Does anyone know the actual performance increase' from the BMW intake and exhaust?

[janus77]

Just wondering out of interest if the performance improvements are documented anywhere? I would assume they improve engine air flow a bit, so there must be some improvement in performance?

[sparoz]

6hp and sound I think. It was minimal. If you are looking at upgrading the 125i, I think you might able to do so with the 130i parts to make it 190kw . I don't plan to upgrade the 125i, so haven't really been following, but there should be info in the drivetrain forum for the N52.

[BrokenVert]

I have the performance exhaust and it makes a real difference in 135i performance. The turbos spool up much fast and the car is faster off of the line.

Forgive my ignorance but is the 125i turbo charged?

[janus77]

No, the 125's an NA 3L straight 6..

[BrokenVert]

Originally Posted by janus77

No, the 125's an NA 3L straight 6..

Ohh so then its what we call the 128i in the States?

There are performance increases that a better breathing exhaust can bring about. Your engine will rev up faster and it will be generally more responsive across the board.

[janus77]

yeah, close though ours is only 160kw and 270nm, whereas I think the 128i's got a little bit more power?

[dontask]

Originally Posted by sparoz

6hp and sound I think. It was minimal. If you are looking at upgrading the 125i, I think you might able to do so with the 130i parts to make it 190kw . I don't plan to upgrade the 125i, so haven't really been following, but there should be info in the drivetrain forum for the N52.

Don't think anyone has done this yet but theres been talk. The main difference between engines is that the 130i has a three stage intake manifold, whilst the 125i has the single stage intake manifold. You'd be looking to change manifolds and updated ECU (to control the extra two stages) as minimum.

[janus77]

how does the 3 stage work compared to the single stage?

[dontask]

I'm not a mechanic, but here's my 2c.

You can think of your engine as a giant air pump. The more efficiently you pump air, the better your engine is. Torque is related to airflow velocity, whilst HP is related to total air volume being pumped. At lower speeds, if the intake manifold was totally open, you would get very low torque. This is because, at low rpm, your engine requires less total air volume. If your intake is is completely unrestricted, you would have low airflow velocity at low RPM. Thats why, at lower RPM, the intake manifold restricts more, so you get higher airflow velocity but the air flow volume would stay the same. I'm guessing at the higher RPMs, the 130i's intake manifold would open up some more (as per the secondary/tertiary stages) to match RPM and therefore hit higher RPM.

Ever heard of extrude honing? You can run an acidic putty through your intake to make it larger - but do it too much and you start to lose torque.

In the same way, if your exhuast is too big, you also lose torque - your engine can't pump out the air fast enough (eg: velocity) and you lose torque.

[qship]

My 2 cents is that regardless of the power increase it would hardly be cost effective. And remember that they are not ADR approved and that BMW Australia will probably wet its nappy regarding warranty. Food for thought.

[jksgoh]

^ have to agree with qship there...
with regards to the manifold, i've heard the 125i manifold is the same 3 stage intake manifold as the 130i, but the 128i is the single stage intake manifold... but havent really been able to confirm this....

[janus77]

cool, thanks all

I'm very happy with the power of the 125i, given mine's spanking new and i can expect it to losen up a bit with some km's it's all good.

[andrew@southernBM]

BMW Australia are having a fit at all sorts of warranty at the moment, soon they will tell me that non genuine air in the tyres will void warranty.

[rawbert54]

Originally Posted by BrokenVert

Ohh so then its what we call the 128i in the States?

There are performance increases that a better breathing exhaust can bring about. Your engine will rev up faster and it will be generally more responsive across the board.

actually, the 125i has less hp i believe and the 130i has more.

[Nifelheim]

Originally Posted by andrew@southernBM

BMW Australia are having a fit at all sorts of warranty at the moment, soon they will tell me that non genuine air in the tyres will void warranty.

Not Surprised. I have an 06 130i that has been with them 5 weeks now. Went in with a sound like putting paper in a fan between 3000 - 4000 rpm. Initially diagnosed as primary cats so waited for new exhaust for 2 weeks. Didnt solve the problem. Changed the valve lifters, noise still there. That was Monday so far no further diagnosis ! Had an oil leak at 2600 kms and I told them the car was a dud and they should take it back...... now 26000kms and definately a lemon.
I see there is an e90 thread running to 46 pages discussing similar problems in the US. Anyone else experienced problems?
http://www.e90post.com/forums/showth...metallic+noise


I will be resisting the return of the car. Pity as I love the car and just had the BMW performance suspension air intake and ss kit fitted.
Only positive is that their service has been great.

On the topic of this thread, the air intake noticeably improves the pick up and power throughout the rev range. Next step would have been the exhaust system.