M54 Madness, the remix

[digger]

the OEM manifolds do not scavenge anywhere near what a proper header can and this hurts torque more than anything. its always a compromise though

[mike25]

The second exhaust is a standard BMW header, so I doubt it is as hopelessly compromised and leaving so much on the table as you suggest..........?
It will be a compromise for sure, but a well optimised one for a DD.

[TheAxiom]

That exhaust is so backwards, I don't know what to tell you - It's compromised in all the wrong areas.

The SS replica exhaust primaries were far too large, and the same with the secondaries - not to mention the exhaust merger is far too close.

The second exhaust is better, but still suffers from the same issues. The primary tubes are too short, the merger is too close but the diameter is better suited for scavenging.

If you're happy, that's great, I'm just saying there is a LOT left on the table with that exhaust.

[hoveringuy]

New exhaust is fitted and, wow, what a difference! Went from being loud and rough to smooth and quiet. Revs crisply to redline without all kinds of annoying harmonics. My 0-60 is 70% more comfortable. I also feel like I've recovered some of my torque.

VANOS seals and cam timing is next...

[TheAxiom]

My goal isn't necessarily to make maximum power. I'll be using the M52 manifold because I think they're actually somewhat effective and because they're quiet and also great for keeping the engine bay (and cabin..) cooler. Plus they're light and easy to work around.

I really did love my S50b32 headers, the sound was divine and the power was great, my only issue with them was that the flange hung a little low and I just didn't have the motivation to deal with re-working them to fit better.

You just described Ebay headers. From my expereince ( 2 different M52tu with headers) great fit, great power and literally no downsides. In DD with a stock exhaust, the car was quiet and sounded stock.

[hoveringuy]

Why not Turner or the like Shorty headers? They seem to add a massive amount of power to the low end in comparison to the stock M52 exhaust manifolds.
And why not SS style long tubes? They are proven power gainers...

My goal isn't necessarily to make maximum power. I'll be using the M52 manifold because I think they're actually somewhat effective and because they're quiet and also great for keeping the engine bay (and cabin..) cooler. Plus they're light and easy to work around.

I really did love my S50b32 headers, the sound was divine and the power was great, my only issue with them was that the flange hung a little low and I just didn't have the motivation to deal with re-working them to fit better.

[Cardude]

I would assemble the motor, trans, subframe and everything all together and install it all from the bottom if you have the means to do it this way. Im quoting the post that Jordan did showing how his all went it in

Pretty awesome build, I like the fact that you used MS3. My buddy is running that on his wifes Turbo Cabriolet and its so easy.

Random question, what is that condenser that you are using?

[TheAxiom]

Take a look at the Spec e46 guys. They are making over 200whp on stock engines using m52 exhaust manifolds (cat-less) and well designed secondaries/exhaust and a Spec tune.

Why not Turner or the like Shorty headers? They seem to add a massive amount of power to the low end in comparison to the stock M52 exhaust manifolds.
And why not SS style long tubes? They are proven power gainers...

[ForcedFirebird]

Take a look at the Spec e46 guys. They are making over 200whp on stock engines using m52 exhaust manifolds (cat-less) and well designed secondaries/exhaust and a Spec tune.

[mike25]

I'll be going back to stock OBD2 headers primarily because they're more civil, but they'll probably be better than my current headers. That will help.

As a scientific experiment it will be interesting to see what just the header change makes?

What do your stock OBD2 headers look like?

Here in UK we have two quite different versions - the simple early version, which is the same as our M52TU,



and had a Secondary Air Pump for emission control, then the later ones have CATs built into the header, which eliminated the SAP?

[hoveringuy]

At 3250rpm you are down by -35HP & -60 Ft lbs - is there something amiss to affect things this badly?

Do you think DISA is giving you the huge 2500-4000rpm gains in the old engine?


This was always an experiment, so what are your current thoughts?

I expected it to be down a little where DISA is most effective because, seriously, DISA kicks-ass where it's effective. The stock M54 is really great in that band. The stock M54 is a good motor, period.

That said, my tuning and configuration isn't as strong as it should be. I'll be going back to stock OBD2 headers primarily because they're more civil, but they'll probably be better than my current headers. That will help.

I'll re-time the cams and replace the VANOS seals, which have been very bad at maintaining cam position.

It'll be better.

[digger]

not 100% tuned yet, but them headers and collector......probably never going to provide as broad a power band

[mike25]

Compared to the original motor with ZHP cams and DISA intake....

At 3250rpm you are down by -35HP & -60 Ft lbs - is there something amiss to affect things this badly?

Do you think DISA is giving you the huge 2500-4000rpm gains in the old engine?


This was always an experiment, so what are your current thoughts?

[hoveringuy]

Compared to the original motor with ZHP cams and DISA intake....

[TheAxiom]

Those headers/close collector are KILLING your low end power and you're probably gaining nothing up top for it.