Exhaust performance

[SE-Rious1]

ok so im putting an exhaust on my 240sx coupe with DE and i just got a great deal on a #1 drag thats 2.5 in and 4.5 out and the barrel is huge as hell but my bigest worry is what effects it will have on my HP and performance ??

I know alot off ppl talk about back pressure and etc.
http://img292.imageshack.us/img292/3010/52238526fr0.jpg

[blackshine007]

ok so im putting an exhaust on my 240sx coupe with DE and i just got a great deal on a #1 drag thats 2.5 in and 4.5 out and the barrel is huge as hell but my bigest worry is what effects it will have on my HP and performance ??

I know alot off ppl talk about back pressure and etc.
http://img292.imageshack.us/img292/3010/52238526fr0.jpg
Is the rest of your exhast the same size? If not, you're just wasting your time and money. Most of the time, when you tend to go with a bigger sized exhaust, you gain HP and sacrifice TQ in the process due to the fact that you're reducing the restriction. That's why most hondas make more hp than tq. Their heads flow real good and the exhaust is opened up to the right size (most of the time). Being that your KA is only a single cam and you plan on doing nothing to that particular engine, a 2.5 inch exhaust is gonna be over kill. Most people is gonna disagree with me. But for what it's worth, I have a 2.5L and I run a 2.5 inch exhaust all the way to the muffler, which is reduced to 2 1/4 ID (inside diameter) so I have good midrange and still have decent top end. I think you'll be just fine with a 2 1/4 inch exhaust and muffler. Like I said, anything else will be overkill. You may gain maybe 2 to 5 hp, but you loose midrange tq.

[SE-Rious1]

Is the rest of your exhast the same size? If not, you're just wasting your time and money. Most of the time, when you tend to go with a bigger sized exhaust, you gain HP and sacrifice TQ in the process due to the fact that you're reducing the restriction. That's why most hondas make more hp than tq. Their heads flow real good and the exhaust is opened up to the right size (most of the time). Being that your KA is only a single cam and you plan on doing nothing to that particular engine, a 2.5 inch exhaust is gonna be over kill. Most people is gonna disagree with me. But for what it's worth, I have a 2.5L and I run a 2.5 inch exhaust all the way to the muffler, which is reduced to 2 1/4 ID (inside diameter) so I have good midrange and still have decent top end. I think you'll be just fine with a 2 1/4 inch exhaust and muffler. Like I said, anything else will be overkill. You may gain maybe 2 to 5 hp, but you loose midrange tq.

well my 240 is a twincam DE not SOHC if that helps any lol

[blackshine007]

well my 240 is a twincam DE not SOHC if that helps any lol
Not really. It's gonna have the same effect regardless

[SE-Rious1]

Not really. It's gonna have the same effect regardless
well damn hmm

[madking411]

so, what size is that engine, in terms of liters? 1.6? 2.0?

[blackshine007]

so, what size is that engine, in terms of liters? 1.6? 2.0?
I don't understand your question

[Sneeky Ninja]

I think he means what displacement is the motor. A KA24DE is a dual cam 2.4L. That is a fairly big 4cyl so yes a larger exhaust will help. As far as losing tq and stuff, there are a lot of other factors then just the exhuast. Finally, unless you change the header and cat you are still going to have pleanty of back pressure.

[madking411]

not tryin to jack the thread or anything but....

i've got my car with a 2.2L ohv engine, and im currently runnin a 2.25" turbo muffler on mine..it used to have 1.75" exhaust on it, and i was wonderin if its tq or hp that i've gained..

[blackshine007]

not tryin to jack the thread or anything but....

i've got my car with a 2.2L ohv engine, and im currently runnin a 2.25" turbo muffler on mine..it used to have 1.75" exhaust on it, and i was wonderin if its tq or hp that i've gained..
Depends on what's done with the rest of the exhaust. GM's 2.2L ohv engine is basicly known for making alot of tq and blowing head gaskets. It's a pretty restrictive design. 2 1/4 exhaust is perfect for that engine, but make sure you buy that with headers and all to get the full effect. With the right exhaust, you'll gain hp as well as tq. Just with the down side of a bigger exhaust, you typically sacrifice mid range tq for higher hp numbers. I don't understand how some of the non VTEC guys try to run 2.5 inch exhaust on their smaller 1.8L's and think their actually gaining from it. For those who has done it, it's nice to know that you're wasting your money by giving it to some shop. That keeps the economy flowing, if less money in your pocket. I think it was Sport Compact Car that had a nice write up on exhaust sizes. I agreed with most of it. It was basicly giving a general idea on what sized exhaust to run with different engines. Like they were saying anything from 1.5L-1.9L to use a 2 inch pipe, 2.0L-2.4L to use a 2.25 pipe, 2.5L-2.9L to use a 2.5 pipe, and 3.0-up to use 3 inch or better. I kinda agree with most of it, but once again, it depends on what's your build on the engine. Sometimes with the particular build, a bigger exhaust is the better way to go. I also like running a particularly larger diameter pipe from the beginning and further along the end of the piping reducing the pipe. It does wonders for your tq and keeps the velocity of your exhaust flow up to further help promote scavaging.

[madking411]

so, the headers should ALSO be 2.25"? because i think i might get some high performance ones a little bit later down the road..now, if i install a bigger set of headers, do i also hafta replace the downpipe too?

[AnTi-PooN]

I don't understand your question

are you retarted :tongue1: :bump: :tongue1:

[SE-Rious1]

i was gona gut the cat and maybe leave the midsection but idk yet but if i do that im sure itll cut down on some the flow but if i lose the midsection and gut the cat then its straight flow and that me be hurting me cause when i do a header swap its gona be like straight pip and sound like ass lol

[Capt._Ron]

aren't you selling a perfectly good s13 exhaust? Oh and btw ill see ya tommorrow at the shop.

[SE-Rious1]

aren't you selling a perfectly good s13 exhaust? Oh and btw ill see ya tommorrow at the shop.

yeah i have a few of them lol..and yeah ill see ya hope peps there when we arrive haha

[Capt._Ron]

we will be no worries. Im putting together my stock 240 tommorow so ill see you there.

[SE-Rious1]

we will be no worries. Im putting together my stock 240 tommorow so ill see you there.

need any parts lol

[KPowerEP3]

i was gona gut the cat and maybe leave the midsection but idk yet but if i do that im sure itll cut down on some the flow but if i lose the midsection and gut the cat then its straight flow and that me be hurting me cause when i do a header swap its gona be like straight pip and sound like ass lol


Don't gut our cat. Honestly, the only noticeable difference it will give you it a more raspy, ricey sound in your exhaust. There are NUMEROUS studies showing that Gutted vs Stock vs Test Pipe vs High Flow really don't differ all that much. In reference to what blackshine said...it's generally true, however your results may differ slightly, also you have to keep in mind if you plan to stay NA or if you plan to boost in the future, would it be worth it to go ahead and go with a larger diameter pipe to make it one less thing to replace at that point.

[iEvo]

if u go boosted then ull want a full 3" exhuast, if not then a 2.5" is perfect

[SE-Rious1]

ahh

[GSRteg®]

Nice exhaust man. :yes:

[SE-Rious1]

Nice exhaust man. :yes:
thanks