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les_garten les_garten is offline
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Join Date: Jun 2003
Location: PSL, FL
Posts: 861
Originally Posted by RarlyL8 View Post
USA pre-'86 heat exchangers are restrictive to the point that they will not allow bolt-on upgrades to work optimally. You cannot get an accurate dyno comparison on a modded engine because of that. If you were to swap the US exchangers for headers on a stock US engine with a stock muffler you would probably see 20HP. I have never done that test.

Euro heat exchangers will support 400HP and when swapped out with headers will add maybe 20HP or so. More importantly though a proper header design will reduce lag, increase torque, and allow bolt-ons and internal mods to function optimally. You cannot say headers are worth 100HP if X turbo is used. X turbo is giving the 100HP, the headers are facilitating that action.

The more mods you have the more important header design is to function.

Free flowing mufflers make a similar difference in power and engine characteristics.
Hi Brian,
Hmmm, not sure I agree with this statement in general. In particular, to Porsche 930's, I'm not sure either. I agree with it in theory though. I have a friend who has some sort of Dodge RAM diesal truck. He is a Professional, ASE Certified Mech by trade for some 30 years. He made a claim to me that there is a Dual change he could do to his truck that would produce some huge HP and TQ increase. It was a air filter and exhaust upgrade. He calimed that the Diesal was so choked that relieving the restrictions in the two end points would have some sort of huge change.

Of course, this is what K&N and others have been touting for years for everything from a Vespa to a 930. However, it is conceivable that you could take a stock motor and relieve the two ends and make more HP and TQ with an air cleaner change, a header change, and a muffler chnage. Along with an AFR adjustment.

So if you did these changes:

1) Air Intake
2) Headers
3) Muffler

And HP and TQ went up, couldn't you say they were responsible for the change? Or just take Headers and Muffler?

I agree with y'all about the chain of "flow" of air thru the engine and how it "all" has to work, but I can also envision where compromises are made for mass production, EPA, Cost, etc, where optimal conditions may not exist from the factory and a Header change, a muffler change, and an AFR adjustment could unleash some power. I'm talking General here, not necessarily Porsche.

---Les Garten---85 930, Andial IC, GHL Headers, Fabspeed Dual, K-27 HF2, 3.4 JE Full Finned 7.5:1 CR, 964 CAM'd, Carerra 3.2 Manifold Cut/Flipped, Tec3r, Siemans 55#, GSF Fuel Rails, Clewett Crank Trigger, Clewett Cam Trigger,Dual Plugged, ARP Head Studs/Rod Bolts, Clewett Wires.Tial 46mm WG, Tial 50mm BOV, WEVO Shifter,934 Boost Gauge, Wideband EGO Sensor/Gauge, C2T Head Gaskets, '88 MB 300TE,BMW R100RT
Old 02-22-2008, 03:04 PM
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