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Open Header vs. Bolted on Exhaust comparison

14K views 32 replies 17 participants last post by  metamorfasis 
#1 ·
Alright before you blow off my head with rants about how I should use the search function... I have been searching all afternoon for this topic... and the ONE THREAD I found that talked about this specific topic did not have the dyno chart anymore and the posts within didn't really answer my questions. SO with that said on to my question....


I want to know if anyone out there has some information about a comparison test between some of the Nice K series swap headers out there running 2.5" but preferably 3" exhaust and testing it against an Open header run, and what the differences were.

There is currently a debate going on where another party is claiming that The difference between an Open header dyno pulll compared to the header being bolted up would be no different and that you really wouldn't see a difference. This is on a completely stock K20 with bolt ons mind you.

So I want to know what some of you NA people think... And if you have some dyno graphs or some other data that proves or disproves this That would be great!

FEEL FREE TO RESPOND THANKS!
 
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#2 ·
Don't have the dyno sheet available but I had my car tuned for open header a while ago and as an after thought wanted to see how much, if any, power would be lost after bolting up my 3" exhaust and there was no measurable loss in power. Maybe 1-2 hp loss here and 1-2 hp gain there but pretty much the same power band. FYI, this is for a DC5 chasis with a k24/20 making 254 whp / 193 lbtq.
 
#12 ·
Id say the key is the 3+inch exhaust . . .

On a stock H2b car i picked up around 1-1.5 with a little over 2hp in the upper rpms of powerband from removing my 3 inch exhaust. 2hp is negligable. . . Although I was running a vibrant race muffler so I'm sure that had something to do with it.

I wouldnt put anything less than 3inch on a K
 
#26 ·
I wouldnt put anything less than 3inch on a K
I would. Electric exhaust cutout with rpm switch and a 2.5" cat back system. Emissions and DD friendly!
 
#13 ·
Thanks for the info AMC. I am running 3" custom mandrel with a WSII muffler, not worried about that power... I am just having a debate with someone about how completely different it is running a K open header from running a K with an exhause bolted up, even if it is 3".
 
#15 ·
i haven't dyno my car with the apexi ws2 but when i run it open exhaust which was the way i tuned it, it fells like i just swaped engines. cause the ws2 has so much back pressure.
 
#16 ·
Talk to Dave a Smsp he can set u up with a great cat ,res, muffler that will not kill ur power.
 
#17 ·
on a typical k setup, i.e. i/h/e/cams/kpro, going from 3 inch to open header u'll be lucky to see a max of 3 whp increase, if that lol. In fact i've seen a car that ended up making 314/217 on final tune gain about 1 whp from swithcing to open header from his 3 inch, with the runs having been done back to back. :up:
 
#18 ·
I am not personally looking for exhaust setups because I am content with the one I have now... It fits my needs.

What I am interested in is just people's real life experiences and what they have seen with various setups and such. SO continue to post up the info its appreciated!

Also Peak numbers is not really my main concern I want to know ab out gains/losses through out the entire powerband. Thanks again!
 
#19 ·
The last two cars we tested this on were:

K24(13.7:1) with a stock 06 tsx head/rcrew header. The car made 247whp with 2.5" exhaust, open header it made the same exact power!

The other car tested on was a H2b EG. Stock block, ported head, pro1's, SMSP Header, 3" Exhaust. The car made 246whp with and without the exhaust on.
 
#22 ·
dude if you are looking for midrange then you aren't looking for it in open header vs exhaust. you will get midrange out of the custom header you get made for your car more than any open vs exhaust you choose. Thats the answer you need to know.

i have talked to john from hytech and he says his 2 1/2 exhaust with their twin loop is good for midrange up to 270hp, so I am gonna go out on a limb and say open header is better for peak, while an exhaust system is better at giving midrange.
 
#25 ·
Lol still lots of people mis reading what I am asking... I am purely asking for info on what people have seen when they have had an exahust system bolted up the compared to when they just left it open header...


I run a SSR 4-2-1 built for my car and motor with custom 3" mandrel I don't feel like paying $40 to go do three pulls on the dyno just to satisfy some curiosity of mine that isn't really that important.... So Again I am not looking for advice on what to do for my car... I have my car completely setup the way I want it I am just curious as to the differences that others have seen because I don't feel like doing it myself on a dyno.
 
#27 ·
Who said you have to out your car on a dyno??? If your car is already dyno tuned tour good. Just plug in your labtop and see what type of a/f your runnin open header. If it needs adjusting it would be the a/f. Do that and then see what you like better. Cost is $0 or $5 of gas for a couple pulls on the street.
 
#28 ·
Go to the track, run 2-3 times without the exhaust, then put it on, run 2-3times and compare MPH! Easiest way without going to a dyno.

On both of the cars we unbolted the exhaust off recently, the graph looked the same, everywhere. Maybe .5-1hp difference.
 
#33 ·
im running a k24/k20 in an rsx on stock exhaust with a e-cut out after the header saw a 35hp gain when open
 
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