2.5 too big?

Post by **Scott McLellan** » Mon Oct 13, 2003 3:20 pm

I was thinking about putting together a custom 2.5 in. exhaust going into a performance muffler (Borla, Flowmaster, Ravin, or???)designed for the late camaros (2.5 inch in, dual 2.5 inch out). I would put a hotshot header on and a 2.5 inch high flow cat, too. My question is is this to much air flow for a NA KA? The stock exhaust is like 2 in. with a dual 1.75 in. out or whatever as you all probly know. The other choices would be HKS hiper that is a little over 2.5 in. (65 mm) I think or a Tanabe that is a little less than 2.5 in. (60 mm) I think. Your thoughts/comments are welcome. Just tell me if this is dumb, too. This is a daily driver so would this much ruin bottom end torque? The thing is, I pieced together what I think I would need and it comes up to $225 out of some parts catalogs (Jeg's, Summit, JCW, PAW). Thanks again.

Checkered-Member · Post by **Checkered-Member** » Mon Oct 13, 2003 3:20 pm

with a 2.5” you should be all right, bottom end TQ will be effected, but not ruined, we are talking about a tuny 25% increase.

Post by **Altiman94** » Mon Oct 13, 2003 3:20 pm

2.5" is absolutely perfect, you will gain power, and lose none.

Post by **Scott McLellan** » Mon Oct 13, 2003 3:20 pm

Hey Checkered-Member, got a couple of quetions. First, what does that magnaflow exhaust on your car sound like? Is it loud? I realize it is 2.25. Second, what exactly do you mean by "tuny 25% increase?" Sorry, I'm dumb. Last one, you say you have a custom exhausts. What did you do for the flanges between say like the cat and the exhaust since it is a 2-bolt flange? I can't find these anywhere or the gaskets and would need them for 2.5 in. pipe. If I can't find one I might just find some scrap steel and use a plasma cutter.

Post by **Asleep Altima** » Mon Oct 13, 2003 3:20 pm

IMO, 2.5 is too big. its only a 1/4 inch bigger i know, but we only have a 4 banger... 2.25 works really well with a ka.

Post by **Scott McLellan** » Mon Oct 13, 2003 3:20 pm

HKS hiper is 2-9/16" in. (65 mm) and a Tanabe is 2-3/8" in. (60 mm). These are both recommended for a NA KA. A guy at Enjuku Racing told me that for my application a HKS hiper would be optimum for power. I guess the only way to find out for sure is trial and error. To bad that can be expensive. Anybody else have experience. Correct me if I'm wrong but here is a thought. A Mustang 5.0, which is basically twice the size of a KA, comes from the factory with a 2.25 inch true dual exhaust. Upgraded exhausts vary from 2.5 and up. If you see what I'm saying. Also a KA revs a bit higher so added airflow up in the RPM's would seem neccesary.

Checkered-Member · Post by **Checkered-Member** » Mon Oct 13, 2003 3:20 pm

Scott McLellan wrote:Hey Checkered-Member, got a couple of quetions. First, what does that magnaflow exhaust on your car sound like? Is it loud? I realize it is 2.25. Second, what exactly do you mean by "tuny 25% increase?" Sorry, I'm dumb. Last one, you say you have a custom exhausts. What did you do for the flanges between say like the cat and the exhaust since it is a 2-bolt flange? I can't find these anywhere or the gaskets and would need them for 2.5 in. pipe. If I can't find one I might just find some scrap steel and use a plasma cutter.

well it’s loud, raspy and deep all at the same time, its not as loud as my SRI after 3K rpm I can't hear the exhausts. So its not that loud.

25% increase in the size of your pipe, from 2.0 to 2.5 is a 25% increase, its very small compared to what some of my friends do, example a civic from a stock 1.0" to a 2.25 an 125% increases which killed his low end, but at high end it pulls like no ones business.

I got my exhausts done in a shop, so I can’t answer your last question...

Checkered-Member · Post by **Checkered-Member** » Mon Oct 13, 2003 3:20 pm

Scott McLellan wrote:HKS hiper is 2-9/16" in. (65 mm) and a Tanabe is 2-3/8" in. (60 mm). These are both recommended for a NA KA. A guy at Enjuku Racing told me that for my application a HKS hiper would be optimum for power.

umm that can't be, 60-65mm is what they use for 15 psi KA's.

Define “optimum power”top end will probably increase, but you will hurt you low end tq

Post by **lessthanjakejohn** » Mon Oct 13, 2003 3:20 pm

60-65 sounds a bought right, many KA guys have the NA hiper and love it...

Post by **Altiman94** » Mon Oct 13, 2003 3:20 pm

How do you know 2.5" is too big Asleep, have you had both on your car so you can compare?

Post by **Altiman94** » Mon Oct 13, 2003 3:20 pm

2.5" exhaust also sounds 10 times better than 2.25" exhaust all day!

