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Re: Brian, the problem you are describing is fuel interruption
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Posted by aero guy (more from aero guy) on Fri, 20 Jul 2001 14:51:58 Share Post by Email
In Reply to: Aero B-b-b-boost Question! Please Help!, Brian, Fri, 20 Jul 2001 11:20:39
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either as a response to trionic signal(excess boost fuel cut off) or defective component. The engine is trying to protect itself through proper control of the item which is causing the problem, Turbo Pressure. I DO NOT think you have an ECU CONTROL PROBLEM. There are three items that directly are related to trionic boost limitation, so why don't we look at this problem from that aspect? First: those components are the inlet boost air temp sensor (IATS),Manifold Absolute Pressure Sensor(MAPS) and the Fuel Pressure Regulator(FPR) I am going to assume you have taken care of your plugs and DI so knock detection is out of the picture because that is a limitation of pressure and not a cut off response.
Check Sully's results on his measurements of the IATS since I don't have any data on you or your car or where you are I can't advise, but this unit comes into action only at high boost when it is normal.
MAPS is the primary input to trionic max boost limitation,(aside from knock detection). Unless you have capability of graduated boost vice voltage measurements, I would suggest you do the two point check: with the switch on, the voltage across the MAPS is 1.9 volts and with engine idling about 0.5-0.6 volts. If you wish to check further and can keep your volt meter enggaged, the voltage at base boost is 2.55 volts(0.41 bar)about 3.3 volts at 0.75 bar. Cut off for your 95 Aero is 4.2-4.3 volts. 1.11 bar-5 speed. If it runs up to 4.4 volts it triggers a fuel pump relay opening and the fuel flow is cut off - BANG, pressure drops instantly and the engine runs up to cut off and BANG! a few more of these and the gears give up the ghost. The same thing happens with the FPR, but the bang is sometimes softer and the recovery longer, but not always. The FPR is a mechanical device subject to manifold pressure overcoming a spring device by applying pressure against a small diaphragm.

If you have screwed in or out with the boost control rod, you are pretty much on your own here and I really can't help you any further unless you wish to get back to basics and try to solve the problem with known parameters. The trionics computer is a really smart device and has some safe guards set inside that also looks ar rates of change especially at pressure rise reported by the MAPS. Hope you find the problem.
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