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Could the wastegate be stuck open?
I'm away on holiday, but before leaving I managed to find out that the (new) boost solenoid doesn't click and the kickdown doesn't work again. I'm also 99% sure that my car has the transient boost kit fitted!

Es
 

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I'm away on holiday, but before leaving I managed to find out that the (new) boost solenoid doesn't click and the kickdown doesn't work again. I'm also 99% sure that my car has the transient boost kit fitted!

Es
Yours has the gold one and the plastic one right? If so I agree you have transient boost. Does yours have cats?

My 1991 only has the single silver one :( would love a bit of transient boost!
 

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Yours has the gold one and the plastic one right? If so I agree you have transient boost. Does yours have cats?

My 1991 only has the single silver one :( would love a bit of transient boost!
Yes, I have both the plastic and the metal one!

Es
 

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Hi guys,
I just had another fiddle, but not much success....
I checked the plumbing, and that looks to be correct according to the RR Transient Boost paper - assuming that "back of wastegate" is furthest away from the exhaust pipe.
I disconnected the two hoses from the wastegate at the plastic solenoid, which should give more boost if my thinking is right, but I'm still only seeing maybe 300mbar.
I sprayed the manifold and intercooler hose with brake fluid at idle to check for leaks, but all seemed OK.

Before I check the signal from the knock sensors at the ECU, which I think might be a PITA, I'd like to check if the wastegate and/or dump valve are stuck.
What's the easiest way to do that?

Cheers

Es
 

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Good question, I think you need the hand held vacuum tool maybe?
I can hear my dump valve clack as I blip the throttle.
Mike
 

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Disconnect valve and blow air from your mouth thru valve. Then apply 12V DC and blow thru again.
I'm not talking about the solenoid - that works - but rather the actual wastegate and dump valve, both of which have no electrical connections.

Cheers
Es
 

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I now see. You will need a source for compressed air and a pressure regulator. Apply .5 bar and listen for leaks.

The type of waste gate used here has a very low failure rate. If it sticks, the car will make too much boost. The spring is stiff to cause low boost.
Dump valve has a diaphram and it may leak. Test with air and listen for bypass leakage. 1 bar max pressure should be used.
30339
 

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Hi!
I checked the dump valve with a vacuum pump.
The line which is attached to the elbow holds vacuum and also audibly engages the valve. The other line, which has a check valve in it, doesn't. My check valve is leaking, so I blocked off that line. Interestingly, with that line blocked, the gearbox now changes down at higher throttle pedal positions, something it didn't do before!

Couple of questions on the wastegate:

When the plastic boost solenoid is energized, it opens the path between the two attached lines, sending boost pressure from the turbine to the front (where it's attached to the exhaust pipe) of the wastegate. Should that cause the wastegate to open and let less gas pass though the turbine?

Es
 

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Hi Again,
I've managed to finally completely understand the boost system, and also found the requisite sections in IETIS confirming this. So that's good, but I still don't have boost...at least not more than about 200mbar, avenue with the pressure line disconnected.

My car has the transient boost system, which in operation is similar to later cars and Continentals, and has two pressure lines going to the wastegate.
The pressure line from the plastic "Saab" solenoid goes to the front of the wastegate (closest to the exhaust pipe) and opens the wastegate when pressure ist let through.
The pressure line to the back of the wastegate (cars without transient boost don't have this) forcibly holds the wastegate closed when pressure is let through.
I tried applying pressure and vacuum to both sides:
The back of the wastegate holds both pressure and vacuum, and when vacuum is applied I can hear the wastegate moving.
The front of the wastegate holds only pressure, and I can't hear the wastegate moving.

-> I think the wastegate might be partially stuck open!

Another thing to check are the pressure sensors. I'm thinking that if the sensors for the Jetronik isn't reading right, the ECU might be underfuelling and hence not producing enough exhaust gas to spin the turbo correctly.

I'll also want to check what the boost pressure in the line from compressor is. If that's significantly higher than the pressure in the manifold, that would indicate that there's a leak in the ducting or intercooler.

Any ideas would be much appreciated!

Es
 

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I have, but I may need to revisit it.

However, thinking logically:
I've tried disconnected the hoses to the wastegate, and that didn't give any more boost than 200mbar or so, which leads me to think that the wastegate is stuck partially open.
I also connected a second manometer to the hose from the compressor, and hardly got any reading. This again speaks for the wastegate being partially open.

Cheers

Es
 

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I think I have boost!
My TPS, which wasn't an original Bosch, appears to be defective. I changed out the original one a while ago, but this one seems to have given up the ghost again!
I managed to wiggle the defective one so that it gives out the full load signal, and I now see 6-700mbar under Kickdown, which would indicate that the overboost ist also working.
I've managed to find a NOS Bosch TPS, so I'll fit that once it gets here!

Es
 

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Very interesting! Is there a way to quickly test whether a TPS is defective? How did you "wiggle it" ...?!
 

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Very interesting! Is there a way to quickly test whether a TPS is defective? How did you "wiggle it" ...?!
The main issue would be the kickdown not being activated!
I measured mine with a multimeter, and then twisted it so that full throttle was detected, but not idle. One of the fuel pipes on my car impedes the movement of the TPS, so maybe check that out!
 

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The main issue would be the kickdown not being activated!
I measured mine with a multimeter, and then twisted it so that full throttle was detected, but not idle. One of the fuel pipes on my car impedes the movement of the TPS, so maybe check that out!
Maybe reposition it and measure again? It should be possible to move and rotate it a little while screws are not tighten.
 
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