Exhaust manifold discussion

[hy_]

Wanted to get some discussion going around the various pros/cons of different exhaust manifold styles, and hopefully some comparisons/personal experience from those that have used different types.

Reason for bringing this up - I am currently running a stainless tubular manifold which has been great for the last 6 years or so but has now developed a severe crack across one of the welds (crack is an understatement, check the pic). Dont know the history on it, was on the car when i bought it and would appear to be a custom job similar in style to a few of the ebay units getting around.

Turbo is a Precision SCM50 (5031e) so has the round exhaust inlet which does limit manifold choices a bit, but am more interested in hearing your experiences on tubular design with longer runners versus the factory/evo 3 short runner design.

Ive actually already ordered a Forced Performance DSM race manifold (link) so will be able to update this later with my comparison of the two styles, but initial observations are a very clean merge/collector on the FP versus my current unit, and being cast hopefully no chance of cracking, but probably at the cost of some extra weight.

Not sure what will happen in the power/torque delivery department, will i gain some spool with shorter runners?
Im currently making 24psi by 3600 so a pretty usable power band (2.3 motor with 280 cams, 380hp atw).

Onto the pics...

The crack:

Current merge/collector versus the FP:

All this had to come off for one little crack:

 

[evo-gsr]

I have the FP race mani on my Evo. No complaints from me and mine would have very similar spool character as you have mentioned above.

 

[bazeng]

Mattresses old car!

Some parts look familiar!

Did you plan on changing the manifold only? It might move your turbo and then require other changes to be made...

What about repairing? And bracing to prevent future cracks.

 

[hy_]

Good to hear evo-gsr, will be interesting to compare the two.
Ive got a dyno print with the current setup so when the FP is on ill touch up the tune, get a new run and over overlay the two prints.

Yep bazeng, it is mattress old car. Much has changed since his ownership but still running a few of the parts that came with the car - big fan of the intake in particular.
I am already onto the repair of this mani, but will keep it on standby - Keen to get the FP on and see how it responds with this setup.
Expecting there may be some minor fab required to get it in, will see whats required when it turns up and i can test fit.

 

[EvoOne]

Look forward to seeing how you go with the FP as I was thinking similar thoughts!

 

[Astrolux]

Hey guys, my stock exhaust manifold has a big crack in it and i will need to get a new one.

I was wondering if someone with the knowledge will know if the FP headers will fit on my galant.
http://www.forcedperformance.net/merchant2/merchant.mvc?Screen=PROD&Store_Code=FP&Product_Code=EMFPRace&Category_Code=DSM-Exhaust

car is completely stock. cheers.

 

[evo-gsr]

Well the OP is talking about putting one on his Galant above, if Im not mistaken......??

 

[Astrolux]

I just wasn't too sure if the different turbos would still mount to it. Sorry for being a noob, i know a little about cars, but not stuff like this.

 

[hy_]

Forgot about this post - Late update, but better than none i guess.

Manifold went on fine, had to redo the oil drain line due to slight difference in fitment.

The tune needed a surprising amount of work given only the manifold was changed, fuel was on the lean side after the change. Suspect the crack in the old manifold may have been there for some time and previous tune changes had accommodated it.

Definitely more responsive down low than the tubular manifold. No real change to top end, though does feel more linear through the rpm range now due to response improvements.

Has not been back on the dyno since the change, so no numbers yet.

The tune needed a surprising amount of work for the change which was a little unexpected

 

[evo-gsr]

Nice looking engine bay you have there now mate.

 

[ENGINR]

I've had no end of dramas with tubular manifolds cracking. When I had my twin-scroll manifold made, the fabricator put slip joints in at either end of the runners, but the minimal bracing that he left in the design still resulted in cracks at the merge collector when the runners expanded/contracted.

I've had the full system braced now - the turbo is supported off a braced cantilever and is free to move on a rosejoint and the wastegates are now supported by a similar setup. The whole intent is to take all the weight off the manifold itself.

 

[bitza]

Too bad forced power don't make one to suit a T3 design.

 

[VIN18M]

6boost do

 

[CLuTZ]

Also Shearer Fab and Punishment Racing.

It's really comforting to see Matt's old car looking better than ever and not pulled apart for parts by someone from NZ :angry:

 

[evo-gsr]

Be wary of Punishment products....they are sometimes not a great finish.
Read plenty about the flanges being warped on the US boards

 

[bj]

The particular weld where the crack occurred looks like they just fused it together, not much of a bead...