Guest Anonymous Posted November 19, 2001 Share Posted November 19, 2001 just had a quick question for you turbo gurus. this isn't for my zx motor. its for my t-bird. it has the turbo 2.3L motor in it and is currently hittin 15 psi. my question is this: i know about the bleeder valve at the wastegate trick to get more boost, BUT my car has a fuel selector switch in it. which you can set to either reg or prem type fuel. i noticed the only differance in switching it to prem (i'm running premium with a octane booster) mode was that it let me boost to 15 instead of limiting it to 10PSI. i was wondering that if i hooked up a potentiometer to where the switch goes instead of the switch. would that work to let me boost pass 15? or does the wastegate not work that way? i'm really new to turbos. i've read maximum boost but that was a while ago and i have to dig it up out of the rest of my books to read it again. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 20, 2001 Share Posted November 20, 2001 so you guy think it will work?? Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 22, 2001 Share Posted November 22, 2001 still waiting for a answer guys. pretty please Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted November 22, 2001 Share Posted November 22, 2001 Difficult to answer the question not knowing exactly what that switch does. Hitting a switch that allows you to go from 10# to 15# boost means something had to increase the boost, add fuel and retard the timing. If the switch did all that, then it must be hooked into a wastegate solenoid to control boost and the ECM to control fuel and timing. Not sure I would fiddle with that w/o knowing exactly how it works. I would jump on one of the T-Bird SC or SVO forums and ask that specific question. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted November 22, 2001 Share Posted November 22, 2001 actually scottie i did that and as far as i can find nobody has done it. i did find out what that switch controls though. it is a long one get ready. If you look at the hose(s) on your turbo, you will notice that there is a "T-connection" (two outlet connector) on the compressor housing of the turbo (if you have a regular/premium fuel switch). Besides having one hose connection to the actuator diaphragm (as shown above), there is a second hose leading to a solenoid on the fenderwell. The other side of this solenoid attaches to a third hose going from the solenoid back into the intake air before the turbo. When your fuel switch is set to premium, and the computer is happy with the signals from the engine's sensors, this solenoid opens. The passages inside the "T-connection" on 84/early 85 SVOs (and reportedly on the 87-88 Tbirds with automatics, too) are sized so that an exact amount of pressure drop occurs in the line leading down to the wastegate actuator when there is flow through the solenoid. This allows the boost to go higher before the wastegate "sees" it and opens. Because the amount of additional boost allowed is set by the sizes of the air passages in the "tee" in the early SVO (and late Tbird automatics?), the solenoid could stay open all the time (or be totally bypassed), and boost would not exceed the amount that the system is designed for, about 14psi. As long as your boost is greater when you have the switch set to premium than regular, this part of the system is working properly. What you want is to allow the solenoid to bleed off even more pressure. The easiest way to do this is to drill out the passage in the "T-connection" that goes to the solenoid slightly larger. You want to do this one drill bit size at a time until you get a little more boost than you want. A little goes a long way! Then you buy a little plumbing valve with hose connections, and install it in the hose to the solenoid so that you can restrict the flow manually to get exactly the boost you want. Also, if you want to keep the computer from turning your boost down at any time, just bypass the solenoid. ***Note***: This was written for the early SVO (and late Tbird automatic?) version of the motor. The other version (85.5+ SVOs and late Tbird 5 speeds) uses a slightly different system. In this case, the "T-connection" is already sized for maximum boost and does not need drilled out. Boost is instead controlled only by rapid opening and closing of the solenoid, with the duty cycle (proportion of time open) doing the boost controlling. Bypassing the solenoid, and using a valve in its place to restrict the flow through the bypass hose will have the desired results, no drilling required. **Warning** Bypassing the solenoid on this type of system, without a restricting valve in place will cause an uncontrolled overboost condition. that is as quoted from a FAQ from turboford.org they even have a nice little picture sombdy made showing te system for the 87 5 speed T-birds. but init they are describing how to insert a bleeder valve and byass the solenoid. i would really like to find a wa to make the potentiometer work since it would be MUCH nicer to be able to control boost from the dash. if anybody can give me any ideas i would really appreciate it. if all else fails i'l just do the bleeder valve mod but i can hope can't i. i would probably take my intercooler out so i could take a better look at the turbo setup and sizzle my noodle on the problem, but my mom has reign of the garage and the weather has been pretty crappy out here so it will have to wait. Quote Link to comment Share on other sites More sharing options...
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