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??
Unfortunately I have no calculation that tells me how much crank hp you have. Fortunately, it doesn't matter. What matters is 309 to the wheels, and that's an impressive result. I bet it's a fun car.
Do you have any information about GM's "ideal" conditions for dyno testing their crate motors? I know nothing about it and I'm curious.
Does the crate motor come with a piece of paper that says "355hp at the crank with x headers, y exhaust, z carburetor with xxx jets, timing set to yy degrees, while dyno'd at this temperature and that pressure"? In other words, does it tell you how to set up your motor so you can duplicate the power output that GM claims? I haven't purchased a crate motor or even looked into them much so I don't know anything about where the power claims come from.
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.
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
Yes friction and temp will cause more loss. But now lets look at your example. Lets say the 25% is driveline loss. So the 100hp engine with a 25% driveline loss will have 75 rwhp. Now you remove the 2.5L and put in the 600hp V-8. On the same driveline. Going by the "percetage factor" as some people are saying is the correct way, The rwhp would be 450. That means that even though the driveline is unchanged, that thee friction caused by the higher power is now losing 125 rwhp more than it did with the 2.5L. Granted friction will cause more loss but not 5 times more loss. That is the point I am trying to make. The loss using a percentage is flawed and not accurate.
We all know that you car run the same car on a dyno and not get the same exact result. As the engine and drivetrain heat up friction causes the losses to vary. But I still can't see frictional losses losing over 5 times the amount of power thru the drivetain. It just doesn't work like that.
Hold on............................................................................
Well I just called the dyno shop and their opinion is the driveline loss from a 200hp engine to a 400hp engine will NOT vary by the same percentage. If you have a 25% loss with the 200hp engine you will have less percentage of loss with the higher HP engine. BUT, if you have a 25 hp loss at 200 hp, you will have roughly a 30-35 hp loss with the higher powered engine on the same driveline. This is due to the frictional forces. They state that calculating 25% loss for the driveline regardless of the power is very inaccurate and that the reason many shops use that "standard" is to make the crank horsepower seem higher. As an example based on what they have seen a 200hp engine dyno's roughly around 170-175 rwhp and the 400 hp engines usually dyno around 360-370 rwhp. Doing the math that works out to be around 15% loss at 200hp and about 11% loss with the 400hp engine. I can believe that if a 200hp engine loses 25-30 hp thru the drivetrain and a 400 hp car loses 30-40 hp due to increased friction and other factors, That all seems logical. Losing 30 hp and 60 hp seems way off.
So my original thought of a consistant loss was wrong, But at the same token, so it the "percentage factor" is also incorrect. So John's assesment is the most accurate.
EDIT: and ryan.hess too.
[This message has been edited by Oreif (edited 02-22-2006).]
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07:14 PM
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
Unfortunately I have no calculation that tells me how much crank hp you have. Fortunately, it doesn't matter. What matters is 309 to the wheels, and that's an impressive result. I bet it's a fun car.
Do you have any information about GM's "ideal" conditions for dyno testing their crate motors? I know nothing about it and I'm curious.
Does the crate motor come with a piece of paper that says "355hp at the crank with x headers, y exhaust, z carburetor with xxx jets, timing set to yy degrees, while dyno'd at this temperature and that pressure"? In other words, does it tell you how to set up your motor so you can duplicate the power output that GM claims? I haven't purchased a crate motor or even looked into them much so I don't know anything about where the power claims come from.
PS. I own page 2.
Doug,
On the Sallee-Chevy website they state (The ZZ4 is a 350 H.O. with aluminum heads and the ZZ4 roller cam.) A prototype H.O. 350 engine with a 600cfm Quadrajet carburetor, 1 3/4” headers, 3" pipes, and low-restriction mufflers produced 355 horsepower (at 5250 rpm) and 405 lb.-ft. torque (at 3500 rpm).
So that is how they "rated" the engines. From that statement I gather it was one engine that they tested, then they built the crate engines using the same spec parts. So most likely just like the typical production engines, then tend to vary off that rating and most likely under the rating. There was no paperwork stating that my particular engine was run across an engine dyno nor any gaurantee that the "rated" power is what my exact engine has.
Based on the rear wheel horsepower, car weight, the 1/4 mile time and the 1/4 mile MPH, around 330-340 crank horsepower is correct.
I am using a 600cfm Edelbrock Q-jet clone with sanderson short performance exhaust maifolds and 2.5" pipes with 2 catalytic converters and resonator tips. At best guess I am most likely putting out about 330-340 hp at the crank. I know it's not 368 hp.
Yes it's a very fun car.
[This message has been edited by Oreif (edited 02-22-2006).]
