V70 Tdi - cleaning airways advisable ?

You can certainly *carefully* clean the AMM which is of the hot film variety (or at least was) on your TDi. I would get a can of aerosol Brake Cleaner (it is less aggressive than carb cleaner) with the attachable tube. After removing the AMM from the car, you can carefully spray *across* the film unit (i.e. the way air passes it) There is alittle hole inside which is the sensing element. NB They are very delicate to high pressure! Gently rock the unit and drain out the residue, allow afew moments for evaporation, and then repeat 3 or 4 times until the run-off is clear..

This may improve your situation, though to be fair these do not last forever, and after 165k it will be past its best.

If your hesitancy is generally on a light throttle and accompanied by some soot, i would be diving right into the EGR valve, and blanking it off before tackling the AMM...

Tim. .

when engine is idling - if lower it could be the intercooler that needs to be cleaned or changed. I had this problem with my 850 TDI, cleaning the intercooler restored the pressure to the desired value and the turbolack feeling became much smaller afterwards!

Another possibility is a vacuum leak desturbing the turbo pressure regulation.

Best regards Per

Hi, Thanks for those tips - had not considered either so will check those too,

Thanks,

Nick

....snip....

Just read again, - surely there will be no boost at all at idle ?

Nick

There will be no boost at idle- only when under load beyond 2000rpm or so. I believe stock boost is 15psi (1bar)somewhere after 2500rpm. If its appreciably low, then replace the wastegate diaphragm or wind up the rod abit...

Tim..

Hi Tim Thanks for the reply - I wasn't sure of the figures as I haven't got( can't get) a workshop manual for this model engine, although I think it is a variant of an Audi engine.... just had a look at the engine - is the wastegate on the top right of the exhaust manifold as you look at the engine from the front, if you are familiar with this engine ? Thanks, Nick

The wastegate is on the turbo, circular tin capsule with a hose connected mounted on the compressor housing, and a rod sticking out connecting to a valve on the exhaust housing.

Tim..

You should measure around 1.5 bar when engine is idling this value stays on at higher rew's. Before I cleaned the intercooler the pressure was 1.2 bar at idling. Under heavy accelaration I measure up to 2.4 bar at 4000 rpm. I am using the VOL-FCR software for the measures.

Cheers Per

Hi Per,

I guess this is absolute pressure you refer to - a turbo is not spinning much at all at idle, but spins up at around 1500 rpm and above to boost the pressure above ambient up to its pre-set level, determined by the wastegate settings, typically somewhere between about 1/2 bar and 1 bar, or 7 and 15 psi. There is no "boost" at idle, unlike a supercharger which is crank driven and may well be producing a little boost at idle.

Nick

Your explanation sounds logical. I am using VOL-FCR Live Data Stream option and this tool displays the desired boost pressure and the actual boost pressure at a given RPM. Cleaning the intercooler helped the actual boost pressure to equal the desired boost pressure at any RPM! I am sure that there are other ways to increase the boost pressure.

Cheers Per