Headers & S/C's Power Loss?
 

I have been doing my homework on this one,

It seems that we SC'ers may lose power with the addition of headers due to the loss of back pressure and overlap of our stock cam design.

I have my stock headers off and they are very restrictive, 1.6-1.7in
collector!! Can you say tiny?

I bought DC headers and the collector is 2.25 plus a clean shot right out of the head instead of the stock "welded" header exhaust port.

Does anyone have any #'s for me on this or first hand experence?

Thanks,
ZNitro

You will have to retune after install . You may lose boost but after retuning you may gain more power . I had my RT cats and headers on when I had the SC installed . And could only get 7lb's of boost . The RT's went bad , went to test pipes , then went to Crawford cats and gained back 1 1/2 lb's of boost . I lost power to . I then retuned and gained the power back that I had lost . Less boost always doesnt mean you lose power when you free up the air flow

Had the vortech installed last week at AAM and I have D.C. Headers on. It dynoe'd at 356HP after tuning the R4 S/W.The boost gauge jumps up to about 6psi but I'm not sure it is working properly. O'h also had the ECU Reflash.

Here is a before/after header dyno of a VQ30 with vortech blower at 12 psi on a maxima. The red line is before the headers, the blue line after. Only other changes were going from 2.25" exhaust to 2.5" exhaust.

http://memimage.cardomain.net/member...62_92_full.jpg

Thanks.

Your results are somewhat what I expected.

lower boost although gained power overall ...... Great!

I installed crawford headers and a TS reflash and gained 21WHP with my Stage3 Z, even though Stillen suggests against it, I made power!

Lower boost is less stress inside right?
I wonder why Stillen is against the headers.Same power, lower boost sounds good to me.

Hey John,

I thought you dynoed at 396whp from your PM last week? I was really psyched for you. I got 357whp with the stock pulley so 356whp is pretty darn good for 6psi. I've seen 10.2lb on my boost gauge a couple times with my 9lb pulley. I'd like to get headers to free up some back pressure ans keep my boost down...

Steve

What did the A/F ratios look like?

Interesting question. I am going to make a guess to say no, it does not. While the pressure in the intake tract may be lower as read by the boost gauge, I would think that cylinder pressure would be just as high. The more open exhaust just allows all of the burnt A/F mixture to escape more easily and makes it easier for the SC/Turbo to refill the cylinders thus, a lower boost pressure. The same volume of air, I would think, is still being compressed in the cylinder. The cylinder should contain a cleaner, unburnt AF charge though.

Thoughts?

what do they use for fuel/timing? maybe headers would cause it to run lean?

Correction. Sorry Steve the car did Dyno at 396HP don't know where the 356 came from..Although I would of also of been happy with 356..The question about less boost equating to less stress on the engine seems straight forward. Additional boost is multiplied by the compression ratio and amplified again in the combustion cycle.The end result is less compressive force on the piston/rod with lower boost..

I agree... Lower backpressure with headers and exhaust simply allows exhaust gases to exit the engine easier and to an exstent on N/A applications allows for additional air to get sucked in the intake stroke. But the additional air coming in due to the loss of backpressure certainly wouldn't create the same cylinder pressure as a couple more pounds of boost.
Once I get my JWT clutch and Nismo Flywheel installed I'll be looking into headers.
Hope your enjoying you new found speed John!

test pipes made my stillen run lean.