a 4-spd manual trans at 3.65 final drive??
quote
Originally posted by Doug Chase: Let's look at transaxle power loss from a few different logical perspectives.
1 Let's say the manual transmission in example 1 takes 22hp to turn. If you grabbed the input shaft by hand could you turn the transmission? Yes. Does your arm makes 22hp? No. (Well, mine doesn't, I don't know about yours). Therefore the transmission can't have a constant loss of 22hp or you wouldn't be able to turn it.
It is not that the trans requires 22hp to turn, But it requires 22hp to drive it in the final gear under a referenced load. (where the dyno is taking the measurement.) Remember that this is at peak power of the engine in the final gear under a given reference load (the dyno) and generally around the same RPM range. I'm not saying it takes 22hp just to turn the transaxle, But in the final gear under the same load, The trans will use/dissapate/convert/lose 22hp and that the power applied to the input shaft vs the power at the tires on a given reference load will only vary by 22hp with a given trans in the final gear. Changing the trans by different style gears, ratio's or load will affect it's loss, But if the trans and load do not change and the power does, the trans will not lose more power.
quote
Originally posted by Doug Chase:
2 Gears slide when they mesh. The more force you apply to the gears the more friction there is between them and the more energy (power) they absorb. Angle cut gears slide even more, plus they make thrust loads, so they absorb more power than straight cut gears. Transmissions have gears in them. They're arranged a lot differently in manual vs. automatic, but they're there.
Yes both have gears and both have ratio's. But the losses at a given reference load will be consistant. Yes different style gears will use more or less power, But we are talking about the same set of gears and load but with different power applied to the input shaft.
quote
Originally posted by Doug Chase: 3 Let's say that you're cruising along a flat freeway at 60mph. The engine is putting out, say, 30hp to keep the car going this speed. Now you start climbing a hill and the hill gets so steep that you have to go full throttle to maintain this speed. Your engine is now putting out 200hp. Is the fluid in your transmission hotter, cooler, or the same temperature that it was when cruising on flat ground? It's hotter. Anybody who has towed in a vehicle with a transmission temperature gauge can verify this. The energy to heat this fluid is power that is coming out of the engine and not making it to the wheels. It's absorbed by the transaxle and dissipated as heat. More power in = more power dissipated as heat.
Yes but now you are changing the load. On a chassis dyno it is a constant referenced load so that all engines and drivetrains can be measured using the same standard reference. Driving a car from a flat road to a hill is changing the load. This requires more power to move the weight as the load increases. I never said that the trans does not change losses based on the load. But rather with a given reference load (the dyno machine) the manual trans used in a Fiero will have an average loss of 22hp regardless of the power of the engine. You can take a 2.8L with a manual trans and put it on a dyno with less load and the drivetrain will have less loss. Increase the load and the drivetrain will have a higher loss. The thing to remember is what the reference is, It is the load. Which is a calibrated constant. If each dyno machine had a different load then there would be no way to compare an engines power with another engine on a different dyno. If the trans loss varied by how much power it had, then there would be no way to compare actual gains/losses of a mod on a chassis dyno.
quote
Originally posted by Doug Chase: Your example 2 is circular logic. You say that 210 - 176 = 34 Then you say that because (210+146) - (176+146) = 34 then the transmission has a constant loss. In other words, you're making the assumption that transmission loss is constant in step 2 when you add the 146hp increase (measured at the wheels) to the stock power of 210hp (measured at the crank). The reality is that we don't know the hp increase at the crank. We have too many variables to be able to solve this equation. The only way to do it would be to do engine and chassis dyno runs before and after.
True the only real way would be to have the engine dyno'd, and that this is all calculated conjecture. But, The data for various engines does support the side that the amount of drivetrain loss on a given trans under the same referenced load remains a constant regardless of the engines power. The only real way to get a true result would be to build an engine and dyno it, install it in a car and run a chassis dyno, modify the engine for more power, run the chassis dyno, remove the engine and run it on an engine dyno.