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07:37 PM
ryan.hess Member
Posts: 20784 From: Orlando, FL Registered: Dec 2002
As a practical matter, though, let's say we're dealing with a 2.8/3.4 L pushrod motor that is making 125-135 hp at the wheels. Then we're going to a 4.9L caddy that's delivering 180 hp to the wheels. Then we go to a SC3800 that is delivering 225 hp at the wheels. (nobody get their panties in a bunch, these are just examples).
Let's say that you determine much as Oreif did that he KNOWS that at 4500 rpm with his 3.4 he has a 17% loss and he's making 223 crank hp there. You can pretty much bet that at 4500-5500 rpm and 180 rwhp the for the Caddy the loss will be the same (given the same transmission). Ditto for the SC3800. Why? Because the hp and rpm variations aren't big enough. Oh, the 3800 might be a percent or so better, but still use waste more actual power through the drivetrain, and the opposite might be true for the 3.4 in that it will have less total hp loss, but a higher % loss, but not much.
That's the reason I intentionally picked a very low power engine and a very high power one for my earlier comparison, to make sure there would be a significant difference. Too often we get hung up on the difference of 1, 2, or even 5 hp and the difference in temps during a day may cause more change than that. What Oreif did provide is a good baseline. I think that with the 125C if you're in the 200 hp range, that 17% is going to be dead on. Get down to 125-135 and you might want to jump that up to 18 or 19%. Go to a 300 hp engine and maybe knock the % down to 15 or 16%. Point is, at 17%, you're going to be in the ballpark and I'd wager it would be within 2% +/- for pretty much all the automatic transmissions.
There comes a point when we have to sit back and say "how much is significant?". If you're building an all out race engine, every little bit is significant. On a street engine, you're not going to know 5 hp +/- unless it's a sudden change of increase or decrease.
John Stricker
quote
Originally posted by Oreif:
So my original thought of a consistant loss was wrong, But at the same token, so it the "percentage factor" is also incorrect. So John's assesment is the most accurate.
EDIT: and ryan.hess too.
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08:13 PM
Doug Chase Member
Posts: 1487 From: Seattle area, Washington State, USA Registered: Sep 2001
So my original thought of a consistant loss was wrong, But at the same token, so it the "percentage factor" is also incorrect. So John's assesment is the most accurate.
EDIT: and ryan.hess too.
[COUGH COUGH] Ahem....
quote
Originally posted by Doug Chase:
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.
The above statement means (mathematically) the same thing as:
quote
Originally posted by Doug Chase:
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.
Anyway, that was fun, and it sounds like we're all on the same page about this. When was the last time that happened?
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)
Ok here is the deal you are comeletely missing the point of what i am saying in this. I want to desgn a car so i KNOW or can GUESTIMATE the setup to make say 300 to the wheels or 302 or 304 or 100. Do you get that? Sertain people - including myself what a goal as acertain numebrt to the wheels so we can keep up with a certain class. Possibly more but no less. So for example if i figure to keep up with people at the lemans track up north that to beat them or keep up - need a certain 1/4 mi timea 60 foot time and 1/8 time - then there is handeling as well- say i need to pull at least a G in the skid pad- or need to make a certain time in the slalom. This is how we design our cars.
To me just throwing money at just hp or jsut torque or jstu handleing or jsut looks or jsut weight or just times in teh 1/4 even- this is stupid (i'll be quite blunt if you will). The best cars are well rounded. It is very difficlt ot have good MPG and a really fast car for example. So figure out hte probelm and there you go. It is difficult to have good handling and to make a car smooth as an old caddilac - so figure ou the probelm and there you go. DO you catch me? Some what the best of everything. and there is a way of desgining a car to do what you want on paper as a estimat of what it will be like. For example what does one need to do so that the car does not spin out so easily? It is rear wheel drive and has a mid engine and the front is extremly light. So one needs to think how do i make these things equal? With taking away weight? Add weight? or screwign around with the suspension? Loosing weight or adding it becomes a problem. How? by adding weight you make the car heavier and thus making it ultimatly slower in the long and possibly short run. By losing weight you lose the structure or the car and so it is less comfortable. The guys who did the RX7 turbo did a good job here. when it came to handling and comfort. They did not think of just weight (which it is NOT perfect now matter what anyone sais) they had two different styles of spring rates and the whatnot. One for comfort and one for racing- litteraly.
Then there is the problem of MPG and fast. Well as far as i knwo ti is impossible to get good MPG and pull a 10 all day long. (and when i say good MPG i mean 23 and up on average) So there is onyl one option that came to mind other than more acurate fuel injection (which is/ can be done). One makes a chip that will hold more than one program for a fuel map. So have two or more. One for good MPG (so less gas a dffernt air micture ect.) - and one for racing (more gas more air more power. in creating this there are many factors- the most is the power to weight ratio.
