Exhaust Size Inquiry

[bratch15]

I haven't been on here in a while. I have been spending the money on my YFZ450 getting it ready for race season (drags and motorcross) next year (15.24 sec @ 77.86 mph best time this year w/only gytr full exhaust and not jetted). Anyhow I was looking into doing a little modification to the trucklero (my tow car for my quad). I'm trying to get a little more power out of her with little money (booo!) for towing and want to go bigger exhaust as a second mod. I have a CAI and I am going to buy the S&S headers with the high flow cat after Christmas bonus. I'm having the local exhaust shop run a custom exhaust from the cat back as straight as possible with a magnaflow muffler or holley afterburner muffler. I was thinking 2" or 2.25", but im afraid that with 2.25" I might lose power. The question I have for you brains on here is what diameter exhaust do you think I should go with? And yes, I know everyone is going to tell me I need to have the PCM tuned after this! I already know, my plugs were white when I changed them.

[[ion] C2]

stock is 2", go bigger, 2.25" is fine N/A

[cherrington17]

2.25" Non Boost

2.5-3.0 - Moderate Boost

>3.0 - omgwtfbbq Boost

[bratch15]

I thought stock was 1-7/8" but if you say so I believe you. Also, are the gains for the S&S headers with the high flow cat really worth the $800+ shipping costs?

[[ion] C2]

i believe it's 2", i measured mine when i cut it off and put the full exhaust on

$800... Headers are expensive for the V6.. it's crazy. Mine was $175 shipped for the I4. How much are they charging for the high flow cat? You can get them pretty cheap.

[cherrington17]

^^i've been debating that myself since i joined the site. :lol:

[billytheman1188]

get a 2.5 in exhaust if you plan on getting headers too. I have the S&S ceramic coated headers....they are WELL WORTH the money. I noticed a pretty big difference in performance after i put them on. You dont have to get the most expensive ones though, they have cheaper options on the site.

[bratch15]

its $717 without shipping for the raw headers with the high flow cat and $514 for just the raw headers. They want $313 for the cat by itself which is expensive IMO

[bratch15]

2.5" is overkill for a car thats only going to put up MAYBE 190hp crank after headers, exhaust and CAI in my opinion. That sounds like you might even lose power with that big of exhaust.

[[ion] C2]

its $717 without shipping for the raw headers with the high flow cat and $514 for just the raw headers. They want $313 for the cat by itself which is expensive IMO

SHIT man, fuck the cat! High flows go for like $50; hell, a universal regular cat will be fine. High flows aren't really that much better.

[billytheman1188]

its not overkill if your putting a high flow cat and headers on......2.5 is the max you should go if your N/A. My baby feels great with the 2.5 exhaust :)

[bratch15]

Yeh you say it feels great but you haven't put a 2" vs. a 2.5" on a dyno to compare the power difference. For all you know, you could have lost power going to 2.5" exhaust with little mods. You might get more power out of a 2" compared to a 2.5". And billy, not to bust your balls or be a dick, but your performance knowledge is not very credible. I have seen plenty of threads you comment on and the questions you ask. Nothing against you, I like what you have done to you Alero except for your choice of the blue paint! Keep up the good work just stay away from painting anything!

[bratch15]

Anyone else want to give opinions of what size would work best?

[billytheman1188]

Yeh you say it feels great but you haven't put a 2" vs. a 2.5" on a dyno to compare the power difference. For all you know, you could have lost power going to 2.5" exhaust with little mods. You might get more power out of a 2" compared to a 2.5". And billy, not to bust your balls or be a dink, but your performance knowledge is not very credible. I have seen plenty of threads you comment on and the questions you ask. Nothing against you, I like what you have done to you Alero except for your choice of the blue paint! Keep up the good work just stay away from painting anything!

http://www.aleromod.com/forums/showthread.php?t=14172


Do you really think your going to lose so much power switching between a 2.25 and 2.5??? AND you think i could get more power out of a 2in over a 2.5? lol. The stock size is 2in.....so you might as well not even change your exhaust if you think u can get more power out of a 2in. either way it doesnt really make that big of a difference if you go with 2.25 or 2.5 (with the mods you are doing). but in the future if you plan on doing P&P with the upper and lower IM then you should go with 2.5

[bratch15]

Billy, theres no point in arguing because nobody has any dyno sheets to compare. And second of all, have you ever looked underneath your car to see how restricting the stock exhaust is and the pipe routing at the muffler? More bends = crappier air flow. All I'm saying is that an aftermarket custom exhaust with less bends and rotation of the muffler with 2" exhaust might give you more power versus 2.5" exhaust but nobody knows because who is going to take the time to put two different size pipes on and run it on the dyno. I'm not even calling you a liar or saying your dumb for thinking 2.5" is better than 2" or 2.25". I'm asking people for their opinions. My opinion is that 2.5" exhaust is too big and so does other people on here. So relax!

[billytheman1188]

Billy, theres no point in arguing because nobody has any dyno sheets to compare. And second of all, have you ever looked underneath your car to see how restricting the stock exhaust is and the pipe routing at the muffler? More bends = crappier air flow. All I'm saying is that an aftermarket custom exhaust with less bends and rotation of the muffler with 2" exhaust might give you more power versus 2.5" exhaust but nobody knows because who is going to take the time to put two different size pipes on and run it on the dyno. I'm not even calling you a liar or saying your dumb for thinking 2.5" is better than 2" or 2.25". I'm asking people for their opinions. My opinion is that 2.5" exhaust is too big and so does other people on here. So relax!

I am relaxed....i wasnt getting mad, just stating my opinion:lol: BUT do you really think that 2.25in over 2.5in will make a big difference? the difference is VERY minimal (probably 1 hp). Think about it......if you put an aftermarket exhaust on, your probably going to gain about 5-6 hp....there is barely a difference....thats all im trying to say. UNTIL you add more mods, thats when the inches really matter. but with what you have now, it really doesnt make a difference.

[[ion] C2]

More bends = crappier air flow
Not true if mandrel bent.

[kwhauck]

I say go with 2.5.........and there are dyno sheets with both S&S and TOG headers with 18-20whp gains with just headers (both dyno run had 2.5 exhaust to begin with just not headers