Today this exhaust "technican" told me that adding a header and 2.5 inch plumbing with out any serious mod like cams and head work would actually make my car slower than anything else. He said all I need is a muffler to release the backpressure and a 2.25would do me fine. Now I am kinda new to the auto modification world, but I don't know if this is true, or not. I was going to get a header, 2.5 custom exhaust, throttle body, motor mounts(upper and lower), and a performance cat to add to my intake. But this guy just came and threw a wrench all in my plans. Someone shed some light please. And what are good size cams that will not sacrifice too much lower end power.
from everything i see posted on here 2.25 is ideal for n/a and 2.5 is to much unless you use force. i am planning 2.25 for mine thise year. read the faq at top and it talks about this i belive in detail
the view is all the same unless your the lead dog.
It would help to know what year car and what engine. But that tech is right.
Fact 1:
“Facts are meaningless. You could use facts to prove anything that’s even remotely
true.
you'll be fine with a 2.25" exhaust, and your other mods sound good too, make sure to add a resonator if u get the header.
what is and where can i get a resonator I am familiar with what it is somewhat.
this "TECH" is full of crap
Im a Xbox 360 fanboy...and damn proud of it!!
a resonator is just something used to take the raspy and bad sounding tones out of your exhauat system. I used a 23" glasspack and love it. plus it was only $14.
Okay bottom line 2.25 is perfect if you run 2.5 you may loose power or stay near the same (seen dyno numbers to prove it), On the other hand if you have or ever get a turbo or a supercharger you will want 2.5 or if you get n20 you will gain HP but only while spraying. You gain while spraying because basically you have a boosted car during that time but when your run is done your back to N/A motor with 2.5 which most likley will not have enough backpressure. Bottom line go with 2.25 unless you get a turbo or super or a lot of mods....
is that tech true?.....fairly new too, but i'vge boughten a set of OBX straight headers, dual cat back exhaust system, plus a high flow cat, with two o2 simulators, and then a dragon intake system...this is goin on a 98 2.4L 5-speed...and i far as i knew this was goin to be a rad setup...so isit true u need more mods with headers????
The "tech" is only partially right. But then he recommended agains headers
? For a mild set-up go for 2.25" exhaust, front to back(not just cat-back, but downpipe from header to catalytic convertor, then a 2.25" catalytic convertor, to a 2.25" cat-back), You really shouldn't have any need for O2 simulators unless you go without a catalytic convertor(bad idea, VERY illegal and you will lose more torque than you gain HP).
I've never heard of this "part throttle" before. Does it just bolt on?
He also said that glasspacks were illegal. Cam anybody answer my ? about the cams and please don't refer me to the post at the top of the forum i have read it many time.
2" exhaust for N/A
2.5 for boosted applications. Reason for higher exhaust for boost is because the faster the exhaust gets out, the cylinder temps. Basically, less chance of detonation.
^^^^^I would think 2.25 for n/a, not 2", that's not enough of an improvement over the stock 1 7/8".
2.25 NA
I know when I went 2.5 n/a I lost tq and only gained overall 3 whp in the high rpms
LE61T PTE6262 Powered 
Kyle Anderson wrote:is that tech true?.....fairly new too, but i'vge boughten a set of OBX straight headers, dual cat back exhaust system, plus a high flow cat, with two o2 simulators, and then a dragon intake system...this is goin on a 98 2.4L 5-speed...and i far as i knew this was goin to be a rad setup...so isit true u need more mods with headers????
um u shouldnt need 2 o2 simulators u nshouldnt even need 1 if u have a high flow cat
kavy kid wrote:He also said that glasspacks were illegal. Cam anybody answer my ? about the cams and please don't refer me to the post at the top of the forum i have read it many time.
Depends, what state are you in?
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2.5 is much too big he was right about that... but not the rest
ive got 2.25 front to back and it feels like a different car on the HW....if you want specifics on the mods i have check profile..
DanteMustDie wrote:^^^^^I would think 2.25 for n/a, not 2", that's not enough of an improvement over the stock 1 7/8".
I was under the impression the stock size was 2"...
Is it really 1 7/8" ??????
I was considering my exhaust upgrade with a 2.5" rear section, then was going to work forward doing all 2.5" after reading a (biased?) dyno write up comparing a 2.25" and a 2.5" exhaust.
Naturally the makers of the 2.5" exhaust were also those who performed the testing....
Does anyone here actually have dyno proof of gains of 2.25" vs. 2.5" ??
I invented the idea of sniffing your fingers when you've spilled gas on them.
2.5 is too big (unless your gonna spray or turbo) everyone has told you already....
Now what if its 2.25" from the header back, then a 2.5" rear section?
I invented the idea of sniffing your fingers when you've spilled gas on them.
z24challenge wrote:Now what if its 2.25" from the header back, then a 2.5" rear section?
You're only as strong as your weakest link. So it would be kind of pointless, I think. Might effect sound negatively, too.
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