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1991 740... Turbo upgrades/replacement?

Wilford Brimley said:
This thread seems odd for performance:lol: i think the needle half way up the boost gauge is the best part
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Yeah... when my uncle had the car the turbo was replaced by a hack mechanic and somehow the car doesn't make much boost like it did before. I remember back in the day the car use to KICK. I've done most of the other stuff to get it to Stage 0. Now I need to figureout what is going on with the turbo. :rofl:
 
If your stock turbo makes no boost why not figure out why? Last time that happened to me it’s because the cotter pin for the wastegate actuator arm had broken and fallen off. Or maybe you have a leaking intercooler or boost hoses. Or a massive crack in the turbo. Either way, that turbo should make around 8 psi of boost and I feel like figuring out why it doesn’t will be helpful in the long term even if you decide to put a slightly bigger one on.
 
I agree with the current remarks - you have what appears to be a stock setup, with everything looking as it should in the pics you're posting. It would be wise to know where the fault lies, since it may not be the turbo. Could be low fuel pressure, bad cap / rotor, or a range of general tuning things needing attention. Checking the wastegate rod would be #1 on the list..
 
"gauge only really reaches half the boost"- that's where it should be on the stock 13C.
Check the transmission kickdown cable connection at the throttle spool.
 
lookforjoe said:
I agree with the current remarks - you have what appears to be a stock setup, with everything looking as it should in the pics you're posting. It would be wise to know where the fault lies, since it may not be the turbo. Could be low fuel pressure, bad cap / rotor, or a range of general tuning things needing attention. Checking the wastegate rod would be #1 on the list..
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I've just done an overhaul on the car to get everything to Stage 0 except fuel injectors.
So I'm going to look into that shortly after replacing or fixing the current turbo on the car.

ZVOLV said:
A cracked turbine housing can cause low boost.

I wouldn't blame the guy that did the work.
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But the guy who worked on it said they installed a new turbo that was smaller than the one originally that was fitted on the car from factory which is why he was saying its not reaching the original boost targets. I'm not sure how much to believe but I feel like its possibly a wastegate rod issue that was preloaded improperly.

PCH said:
"gauge only really reaches half the boost"- that's where it should be on the stock 13C.
Check the transmission kickdown cable connection at the throttle spool.
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Never goes beyond half though. Apparently when my uncle owned it he said it passes half by 1/4 or more.
 
So, there may be a communication issue - do you mean half of the gauge or half way up the boost section (so approx 3/4 gauge)?

Half the gauge is where you go into positive pressure. If it doesn't go beyond the middle, it's not making any boost at all. Doesn't matter what turbo it is, that would be a setting issue (wastegate, etc.)
 
lookforjoe said:
So, there may be a communication issue - do you mean half of the gauge or half way up the boost section (so approx 3/4 gauge)?

Half the gauge is where you go into positive pressure. If it doesn't go beyond the middle, it's not making any boost at all. Doesn't matter what turbo it is, that would be a setting issue (wastegate, etc.)
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Yeah it doesn?t really pass the middle much. So I suspect it?s barely making any boost at all. :rofl:
 
oldschoolvolvo said:
This. There should be a bit of preload on the wastegate flapper (~1/2 the diameter of the pin). If there is zero preload there will be little to no boost.
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I suspect that's the case.
On peddle to the metal, the boost gauge only reaches less than 1/4 after the half.

I ordered a digital boost gauge to figure out how much boost the car is making and we will go from there. Going to get some ramps and get under the car to adjust the turbo sometime this week. :cool:
 
Update:

Was able to get underneath the car and take a look at the wastegate arm. Pre-load wasn't set properly and essentially it was only fitted on loosely once the clip was taken off.
I couldn't adjust the arm because the lock nut to keep the arm in place was seized. Used a 10mm wrench and turned it as hard as possible and it wouldn't spin loose. The nut eventually gave out and rounded itself with the Openbox wrench. Turning it counter-clockwise felt so tight it wouldn't turn at all.

Any ideas?
 
Take the wastegage actuator off of the turbo and try to free things up off of the car where you have more room to work. Soaking in some PBlaster and a vice grips should help.
 
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