North American Turbocoupe Organization



surging @ 10 psi.
tyreid1 Offline
Junior Member
#1
I'm new to turbo charged engines, (bought my 88 tc a week ago). The problem I'm having is @ around 10 psi.(stock gauge) the car will surge, the psi. will drop a little then go back up. When I flip the dash mounted switch it will go up to around 12-13 psi. before it surges. Is this normal wastegate operation? I'm no rocket surgeon but it seems to me that it should hold a steady 10 psi. and not surge. Will an aftermarket boost control valve resolve this issue?
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zip Offline
Member
#2
I would check your hoses that see boost, if they have cracks they may open up. Make sure your intercooler hoses are tight. The boost control valve will only fix the problem if you have a leak on your boost control solenoid.
Matt
86 TC 5spd:QH/SD,Walbro190,CFI 52#, AFPR,WB,FMIC,3"dp to axle, .63 T3, E6,Stock Longblock.
Shelf:N/A 2.3, Die grinder, Carbide Burrs.
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Pete D Offline
Administrator
#3
Temporarily bypass the stock BCS and run the boost source straight to the WGA. See if it still surges at 10psi.
Pete Dunham


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tyreid1 Offline
Junior Member
#4
ok. I'll try that.Thanks
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tyreid1 Offline
Junior Member
#5
Pete, I didn't run the boost source straight to the WGA. I reattached it to the brass tee fitting on the compressor housing, where the hose came back from the BCS. I essentially took the BCS out of the loop. And that's where I ran into a problem,.... full boost! Should I pull the brass fitting out of the housing,plug it and run the hose straight to the WGA? When I was out test driving the car the gauge went up to 18 psi. with no overboost alarm. Do these cars come with alarms or is that something I have to install?
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tyreid1 Offline
Junior Member
#6
Oh, and while I was on said test drive I had one of those head up my a** moments and thought it would be fun to step on it a little, or a lot as it turned out.Boost got up to 18 psi.( and quickly I might add) I didn't hear any overboost alarm, but what I did hear was a sputter and a pop. Sounded like a backfire, I assume it was from leaning out, since my fuel pump is a stock replacement I'm sure. Anyway, after the "incident" the car still runs good, nothings leaking anywhere,misses so maybe I got lucky and didn't hurt anything. I usually learn my lessons the hard way.
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Pete D Offline
Administrator
#7
You got full boost because the full boost signal was not going direct to the WGA. The line going from one side of the fitting on the compressor outlet to the BCS is the line that can bleed boost signal away from the other side of the fitting where the hose goes to the WGA, if the EEC opens up the BCS to allow boost through and bleed into the line that connects to the compressor INLET. If the EEC keeps the BCS closed then the full boost signal at the compressor outlet flows out the fitting and directly to the WGA such that it starts to open around 9.5 psi. Clear as mud isn't it?
http://www.turbotbird.com/FAQpage/Vac_Diagram.htm

Anyway, to make it easy, the WGA has to be connected to a source that sees all boost, like the vacuum tree. Or disconnect the BCS hose AT the fitting and plug off that port on the fitting. Then the hose fromt the fitting to the WGA should see the actual boost signal and not go over 9.5psi

Quote:I usually learn my lessons the hard way.
Yeah, I can relate! Big Grin
Pete Dunham


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