3s manifold, since jay thinks my post need help ;) Options

[playr158]

We've all seen the big, blingy exhaust manifolds on some of the expensive turbo kits with long pipes running up and over and under and down. The manufacturer says it provides equal length tuned runners to scavange the exhaust away from the cylinders. Worth the money? Usually not.

Turbines run on heat. The hotter the exhaust, the faster they spool and the more boost they can make. Need proof? Try this for an experiment on your EMS: take out several degrees of timing in the spoolup and boost region of your maps. The EGTs climb and you'll notice faster spooling and, if your turbo setup is right on the edge of boost creep, you'll get more boost creep.

The problem is, those beautiful, long, shinny pipes act as radiators. They lengthen the distance that the hot exhaust must travel between the port and the turbine and radiate that heat off into the engine bay where it becomes a liability rather than a benefit.

What about the scavenging effects? Bogus! As you start to push your turbine to make big power (whatever big power is for your turbo) exhaust manifold pressure will increase substantially and the scavenging effects of the returning finite pressure waves is greatly minimized. So much for all those beautiful pipes snaking all around the engine bay.

What works best? Short pipes coated with a thermal coating. In fact, the stock exhaust manifold coated and ported is probably going to outperform just about anything you can get out there.






-Thick-walled mild steel pipe elbows
-Ceramic coated inside and out
- around 5" flange-to-flange.

Log style manifolds are AWEFUL... Nearly ANY other design you can come up with will increase power over a log-style manifold. The problem is that exhaust gasses have to sharply change directions when they ram into the back wall of the "log". Some log manifolds even have the two cylinders on the ends fire directly into each other. Hardly ideal.

If you look at the picture of my manifold I posted above you'll see that the transitions are smooth. Whenever two runners merge together the exhaust gasses are flowing nearly parallel before they merge. The two center runners have nearly a straight shot out of the head into the turbine. You can actually see right through the manifold when you look into those two runners.

I absolutely love to see these "I have no data or can state no physical principle as to why your logical argument is wrong, but I remember somewhere maybe seeing a car that might or might not have had 4 cylinders or even a turbo with a manifold that had longer pipes making more power across the entire powerband" statements followed by a request for somebody show dyno proof that the stock manifold makes more power.

Just to keep things honest, lets all keep in mind that the stock exhaust manifold is not a "log type" manifold. With the two modifications I mentioned, I would feel comfortable recommending that it be used on setups aiming to make 500rwhp or more.


CREDIT TO:(mrcontrols team http://www.mr2oc.com/showthread.php?s=&threadid=66293)

This post has been edited by playr158: Feb 16, 2006 - 4:36 PM

[jgreening]

Hey Dan, you missed the part where this was posted by Ricky in 2004 and he is now changing to a tubular exhaust manifold due to the restriction of the stock unit. I am sure this was influenced in part by the results obtained by CJ Motorsports and Full Race. This information is old, outdated, and highly misleading. A properly made tubular manifold will DESTROY the stock unit in terms of power delivery.