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09:34 PM
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
I remember reading some article about this in CarCraft or other car magazine and they did some tests and the power loss was not a constant. I need to find that one on my pile of mags...
Article from 5.0 Mustang & Super Ford magazine February 2002, page 54, sub content titled "What's the loss" from the article "Heads or Tails", page 47, by Eric English "What's the Loss?
When we began to contemplate flywheel horsepower figures for our different combinations, we bantered about some concepts that can be deceiving. Most enthusiasts have been exposed to the idea that flywheel and rear-wheel horsepower can be equated by factoring in a given percentage for drivetrain loss - the drag that occurs from all the items between the flywheel and the rear tires. You may have seen factors such as 15 percent for stick-shift cars and 25 percent for automatics, applied by dividing rear-wheel horsepower by either 0.85 for stick-shifts or 0.75 for automatics.
Now take a time-out and consider the following. Our original baseline indicated 195 hp at the rear wheels, which when divided by 0.85 equates to 229 flywheel horsepower, and implies that the drivetrain is absorbing some 34 horsepower. On the other hand, our combination of blower and traditional bolt-ons netted nearly 340 hp on the Blood Enterprises dyno, which when divided by 0.85, equates to 400 flywheel horses, and implication that the drivetrain is now absorbing 60 hp.
Nothing has changed between the flywheel and the rear wheels on our '93 LX, so does it make sense to figure the drivetrain is now absorbing nearly twice as much power? Such a concept just doesn't jibe in our little brains, so we asked a couple of people in the biz what they thought. Lee Bender of C&L Performance and Paul Svinicki of Paul's High Performance are both well versed in evaluating Mustangs on the dyno, and they both agreed that extrapolating drivertrain horsepower loss via percentages is flawed. Lee believes that the stick Mustangs experience roughly a 35hp loss through the drivetrain, whether they make 200 hp or 400 hp. He did explain that ultra-high-powered vehicles - typically race cars - can be and exception to this rule, but that's a topic for another time. Interestingly, a 35hp loss for stick-shifted drivetrains is strikingly similar to the difference between Ford's horsepower ratings and the rear-wheel numbers we've observed on dynos across the nation."
I love the oreif debates. But um- yeah ... since orief is righ as proven .... again.... (excelent dave)
does anyone one know the rating and hp loss of the common trannies we swap into the fiero. From teh 4 speed to the 5 speed sticks- to all the 4 speed autos. i think seeing that we have come to the concllusion that the 20 % rule is non existant as is the 14-17% rule. I think it be wise to find out the hp loos and the tq ratings of our trannies. I think this will make and break the use of our trannies. Although i think alot of 5 speed getrags have been proven to hold to at least 300-350 hp at engine... correct me if i am wrong as i was in my previous calculations.
and yes as always the hp for 1/4 mi time was on paper. of coruse there is way too many things to consider so i just came to the most logical end. what would happen in perfect/ideal conditons whihc would include a perfect driver.
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10:45 PM
Formula88 Member
Posts: 53788 From: Raleigh NC Registered: Jan 2001
So what is it you want to accomplish? Get a chart defining the "best" transmission? In most engine swaps, the transmission loss is a low priority. Strength and gear ratios are far more important.
You can't plan everything out on paper and expect the reality to match it. You can make educated guesses based on verifiable data, but there is no hard and fast rule that says "x" transmission takes "y" amount of power, so it's best.
I do know and understand that and i do think a you do there. But it will be helpful at the level that for those with a 4 speed izuzu will know what it SHOULD be able to take or as i said what it is rated for. The same for anyother transmition. One should be able to say YES this is going to be the best stick or auto for MY aplication. Yes that is onyl th e first step. They will want to know the weight of the transmition itself. If anyone was at the last MFF meeting on monday they would know that even GM in all there planning did not get it right the first time through. So they had to rework it until it would. THe same goes here. You pick the best tranny fro your app. then you build that and the egnein and everythign around that setup. With you knwoing your weeknesses and strengths and taking advantage of both for drving style and the way you build the rest of the vehile. Catch me?
