I just picked up an inter-cooler from my local import car repair shop. The owner gave it to me to try, but it looks like it will fit perfectly within the confines of the driver's right-rear quarter-panel. He said it was from a SAAB 900 (older one) and originally fit in the front of the engine compartment below the driver's headlight.
Discovered that most Ebay turbo sellers (businesses) are worthless. Ask for a turbo map so you can decide if their products are right for your application..
My response from them, "what is a turbo compressor map?"
Basically I dont trust any of the turbo retailers on there. None of them from the $199.00 to the $799.00 turbo retailers have a clue, therefore their product needs to be avoided unless they can prove it's a real Garrett or other brand.
Try G-pop Shop. Other than the big boys like Turbonetics, they seem to be knowledgeable and friendly. They have the rebuild kit for the T3 at about $90. http://www.gpopshop.com/
Also, I found a nice shop selling silicone hoses. http://www.siliconeintakes.com/ I ordered two 45 degree reducers on Monday night and they arrived Thursday. (USPS) Good quality too.
Last, I bought 2 aluminized steel mandrel bent pipes from Mandrel Bending Solutions. http://www.mandrelbendingso...m/servlet/StoreFront I avoided the e-bay store so I could get single cost shipping. Again, ordered Monday night and arrived Thursday (UPS).
IP: Logged
08:02 PM
Sep 3rd, 2007
Ace McCloud Member
Posts: 167 From: Marble Hill, Missouri, United States Registered: Jul 2007
I have a kind of off topic general turbo Idea. What if you cut out the trunk and put the turbos at the top of the trunk just under the decklid. It would drop engine compartment temp and it would have the turbos up high enough for oil to return by gravity (and it would look really cool)
Go for it. I'm thinking you would need to remove the carpet and provide some type of cooling and shielding. The engine compartment is hot but it is not sealed up like the trunk.
IP: Logged
01:11 AM
vortecfiero Member
Posts: 996 From: Toronto Area, Canada Registered: Feb 2002
lots of good reading here wow Maximum Boost is a good book to learn the basics but as some ppl may have noticed in the text, several times, he says to avoid something then in the pics he says it's a good set up... complete contradictions especially in the exhaust manifolds and exhaust routing sections
A. Graham Bell's book is also good "Forced Induction Performance Tuning"
------------------
87 Fiero GT 5sp with Vortec L35 4300 Turbocharged V6 Bully Stage 2 clutch Syclone intake manifold and engine management with Moates adapter and chip burner Air/water intercooler and Devil's Own progressive water/alky injection 50lb injectors, 3 bar map sensor, Walboro fuel pump and Jabasco Intercooler pump LM1 wideband on custom manifolds and 3" stainless exhaust system T31/T04B S4 turbo with a Super T61 in the box S10 caliper conversion. Murphy's Constant Matter will be damaged in direct proportion to its value Murphy's Law of Thermodynamics Things get worse under pressure. Arthur C. Clarke "Any significantly advanced technology is indistinguishable from magic"
[This message has been edited by vortecfiero (edited 09-04-2007).]
IP: Logged
11:57 AM
RCR Member
Posts: 4409 From: Shelby Twp Mi Registered: Sep 2002
Ok does anyone have the volumetric efficiency of the Stock 2.8 engine? I am going to step through the steps on figuring out what turbo is for the car. Basically make a spoon-fed step through for the newbie on the details and steps for sizing the compressor. I do not have the numbers I need for calculating the Volumetric efficiency, and dont have the time to go out and put a mass air flow sensor on the fiero to get he numbers.
Also If anyone has any tips for figuring it out without runnining the engine and getting live engine readings that would be awesome.
Let's start figuring out what is needed for doing a low boost 6psi turbo on the stock 2.8 engine in the GT.
first we need to calculate our boost numbers. 14.7 is the standard around all of us air pressure (except denver, CO, those people are wierd) WE want a 6PSI boost so we calculate as follows.....