Post by **Asleep Altima** » Mon Oct 13, 2003 3:20 pm

why do i feel that that was a sarcastic question? ive seen enough of both on different altimas to know the difference. ill be going 2.25 on mine when its done. too many similar setups on altimas. its not like anyone has anything extremely different. at least not around here. we have grunt going for us, why not capitalize on it?

Post by **I am Technoman** » Mon Oct 13, 2003 3:20 pm

the goal is to have it as big or a little bigger than your throttle body!;) unless its turbo

Post by **I am Technoman** » Mon Oct 13, 2003 3:20 pm

It also depends on if you are going to use a Kat or not. If you do use a Kat go 2.5 if you are using a header with no kat go 2.25

Post by **Scott McLellan** » Mon Oct 13, 2003 3:20 pm

I know this is a matter of preference, but does anyone have a specific muffler type/brand or something they think sounds awsome with the KA24DE? I'm not talking too loud here...

Post by **Asleep Altima** » Mon Oct 13, 2003 3:20 pm

ive got two styles that sound great. my 2 chamber 40 series flowmaster sounds beautiful. a friend of mine has a 3 chamber 40 series and shes loves it. its quieter than mine but still sounds aggressive. ive also heard a 3 chamber 60 series flowmaster on a ka and it sounds good to, although, imo its TOO quiet.

Post by **I am Technoman** » Mon Oct 13, 2003 3:20 pm

I use a HS header o2 plumbed into the collector 2 1/4 back pipe with Borla muffler! sounds to sweet!:D No kat

Post by **SHiFT** » Mon Oct 13, 2003 3:20 pm

I have 3" on my APEXi N1 Single...yeah theres some low end loss and such but the KA has enough torque that you won't be bothered with it too much. I plan on turboing it someday so I just figured I'd do this now. I wish I had 2.5 but oh well, thats how it goes. I raced my friends 240 with the same mods except he had 2.5" piping, there was absolutely no difference in acceleration. Mine sounds deeper though.

Post by **WongFeiHung** » Mon Oct 13, 2003 3:20 pm

Checkered-Member wrote:well it’s loud, raspy and deep all at the same time, its not as loud as my SRI after 3K rpm I can't hear the exhausts. So its not that loud.

25% increase in the size of your pipe, from 2.0 to 2.5 is a 25% increase, its very small compared to what some of my friends do, example a civic from a stock 1.0" to a 2.25 an 125% increases which killed his low end, but at high end it pulls like no ones business.

I got my exhausts done in a shop, so I can’t answer your last question...

Which Magnaflow muffler did you install? and which size?

Post by **MikeMurphy** » Mon Oct 13, 2003 3:20 pm

Checkered-Member wrote:with a 2.5” you should be all right, bottom end TQ will be effected, but not ruined, we are talking about a tuny 25% increase.

Check your math again bro. Its definitly more than 25% increase from 2". We are talking circles! If I did it right it flows 56% more.

I know for a FACT that the 2.25" exhaust is the best for the QR25DE so the KA will also benifit from a 2.25".

Post by **F4ucc** » Mon Oct 13, 2003 3:20 pm

Well, I too have a HKS Hi-Power Cat Back exhaust. Piping size is 65mm diameter.

Personally, I think HKS Hi-Power is my best investment ever, Period! well, besides my KAAZ 2way, expensive suspension setup.

It sounds so sweet, not too loud, honestly compare to my friend's Apex, HKS Hi-Power is relatively quite.......below 2500 RPM is like a stock exhaust, kind of deep tone.Well if you floor it that is another story though.

As for losing power due to its 2.5" pipe? I would say, Not Really.I do notice the low end power suffer a bit below 3000 RPM, however the power gain above 3000 rpm is way better than stock. Best of all, the moter revs definitely faster through out all RPM. That's where it shines.

BTW, I made a small spread sheet with comparison of common piping diamter in both mm and inch along with total flow area and % incease in area.Here is the result:

mm inch area in cm^2 % increase55 2.17 11.88 60 2.36 14.14 1965 2.56 16.59 4070 2.76 19.24 6276 2.99 22.68 9180 3.15 25.13 11285 3.35 28.37 13990 3.54 31.81 168

Hope this helps

Peter91 S13 hatchback

Post by **apzak** » Mon Oct 13, 2003 3:20 pm

I didn't see any low power loss with the apexi n1. I used to have a crush bent 2.25 exhaust and it was easier to bog the car down on launch with that. With the 3 inch apexi n1, I can ride in a gear too high (i.e. 4th @30mph) and I feel more response than before.

Ofcourse I went from STOCK>2.25 crush>STOCK>apexi N1

The crush bent also did not have a resonator, and the apexi does. I'm thinking of getting RSR next (the quiet one). I would suggest buying used exhausts because you could always sell them at little or no loss. This way you can test out the exhaust and see how you like them. Course this requires lots of time, and I'm sure most will see it as a waste but its the best way to see what you like the most.

2.5 too big?

2.5 too big?

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