overboost

[dwall]

i have a 1987 supra turbo. and it over boosts at 3500 rpm and jumps from 10psi to 15psi then hits fuel cut. it is not running an aftermarket boost controller or any other engine mods besides it bored.020. i found it had a stuck wastegate but it was stuck open :aigo:. so how was it overboosting with a stuck open wastegate. i will drive it again tomorrow and see if that fixed it but. i guess my main question is how was i overboosting with a stuck open wastegate.

Dan

 

[Supracentral]

i guess my main question is how was i overboosting with a stuck open wastegate.

If it wasn't stuck all the way open, you can still overboost.

 

[dwall]

ya it wasn't stuck fully open just a little. so it makes sence that it was still over boosting.

Dan

 

[nofx230]

is it the factory ct26 the car came with?

 

[ForcedTorque]

If you have no mods how are you even getting 10 pounds?

 

[nofx230]

poor turbo must be fighter for its life trying to push air with no other mods

 

[Supracentral]

If you have no mods how are you even getting 10 pounds?

I've seen a few that could squeak out 10psi with no mods before hitting fuel cut. With a Lexus and S-AFC, I've seen them hit over 20 on stock fuel (but not for long before either the motor melted down or the turbo blew apart).

 

[dwall]

im sorry it has a fmic, lexus afm, k&n cone, and its bored but that's it. it might be a shitty boost gauge. the gauge came with the car. but the stock 1 says 8 and the other 1 says it goes from 10 to 15. and yes its the stock ct26

Dan

 

[nofx230]

but your still running stock turbo elbow and down pipe???

 

[Supracentral]

but your still running stock turbo elbow and down pipe???

Modded elbow and DP will give you quicker spool and will support higher flow, but the stock stuff is capable of way more than 10 psi.

 

[Supracentral]

but your still running stock turbo elbow and down pipe???

Modded elbow and DP will give you quicker spool and will support higher flow, but the stock stuff is capable of way more than 10 psi.

 

[dwall]

yeah still full stock exhaust

 

[ForcedTorque]

Lexus AFM, but no injectors?

 

[JStoked]

Dude check to see if your waste gate is shimed? It really sounds like a waste gate problem to me.

 

[dwall]

Still stock injectors, how would I check to see if my wastegate is shimed?

 

[TRDownShift]

If there are washers under the bolts that hold the waste gate arm to the turbine housing then it's shimmed (thats all shimming is... just lob some washers in there and it holds the waste gate shut longer)

 

[dwall]

There isnt any washers but there is a v looking thing on there that has a rivot through it.

 

[IndigoMKII]

Still stock injectors, how would I check to see if my wastegate is shimed?

So lets see.. a lot of boost on lex afm and stock injectors. I'd start saving your money because at this rate something WILL let loose inside the engine and/or turbo.

Try to pull on your wastegate with your hand and see if it even moves. The bracket holding the wastegate will sit flush against the compressor housing.

 

[ForcedTorque]

Get a stock AFM on there until you have the upgraded injectors to match the added air flow. BTW, look at your injectors as best as you can, and tell us what colors you see.

And when messing with the wastegate, pay some attention to the rubber boot on the back side. It might be hard to get to in the car, but you could take the two bolts out of it, so it hangs down a bit. This is what you are looking for. Notice I am pulling out on it to expand it. If not expanded, you would never see this hole. BTW, there are actually 2 holes in this picture.

 

[dwall]

The injectors have black plugs but the bodie part is silver