the nissan altima has a 2.5liter 4 banger...

 

Yep, the 2.4 hasnt been the largest displacement 4 banger for a while.. and that doesnt mean it needs 3" exhaust. Hell, I know of some v8s that will waste most of the boosted 4 bangers on here that are running 3" exhaust.

As for the reccomendations, I dont reccomend duals at all for performance. You probably wont lose anything, but you arent going to gain anything you cant gain with a well designed single exhaust. If you are just looking for the bling factor, then go ahead.

On an NA setup, the scavenging is effected more by too large of an exhaust, so it can hurt you there. With a turbo in the line, you are a little better off in this area due to the resistance it produces.

Too large of a pipe can also cause another issue. The larger the pipe, the slower the flow. The slowe the flow the more the gasses cool within the system. The more they cool, the denser they become.. and the harder they are to push. So in a small way, too big is worse in some cases. A huge exhaust is in no way the same as an open header; some have the incorrect assumption that it is. The gasses are still in the system until they reach the end of the pipe, so design must take this into account.

 

Well, if you read my post above, I based it on an N/A motor with the same displacement and relatively identical horsepower rating. Look up the specs of a Nissan KA24DE motor on google. A lot of people say 3" is too big for an inline 4 N/A motor but how many of them have actually dyno tested that theory???

If I have to I can post my dyno sheets just to prove my point.

 

^^ I saw that you compared stock exhaust to a header-back custom 3" setup. Were the bends the same, was the cat installed on the stock pipe, what cat was installed on the 3" portion and how long did you run the car on the combination before running the dyno run? Was the second dyno on the same day, in same conditions at the same air and engine temp?

I am not trying to be rude or question your knowledge, but most, if not all, dyno proven results I have seen have a ton of holes in them as far as a scientific comparison. A million variables and no controls usually, so I have a lot of questions when it comes to them, especially when custom exhausts are replacing stock exhausts and we are only discussing the effects of sizing.

And I was aiming my other comments at your assumption that because it is a large displacement 4 banger it can benefit from a 3" exhaust. Compression, stock exhaust setup, tuning, setup, etc all play roles in this, so it cant just be based off of displacement.

 

I admit I should've done more research before running my mouth on here but let me correct a few things for you, mr expert.

Scion TC = 2.4L I-4

Bmw 325 = 2.5L I-6
Subaru Impreza = 2.5L H-4

Those cars aren't even close except for the new Nissan Altimas equipped with QR25DE 2.5L (2488cc) I-4 motors that someone else had brought up in this thread.

Please allow me to rephrase myself. The Scion TC has a 2.4L inline 4 motor which is only .1 liter away from being a 6 cylinder motor. It still doesn't take away the fact that 2.4 liters is about as high as it can get for a stock displacement inline 4 engine compared to the Honda B series motors, Lancer Evo and Nissan SR20s

So there, does that make you feel better now?


Nowhere did I mention any of those cars but I didn't know Corvettes, Mustangs (a GT at that, ) and Vipers were the only cars considered as muscle. Well, I'm sorry for offending your "getonmylevel" expertise but let me ask you something, have you ever had or heard a straight 3" exhaust on a 2.4 inline 4 motor? Yes? No??? So how would you know how they sound like? I hope you didn't base your statement on how Hondas sound like with aftermarket rice muffler and stock exhaust piping...

Bottom line, the difference between a 2.5" and 3" exhaust is not that big of a deal. I believe it's a matter of preference and I personally prefer to have a 3" exhaust because I believe it performs better in certain applications.

I rest my case

 

Are u talking about mine?

 

To answer your questions, the dyno was done on a 2 day weekend dyno day at a shop called Racetune in Hayward. The 1st dyno was with the stock exhaust on day 1 and 3" exhaust from the header-back on day 2. I doubt a hi-flow cat would make any difference with power compared to a test pipe but the bends on the 3" exhaust is obviously not the same as the stock exhaust if you're talking inch per inch.

As far as condition goes, both dynos were done around 4-6pm inside the shop with a fan blower facing the motor. I'm sure there are a lot of factors that could yield horsepower gain but with 15whp increase, I think it's pretty obvious that the 3" piping made most of the difference.

 

just got with 2.5inch piping from the turbo back, and run it into a single exhaust.. no need for two mufflers.

 

happy bday bronxblaza

 

Dyno sheets!

DAY 1 DYNO
Mods:
ASP pulley, OBX header, Fidanza flywheel,
air filter, z32 fuel filter, Magnaflow hi flow cat,
stock exhaust, advanced timing, 150k miles




DAY 2 DYNO
Changes:
91 octane, ebay intake pipe,
advanced timing and new spark plugs

 

<---yes i should have researched that my bad...but when did we say boxer 4 or inline 4 or whatever...?



Well let me reply to this so you understand as muscle goes i was goin for a broad spectrum...
Actually yes i did....because only a forced induction four sounds any good with that size piping...otherwise yes you do sound like the geek down the street with the 20s on his accord and green neons and NOS stickers all over his windshield




By the way...My name is tC Get On My Level because i will not, cannot lower myself to drive rice. Because in case you didn't know before my tC i drove an SR powered 240 not the truck powered crap your postin up. So really before you get all butthurt over my post that i apologized for afterwards ---that is--- before you made a big stink, Just know that I am above you already in the game. I never attack people on the internet but you are truly pathetic. And when some newb like yourself feels the urge to keep on and on about some stupid $#*! people who have been here like myself will always come at you.

Just wait three days when i post up my new wheels homie


So while i may not be Mr. Expert you can call me Mr. I wishicouldbelikeyou

 

Sound Clip:

 

please let me know what you guys think

 

I'm not a Fan of that kind of muffler, but the setup looks good.

 

how did you get the tips to bend on the mufflers? looks pretty good

 

That looks really freakin good! My suggestion: Paint the piping thats visible black. Not the tips or mufflers.

 

What should i paint it with? Spray paint? If so won't it get all over the chassis? Because this is a full cat-back

 

Some high temp engine paint or something. Not the whole piping just the parts you can see in the pics. Up until that point or you can do the whole piping if you want. Im sure you could put something behind the pipe as to not get paint on the car. Nice exhaust though! I really really like it.

 

Thanks I really appreciate it. I just love the way it sounds.