Which equals 1.41 Atmospheres. Cool we can easily use a cheap 2 bar Sensor.
Now we need to calculate air temperature. WE assume 85 Degrees F outside for fun.
Perfect Air temperature = ((AirTemp + 460) X Atmospheres^0.283)-460 the ^0.283 is Atmospheres to the 0.283 power. you need a scientific calculator for this.
Perfect Air temperature = ((85+460)X1.41^0.283)-460
we gat 142 degrees F is out perfect world air outlet temperature feeding the engine. Not so bad, but not real. we need to get the real tempreature.
Real Air Temperature = (Perfect Air temperature - AirTemp) / Compressor Efficiency + Air Temp
Real Air Temperature = (142-85)/75%+85
Real air temperature = 161 Degrees F is what we are pumping into the engine. Hot sweaty power robbing heat, but not bad. Honestly most turbo guys say that anything under 210 degrees is fine and you dont need an intercooler. But let's look at what an intercooler will do.
First an intercooler will lose from 1 to 3 PSI of boost. 1 PSI for a good intercooler, 3 for a really undersized one. Let's assume we got a correct sized intercooler for now. Let's also assume it's a good intercooler and it has a 70% efficiency. We bought the good stuff!
Intercooler temperature out = Real air temperature - (Efficiency of inter cooler X (Real air Temperature-Airtemp))
Real air temperature = 161-(70%X(161-85))
we get a 108 degrees F air temperature after the intercooler! wow that was a decent drop! is it worthwhile? that is for later when we get into the rest of the math.
Let's get a engine displacement, displacement in Cubic inches is easy Liters X 61.0237 = Cubic inches. The fiero engine is a 171Cin engine. Now we can calculate the 100% Volumetric efficency airflow of the engine.
100%VE airflow = (displacement X RPM) / 3456
so at 3500rpm we get 100%VE air = (171X3500)/3456
or 173.18 CFM of air at 3500rpm.
Let's calculate some theoretical Horsepower numbers...
First let's find our density ratio. This is done by the following formula. DR=Atmospheres X ((Temp in + 460) / ( Temp out + 460)) Plug in the numbers.... non intercooled.
DR = 1.41 X ((85+460) / (161+460))
DR = 1.24
With an intercooler - DR = 1.41 X ((85+460) / (108+460))
DR with intercooler = 1.35
Now calculate air density at your altitude and chosen outside air temperature. For 14.7psi and 85degF
AD = (2.703 X pressure) / (outside air temp + 460) AD = (2.703 X 14.7) / (85 + 460) AD = 0.073 lb/cuft
Mass Flow rate is a good number to get a good gesstimate of Horsepower. so let's calculate that to see what we are going to get at our chosen Boost.
MFR = (2.703 X air pressure where you are X CFM your engine puts out from above) / (otuside air temp + 460) MFR = (2.703 X 14.7 X 173.18) / (85 + 460) MFR = 12.62 Horsepower = MFR X 10 Horsepower = 126.2HP with no boost. This is darn close to what the 2.8 is supposed to make, so our calculations are somewhat right. Now, let's get HP numbers from boost,
MFR with boost = MFR X DR so our 6psi boost with NO intercooler is as follows....
MFR = 12.62 X 1.24 MFR = 15.65 or 156.5 Horsepower. not bad for a mild boost. Lets see what the intercooler gives us.
MFR = 12.62 X 1.35 MFR = 17.04 Or 170.4 Horsepower with a intercooler ASSUMING no loss for the intercooler. In reality we will need to boost the Turbo to 7PSI ot get our 6PSI at the valves. well this will cause more temperature and reduce the numbers a bit. These numbers are good ballpark numbers that get you somewhat near what you should get. they are not dead on accurate as we are making lots of assumptions and calculated on 100% Volumetric efficiency. (which is possible, but not without a TON of work on the intake and engine) when we get our VE for the engine we can make a more accurate calculations.