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08:48 AM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
For Oreif's statement to be correct it would mean that any engine that made less than 34hp couldn't turn the transaxle over. That's obviously not true. If you hook a 5hp Briggs and Stratten to the thing, it will make a golf cart or something similar go. Not very fast, but it will go. Obviously, the transmission is then using less than 34 hp.
For any drivetrain, be it transaxle or longitudal, there are two components (at least) involved in how much hp they require.
The first is a fixed, constant amount of power. This is generally not a large number, but it IS there. In the case of an automatic it is more pronounced. An automatic has a pump that is being driven all the time, whenever the engine is running, and is making pressure. Since there ain't no such thing as a free lunch, this is consuming hp. Now the faster you drive it, and the more pressure it puts out, the more power it's going to consume, but as a baseline, anytime the engine is running it's consuming power. Also, anytime you have things (shafts, gears, whatever) that are not 100% rigidly connected, you have a definite power loss. An example of this is a simple air impact wrench. Take a bolt that is as tight as the impact wrench can remove and put a socket on the end of an extension. It won't take it out because you're having a power loss in the two connections between the wrench and the socket. Now take the extension off the wrench and put the socket directly on the impact and it will spin it out.
As Oreif pointed out, how the transmission is built, how much slip is in the converter, how tight the clutch packs are set up, even the weight of the oil will all have an effect on how much power the transmission is going to consume. To make matters even MORE complicated, that number DOES CHANGE DEPENDING UPON INPUT HP AND RPM! Why? It always takes MORE POWER to spin things faster. ALWAYS. Again, in the case of an automatic, you also have other things going on like converter slip changing with input speed and power load and pumps requiring more power (and not in a linear curve) with higher rpm and pressure.
There is no "one number" that you can use to figure out how much loss you're going to have through a transaxle, all you can do is best guesses. For Oreif's engine/trans combo, he doesn't have to guess because he had the engine dyno'd and also had a chassis dyno done. He could actually go back and plot the engine dyno curves against the chassis dyno curves and see how much his loss varied with power input and rpm. I'd wager that at lower power levels and rpms, his loss is under 10% in some cases, but that's a guess on my part.
Don't forget that when you run a chassis dyno you have another loss to consider (actually more than one, but.........) and that is the loss of friction through the tires. Tires take a LOT of power to turn and the faster you turn them, the more power they require. They're big, heavy, and when worked hard, sticky. That's their job, but they are sucking power out of the engine and the only thing that counts is how much you get to the ground.
John Stricker
quote
Originally posted by Doug Chase:
That's not true.
A transaxle will absorb some constant amount of power (ie, there will be a minimum amount of power required to drive it), and in addition to that it will absorb a percentage of the engine's output.
In your case since your baseline for transaxle loss came from an engine with similar power as yours, you are probably very close in assuming a 34hp loss when installed in your car.
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09:35 AM
PFF
System Bot
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
For Oreif's statement to be correct it would mean that any engine that made less than 34hp couldn't turn the transaxle over. That's obviously not true. If you hook a 5hp Briggs and Stratten to the thing, it will make a golf cart or something similar go. Not very fast, but it will go. Obviously, the transmission is then using less than 34 hp.
Doug is not correct. A Briggs and Stratten is not going to turn a Fiero transaxle when it is in it's final gear under a load on a dyno at 4500 rpm. It may work for the first and possibly 2nd gear but the gearing makes the huge difference. Think of it as a 10-speed bike, First gear is very easy to pedal at say 5mph, Now try pedaling in 10th gear at the same speed. It requires more power.
It is true that at the lower gears you use less power and most likely have less loss, But we are discussing the loss of the trans and driveline at a given load (the dyno) in the final gear at a given RPM is not going to have more loss just because the power of the engine increases.
