I would be more concerned on space. Its hard enough to jam a T-3 turbo on a V6, and now you want to stuff 2 turbos on a V8. But, I do like the thinking - using a pair of chrysler 2.2 turbos. sounds like exactly the right size, being the 4.9 redline is so looow (4500 is it?)

I think most are missing the point that for the 4.9 the redline is 4500 because that is where it stops breathing but with a turbo that can be extended by 1000 rpm or more depending on the valvetrain because it dosen't have to strain to get the air into the engine.

With valve train modifications and cam change the redline can be far surpassed easily to 5500+rpm also why use two small quick spooling turbos when you need the power at mid to high end where the engine tend to go flat?,the 6.5 turbo would be more suitable to this application......just an observation as I have tried a 300zx turbo on a 4.5 and it did not make much of a difference either way for the effort involved.

------------------
Tuners of the Quickest 4.9
12.51@118 mph

4.5/4.9 (RSR)Hi Perf. Caddi-V8 Fully Blueprint&Balanced Rotating Assembly
Custom Intake Manifold
Custom Machined Heads
Victor Reinz Head Gaskets
50-150HP Nos Power Shot.
Holley 510-0-4412C Carb.

[This message has been edited by Master Tuner Akimoto (edited 01-20-2004).]

i have seen many turbo and supercharged fieros in my life (and drove many) in my opinion i would recomend using a supercharger. but that is my opinion. the best set up i have seen for a turbo set up on a fiero was as follows (it cost the person who did it almost $15,000 in just the turbo system)

2 turbos (out of two semis [internatioal DT466] rebuilt and upgraded by banks turbo systems). one on each manifold. the intake system consisted of a custom intake manifold built by a local machining co near him (not sure of the name right now), 2 throttle bodies (one turbo connected to each one) he had a more stuff in the turbo system and alot more in the engine (another $30,000-$40,000 in the motor and trans) but i would be typing forever. the car ran very well and was VERY fast. im not saying this is the best set up mainly becasue of the $ factor but i thought you might like to think about this for a while. good luck with your project.

quote Originally posted by Will: I think 85% is a bit high. Varoius things I've seen and read lead me to estimate 100% VE to be about 85 ftlbs/litre at streetable compression. Do the math for the 4.9, and you get about 66% VE.

The whole point of the turbo is increasing volumetric efficiency, no? In some cases, beyond 100% !! (remember that volumetric efficiency is based on air at atmospheric temp and pressure)

At 100% VE, by your formula (88 ft lbs / L) The HP produced by a 4.9 @5500 RPM would be:

85 ft lbs*4.9* 5500RPM *1/60*(2*PI radians /revolution)*(HP/550 ft lbs/sec)=436 HP.

If we're aiming for 85% volumetric efficiency, the HP is 85% of that, which is 370 HP.

If the goal is 300HP, we require 69% volumetric efficiency at 5500 RPM.

Stock VE at 5500 RPM is about 45% for 200 HP (I'm assuming this is where max stock HP occurs - I dont know).

The question is, what is the HP goal, not what is the stock VE.

Well... yes and no. VE is unchanged if you measure flow just in front of the throttle body. That's what I'd be inclined to do, as it makes the math easier. We can infer the stock engine's VE curve from the stock torque curve, which starts off at 275 ftlbs at 1,000 RPM or so and drops to 233 ftlbs at 4500 RPM ( I think peak horsepower is about 4500, more likely lower than higher, though), which translates to 66% at 1,000 RPM and about 56% at 4500 RPM. This will not change significantly unless there are mechanical changes made to the engine. You can then do what bushroot did and calculate mass flow at each RPM data point and use this information to figure out proper compressor sizing. I think there are a couple of 4.9 chassis dyno sheets somewhere on the forum. You could look at those curves, infer flywheel numbers, plug the data points and equations into a spreadsheet and have a really nice setup for computing compressor flow requirements.

In saying that VE will not change, I am intentionally ignoring the increase in back pressure due to the turbo. In other circumstances, this would hamper scavenging and reduce VE, but since this is a Caddy engine and has almost no valve overlap, I don't think the effect will be worth worrying about.

------------------
'87 Fiero GT: Low, Sleek, Fast, and Loud
'90 Pontiac 6000 SE AWD: None of the Above

Do that again, only mean it this time