Ok, a low boost of 6psi which will be really really safe for the 2.8 engine will give you the same Horsepower upgrade as swapping to a 3.4 engine. Our intake temperature is only around 160 degrees F which is not bad at all, most turbo guys are very happy to have temps around 210 degrees F after their intercoolers so we are doing good. so far. There are some other advantages though. The intake piddling out will not happen as we are forcing air in, so the major power loss at higher RPM's will not happen as drastic because we are running at 6PSI boost. what WILL happen though is that your boost PSI will drop down as you reach the air volume limit of that intake system. It just will not be as drastic, and even though you are at close to 3.4 HP numbers I am betting a 2.8 with a low boost will possibly eat the stock 3.4's lunch at the dragstrip.
Next time, reading a turbo map. Why you really need to get the right turbo instead of just slapping something in there and hoping it does what you want.
[This message has been edited by timgray (edited 09-04-2007).]
Originally posted by timgray: Ok does anyone have the volumetric efficiency of the Stock 2.8 engine?
Yes, I think so.
quote
Originally posted by timgray: These numbers are good ballpark numbers that get you somewhat near what you should get. they are not dead on accurate as we are making lots of assumptions and calculated on 100% Volumetric efficiency. (which is possible, but not without a TON of work on the intake and engine) when we get our VE for the engine we can make a more accurate calculations.
I agree; 100% Volumetric Efficiency with the 2.8L would require a great deal of work. Here are the 2.8L VE numbers I found:
quote
Originally posted by project34: On page 94 of his book, "High Performance Fieros," Robert Wagoner lists the MAXIMUM volumetric efficiency of the 2.8L Fiero as 0.83 at 3600 RPM. My interpolation from a graph he also shows on page 94 of that book indicates the VE for that engine declines to about 0.71 at 5200 RPM.
I can't vouch for the accuracy of his numbers, but at least they make sense in that the maximum VE he reports for the Fiero 2.8L is much lower --- and occurs at a lower RPM ---than the maximum VE he shows for various incarnations of the LSx engines in recent years of the Corvette. For example, he reports the 2001, 2004, 2005, and 2006 Corvette LSx engines as having a maximum VE ranging from 0.99 at 4000 RPM, to 1.05 at 4800 RPM.
Great stuff guys I'm lovin this thread and seriously considering a turbo in the future (I look at things in long term so soon would 5 years or so) especially with my Trueleo intake coming in that should boost the VE a fair bit by the way what does it take to check that out so we can get some numbers with the new intake
[This message has been edited by jstntlvr (edited 09-05-2007).]
SWEET! I was guessing at 80% as most GM engines are in that range. I am guessing that the 71% at top end is because of the intake. those numbers will translate DIRECTLY to the 3.4. This rocks.
I am going to edit the first calculation section to reflect the VE and change the numbers.
BTW guys, the more I am learning about this the more I realize how incredibly simple this is. Even custom exaust headers for turbo are easy. I had a long talk yesterday with a local HotRod builder. he said I was on the right track and gave some advice. Hudini your cast els idea is dead on and what most hotrodders do already because of the strength in them. he also said that intercooler calculations are misleading, intercoolers do not give the power boost they seem to because they never flow as good as they claim. he recommended that you add 1 psi loss to whatever the intercooler maker claims to get more accurate he also said to remove 5% from their efficiency claims as well.
Ok Let's cover a little bit about Compressor maps. If you asked a Real Car engineer about a turbo the first thing they would do is grab some compressor maps for stock models. So let's look at some Stock Garrett Compressor Maps.