In order to calculate the crank horsepower of an engine on a chassis dyno you need to know the driveline loss. If I dyno an engine at 140 hp and then install it in a car on a dyno then I find out at say 4500 rpm in 4th gear the driveline has a loss of 34hp, Then I increase the engines power to 300hp and run it at the same load, gear, and rpm, the driveline will still have 34hp of loss, Not 45hp as would be indicated if you used the "percentage theory" of loss.
If the flywheel to rear tires does not change and the load of the dyno is the same, The loss will not change just because you add 100hp to the engine.
Per the "percetage loss" theory the driveline would have more loss just because the horsepower was increased.
Please remember we are talking about a chassis dyno so everything between the flywheel and the rear tires is the same and the load of the dyno is the same. On the street, the losses will change with friction, temp, weight, load changes, etc. The discussion was not that the losses vary depending on the conditions. The discussion is that under the test conditions on a chassis dyno, does the driveline loss change just because the horsepower of the engine increases.
My argument is that the driveline will have a certain amount of loss in the final gear, under the same load and RPM on the dyno regardless how much horsepower the engine has.
Going back to my 3.4L set-up, It was confirmed that my TH125 used 34hp when it was in 3rd gear at 4500 rpm on the dyno. It doesn't matter if the engine had 140hp or 300hp the driveline is still going to have 34hp of loss at the same test environment.
The "percentage loss" theory would state that I would lose 34hp with a 140hp engine and 45hp with a 300hp engine. Where the only change is the horsepower. I say that is incorrect.
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11:03 AM
ryan.hess Member
Posts: 20784 From: Orlando, FL Registered: Dec 2002
Originally posted by Oreif: A transaxle will require the same power to drive it regardless how much power the engine has.
100% wrong
the amount of power used by a transmission increases as a factor of load and rpm - its also not linear
to say that the tranmission will use 34hp no matter what is just dumb because that would mean you have to apply 34hp to it just to get it to turn.. i can turn one by hand and i guarantee you I am not that strong
Originally posted by Oreif: But we are discussing the loss of the trans and driveline at a given load (the dyno) in the final gear at a given RPM is not going to have more loss just because the power of the engine increases.
chassis dyno's don't apply load - they simmply resist acceleration - how ever fast the engine is capable of accelerating the drum adds the time variable to the equation to calculate HP
Originally posted by Oreif: The "percentage loss" theory would state that I would lose 34hp with a 140hp engine and 45hp with a 300hp engine. Where the only change is the horsepower. I say that is incorrect.
due to there being multiple factors the rate of loss is not linear - infact the % loss is higher will less power and lower the higher the power goes
So then how what is the quation with how much a transmition takes to turn based onthe power of the engine then? If it is not a constant 20 pecent (and if it is not at 34hp loss always for the more specific tranny we are currently making reference to the 125c) where does the number start. say with a low hp enigne like 100hp then what would the percent then be for the same tranny if it were at 200? there must be an equation for what you say to work.
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02:45 PM
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
drive train loss is NOT a fixed number. the "it looses 30 hp" is misleading. when you say your engine makes 200 hp, it is not ALWAYS making 200 hp. same goes for the tranny/driveline. most people look at the highest HP achieved, add an estimated loss, and thats that. gears do have friction, and when you apply more power to them, the friction is greater. same with the bearings, same with the CV's, etc. RPM's attained also changes the number. same tranny on a diesel & on a DOHC rev monster - both with same peak HP - the rev monster will have more loss - and thats with the SAME HP's. while I'm sure the actual loss can be calculated, using a fixed number when dealing with simelar engine layouts is perfectly fine. and using a pecentage is perfectly fine. its called an ESTIMATE. and anyways - the power to the ground is what counts. eliminating driveline loss is a valid way to gain performance - synthetic fluids, lighter fluids, better bearings, lighter gears, lighter flywheel, even lighter wheels. yes, your wheels do count in driveline loss. an out of balance tire can cost HP's. any vibration is power the engine is making, but not making its way to the pavement.
