I have a 87 gl-10 wagon thats seems to be falling on its face after 5000rpm.

I am running stock turbo top mount intercooler boost set at 8lbs. and a HKS super afr fuel computer. It feels like the valves are floating sometimes at 4500 and higher. Sometimes it doesn't come on till after 5000. Today I noticed that at this point my a/f gauge goes lean really fast. So I tried putting more fuel into the motor at this rpm with the super afr. It works, right before 5000 it goes really rich from my adjustments to the fuel curve and then after 5000 goes instantly lean. I unplugged the super afr and still same problem. It is not a gradual change on the gauge. On my autometer gauge it goes from middle point in the green to red instantly.

 

Could this be the fuel cut. I heard it was supposed to kick on at 10 lbs. But I am only running 8lbs. I watch the boost gauge and it is staying exactly at 8 before and after the motor falls on its face. I am not hearing any signs of knock though. Has anyone had this problem. I pulled the spark plugs and put a scope in to check the tops of the pistons. No sign of detination.

 

What does it feel like when the fuel cut comes on.

Where is your 8psi measured? (before/after the IC?) if its after the IC, there may be close to 10psi before it.

It is measured right off the turbo before the intercooler

You might want to plumb your boost gauge in after the intercooler, like somewhere on the intake manifold, instead of before. This way, you will get a true reading of your boost, as it is exactly what the engine is recieving.

 

To answer your original question, fuel cut feels like hitting a brick wall while you're driving, literally. It is a very violent and unpleasant jerk when you hit fuel cut. Almost as if you were driving and someone chained your drivetrain down and it reached the end of the chain's length. I hate hitting fuel cut. It is no fun at all.

 

Oh, and I'm pretty sure that you already know that if your A/F gauge is showing that you are leaning out really quick, you need to make some fuel system mods. A higher flow fuel pump or brand new OEM replacement, an adjustable FPR, a piggyback fuel computer(i.e.: APEXi SAFC, Field SFC, Greddy EManage, etc.) or a standalone fuel computer like a MegaSquirt. You may even want to add a 5th injector (comprised of a Hobbs switch and a cold start injector from either a VW or a Saab.) It is absolutely crucial to get more fuel into the engine somehow. Otherwise, bad JuJu!!! You can cause all kinds of engine damage if you don't.

Hey thanks alot. For some reason it never came to that it is just running out of fuel. I have a high performance pump and adjustable regulator with boost reference port that I will try to install this weekend. See if that cures my problem.

 

 

Also does anyone know what voltage the fuel cut does come on at. I have been talking to a guy at HKS to see if their fuel cut defender can be made to work for the older subarus. thanks everyone