This is a Garett T3 .40 trim compressor Map. Up the left side is the PR Or Atmospheres of boost, along the bottom on this one is the Air flow in LBS per minute. some compressor maps have it in CFM instead, just multiply the lb/min by 13.7 to get CFM and visa versa. If you hvae only a CFM reading and you need LB/min then divide by 13.7.
in the compressor map you see circles or efficiency islands. you want to be in the higher % numbers. lower % = more heat generated. The left sloping line is the surge limit line. to the left of that means your turbo will eat it's self, running to the left of the surge limit line for any time will destroy the bearings. If you know someone that simply slapped in a turbo and keeps having leaks and turbo failures, this is probably what is happening, he got to big of a turbo and is running a lot to the left of the surge limit destroying the bearings.
to figure out of a turbo is right you need to calculate the PR and CFM for a range of rpm points. plot them on a turbo map and see where they sit. you first want them all to the right of the surge limit line, honestly you really want them away from it by a bit as you are calculating and real world is always not as rosy as your calculations.
Also remember as you go up in RPM, you will stop going up in PR when you hit your wastegate setting. for us that will be a max of 1.41 on the left scale. Already I can see that this turbo is not right for us, all the way across at 1.41 we never hit the 72% zone and we really ony live in the 70% zone for a little bit. Nope this turbo is wrong as it's designed to make way more pressure.
This is for a Garrett T3 .60 trim turbo, or specifically the turbo found in the older Ford thunderbird.
it's still a little gloomy as we are still at the bottom end of the map but we now pass through the 74% island and live in the 70% island for a lot longer! this is a good thing and this turbo needs to go on our check out further list. We really need to look at lots of other turbo maps and by using our desired PR number we can find a group of them that we can put in a pile to look at in more detail and rule out a lot of others.
both of these turbos are T3 turbos! the trim for the compressor is what has changed. This is why you cant just go and get a "t3 turbo" because someone said that is what you need.
We still have not figured out if as we go through the RPM's if we violate the Surge line, but we have a good start.
NOTE: I will give up a secret here, this turbo will work for our application, it's not perfect but it is something that will work and not kill it's self. if you were to buy one right now for this low boost project you will not have wasted your money mostly because the pre 1987 Tbird T3 turbo is cheap and can be rebuilt cheaply. I have found them for $35.00 on ebay, and $85.00 for a rebuild kit = dirt cheap turbo!
[This message has been edited by timgray (edited 09-05-2007).]
IP: Logged
09:53 PM
Sep 6th, 2007
lou_dias Member
Posts: 5347 From: Warwick, RI Registered: Jun 2000
I picked up a mint K26 on ebay for $171. Looks rebuilt. I want to swap it in to replace the one I have that is noisy and leaks coolant and/or oil when cold. That one, I will try to find a K26-8 hot side and see if a rebuilder can put in a K27 cold wheel.
The K26 seems like a good fit for the 2.8 as it was made for 2.5L Porsche/Audi/Volvo engines. It's lacking in the top end on my 3.1, though I have 2 exhaust leaks that I intend to fix when I replace with the one I just got. I also intend to port the intake and heads.
The K27 compressor should put me in the league of a T3/4 hybrid. A full K27 is good for 450+hp.
IP: Logged
07:55 AM
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
this thread has inspired me to put in a turbo, while I have my cradle dropped for a cam. so, now to choose a cam. I have always thought the CompCams 260 is a good candidate for a off-the-shelf cam. money is VERY tight, so I am not sure I can swing a custom grind. I have a turbo - I think it is a T3 - but not sure. I never seen a T3 with a water connection also. but, everything else about it looks T3. I also have the same old tiny Saab 900 intercooler someone mentioned above. I plan on haveing it inside the rear fender area, and shrouding it, so all the incoming intake air goes over it.
My T3 .60 Trim from a 1984 T-bird has the water-cooled fittings but they have been plugged. Looks like they came that way from the factory. The plugs look like the same type plug on the front head where the gauge sensor would go if installed. You can see the threads sticking out below the oil return fitting in this photo:
The turbo will have a serial number on the compressor section. Use this number to figure out the rebuild kit.