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02:52 PM
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
the amount of power used by a transmission increases as a factor of load and rpm - its also not linear
to say that the tranmission will use 34hp no matter what is just dumb because that would mean you have to apply 34hp to it just to get it to turn.. i can turn one by hand and i guarantee you I am not that strong
No, You don't get it. I NEVER said that it takes 34 horsepower to turn the trans!!!!!!
I said the TH125 transaxle requires 34 hp to drive the driveline (or maybe it should be stated it has 34 hp of loss) when it is in the final gear on the dyno at 4500 rpm! AND that that total driveline loss AT THAT TIME WILL NOT CHANGE if the engine has 100hp more.
Geez, when will you people quit changing the parameters.
YES the driveline loss will vary based on load, gear, temperature, and friction but it doesn't matter if it's a 200hp engine or a 400hp engine the drivetrain loss will be the same thru the drivetrain at that given moment. If the driveline has only a 5hp loss in first gear and a 30 hp loss in the final drive gear, those losses will not change just because I added 50 hp to the engine. The driveline will still have the same losses at a given time. The problem is you cannot see the entire picture. You are taking things out of context.
True a dyno resists accelleration, The point is that no matter where you go the chassis dyno's are calibrated to supply the same resistance. The reason is that is the standard so that an engine dyno'd in Florida is tested under the same standard as in California. OK you got me on using the load. I used the term "load" so that it would make it easier to understand. Obviously, nobody understood it.
What you are failing to realize is I'm am not saying that in all conditions and environments the trans will only use 34 hp.
I am saying that on a chassis dyno at 4500 rpm in the final gear the driveline loss from the flywheel to the rear wheels on the roller will remain constant regardless if the engine is a 200hp engine or a 400hp engine. Did you even read the quote from the Mustang magazine and understand it??????????????????????????
I have yet to see anyone explain how my ZZ4 engine is suddenly making 368 estimated crank horsepower. If you use the "percentage factor" theory I should have 368hp with a chassis dyno of 309 rwhp. I say that is incorrect. But hey if you want to go ahead and prove that my engine has a calculated 368hp at the crank, by all means prove it.
Maybe you should go to a dyno shop and see what is really happening.
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02:55 PM
ryan.hess Member
Posts: 20784 From: Orlando, FL Registered: Dec 2002
Originally posted by Oreif: I have yet to see anyone explain how my ZZ4 engine is suddenly making 368 estimated crank horsepower. If you use the "percentage factor" theory I should have 368hp with a chassis dyno of 309 rwhp. I say that is incorrect. But hey if you want to go ahead and prove that my engine has a calculated 368hp at the crank, by all means prove it.
Loss % goes down as power transmitted goes up. Not linearly. If your 200HP engine created a loss of 17% through the drivetrain, and lost 34hp, then your 309rwhp engine created a loss of (for example) 15%, and lost 54hp, of the 363 it originally had. It's possible it slipped down to 10% with the increase in HP. I don't know enough about the topic to say it can or can't.
However, I can ask you this. You said you had your transmission dynoed with a 200hp reference engine. Did they have other engines there? If so, why, if all they need is one engine to calculate loss?
Also, I wanted to ask what conditions (if any) the different dyno's were corrected to. Uncorrected dyno readings can be very unaccurate when you consider one day it might be 30 degrees, and the next it might be 90.
[This message has been edited by ryan.hess (edited 02-22-2006).]
No, You don't get it. I NEVER said that it takes 34 horsepower to turn the trans!!!!!!
I said the TH125 transaxle requires 34 hp to drive the driveline (or maybe it should be stated it has 34 hp of loss) when it is in the final gear on the dyno at 4500 rpm! AND that that total driveline loss AT THAT TIME WILL NOT CHANGE if the engine has 100hp more.
Geez, when will you people quit changing the parameters.
YES the driveline loss will vary based on load, gear, temperature, and friction but it doesn't matter if it's a 200hp engine or a 400hp engine the drivetrain loss will be the same thru the drivetrain at that given moment. If the driveline has only a 5hp loss in first gear and a 30 hp loss in the final drive gear, those losses will not change just because I added 50 hp to the engine. The driveline will still have the same losses at a given time. The problem is you cannot see the entire picture. You are taking things out of context.
