This debate will still rage on, but here is proof. Open header didn't give the magic gain that a few on this board claim. While the peak tq number looks good, take a closer at the plot. Just a bump in plot! Not worth it to me.

Blue line - Open header
Red line - SMSP Test pipe & full 2.5" exhaust system




[Modified by RStoR, 11:53 PM 8/16/2001]

 

Looks good... Did you happen to do a run with a 2.5" cat to compare with the testpipe?

 

See other thread I posted! Did this for easy "Search" in future.

 

Actually Chris I think you would need to show run 2 vs 5 for the proper cat vs test pipe comparo. The Run01 vs 07 is the baseline before changing fuel and 07 is test pipe and no PS belt.

 

190

 

now that's one nice looking fuel curve!


[Modified by itrhybrid, 5:29 AM 8/17/2001]

 

When you ran the open header, did you adjust anything? I know when running open header versus full exhaust, my settings are totally different. Cam gears and fuel are the two that I have to play with.
What did it turn out was wrong with your car?
Oh, I did get you call, today. Voice mail is on the fritz, or the phone is. Oh well, more money to spend. If you need to catch me, I will be at the restaurant, 380 0080.

 

Can we conclude from this dyno plot that a fully optimized header-back system is almost the same as open header? Can this cat-back system be optimized further?

 

I always wondered why all those guys trying to make the most hp possible in drag racing etc don't use mufflers. Even if forced to use some sort of muffle....they invented dump tubes

 

James~

Thanks! Definitely not much there to work on anymore.

Jason~

No sweat! I figured it out. Make sure to call Mark, he wants to talk with you. I feel much better about the car after the leak-down and compression test yesterday. The lash was way off and we got that back in check. Hopefully, everything is good. I may replace the valve seals when I install the valvetrain for piece of mind.

I didn't change any settings from the test-pipe to open header. We forgot to iinstall the wideband, so no a/f plot. Mark feels that the slight tq gain was probably due to a lean condition at the rpm point. Just wanted to prove that dropping the exhaust isn't really worth it with a good set-up in the first place.

EuroITR1689~

The plot speaks for itself! A tuned length of exhaust pipe added to the header may have been able to pull a bit more out of the set-up, but I'd never go to that extreme.

 

Don't forget the CART and Formula 1 cars. All open header!!

 

yupper.

My point is.... you can make more power open header...but most don't run an open header normally. So....dyno with an exhaust system if thats what you normally use. You could always dyno both ways for the best of both worlds...just take note of both final settings and adjust accordingly.

 

Your right, so are most NHRA drag cars. YET.....who is to say the tuned length isn't in the header. Those Top Fuel headers aren't extremely short. Just something to think about.


[Modified by RStoR, 9:43 AM 8/17/2001]

 

Not what we were originally commenting on.....but yup...your absolutely correct.

tuned length open header=max hp

add stuff after that? loose power. question is....how well you can minimize it. this is why John at hytech did his 2.5" system

 

In Formula One cars the collector is about 4 inches long. They don't have more space for a longer collector. But you can tune your engine for that header......