2.5 inch exhaust vs. Open header **DYNO**

[JDogg]

this is a test done on my buddys car.. its an 85mm gsr motor 11.5ish:1 compression, etc, etc it has a knock off hytec header with a straight 2.5 inch mandrel bent exhaust and a straight through apexi muffler. no cat, no resonator. notice there was NO power lost anywhere. in the midrange there were significant gains and past the power peak the gains were pretty good there too. Almost 10ft/lbs and 13hp at 6500 rpms. the tach pickup lost the signal on the open header run, but at 9500 rpms there was a 14hp gain. i did NO retuning with it open header, it deffinatly wanted some more fuel so there would have been even more gains... we just ran out of time on the dyno. Modified by JDogg at 2:06 PM 5/23/2008

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[Teamdiesel]

What was his exact setup? I have a similar build with alittle less compression. Only a fuel tune, no ignition timing change. Cam gears were left at 0!
85mm GE sleeved GSR block
Wiseco 11:1 cr pistons
Eagle rods
s2s2 cams
Supertech valvetrain
SK2 Pro camgears
Hytech bigtube header
PerformerX IM
68mm TB
550cc RC injectors
custom 3" CAI
Skunk2 Megar R exhaust
Hondata S300

[integratuner77]

The gains in the mid range are very nice and like you said with more tuning could be better, but that torque curve falls off rapidly starting at 7500. So the gains up at 9500 are pretty useless as at that time you have dropped down to 100 ft-lbs. Good looking peak numbers though.

[JDogg]

this car has pro1 cams, victor x intake manifold and a small tube header.. kinda missmatched parts.. it also still has a/c and p/s.. taking those belts of would have given a good 15hp.

the hp dosnt really fall off that fast... so power at 9500 is key. the car will go faster down the track shifted at 9500 than it would any earlier. 14hp out there is a big deal at the track.

[polishedturd]

sorry for being stuipid but which line is which?
is the 207 the open header or the 2.5 exhaust?
im color blind so colors mean nothing, lol.

[Shadowz7429]

green= open header

[JDogg]

run 11 is with exhaust
run 15 is w/o exhaust

[polishedturd]

yeah i have had this argument many times with people that open header makes more power and they argue about back pressure and blah blah blah, thanks for some proof.

my next mod is going to be to replace my test pipe with an electric exhaust cutout like this one http://www.quicktimeperformance.com/QTEC/index.php

[b20beast978]

electric cutout FTW!

[b19coupe]

So you are saying that less exhaust restriction=good?
Amazing!

[SMSP]

Originally Posted by JDogg

this is a test done on my buddys car..

its an 85mm gsr motor 11.5ish:1 compression, etc, etc

it has a knock off hytec header with a straight 2.5 inch mandrel bent exhaust and a straight through apexi muffler. no cat, no resonator.

Isn't the Apexi muffler 60mm?

[mar778c]

JPoop, educating the masses.

[ESP.net]

3" mandrel bent exhaust would be a nice next test bed id imagine 210 whp would be achievable. 3" is the new 2.5"

[clean rice]

Originally Posted by polishedturd

yeah i have had this argument many times with people that open header makes more power and they argue about back pressure and blah blah blah, thanks for some proof.

I wouldn't neccesarily say that this is "proof" that this will apply to all motors. This is a large motor, and the guy could've had a super restrictive muffler with like 2 resonators for all we know, so of course it would gain power. Would a sockish B16 net the same results? Probably not. SMSP has done dyno's doing the same thing where he has only realized 1-2 whp by dropping the exhaust.

[Shadowz7429]

Originally Posted by JDogg

it has a knock off hytec header with a straight 2.5 inch mandrel bent exhaust and a straight through apexi muffler. no cat, no resonator.

Modified by JDogg at 2:06 PM 5/23/2008

[Teamdiesel]

Originally Posted by clean rice

I wouldn't neccesarily say that this is "proof" that this will apply to all motors. This is a large motor, and the guy could've had a super restrictive muffler with like 2 resonators for all we know, so of course it would gain power. Would a sockish B16 net the same results? Probably not. SMSP has done dyno's doing the same thing where he has only realized 1-2 whp by dropping the exhaust.