True a dyno resists accelleration, The point is that no matter where you go the chassis dyno's are calibrated to supply the same resistance. The reason is that is the standard so that an engine dyno'd in Florida is tested under the same standard as in California. OK you got me on using the load. I used the term "load" so that it would make it easier to understand. Obviously, nobody understood it.
What you are failing to realize is I'm am not saying that in all conditions and environments the trans will only use 34 hp.
I am saying that on a chassis dyno at 4500 rpm in the final gear the driveline loss from the flywheel to the rear wheels on the roller will remain constant regardless if the engine is a 200hp engine or a 400hp engine. Did you even read the quote from the Mustang magazine and understand it??????????????????????????
I have yet to see anyone explain how my ZZ4 engine is suddenly making 368 estimated crank horsepower. If you use the "percentage factor" theory I should have 368hp with a chassis dyno of 309 rwhp. I say that is incorrect. But hey if you want to go ahead and prove that my engine has a calculated 368hp at the crank, by all means prove it.
Maybe you should go to a dyno shop and see what is really happening.
you are making up parameters that don't exist
dynos don't measure the HP of an engine at a maintained RPM - it torque based on acceleration at that moment when the engine is at that rpm - hp is just a function of torque and rpm
you are wrong but hey - you've never been willing to admit it before so why start now -
fact is you are wrong and nobody should believe what you are saying because it is incorrect information - - if they want the truth and can't tell from this thread what is true then they should seek outside sources like a physics book
So then how what is the quation with how much a transmition takes to turn based onthe power of the engine then? If it is not a constant 20 pecent (and if it is not at 34hp loss always for the more specific tranny we are currently making reference to the 125c) where does the number start. say with a low hp enigne like 100hp then what would the percent then be for the same tranny if it were at 200? there must be an equation for what you say to work.
its different for every tranmission - and the reason people don't do the work to develop the equation for each tranny is because crank HP is irelevant.. the only thing that matters is what is reaching the ground (unless you are trying to design a more effecient tranny)
[This message has been edited by Kohburn (edited 02-22-2006).]
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03:32 PM
Formula88 Member
Posts: 53788 From: Raleigh NC Registered: Jan 2001
Let me ask a hypothetical question: If I have a transmission running at 200°F, turning 5000 rpm in final gear (1:1 ratio) and a chassis dyno measures 180HP. Now, that engine is put on an engine dyno, and at the same operating temp and rpm, it measures 200HP. That means 20HP, or 10% is lost through the transmission, right?
Now, what if I add a 100HP shot of Nitrous to the engine? Does the transmission still waste the same 20HP at 5000rpm in final gear, or has the power wasted by the transmission gone up? You've got a measured 300HP at the flywheel. Will that translate to 280 HP at the wheels, or 270 HP?
I see both sides of what you two are arguing, but I've seen no data that suggests a transmission always uses the same PERCENTAGE of power an engine puts out, or that it consumes a fixed amount of power (at a given rpm, gear ratio, etc.)
What is it about a more powerful engine that makes the transmission less efficient? If the percentage is constant, you waste more power as input power goes up. (i.e. 20% of 500 HP is 100HP, whereas 20% of 100HP is only 20HP). So, if the percentage is constant and the amount of waste goes up, I'd expect transmission temperatures to climb proportional to engine output. Is this the case?
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03:44 PM
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
Originally posted by Formula88: What is it about a more powerful engine that makes the transmission less efficient? If the percentage is constant, you waste more power as input power goes up. (i.e. 20% of 500 HP is 100HP, whereas 20% of 100HP is only 20HP). So, if the percentage is constant and the amount of waste goes up, I'd expect transmission temperatures to climb proportional to engine output. Is this the case?
friction. gears have friction, and the more they are loaded, the more friction there is. I will agree it is MOSTLY a fixed number. but gears & bearings do have friction, and with more power/torque applied to them, the friction will be greater. just rub your hands together. easy enough. now add some pressure, and it becomes harder. not an exact example, but the gears are not frictionless - even with synchromesh. and again, the RPM's. back to my old example of the 3500 rpm deisel & the 8000 rpm dohc turbo. both hitting 300 hp's but at VERY different rpm's. the diesel will have MUCH less loss at the lower rpm, then the dohc at the high rpm's with the exact same trans.
