Does Exhaust Increase Performance?

[SporTi]

I have been going through threads here. I recently got a 97 Sport and was planning to go with an "upgrade" exhaust behind a stock Cat. However, I read some posts that said "since there is no performance gain on a Ti...".

So would I be spending $$ just to get a different sound and maybe lighter weight? Or is there a performance gain? (I was thinking Stromung)

[1996 328ti]

The performance gain is negligible.

[pdxmotorhead]

Look at the stock piece,,, Its nicer than most aftermarket headers.

Dave

[scabzzzz]

I dunno what ur talking about pdxmotorhead, but yeah you might feel a little bit of difference in top end. I would just cut the resonator off and do a high flow cat if anything. Sound cooler. Free up some flow. Cheaper.

[pdxmotorhead]

I was just pointing out the stock header is pretty nice....

I agree, good cat, ditch the resonator, Maybe upgrade the muffler.
after all that I'd expect a 4 or 5 HP gain up at about 4000 to 5000
rpm. (When the secondary throttle opens mainly...)

Unfortunataly that cat is a 240 to 600 dollar part....

Random Tech or Other matrix all metal cat.....

IMHO it makes them a bit buzzy for the street, but I do
LONG stints in mine and noise counts more for me...

Dave

[jflip2002]

The key to power is breathing. Thus the purpose of superchargers, forcing air in. If your car can exhale (or exhaust), it is easier to Inhale (or intake). The exhaust is a step in the right direction, for further power. But then you gotta work on the intake side of it all!

[sublimeti]

Originally Posted by jflip2002

The key to power is breathing. Thus the purpose of superchargers, forcing air in. If your car can exhale (or exhaust), it is easier to Inhale (or intake). The exhaust is a step in the right direction, for further power. But then you gotta work on the intake side of it all!

I totally agree! There are many posts on here about no performance gains from Headers, Intake, Exhausts....even chips??? This just does not make any sence to me. If someone installs an intake, but nothing else....they may not feel crap, but instal intake + exhaust...cmon, there has to be a difference. Is there anyone out there who has Dino'd their ti on every step of modification to back up these posts?? If I add intake, exhaust, headers and computer---there has to be a significant increase....right??

[mohaughn]

Originally Posted by sublimeti

I totally agree! There are many posts on here about no performance gains from Headers, Intake, Exhausts....even chips??? This just does not make any sence to me. If someone installs an intake, but nothing else....they may not feel crap, but instal intake + exhaust...cmon, there has to be a difference. Is there anyone out there who has Dino'd their ti on every step of modification to back up these posts?? If I add intake, exhaust, headers and computer---there has to be a significant increase....right??

The issue comes in with the adaptation that the OBDII computers do to control the amount of pollutants in the exhaust. If you don't get a custom tuned ECU to take advantage of the intake, exhaust then the stock ECU is going to either run the engine a little lean or rich depending on your situation. So yeah, there could be a gain, but the computer changes the tune to try and maintain the proper content of pollutants...

That is why you will get more gains on the m42 vs the m44, the ECU is not as advanced on OBDI and does not detune the car as much as you start making modifications.

If you want to really get power out of an M44 short of installing a sc/turbo you would have to start disabling a lot of the emission controls in the ECU. Slapping on a new high flow muffler or a CAI with the dinan/TT/conforti chip is really not going to get you a lot. A little, but nothing major. These engines are tuned very well from the factory.

[pdxmotorhead]

The point is that exhaust just doesn't buy you much when the manufacturer did their homework. BMW sized the pipes right, Uses good parts etc. So if you replace the whole exhaust on the car with say a track oriented non cat light muffler unit it just won't give a big percentage as you would get on a 350 chev with smogger exhaust manifolds and a cat from hell.

It will get louder, if you put big cams in the exhaust will help them work better but in the end on a 318 the exhaust is about 3% of the power equation, UNLESS you go full tilt boogie, 14:1 compression, massive forced induction etc. The head will flow what its gonna flow ....

It has a header stock. A nice little 4 to 2 to one unit as a matter of fact. (On my 95 anyway.) And Other than the final runner being a bit shorter than most aftermarket units it should and does give great mid to upper RPM performance.

With a finely engineered engine its costs exponentially more $$ to get more power. Talk to any Porsche owner. Their engines cost 20 grand to add 50 to 100 HP.

Just my 2 pence worth...

Dave

[J3553]

the '99 ti i just got has a dinan intake, aftermarket high-flow exhaust, chip, and throttle body upgrades. the guy who gave it to me had it tested after he got the upgrades and he said it's at about 165-170hp now. so there ya go.

it should be noted that the guy i got the car from is a good friend of mine and he knew i didn't care how much horsepower it has. he wouldn't lie to me.

[bullmand]

There's no way an M44 is making that much power with just those upgrades. The stock horsepower claimed by BMW is 140 and I believe that's at the crank. If you use the internet standard 15% drivetrain loss, that's 119 at the wheels. You can't get 46 to 51 horsepower with those modifications. Even if it's 140 at the wheels to start with, the Dinan web site shows 153hp with the intake, exhaust and chip. The throttle body won't make much difference in that number and they don't even list that part anymore.

[318tiRedLeather]

Originally Posted by bullmand

There's no way an M44 is making that much power with just those upgrades. The stock horsepower claimed by BMW is 140 and I believe that's at the crank. If you use the internet standard 15% drivetrain loss, that's 119 at the wheels. You can't get 46 to 51 horsepower with those modifications. Even if it's 140 at the wheels to start with, the Dinan web site shows 153hp with the intake, exhaust and chip. The throttle body won't make much difference in that number and they don't even list that part anymore.

He had also added the big bore throttle body which dinan has stopped selling for some reason. IIRC his numbers would be right with the throttle body.

[DustenT]

Originally Posted by J3553

the '99 ti i just got has a dinan intake, aftermarket high-flow exhaust, chip, and throttle body upgrades. the guy who gave it to me had it tested after he got the upgrades and he said it's at about 165-170hp now. so there ya go.

it should be noted that the guy i got the car from is a good friend of mine and he knew i didn't care how much horsepower it has. he wouldn't lie to me.

Chad's supercharged 318ti put 170hp to the wheels on a HOT day. I call B.S.

[318tiRedLeather]

Originally Posted by DustenT

Chad's supercharged 318ti put 170hp to the wheels on a HOT day. I call B.S.

I dont think that he was talking to the wheel. His 165-170 was to the crank

[pdxmotorhead]

So assuming he did a chassis dyno run and they normalised to crank horsepower.
I deal with several tuner shops and I have found that their chasis dyno numbers are all over.
You can get a 10HP difference just with Tire pressure.
Between the half dozen or so local ones there is a consistant
15 HP spread. so don't take any numbers too seriously.

Dyno numbers are for peaking YOUR engine,
relative to what it was before on the same dyno.

Dave