1-2 hp....IMPOSSIBLE. Where I am from people race their honda's with full PERFORMANCE exhausts during regular track days, and every one of them run open header during an official race day. EVERY single honda that has raced open header down here, has seen ATLEAST a .3 drop in 1/4 mile time due to this change. My car has seen up to 32hp and 32tq from dropping my exhaust and retuning fuel ONLY. The graph is above for proof. I have also seen up to .8 of my time by dropping my exhaust ONLY. Went from 14.6 to 13.8 on street tires in my old ITR.

[GoldLudeRay]

tunning my car open header
cause thats how it ran at the strip

[polishedturd]

well my butt dyno noticed gains in low and top end by running with an open header and it doesnt lie! lol

[an2ny888]

i wouldn't say a 1-2 hp difference is impossible... on my car i only gained 2 hp peak when i dropped my tl exhaust during my last dyno

[VtecKiDD]

from all my testing, i have seen that a PROPERLY MATCHED exhaust is just as good as open header.

BIG MOTOR=3in exhaust
1.8L an under 2.5in

[blacK_Dc4]

i have a 2.0L 11.5 compression with a SMSP b19 header , SMSP high flow cat , and a 70mm T1R catback. I had the car dynoed back to back with open header and it actually lost power before vtec , dipped at 5500 which is what vtec was set at , and stayed the same from there on . My tuner told me that most likely there would be small gains if he had tune it for the open header , but with no tuning , open header did nothing for my motor. I guess every motor has little differences or maybe exhaust setup

[4dooritr]

Originally Posted by blacK_Dc4

i have a 2.0L 11.5 compression with a SMSP b19 header , SMSP high flow cat , and a 70mm T1R catback. I had the car dynoed back to back with open header and it actually lost power before vtec , dipped at 5500 which is what vtec was set at , and stayed the same from there on . My tuner told me that most likely there would be small gains if he had tune it for the open header , but with no tuning , open header did nothing for my motor. I guess every motor has little differences or maybe exhaust setup

70mm is close to 3", slightly smaller.

when you pull your exhaust and it doesnt gain power.. thats when you know your running the right exhaust size..

[Teamdiesel]

Originally Posted by blacK_Dc4

i have a 2.0L 11.5 compression with a SMSP b19 header , SMSP high flow cat , and a 70mm T1R catback. I had the car dynoed back to back with open header and it actually lost power before vtec , dipped at 5500 which is what vtec was set at , and stayed the same from there on . My tuner told me that most likely there would be small gains if he had tune it for the open header , but with no tuning , open header did nothing for my motor. I guess every motor has little differences or maybe exhaust setup

I think that maybe there is something wrong with your car then. I can gaurentee that if you tune with exhaust and then tune open header (with the RIGHT length of backpressure pipe), and go to the track your car will run a faster time open header. No matter WHAT the dyno says, it will run a faster track time open header, PERIOD. The graph i posted above is a perfect example. The red line is full Skunk2 Mega R 70mm exhaust, fully fuel, ignition, and cam gear tuned with 12:1 compression. The blue line is OPEN header, with 11:1 compression and ONLY a quick fuel tune. That is a 32WHP and 32WTQ gain from LESS compression and OPEN header!

[DonF]

If teamdiesel says its true, then it is true. Drop your Ex and pick up 32 whp.

[2fastGSR]

Originally Posted by Teamdiesel

I think that maybe there is something wrong with your car then. I can gaurentee that if you tune with exhaust and then tune open header (with the RIGHT length of backpressure pipe), and go to the track your car will run a faster time open header. No matter WHAT the dyno says, it will run a faster track time open header, PERIOD. The graph i posted above is a perfect example. The red line is full Skunk2 Mega R 70mm exhaust, fully fuel, ignition, and cam gear tuned with 12:1 compression. The blue line is OPEN header, with 11:1 compression and ONLY a quick fuel tune. That is a 32WHP and 32WTQ gain from LESS compression and OPEN header!

You are being completely biased to your own opinion and very ignorant to the situation.

32 hp by dropping your exhaust? Did you have a 270hp 86x95 and run a stock dx exhaust or something?

Come on man, while I am not discrediting your extremely rare scenario, it is by far the norm. The fact that you keep going ON AND ON about it shows your complete lack of knowledge in the area.

My car = Lost around 3 hp with my 3 inch exhaust.
My friends 85.5x95 lost 3 hp with a 3.5 exhaust.

Can more be gained on MOST cars by tuning open header? Absolutely. But to the sound of 30+ hp, Highly doubtful.