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Gang;

Been in an ongoing discussion with a fellow M5 owner relative to exhaust upgrades & whether the OEM exhaust ('headers' in particular) are designed with tuning in mind & thus represent at least, a somewhat 'tuned' (equal length) header.

Is the above consideration true?
Thanks
 

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I think they were designed for emissions, possibly for fast catalytic converter light up, and for packaging/cost of production.

Most owners get ~30HP from a set of aftermarket headers, so I highly doubt the stock "headers" were tuned at all.
 

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they are the same part as early 540's (before pre-cats), it's safe to say they are not optimized for performance.
 
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And with that fact, how can the SS headers work properly with the 540i and M5 engines?
If you look at the stock manifolds they are grouped into cylinders that fire 180 degrees from the other. This helps in the time each pulse is pushed (or pulled) through the pipes.
 

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And with that fact, how can the SS headers work properly with the 540i and M5 engines?
If you look at the stock manifolds they are grouped into cylinders that fire 180 degrees from the other. This helps in the time each pulse is pushed (or pulled) through the pipes.
The SS headers are 4-1 collected, hence the reason you lose low end torque when you put them on. The stock headers are somewhat optimized...at least a lot better than old school V8 cast iron manifolds anyway.:)
 

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I'm looking into the SS x-pipe. What gains should I expect to see?
 

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I didnt lose much, if any....tires spin violently where they didnt before.
Correct me if I am wrong, but IIRC isn't it more like a blip or dip while true it "drops" it's something you'd never really feel or notice on the street? Just see on a graph spit out from a dyno machine? I think the increase in perfomance outweighs the nickel and dime type of loss of torque.
 

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Put it on a dyno...it's easy to see.
Already have an appt for the 16th. AFAIK, you dont so much lose low end tq as shift the tq peak higher up the rpm band. The low end # is numerically higher, but you dont feel the "rush" until higher in the rpm range leading people to believe that you're losing low end.

Im going to do a few passes each, with the TMS Race, and no software at all. Im curious to see what it did, if anything at all. The power feels more linear, but there doesnt seem to be any more of it (as far as I can feel via my super calibrated butt dyno :blabla:).
 

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Correct me if I am wrong, but IIRC isn't it more like a blip or dip while true it "drops" it's something you'd never really feel or notice on the street? Just see on a graph spit out from a dyno machine? I think the increase in perfomance outweighs the nickel and dime type of loss of torque.
Quite possible, we'll see on the 16th hopefully
 

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Already have an appt for the 16th. AFAIK, you dont so much lose low end tq as shift the tq peak higher up the rpm band. The low end # is numerically higher, but you dont feel the "rush" until higher in the rpm range leading people to believe that you're losing low end.

Im going to do a few passes each, with the TMS Race, and no software at all. Im curious to see what it did, if anything at all. The power feels more linear, but there doesnt seem to be any more of it (as far as I can feel via my super calibrated butt dyno :blabla:).

There have been plenty of dyno runs that show the loss of low end torque.
 
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