IP: Logged
10:53 AM
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
My T3 .60 Trim from a 1984 T-bird has the water-cooled fittings but they have been plugged. Looks like they came that way from the factory. The plugs look like the same type plug on the front head where the gauge sensor would go if installed. You can see the threads sticking out below the oil return fitting in this photo: [/IMG]
The turbo will have a serial number on the compressor section. Use this number to figure out the rebuild kit.
thanks! yes, that looks exactly like what I got. I'll dbl check the water ports - they look open & usuable. anyways - what do ya think of the idea of having the incoming intake air going over the intercooler? at first I thought "that would heat up the intake air", until I thought about how much the turbo will raise that same air anyways. I figure having airflow over intercooler - even when not moving would be a good way to go. especailly being such a dinky intercooler anyways.
I picked up a mint K26 on ebay for $171. Looks rebuilt. I want to swap it in to replace the one I have that is noisy and leaks coolant and/or oil when cold. That one, I will try to find a K26-8 hot side and see if a rebuilder can put in a K27 cold wheel.
The K26 seems like a good fit for the 2.8 as it was made for 2.5L Porsche/Audi/Volvo engines. It's lacking in the top end on my 3.1, though I have 2 exhaust leaks that I intend to fix when I replace with the one I just got. I also intend to port the intake and heads.
The K27 compressor should put me in the league of a T3/4 hybrid. A full K27 is good for 450+hp.
Can I ask who makes the K26 and K27 turbos? Maybe we can find some compressor maps and such to compare.
IP: Logged
11:05 AM
lou_dias Member
Posts: 5347 From: Warwick, RI Registered: Jun 2000
thanks! yes, that looks exactly like what I got. I'll dbl check the water ports - they look open & usuable. anyways - what do ya think of the idea of having the incoming intake air going over the intercooler? at first I thought "that would heat up the intake air", until I thought about how much the turbo will raise that same air anyways. I figure having airflow over intercooler - even when not moving would be a good way to go. especailly being such a dinky intercooler anyways.
Ok, I see. I'm no physics major but it seems the air will be the exact same temp. The incoming air is heated by the intercooler, further heated by the compressor, then cooled by the same amount it was heated to in the first place as the intercooler will have the same efficiency (?) in both directions. That make sense?
IP: Logged
11:18 AM
PFF
System Bot
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
Originally posted by Hudini: Ok, I see. I'm no physics major but it seems the air will be the exact same temp. The incoming air is heated by the intercooler, further heated by the compressor, then cooled by the same amount it was heated to in the first place as the intercooler will have the same efficiency (?) in both directions. That make sense?
hmm - I was going on the assumption the turbo will heat the air to X temp, no matter what temp it was when it entered the turbo. as in, 0* air, 100* air & 200* air will all be heated to 500*
I guess this is what I need to verify....does it heat to a fixed temp, or does it add X amount of heat....
Ok, I see. I'm no physics major but it seems the air will be the exact same temp. The incoming air is heated by the intercooler, further heated by the compressor, then cooled by the same amount it was heated to in the first place as the intercooler will have the same efficiency (?) in both directions. That make sense?
Exactly right, putting the intercooler before the intake air will simply heat the intake air causing the air charge after the compressor to be even higher causing the intercooler to dump more heat into the intake air, and so on. Never ever put your intercooler in your intake air stream. intercooler needs to go elsewhere, down low scoop air from under the car into the intercooler and then up into the engine compartment, do not under any circumstances have air that went through the intercooler ever enter the intake or you form a closed loop for the heat.
Turbos ADD heat, so if you have 200 degree air coming into a turbo that add's 200 degrees you get 400 degree air. everything always adds in heat, intercoolers take away heat by putting it in the other air stream that is going through the fins in the other direction.
[This message has been edited by timgray (edited 09-06-2007).]
Originally posted by timgray: Exactly right, putting the intercooler before the intake air will simply heat the intake air causing the air charge after the compressor to be even higher causing the intercooler to dump more heat into the intake air, and so on. Never ever put your intercooler in your intake air stream. intercooler needs to go elsewhere, down low scoop air from under the car into the intercooler and then up into the engine compartment, do not under any circumstances have air that went through the intercooler ever enter the intake or you form a closed loop for the heat.
