oh the joy

[bentvalves]

so, I decided to swap back to the stock cast iron turbo manifold on my setup. I like that 1/4 and 2/3 runners are paired, and therefore energy at turbine wheel per engine revolution theoretically should be greater.

Im using the same turbo as before, 2871R / 63hotside / 3" inlet. With the XS power tubular manifold I could hold actuator pressure to 25 psi no overboosting issues. Now with the stock turbo manifold, Im having issues where I absolutly cannot control boost. To simplify diagnosing the problem, I physically removed the actuator arm off the wastegate flapper and it still makes 25+ psi slowy no problem but directly related to engine RPM.

I have a few options, both of which I think will get me nowhere.

-I have an 86 hotside kicking around....I could install that, but I think its just going to take longer to overboost

-Port the hole in the turbine housing as big as I can go with a fair amount of overlap still being provided by the flapper.

what I am thinking of doing is installing ca18de camshafts or ca18det cams to bump VE down a bit. Right now I have tomei 256 cams in the head. Theoretically they are going to provide the turbine with more energy.

anybody using a stock cast iron turbo manifold with an upgraded turbocharger pleasse chime in.

[float_6969]

That's crazy, are you sure you're timing is retarding too much under boost? That will make the turbo over-spool.

[bentvalves]

pretty sure its good, but I will add some and see if it remedies the problem.

[r34 gtr]

So.... The problem is?

[bentvalves]

pretty sure I have to much turbo on the stock mani with small runners and velocity at the turbine wheel as a result is through the roof. with the flapper door physically unhooked it still climbs past 25psi

[zmannz]

Are you saying with a totally open wastegate, you can build boost still?

[zombieslider]

thats what im reading

[bentvalves]

indeed mates 20+ psi is what i was seeing with the flapper flapping in the wind.

I capped a -3 AN fitting on the downpipe however (used to reference exhaust pressure) and with the actuator hooked up I build boost at a more realistic rate and all is well 25psi target though, any lower and it will briefly stabilze and then begin its climb past 20psi slower but related to engine RPM.

car rips tits by the way. turbo spools harder (sound/tq) surges harder and louder and has a much broader tq curve

super exciting
Modified by ks13 at 6:53 PM 10/31/2009

[float_6969]

Building boost with the wastegate open on and internal gate isn't uncommon. My S15SR T28 would do it with the SSAC manifold. It didn't build boost till about 6K though and only made 8psi, but it would still do it. I also had WAY too much timing retard due to the high compression I was running.

[r34 gtr]

Oh, I was just saying I didn't see anything wrong with 25psi. That is all.

[bentvalves]

nothing wrong with 25psi, but 2 bar right when you put your foot into doesnt make happy engine parts and turbos.

[mbmbmb23]

http://www.aaroncake.net/rx-7/s4wastegate.htm

[bentvalves]

http://www.sxoc.com/vbb/showthread.php?t=394914