Porsche Enthusiasts Club Forum

Hi
can any tell me what the correct boost is on a stock 1991 944 turbo?

I have had all the performance parts removed from mine it now shows about 1.1 max is this correct?

thanks ken

Service manual says

Maximum boost pressure of 1.75bar (absolute value) is reached at approx 3000rpm. At higher engine speeds (engine type M44.51) the boost pressure drops again and reaches a boost pressure of 1.52bar at 5800rpm. With engine type M44.52 the boost pressure remains constant at 5800rpm of 1.75bar and drops only after this value has been passed.

You have the M44.52 or 952 engine so max boost for longer If your looking at the stock gauge on the dash it ain't all that accurate. Manual says theres a special tool 9103/2 to measure charging pressure accurately.

Maximum boost pressure of 1.75bar (absolute value) is reached at approx 3000rpm. At higher engine speeds (engine type M44.51) the boost pressure drops again and reaches a boost pressure of 1.52bar at 5800rpm. With engine type M44.52 the boost pressure remains constant at 5800rpm of 1.75bar and drops only after this value has been passed.

You have the M44.52 or 952 engine so max boost for longer If your looking at the stock gauge on the dash it ain't all that accurate. Manual says theres a special tool 9103/2 to measure charging pressure accurately.[/quote]

Thanks

So should I be worried if the dash gauge only goes up to 1 bar position?........

Quite honest I never look at my gauge, always hanging on for dear life But I suppose once you've seen its a bit out it'll always be on your mind so it maybe an idea to get it checked as per the manual by the guys who put the stock items back on. You've gone back from a DPW and boost controller etc haven't you so I guess just as many problems could occur putting it back as it could of modifying the boost in the first place (I've been round Jon Mitchells garage to long I think and seen to many bodges, it's made me very sceptical )

yes your probably right it's me being overly fussy ........the car runs great and the garage seems to have done a fantastic job
...........If it aint broke don't fix it .......

The standard dash gauge shows boost including atmospheric pressure (which is 1 bar). So if it reads 1.1 bar, it’s actually saying 0.1 bar of boost. That’s not very much.

If the car feels like it’s boosting well, then it’s probably a gauge problem and not a big deal. I’d probably at least make a phone call to the garage who did the work and ask what they think though.

I'm sure its doing more than that the gauge needle goes from the 10 o'clock to the 12 o'clock.....garage tells me this is correct......

.......

The garage doesn't seem to know 944 Turbos. A stock 1991 Turbo should make 0.75 bar of boost as already said, so your needle should be very close to the 2 bar reading at the far right of the boost gauge. This is because the gauge also includes atmospheric air pressure of 1 bar.

If you really are making only 0.1 bar of boost then your car will be very slow and possibly has less power than a normally aspirated 2.5 Lux due to the lower compression engine. I would get it checked asap and hopefully it's just the gauge but if you've had all the modifications removed and an old wastegate refitted I would suspect a boost leak somewhere or a worn out spring in the wastegate

Thanks Paul ...I will get it checked

OK I think I understand now if I turn the ignition on but do not start the engine the gauge reads just under 1bar ......so I guess the gauge is reading OK.........So yes I am only getting about 0.2 bar max boost.........got a noisey tappet as well!

Spoke to the garage today they have told me that they had to bypass the cycleing valve ...not sure of the reason why but they have ordered a new one

would this bypass give me low Boost?

Very likely without a manual boost controller, when the boost is restored it should feel much quicker, though it may be worth refitting the boost enhancer to bring the boost on earlier.

thanks
I am inclined to keep it stock.....if goes half as fast as did before I will be more than happy