injector control

I have an 88 930 turbo with 35000 miles, upgraded turbo, 1.0 bar spring, B&B exhaust, additional injector. The previous owner installed an additional injector that is controlled by an HKS "AIC Additional Injector Control" unit.

When accelerating hard I can hear what sounds like a metal on metal sound (?) (ouch!)coming from the engine area. (The exhaust makes it hard to hear clearly what the metalic sound is.) It has been suggested to me that the metalic sound is originating in the engine and that the remedy is to "adjust" the settings on the HKS unit to better coordinate the fuel/oxygen mixture, thus eliminating the possibility of internal damage to the engine.

My question is two fold... 1. Any thoughts as to the cause/origin of the metalic sound? and 2. Any recommendations for a shop that has the technical know how to adjust the HKS control unit (the manual is VERY technical)?

As always, your thoughts are greatly appreciated!!

If the "metal on metal" sound occures only on hard acceleration, I think it is detonation. The additional injector is there to make sure the engine has "extra" fuel so that it goes a little rich under a heavy load. For a turbo this extra fuel will help cool things down and stop the detonation. The extra injector sounds like it does need tweeking. Assuming that everything is working properly; there are other things that can do to help reduce the heat load. You can back off the timing a small amount, 2 or 3 degrees. You can use higher octane fuel. Can you reduce the boost a little under load?
Bob W.

Thanks for the info. What you describe seems to make sense. I found a mechanic who is familiar with the HKS unit. I'll let you know what he says.

Thanks.

You don't mention a larger intercooler as part of the upgrades. Without the benefits of further intake charge cooling you will have much difficulty avoiding detonation @ 1bar. The extra fuel may help the keep the air/fuel ratio where it belongs under boost, but only increased octane or decreasing intake temperatures will solve the problem.