DOHC exhaust, Nando's recipe

[hoveringuy]

Another data point:

I've been pretty good about logging all of my configurations. When I changed from OBD2 manifold to euro headers my WOT A/F richened 3/4 point.

Larger bore TB, WOT A/F richened a tad.

This exhaust, my WOT is again slightly richer.

By indirect measurement it appears that his exhaust flows better. The M54 is more of a torque motor so the 2.5" is perfect, but I would strongly consider 3" for an S50 or S52 that can flow more on the top end (or any turbo)

[nando]

the pipes past your Y-merge don't aid in any torque development. ;)

[hoveringuy]

the pipes past your Y-merge don't aid in any torque development. ;)

Correct, point being I don't need to support flow for large cams at 7000 rpms.

[Gnarles]

looks good. Any reason you do not run the shielding between the exhaust and driveshaft? Are there any issues with not having the shielding in place?

[nando]

Correct, point being I don't need to support flow for large cams at 7000 rpms.

point taken

for me the 3" exhaust raised the knock ceiling at peak torque and stopped choking the engine past ~6500 or so. 2.5" may have worked too but if I ever do something like a turbo, I won't have to rebuild the whole thing for a 3rd time.

[hoveringuy]

looks good. Any reason you do not run the shielding between the exhaust and driveshaft? Are there any issues with not having the shielding in place?

In Texas, maybe. In Seattle, I haven't had shielding for 2 years. No issues. Single 2 1/2" has less radiating area than dual 2" ??

[FredK]

and stopped choking the engine past ~6500 or so.

Yes, you have the M20 head's intake ports for that.



:p

[nando]

pffft

[MikeDE]

Just about every diesel-engined vehicle here in Germany has a turned- down tip on its' factory exhaust. I think that's why I like it so much, to me it says 'sleeper'.


Nice Work, flows well AND it's quiet. Imagine that.