So do you see my point at all. The point of nowing HP loss with the tranny is to guestimate the power to the wheels with the tranny you have chosen with teh engine you have chose. With this you cn either add more or less Hp to get what you want to the ground.
Well I just called the dyno shop and their opinion is the driveline loss from a 200hp engine to a 400hp engine will NOT vary by the same percentage. If you have a 25% loss with the 200hp engine you will have less percentage of loss with the higher HP engine. BUT, if you have a 25 hp loss at 200 hp, you will have roughly a 30-35 hp loss with the higher powered engine on the same driveline. This is due to the frictional forces. They state that calculating 25% loss for the driveline regardless of the power is very inaccurate and that the reason many shops use that "standard" is to make the crank horsepower seem higher. As an example based on what they have seen a 200hp engine dyno's roughly around 170-175 rwhp and the 400 hp engines usually dyno around 360-370 rwhp. Doing the math that works out to be around 15% loss at 200hp and about 11% loss with the 400hp engine. I can believe that if a 200hp engine loses 25-30 hp thru the drivetrain and a 400 hp car loses 30-40 hp due to increased friction and other factors, That all seems logical. Losing 30 hp and 60 hp seems way off.
So my original thought of a consistant loss was wrong, But at the same token, so it the "percentage factor" is also incorrect. So John's assesment is the most accurate.
Well this being stated. There must and always be an equation to figure out the loss at 100 to 200 hp. Do you know FOR A FACT- what the 197 hp enigne to the wheels was making at enigne at final gear at the highest available rpm? Because knowing that number we give a percentage to that- and then we can find what it would make to the ground at say 297hp. Or we can make it easier and say that It makes such and such power to the engine with 100hp to the ground and the percent loss is such and such at 50. so we then have a more finite percentage to add or subtract to find out what kind of power one would make to the ground with the same engine tranny combo at 100 vs 200 hp. How does that sound then?
Originally posted by Oreif: So my original thought of a consistant loss was wrong, But at the same token, so it the "percentage factor" is also incorrect. So John's assesment is the most accurate.
per my first couple of posts in this thread
quote
Originally posted by Kohburn: the amount of power used by a transmission increases as a factor of load and rpm - its also not linear
quote
Originally posted by Kohburn: due to there being multiple factors the rate of loss is not linear - infact the % loss is higher with less power and lower the higher the power goes
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10:00 PM
ryan.hess Member
Posts: 20784 From: Orlando, FL Registered: Dec 2002
Do you know FOR A FACT- what the 197 hp enigne to the wheels was making at enigne at final gear at the highest available rpm?
Yes I know for a fact that the trans had 34hp loss. The original engine dyno of my 3.4L (223hp) minus the baseline on the dyno (189 rwhp). Since the tuning only increased the power by 8hp, the crank horsepower was 231hp. The 8hp difference would not have much if any effect on the driveline loss.
There is no definate loss figure that you can know without doing actual testing. Using a thinner synthetc oil, different size wheels and tires, different torque converters, an aluminum flywheel, different clutches, gear ratio's, etc all will play a part in driveline loss. You cannot say that 2 identical transaxles will have the exact same loss because many variables like part tolerance's also play into it. You can use an average loss value and get close.
The above discussion was using the same driveline, But if you change any part of the driveline the loss will change as well. You can select parts that will help reduce the loss, But unless you do actual testing you cannot KNOW the loss. It will always be a calculated guess. Just like building an engine. Using a specific set of parts on one engine may get 300hp, but on an identical engine with the same spec parts may only have 295hp. So again without testing you will never really KNOW.
Kohburn, I guess I didn't read that statement as the "your wrong" seemed to deter me from that. (Or maybe it's your two-faced attitude. )
Doug, I mis-read the statement in that I thought you were stating the loss percentage stayed the same. That is most likely where the confusion came from.
Anyhow, all is good.
[This message has been edited by Oreif (edited 02-23-2006).]
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11:21 PM
PFF
System Bot
Formula88 Member
Posts: 53788 From: Raleigh NC Registered: Jan 2001
Do you have any information about GM's "ideal" conditions for dyno testing their crate motors? I know nothing about it and I'm curious.
Does the crate motor come with a piece of paper that says "355hp at the crank with x headers, y exhaust, z carburetor with xxx jets, timing set to yy degrees, while dyno'd at this temperature and that pressure"?