Originally posted by Pyrthian: both hitting 300 hp's but at VERY different rpm's. the diesel will have MUCH less loss at the lower rpm, then the dohc at the high rpm's with the exact same trans.
actually - the lower RPM will require higher torque to have 300hp but at higher rpm you also have more fluid resistance..
but for the same torque applied to low rpm and higher rpm there is more friction at higher rpm
also remember that most trannies use helical gears which push on a thrust bearing - the less torque being applied the less they push..
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04:01 PM
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
dynos don't measure the HP of an engine at a maintained RPM - it torque based on acceleration at that moment when the engine is at that rpm - hp is just a function of torque and rpm
you are wrong but hey - you've never been willing to admit it before so why start now -
fact is you are wrong and nobody should believe what you are saying because it is incorrect information - - if they want the truth and can't tell from this thread what is true then they should seek outside sources like a physics book
I NEVER said a dyno only measure HP!!! Quit assuming what I'm saying. As for if I'm wrong I don't admit it is pure BS!
Have you ever been to a dyno shop??? Did you understand what was going on??
OK, Lets see if I can’t make an example of what I mean: (Maybe this will explain my point better.)
A Chassis Dyno is designed to read the engines output power by reading the torque and the time it takes to go thru the RPM range. This in turn gives us the horsepower at the wheels by using the formula. The dyno uses the gear closest to a 1:1 ratio which is generally the top gear (some overdrive transmissions are tested in the final drive gear and not the overdrive gear.) so that gearing does not affect what they are trying to measure.
NOTE: The below is just an example, NOT what you would really see as the power would be higher due to gearing.)
Now as a Baseline we take a 200hp at 4500 rpm engine and run it on the dyno and get these results: First gear at 4500 rpm we have 195 rwhp which equals 5hp or 2.5% loss Second gear at 4500 rpm we have 188 rwhp which equals 12hp or 6% loss Third Gear at 4500 rpm we have 182 rwhp which equals 18hp or 9% loss And the final gear (fourth) we have 170 rwhp which equals 30hp or 15% loss
OK, So now we add a NOS system to the car and now the engine has 400 hp at 4500 rpm. Which answer do you think is correct “A” or “B”??
A (Using the same amount of horsepower loss) First gear at 4500 rpm is 395 rwhp Second gear at 4500 rpm is 388 rwhp Third gear at 4500 rpm is 382 rwhp Fourth gear at 4500 rpm is 370 rwhp
B (Using the “percentage factor” loss) First gear at 4500 rpm is 390 rwhp Second gear at 4500 rpm is 376 rwhp Third gear at 4500 rpm is 364 rwhp Forth gear at 4500 rpm is 340 rwhp
Now pick your answer and explain why?
What I say is answer “A” is correct. The driveline loss is the same horsepower loss at the same point under the same conditions. There is no way that an increased amount of friction is going to cause twice the driveline loss under the same conditions. If friction caused that much loss, Then by that logic a Grand Prix with a 200hp 3800 would have only 5 rwhp less than the same Grand Prix with the same transmission but using a 260hp 3800SC engine. That is not the case.
Does this make what I am trying to say clearer??
[This message has been edited by Oreif (edited 02-22-2006).]
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04:10 PM
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
actually - the lower RPM will require higher torque to have 300hp but at higher rpm you also have more fluid resistance..
but for the same torque applied to low rpm and higher rpm there is more friction at higher rpm
also remember that most trannies use helical gears which push on a thrust bearing - the less torque being applied the less they push..
ug. was trying avoid adding more confusion....yes, lower rpm hp requires more torque to achieve the same HP, and loads the gearing up. but I'm sure the 2x + RPM load will far outweigh the torque load.
