3sgte fuel cut question - Toyota Nation Forum : Toyota Car and Truck Forums

MrJoe · 06-25-2005, 09:20 AM

i need some tips on what sort of issue im dealing with
my car is currently cutting at about 15psi (91 turbo)
this started happening after i put on exhaust/downpipe(ko racing)
besides this cut it seems to run and boost just fine
i have a boost controller but have not put it in yet, im also planning to make an fcd but what i want to know if this problem could be the wastegate acting screwy and if so how do i check to make sure the wastegate is working properly
i dont want to put in the fcd and boost controller thinking that it will solve the problem only to find out my wastegate is screwed up and end up pushing 25psi...that might not be a good thing

suggestions welcome

JekylandHyde · 06-25-2005, 03:56 PM

Do you have a boost gauge?

OEM fuel cut comes on at 12 psi, not 15.
A healthy running stock MR2 runs 7-11.8 psi of boost, so opening the system up with intake & exhaust is more than enough to just get you over 12 psi to hit fuel cut.

IF you have a boost gauge and you are confident that it is accurate, you can eliminate fuel cut by corking the vac line to the OEM map sensor. You will lose function of the OEM boost gauge as well, but that is worthless anyway.

Buying or building an FCD is good if you want to RAISE fuel cut and keep it as a safety measure.

MrJoe · 06-25-2005, 05:51 PM

i have an autometer gauge and it seems pretty accurate
but the cut seems to happen on that gauge when it hit 14-15 pounds or so
on the vacuum at idle it shows about 20 in hg, i think thats about right so i guess its accurate
ill try what you said with the map
wish me luck i dont blow up my engine

ill be trying it probably the first night i get my car back (its in for paint now) so ill be pissed if i fry it all...
i assume i should put in the boost controller first?

Dr Tweak · 06-25-2005, 06:32 PM

Quote:

Originally Posted by JekylandHyde

Do you have a boost gauge?

OEM fuel cut comes on at 12 psi, not 15.
A healthy running stock MR2 runs 7-11.8 psi of boost, so opening the system up with intake & exhaust is more than enough to just get you over 12 psi to hit fuel cut.

IF you have a boost gauge and you are confident that it is accurate, you can eliminate fuel cut by corking the vac line to the OEM map sensor. You will lose function of the OEM boost gauge as well, but that is worthless anyway.

Buying or building an FCD is good if you want to RAISE fuel cut and keep it as a safety measure.

Actually I think in '93 the fuel cut went up to 16 psi. And yes, you need a FCD (fuel cut defenser) to boost higher than that.

-Doc

JekylandHyde · 06-26-2005, 05:03 AM

I would not assume your boost gauge is accurate. Without a boost controller, you should not be able to boost that high. Opening everything up you might hit 13 ... 14 if you are lucky.

Dr. Tweak, I think you are correct that FC was raised in '93, but he stated in the first post he has a 91.

MrJoe · 06-26-2005, 06:57 PM

what would be the best way to verify how accurate my gauge is?
it was purchased brand new...
it shows the exact same amount of vaccuum at idle as my friends all-trac, but beyond that thats all ive been able to do to verify accuracy
is there any easy way to verify the wastegate is working properly?
thanks for all the help with this everyone...this problem has been bugging me for a while, im just apprehensive to start throwing parts at it or adding new variables....i dont really wanna blow anything up

MrJoe · 06-26-2005, 10:53 PM

i forgot to mention that after having the exhaust put on it does make a sort of "jingle" sound

the sound seems to happen mostly at idle and accel, but seems to go away when i dont apply throttle
someone suggested that the sound may be that actual gate part is not attached to the actuator arm and is just moving freely....