The headers, exhaust, carb, timing, etc. are all specified by the engine's base tune up specs. Kind of like how you know to set a Fiero 2.8 V6 to 10°BTDC. Just like any engine, you may get more by tweaking those settings.
It's the same way GM rates engines they put in cars. Have you ever bought a new car from GM that came with a dyno slip? Or did you just read the owner's manual?
Also, SAE J1349 is not the same standard used by most private dynos. Most dyno charts are adjusted to STP (Standard Temperature and Pressure) which is 60° F. STP numbers tend to be around 5% higher than SAE J1349 numbers. That's why many people who buy late model cars and have them dynoed think GM is underrating the engines. They aren't. They're just rating them differently.
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11:40 PM
Feb 23rd, 2006
Alex4mula Member
Posts: 7405 From: Canton, MI US Registered: Dec 1999
Well I just called the dyno shop and their opinion is the driveline loss from a 200hp engine to a 400hp engine will NOT vary by the same percentage. If you have a 25% loss with the 200hp engine you will have less percentage of loss with the higher HP engine. BUT, if you have a 25 hp loss at 200 hp, you will have roughly a 30-35 hp loss with the higher powered engine on the same driveline. This is due to the frictional forces. They state that calculating 25% loss for the driveline regardless of the power is very inaccurate and that the reason many shops use that "standard" is to make the crank horsepower seem higher. As an example based on what they have seen a 200hp engine dyno's roughly around 170-175 rwhp and the 400 hp engines usually dyno around 360-370 rwhp. Doing the math that works out to be around 15% loss at 200hp and about 11% loss with the 400hp engine. I can believe that if a 200hp engine loses 25-30 hp thru the drivetrain and a 400 hp car loses 30-40 hp due to increased friction and other factors, That all seems logical. Losing 30 hp and 60 hp seems way off.
...
This is exactly what I remember reading in that CarCraft test article. I'm glad we reached to the real truth here ;-)
Originally posted by Oreif: Kohburn, I guess I didn't read that statement as the "your wrong" seemed to deter me from that. (Or maybe it's your two-faced attitude. )
the actual quote would be:
quote
Originally posted by Oreif: A transaxle will require the same power to drive it regardless how much power the engine has.
quote
Originally posted by Kohburn: 100% wrong
as shown my comment was reffering to the single statement you made, but i supose that since you made it that would in-fact mean "you're wrong"
hmm don't see anything 2 faced - stated facts.. which you didn't believe and argued over - then when the dyno shop agrees with everything i've said then you want to act like you discovered the truth. perhaps you didn't read my posts because you were offended by the thought of being wrong. feel free to edit your post to add more little snide comments it doesn't bother me. I don't get emotional from these threads because all i'm doing is tossing the truth out to attempt to stop bad information form spreading. We all know how much people love to repeat things they've heard without checking its validity (otherwise there wouldn't be so many chain emails)
[This message has been edited by Kohburn (edited 02-23-2006).]
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10:53 AM
Oreif Member
Posts: 16460 From: Schaumburg, IL Registered: Jan 2000
as shown my comment was reffering to the single statement you made, but i supose that since you made it that would in-fact mean "you're wrong"
hmm don't see anything 2 faced - stated facts.. which you didn't believe and argued over - then when the dyno shop agrees with everything i've said then you want to act like you discovered the truth. perhaps you didn't read my posts because you were offended by the thought of being wrong. feel free to edit your post to add more little snide comments it doesn't bother me. I don't get emotional from these threads because all i'm doing is tossing the truth out to attempt to stop bad information form spreading. We all know how much people love to repeat things they've heard without checking its validity (otherwise there wouldn't be so many chain emails)
As for the statements on the topic. Uh, I admitted that I was incorrect. I wasn't "offended" And just for the record, I was arguing that the "percentage factor" way of calculating driveline loss was incorrect. Which is in fact wrong. The same loss under the same conditions was closer to what really happens, Just not taking into account the frictional losses with increased power. Once Doug, John, and the dyno shop clarified that point on the frictional losses, did we come into agreement. Anyhow, The discussion is over and everyone agree's.
As for the "snide" comment, I sent you a PM as it isn't related to this topic.
[This message has been edited by Oreif (edited 02-23-2006).]
Originally posted by Oreif: The same loss under the same conditions was closer to what really happens, Just not taking into account the frictional losses with increased power.
I sent you a PM as it isn't related to this topic.
if by "same conditions" you mean the same rpm and same hp output, then yes.. other than the tranny's resistance from the oil inside being pushed around by the gear teeth there is no resistance to lose power to other than friction.. friction is almost all of the power loss, so i never understood how it could be ignored since without friction power loss would be proportional to rpm and oil viscosity.