Turbos ADD heat, so if you have 200 degree air coming into a turbo that add's 200 degrees you get 400 degree air. everything always adds in heat, intercoolers take away heat by putting it in the other air stream that is going through the fins in the other direction.
thanks - I was thinking a turbo heats the air a fixed amount, not an additional amount. I know a fresh air spot is ideal - its just hard to find a good spot. I guess I'll re-think my layout
IP: Logged
01:28 PM
Firefighter Member
Posts: 1407 From: Southold, New York, USA Registered: Nov 2004
Perhaps some obvious points might be helpful. An apology if some of this is really overkill. Maximum Boost is a book by Corky Bell and the bible of turbocharging. Read it 2 or 3 times before doing anything. Drilling the oil pan for the return oil line; you have to remove the oil pan first so there are no metal shavings in the oil pan. (Overkill, I know). The oil pan return line fitting has to go 1" below the top of the oil pan, way above the oil level in the pan. You do not need a high volume oil pump for a low boost turbo on a 2.8.In fact you might need an oil restrictor to protect the turbo seals. Turbos need oil FLOW not OIL pressure; there is a large difference between the two. Turbocharged / heated air can only be cooled by 50% of what the turbocharged added in heat, by use of an intercooler. Intercoolers equal resistance to air flow and that is already your biggest problem with the stock 2.8 intake manifold, do not make it worse. Choose an intercooler carefully whether via water/alcohol injection or the more expensive "plumber" type intercoolers.
------------------
IP: Logged
02:41 PM
Firefighter Member
Posts: 1407 From: Southold, New York, USA Registered: Nov 2004
I was at work when I looked at some of the posts. I clearly missed many and repeated stuff above. Just a note (FACT); you do not loose any boost with a water / alcohol injection " poor man's intercooler". There is no resistance whatsoever. Take a look at www.rbracing-rsr.com/waterinjection.html or Snow Performance or Aquamist on the internet. These are the best units out there and inexpensive. They are also easy to install and reliable. The technology here is not new and has been around since the 1930's. The use of water injection on the Packard built Merlin engine powered P -51 Mustang was the reason that it was the fastest propeller plane in WWII. Used on the B-29 also. The technology has been used on race cars since the 1970's and was first banned as it allowed the cars to go "to fast". It is now more popular than ever and many companies manufacture high quality water / water / alcohol injection units. The unit I have kicks in a 3 lbs. of boost and drops out when the boost drops below 3 lbs. I have a dash light which shows its activation, right above the boost gauge. Detonation is prevented at stock timing or higher (I'm about to try that) and as all the Fiero guys will tell you, the best way to keep your engine free of carbon is to spray a mist of water into the intake every 10,000 or so; my engine is cleaner inside than my kitchen dishes; sort of. Ed
[This message has been edited by Firefighter (edited 09-06-2007).]
This is in regard to a question about choosing a cam for a turbo engine:
quote
Originally posted by Pyrthian:
this thread has inspired me to put in a turbo, while I have my cradle dropped for a cam. so, now to choose a cam. I have always thought the CompCams 260 is a good candidate for a off-the-shelf cam. money is VERY tight, so I am not sure I can swing a custom grind.
Here is what I found on page 163 of the 'Maximum Boost" book, which seems to be getting some good press in this thread: "The street turbo, which is generally small, operates with exhaust manifold pressure somewhat higher than intake boost pressure. This situation, when presented with long-duration, high-overlap cams, creates a huge amount of reversion. Thus, the `turbo cam' tends to become a low-duration, very limited overlap cam."
I suppose that "low duration, very limited overlap" statement didn't surprise me much, but that book's NEXT statement did: "RULE: It is hard to find a turbo cam that works better than the stock item."
