boost problems

[MR2vsAMXbeast]

I have the GReddy Profec B boost controller and when it is set on the low boost dial I can boost up to 10 psi. When the high boost dial is on I can boost up to 13 psi. and then my engine light comes on. After this i cant go over 0 psi. The only thing I can think of is that The controller is set wrong or something was set up wrong.

[scarecrowX]

say hello to fuel cut. search that term and you'll find all the answers you're looking for and thensome.

[JekylandHyde]

The MR2's ECU cuts fuel at 12 psi of boost.
You will need to get a Fuel Cut Defencer or disable FC if you want to boost over 12 psi.

scarecrow, have you been following the BPV thread on mr2oc? I have done some testing with my BPV and it does appear that the valve does NOT stay open at idle.

[scarecrowX]

really? the spring in that sucker is actually pretty stiff (though i can still open it by sucking on it with my mouth- though i don't know whether that points more to spring rates or my sucking ability).

i actually got my hands on one from a local owner that sold his car. i had to make my own VTV but i've been driving it the past few days trying to discern a difference. i'll know more in a little while. i was going to do some pressure datalogging vs time to try to quantify the difference of pressure drop in the pipes, but i'm trying to develop an EMS at the moment as well so most of my time is consumed with that.

so far, all i can tell is that it doesn't sound as cool i need more hours in the day.

[JekylandHyde]

From everything I have tested/seen the 3SGTE, at idle and cruise is getting air from the HUGE hose right after the AFM. That hose goes to directly under the TB and into the idle contorl valve.

[scarecrowX]

that makes sense..

i guess though, my position is still the same- with no pressure differential across the ports, the valve should be closed. i've noticed thus far that it definitely opens easier than the greddy (it does open and close off boost, but i haven't noticed it actually staying open for any length of time), but whether that results in any quantitative performance difference remains to be seen. it's just a feel thing, and it's only my opinion, but throttle response and spool actually feel better with the greddy- though that could be more psychosomatic than anything. i've noticed on my boost gauge as i shift that the greddy, once the throttle closes, returns to a higher psi than the oem valve does. presumably this is due to the OE valve not closing until pressure in the top port exceeds pressure in the bottom port which, due to the VTV, would be ever-so-slightly slower than a normal spring type valve, taking longer to build boost back in the manifold.

as i said though, i've only had it on the car for a few days- not really enough time to draw any REAL conclusions.