SAE technical article - looking to improve on Toyota.

[boostjunkie]

I found this:

http://www.radphys.com/2zz_ge_article.pdf

I noticed that the header seems to be pretty symmetrical WRT pipe lengths between the cylinder extractors (is it a 4-1 design with that middle plate between the header outlet or a 4-2-1?).

Now judging by that diagram, it would seem to me that more gains could be had (or at least similar gains) by porting the exhaust manifold vs. getting an aftermarket (and VERY expensive) header. I would be keeping the cast iron design which would promote heat retention as well.

Any other ideas for modifying the existing engine design?

[vrg3]

Yeah, it does look like porting the stock exhaust manifold (to eliminate casting flash and other roughnesses) would get you a pretty good setup. The stock design is very similar to a header. I can't tell for sure, but it does kind of look like it's mimicking a 4-into-2-into-1 header.

Incidentally, it looks like it'd be a good kind of exhaust manifold for a turbo just downstream...

Do you know if people ever have issues with the different cylinders running different fuel mixtures? I know on inline-6 turbo Supras a lot of people do something similar to what we call the "parallel fuel rail mod." Those are of course pushing a lot more air than your car though... And maybe your inline intake manifold with the throttle body on one end partly cancels out the fuel discrepancies... I dunno. You have a returnless fuel system, right?

Knife-edging the throttle body would probably help you a teeny bit too. And, assuming the throttle body has coolant running through it, a throttle body bypass might help a little. You'd probably be able to notice an improvement if you did these two things.

How smooth is your intake manifold? I know the Subaru intake manifolds are just about as bumpy on the inside as on the outside.

I'm curious; are you running synthetic lube?

[boostjunkie]

Still trying to get me to go turbo, eh?

As for the manifold porting, I was told that a company did this and got 3whp. Nothing to write home about. They did assure me that it was as close to equal length as you can get given the tube lengths. Also, it's a 4-2-1.

The intake manifold is actually really rough on the inside, so there's some gains to be had with honing, if not just polishing it.

I'll have to take a look at that TB and plug the coolant passages. Might think about knife-edging the throttle plate, if I can find another one to work with. This can only be done with the 00-02 models, as the newer ones come with drive-by-wire TBs. YUCK!

[vrg3]

Hey, I know your ... erhm... "habits."

Why does a drive-by-wire throttle mean you can't knife-edge?

[kelley]

I would recomend our stage2 ecu for your car.
then you could go force induction safely or just leave it na.

[FG!!]

flow work makes me feel like a nerd. i avoid it at all costs now.