B35 exhaust manifolds or headers for high compression B34

[E9Wayne]

My recently completed B34 piano piston motor upgrade coupled with motronic 1.3 and L-jet intake manifolding has gone well overall. With a Dinan chip installed (from a 1989 USA 635CSi) she should be putting out about 240 hp but I'm convinced the stock M30 exhaust system is really holding things back and she sounds overly muffled at anything above 3000 rpm. I do miss the sound of those Zenith carbs!

I'm considering Coupe King's stainless exhaust system but want some opinions or previous experience from other owners who have done exhaust on a high po B35 or B34 regarding what to mate up to the Coupe King system. The more typical route seems to be B35 exhaust manifolds but the downtube solution with that is not clear. Then there are used headers from Hartge, Stahl or new ones from Ireland or Korman and I can avoid the downtube issue all together.

My goal is great power with proper backpressure, but I don't want a boy racer exhaust sound. I'm looking for a refined but louder, free flowing note and I'm hoping I can do something that sounds more old school six than modern BMW. I also hear headers, unless they are ceramic coated, don't last as long.

Thanks in advance.

 

[pmansson]

I have Coupeking´s system on one of my cars with a 3.5L engine with modern FI, fully mapped ignition and 244 HP. It sounds and performs really well. Probably too loud and rough for a cruising car application, but on my modified car it is absolutely perfect.

 

[x_atlas0]

Long tube headers will be of the most benefit, as it is at the header area that the local flow velocity (and therefore the exhaust shape, size, length, internal roughness, etc. ) plays the largest role in determining exhaust performance. Ceramic coating will help cut down on the corrosion, as it is hot steel in atmosphere. Realistically, the exhaust after the headers plays a much smaller role in engine performance, as the enthalpy (and specific volume) of the exhaust gas has significantly dropped by the time it leaves the headers. This drop translates into a reduced exhaust velocity, which reduces any fluid inefficiencies.

I'm not sure about how the different coupe exhausts sound, but I do know two of the typical aftermarket exhaust setups sound pretty good: Remus/Magnaflow, and SuperSprint. I've got a SuperSprint setup on my E34 540, and it sounds great. No droning, deep sound, sturdy construction. You may be able to use one of the universal SuperSprints if you fab up your own system, but it will not be particularly cheap.

 

[E9Wayne]

Headers with modified stock exhaust system perhaps?

Thanks xAtlas and my friend from Europe. If the headers play the largest role in the performance increase, maybe I should try those joined to my stock center resonator and pipes but ditch the rear can for a magnaflow unit. Anyone out there try this approach? Happy Sunday...

 

[shanon]

Howdy there Wayne,

I am using a similar set-up on my carb'd car: ceramic coated headers + NOS OEM center resonator + a turbo muffler (when the side exhaust is not on).

I think it works and sounds great.

HTH
-s