Personally, I'd think a limited overlap cam, but one with a bit more duration than stock, would be desirable to allow one to run the engine to an RPM level a bit higher than would the stock cam. Maybe the author's comment about using a stock cam was simply a diplomatic way for him to say, "Don't go nuts with cam selection if you've a turbo."
IP: Logged
08:58 PM
Sep 7th, 2007
RCR Member
Posts: 4409 From: Shelby Twp Mi Registered: Sep 2002
Is it true that if one were to pick up a "cheap" T3 and rebuilt it. One could use different wheels to change the trim and thus modify the map to where one needs to be?
That is how I understand it. The T3 60 Trim with the .60 a/r is the largest that turbo goes. You would need to do the math to find one that fits your setup and your taste. I bet the T3/T4 Hybrid with the proper trim. Speaking of which, I found a little info on "Trim": "Two key parts of a compressor are the inducer and the exducer. The inducer (sometimes called the minor diameter) is the part of the wheel that first takes a "bite" of ambient air. The exducer (sometimes called the major diameter) is the part of the wheel that "shoots" the air--now compressed--out of the turbo. Just remember that the inducer is where the air comes in and the exducer is where the air exits. Got it? Good.
You need to understand those two terms in order to grasp the concept of trim, a bizarre bit of tech-speak which is often thrown about. Trim is simply a term to describe the size of a specific compressor within a family of wheels. It can be expressed in abstract ways (such as when Turbonetics says they have P-trims, Q-trims, etc) or you can use the actual numeric measurement (50 trim, 57 trim, etc). Here's how you calculate the measurement:
Trim = (minor diameter / major diameter) ^2 * 100
So now we have a way to perform some math and get a number. What does it all mean? Generally speaking, the larger the trim the more flow the wheel will have. Nevertheless, one should not rely solely on a trim measurement when selecting a compressor wheel! Find out specific wheel measurements (inducer and exducer), understand how subtle differences will affect airflow and response, and then choose a wheel accordingly. "
This is in regard to a question about choosing a cam for a turbo engine:
Here is what I found on page 163 of the 'Maximum Boost" book, which seems to be getting some good press in this thread: "The street turbo, which is generally small, operates with exhaust manifold pressure somewhat higher than intake boost pressure. This situation, when presented with long-duration, high-overlap cams, creates a huge amount of reversion. Thus, the `turbo cam' tends to become a low-duration, very limited overlap cam."
I suppose that "low duration, very limited overlap" statement didn't surprise me much, but that book's NEXT statement did: "RULE: It is hard to find a turbo cam that works better than the stock item."
Personally, I'd think a limited overlap cam, but one with a bit more duration than stock, would be desirable to allow one to run the engine to an RPM level a bit higher than would the stock cam. Maybe the author's comment about using a stock cam was simply a diplomatic way for him to say, "Don't go nuts with cam selection if you've a turbo."
thanks - I think the crane 272 has a bit much duration, which is why I am looking at the CompCams 260. and, since I think my old Ford Thunderbird T3 probably wont be making much boost past 5000 on my 3.1, I think it is in the right power range. The other thing I was gonna look at is the specs of the Pontiac GrandPrix which was turbo'd, just as a referance point. Its probably just a stock 3.1 cam.
once my roof is done, which should be just a few days - the tear down begins. fresh bearings - cam, rod & main. cant beleive I've put 3 sets of rods bearings in this motor sofar....but - your not having fun until you break something, eh?! this turbo should aid much in breaking stuff
IP: Logged
08:23 AM
PFF
System Bot
Sep 10th, 2007
KaijuSenso Member
Posts: 911 From: Westland, MI Registered: Jan 2007
ok i plugged in the formulas above for horsepower rating for our 2.8 into MatLab (our engineering computing program) Here are the results.
airtemperature = 85* Volumetric Efficiency = 100% (because i wasn't sure about the results with 83% at 3600 RPMs) RPM = 3600 (let me know if i missed any important variables)
Very Close, STOCK fiero 2.8 has 80% efficiency at idle and drops to 71% at 5800rpm I would almost call it a linear change just for simplicity.