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04:12 PM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
Given all identical conditions, you have the car on a chassis dyno. To make things more dramatic we have two engines, one a 2.5 that is delivering 75 hp at the wheels at 4,500 rpm. The second a small block Chevy developing 600 hp at 4,500 rpm.
Run them both on the dyno for a given time. Measure your transmission temperatures. Which do you think will be hotter? Is not heat an indication of waste (lost) horsepower?
It takes more friction in the clutch packs, torque converter, and even tires to the rollers to hold 600 hp at a given rpm than it does to hold 75 hp at a given rpm. More friction is equal to more lost horsepower.
John Stricker
quote
Originally posted by Oreif:
My argument is that the driveline will have a certain amount of loss in the final gear, under the same load and RPM on the dyno regardless how much horsepower the engine has.
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04:19 PM
jstricker Member
Posts: 12956 From: Russell, KS USA Registered: Apr 2002
Yes, take the same example I gave before with a 75hp measured at the wheels 2.5 and a 600 hp SBC. In the first engine, at the 4500 rpm, let's say the engine had an engine dyno reading of 100 hp, losing 25% and 25 hp. In the SBC, lets say that it engine dyno'd at 660 hp for a loss of 60 hp, but a % loss of only 10%. That's why the losses do not vary the same at different hp readings. There are many variables involved on a chassis dyno and the lower % loss will still be a higher total loss because of the increased friction generated.
John Stricker
quote
Originally posted by ryan.hess:
Loss % goes down as power transmitted goes up. Not linearly. If your 200HP engine created a loss of 17% through the drivetrain, and lost 34hp, then your 309rwhp engine created a loss of (for example) 15%, and lost 54hp, of the 363 it originally had. It's possible it slipped down to 10% with the increase in HP. I don't know enough about the topic to say it can or can't.
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04:28 PM
Doug Chase Member
Posts: 1487 From: Seattle area, Washington State, USA Registered: Sep 2001
But if the trans and load do not change and the power does, the trans will not lose more power.
quote
Originally posted by Oreif:
Yes but now you are changing the load. On a chassis dyno it is a constant referenced load so that all engines and drivetrains can be measured using the same standard reference. Driving a car from a flat road to a hill is changing the load. This requires more power to move the weight as the load increases.
quote
Originally posted by Oreif:
If the flywheel to rear tires does not change and the load of the dyno is the same, The loss will not change just because you add 100hp to the engine.
quote
Originally posted by Oreif:
YES the driveline loss will vary based on load, gear, temperature, and friction but it doesn't matter if it's a 200hp engine or a 400hp engine the drivetrain loss will be the same thru the drivetrain at that given moment.
I think we've found the point where we're not connecting with each other.
It is not possible to have the same load at the same RPM and have a different horsepower number. The load and the RPM are what define hp.
Chassis dynos (usually inertia dynos) do not have a "constant reference load." They do have a constant reference mass. (and actually this mass isn't always constant between dynos, but that's not important to this discussion). They measure the acceleration of this known mass and use that to calculate torque/horsepower. It's exactly the same principle as calculating hp based on 1/4 mile ET/mph, but with a few variables (driver, etc) removed to give consistant results.
Engine dynos are typically brake dynos. Brake dynos apply a load to the motor. They measure how much load it takes to hold the motor at a constant RPM, and from this they calculate torque/horsepower. This is similar to driving a car up a hill. The more load you have to apply to the motor to hold it at a constant RPM, the more power it has.
So in your above statement where you say...
quote
YES the driveline loss will vary based on load...
...you are in fact saying the same thing that the rest of us are.
Power is proportional to load. The only way to put more load on the drivetrain is to add more power. This is what you do when you push your right foot down.
Are we making sense yet?
Note that I (and most others) are not advocating a "constant percentage" loss. It will be a decreasing percentage but increasing loss as power increases. John Stricker explains this quite well in his post directly above this one.
