20v exhaust manifold, s/t compared to b/t

[lucasthefallen]

ok, as most of you probly know now i've got a smallport 16v in a fxgt.
im looking at upgrading the exhaust and have decided i want to use a 20v manifold, simply for the fact good aftermarket ones are difficult to get ahold of and they arent cheap.

i already know the the b/t manifolds have bigger pipe diameter, so my question is does that extra size really make a difference over the s/t ones?

and how important is the 2-1 section design? any suggestions on the length?


cheers
lucas

[frost]

well on the 16valve engines i think you could use any of the two st bt size wise maybe the bigger bt is over kill,
have you heard of stepping the exhaust ports? its when you make the diameter of the extractors bigger then the port so there is a step, this is for keeping exhaust gas from re-entering the runner
best way to do it is to have the bottom of the port flat wit the bottom of the manifold. and the top of the manifold higher then the top of the port, so the step is pretty much only on the top half

[cogent]

If you decide to go for it, I have a silvertop exhaust manifold for sale at the moment .

[ants_ae92]

There is one downfall with the 20v manifolds. You have to remove the standard mounting from the 20v collector to the engine has to be removed as it won't fit.

I found I went through several exhaust manifold gaskets and one muffler because there was no lower mounting point to the engine and the vibrations even with new exhaust mounts created several exhaust leaks. It was something I never got around to on the those extractors.

Also the 2-1 section that was made on that exhaust is quite small. It effectively made it more of a 4-1 design as the secondaries were so short.

As for the 2-1 section, it will need to be a tuned length otherwise you will probably lose mid range torque. Working out that length I don't know how.

[AceSniper]

I found I went through several exhaust manifold gaskets and one muffler because there was no lower mounting point to the engine and the vibrations even with new exhaust mounts created several exhaust leaks.

Odd, mine are bolted to the head then no mounting till it gets to the rear muffler (really should put a flexi in ) havent had any leakage issues

[ants_ae92]

I found I went through several exhaust manifold gaskets and one muffler because there was no lower mounting point to the engine and the vibrations even with new exhaust mounts created several exhaust leaks.

Odd, mine are bolted to the head then no mounting till it gets to the rear muffler (really should put a flexi in ) havent had any leakage issues

Had a flexi on mine as well and 2 new engine (gearbox) mounts front and rear but it still happened.

Anyway I would recommend putting a brace to the engine for rigidity and longevity of your setup. Toyota obviously put it there for a reason.