If you upgrade your intake I would increase VE by 5% only. it would take a LOT more work to get the 2.8's intake up to 90% or 100% than slapping on a race intake and mild porting. If you increased the valve duration, went to larger unshrouded valves, and had a performance grind on the valves as well as really good head work I think the Fiero 2.8 could hit 92-93%.
I am working on the next installation of Turbo technical info. This past 5 days have been incredibly nuts around here.
IP: Logged
05:57 PM
Sep 16th, 2007
Dan010 Member
Posts: 776 From: Katy, Texas USA Registered: Oct 2001
As I understand it, it's only better because of the ability to accept a knock sensor input which the 86-88 do not have. There are much better ECM's than any that came on the Fiero though. Faster processing speeds, knock sensor input, more cells in the tuning table, faster output for datalogging (8192 baud versus 160 baud). The 7730 ECM comes to mind. There are several more.
IP: Logged
08:36 PM
rjblaze Member
Posts: 1159 From: Bethlehem, Pa., United States Registered: May 2006
I keep hearing about the need for a 2 bar map sensor in this thread (and others), but I noticed in Jeff Wagoners book he talks about a 2 bar sensor with some additional electronic parts (to the wiring) that makes the sensor work like a 1 bar for part of the time and a 2 bar as boost climbs. No one else has mentioned this "change"....is this taken care of with the 7730 ecm or do we still need this thing placed between the sensor and the computer?
BTW, where did those great expansion joints come from for the cross-over? I was looking at the SS braided types, but I believe those are more for flex than expansion.
As I understand it, it's only better because of the ability to accept a knock sensor input which the 86-88 do not have. There are much better ECM's than any that came on the Fiero though. Faster processing speeds, knock sensor input, more cells in the tuning table, faster output for datalogging (8192 baud versus 160 baud). The 7730 ECM comes to mind. There are several more.
Yes you are right, and modding a 7730 witha $88 prom in it to work for a fiero is easy and the best choice if you know how and have the right software, otherwise It's cheap to get a chip from darth here. If you are low on cash and want to do it "old school" a 85 ECM, knock sensor and Knock module from a buick will be all that's needed for a safe low boost setup for cheap and easy.
NOTE: I have not forgotten about this thread, It's been nuts with my oldest son moving his family out to NY and them living back home until they move this week, I haven't been able to touch my books and calculator to finish up the turbo selection and Intercooler selection so we can move on to the rest of the parts... the fiero is sad trapped in the garage with all their boxes blocking it's only exit.
No need to add anything except the 2 bar MAP itself. The ECM is then programmed to make use of it through the tuning tables. Rock Auto sells the AC Delco 2 bar MAP for a '99 Grand Prix SC engine for about $54. They also have a nice vacuum/boost gauge for $24.
I found those expansion joints at a u-pull-it yard on a couple early 90's 3.1L crossover pipe. I think they were Grand Ams or Grand Prix or Cavaliers. That type car. The 2.8L's were the same. You can't see them because of heat shielding. Just pry the shielding off with a big screwdriver.
My old car is about 98% complete. I found at Autozone the turbo downpipe for the original Ford T-bird T3 turbo. You look under catalytic converter and it shows the whole pipe from the turbo (including the cat) for about $100. Sweet.
[This message has been edited by Hudini (edited 09-20-2007).]
IP: Logged
09:57 PM
Sep 20th, 2007
KaijuSenso Member
Posts: 911 From: Westland, MI Registered: Jan 2007
reading "Maximum Boost" i ran into this formula but it was all divided by 1728 (half of what you said) i then looked up the conversion and the book is correct. just wondering why you doubled that number (it is to convert cubic inches to cubic feet). i plugged the number i think is correct into my program(along with 83% efficiency at 3600 rpms) but it gave me 215 bhp for our 2.8L...something's not right here.
