300tdi turbo

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danny6801

danny6801

Well-Known Member
Posts
1,665
Location
North Wales
Hi i have changed my turbo on 90 300tdi as was having problems with power and overboosting. But the problem still occurs can get to 1.5 bar if I let it. Another problem is the speed doesn't seem to match the boost goes of its head but doesn't go fast. My father in laws disco would leave mine and his can sit at 70 no problem as I also have a disco transfer box in mine. I've checked the hoses but they are all silicone no problem there boost actuator moves freely intercooler is uprated 1 it also has a boost pin in if that helps.
 
1. The boost actuator shouldn't move freely, there is a fairly strong spring that should keep the wastegate closed until boost pressure opens it.
2. The wastegate flap itself should be free (when the actuator is disconnected).
3. Have you actually tried adjusting the boost pressure using the threaded rod on the actuator shaft.
4. Are you sure your gauge is accurate (being new doesn't necessarily mean its accurate)
 
Hi yes actuator moves when I've got pair of grips on it but not easy. I've never tried adjusting the rod. How do you tell if gauge is out as never had an issue with it before.
 
I'd remove the boost pin, reset everything to standard, timing, fuelling etc, give it a service and get it running correctly, than take it from there.

What else is not standard, apart from the boost pin, for instance, is the fuel pump altered, the timing, etc etc.

And when you do mods, do them one at a time, but mark known 'running well' parts and/or positions before you adjust them.
 
danny6801 said:
Hi yes actuator moves when I've got pair of grips on it but not easy. I've never tried adjusting the rod. How do you tell if gauge is out as never had an issue with it before.
Click to expand...
Not too sure if this would work, but try applying varying regulated air pressure to the wastegate servo, to see if in fact the servo is functional, the wastegate may be free to move but the servo may not be pushing it, the engine of course should not be running whilst doing this, my 300Tdi Disco runs only one atmosphere of boost, so 14.7psi, at full boost, it is bog standard.
If your tiurbo is overboosting it should not make a lot of difference but to get benefit from any extra boost you also need more fuel to burn with the extra air supplied, a guy I know has a variable vane turbo fitted to his Tdi and it runs easily up to 21psi boost regularly, he has fuel increased to make use of the extra air which equals more power.
Also remember that engine rpm has no strict relationship to boost, it is expanding exhaust gas via burning fuel that spins the turbine up generating the boost.
Has anyone made adjustments to the fuel injection pump, and where does your boost gauge tap its pressure from?
 
Yeah thanks I will try that. Also would checking valve clearance be a good idea to check with lack of power as I've never checked them in the 8 years I've owned the car.
 
danny6801 said:
Yeah thanks I will try that. Also would checking valve clearance be a good idea to check with lack of power as I've never checked them in the 8 years I've owned the car.
Click to expand...

Jeez yes .. bearing this in mind, give it a full and complete service including all oils and filters. I'd also remove the inlet and exhaust manifold to see if there is any blockage, and the exhaust. Diesels like free running air and lots of it!
 
danny6801 said:
Hi yes actuator moves when I've got pair of grips on it but not easy. I've never tried adjusting the rod. How do you tell if gauge is out as never had an issue with it before.
Click to expand...
15 PSI is 15PSI, if you can set a spare tyre to this pressure (use a garage pump if you don't have your own tyre pressure gauge) and have a schrader valve / tube (from an old foot pump) that you can connect to your boost gauge then the gauge should read 15PSI / 1 Bar
 
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