951 Overboost?
Discussion
Hi Guys,
A quick question about my 944 Turbo. Ever since I have had it maximum boost has read at just over 1.2bar. It has always pulled hard and I have had nothing but compliments. However over the weekend it has decided that 1.2bar is no longer cool and that at 6000rpm it will boost to 1.8bar (which is another swift kick in the rear). As of this morning it will boost to the gague maximum of 2.0bar. I don't think that this is a faulty gauge issue - The thing is going ridiculously quickly all of a sudden...
I am pretty sure that this will prove unhealthy for all parties if allowed to continue...
Let me know what you think - am I wrong about recommended boost levels?
Ash
A quick question about my 944 Turbo. Ever since I have had it maximum boost has read at just over 1.2bar. It has always pulled hard and I have had nothing but compliments. However over the weekend it has decided that 1.2bar is no longer cool and that at 6000rpm it will boost to 1.8bar (which is another swift kick in the rear). As of this morning it will boost to the gague maximum of 2.0bar. I don't think that this is a faulty gauge issue - The thing is going ridiculously quickly all of a sudden...
I am pretty sure that this will prove unhealthy for all parties if allowed to continue...
Let me know what you think - am I wrong about recommended boost levels?
Ash
The gauge on the dashboard actually only reads a maximum of 1 bar boost.
The dial goes to 2 bar, but you must remember that atmospheric is 1 bar, so when your gauge reads 2bar you are actually getting 1 bar of atmospheric and 1 bar of boost.
Turn on your ignition but dont start the car and the needle should sit at 1 bar.
In normal use you should hit a maximum of 0.8 bar boost (1.8 on the gauge), but it is very hard to read on the dash gauge as the lines get closer together as it aproaches 2 bar. If you want to run at higher boost than factory you really need to get a proper auxilliary boost gauge to keep an eye on things
The dial goes to 2 bar, but you must remember that atmospheric is 1 bar, so when your gauge reads 2bar you are actually getting 1 bar of atmospheric and 1 bar of boost.
Turn on your ignition but dont start the car and the needle should sit at 1 bar.
In normal use you should hit a maximum of 0.8 bar boost (1.8 on the gauge), but it is very hard to read on the dash gauge as the lines get closer together as it aproaches 2 bar. If you want to run at higher boost than factory you really need to get a proper auxilliary boost gauge to keep an eye on things
diver944 said:
The gauge on the dashboard actually only reads a maximum of 1 bar boost.
The dial goes to 2 bar, but you must remember that atmospheric is 1 bar, so when your gauge reads 2bar you are actually getting 1 bar of atmospheric and 1 bar of boost.
Turn on your ignition but dont start the car and the needle should sit at 1 bar.
In normal use you should hit a maximum of 0.8 bar boost (1.8 on the gauge), but it is very hard to read on the dash gauge as the lines get closer together as it aproaches 2 bar. If you want to run at higher boost than factory you really need to get a proper auxilliary boost gauge to keep an eye on things
The dial goes to 2 bar, but you must remember that atmospheric is 1 bar, so when your gauge reads 2bar you are actually getting 1 bar of atmospheric and 1 bar of boost.
Turn on your ignition but dont start the car and the needle should sit at 1 bar.
In normal use you should hit a maximum of 0.8 bar boost (1.8 on the gauge), but it is very hard to read on the dash gauge as the lines get closer together as it aproaches 2 bar. If you want to run at higher boost than factory you really need to get a proper auxilliary boost gauge to keep an eye on things
The car should be pulling vacuum at idle surely?
My factory gauge shows zero bar when running at idle... it will also tend towards zero when I change gear. I had never considered that it should be registering 1 atmosphere the whole time - but I don't think I have seen any other gauges do this either... can I get a definitive answer from the 951 owners on this one???
Ash
Ash
0 at idle and somewhere around 1.8 - possible a bit more mometariy at full boost. If you are geting 1.2 you are hardly booting at all and need to get it looked it. You are getting nothing likes the car's full potencial.
first thing to do is check the valuum hoses are all connected - they are pesky little blighers but really easy to fix
first thing to do is check the valuum hoses are all connected - they are pesky little blighers but really easy to fix
My 951 (250 bhp) showed about 1.8-1.9 bar at full boost and I am sure the explanation of 1 bar atmospheric pressure + 0.8 bar turbocharger boost is correct. The performance you are getting is the one you should have had all along - they are very quick cars.
Do not know why you had such low boost before, but hopefully the problem will not come back.
Do not know why you had such low boost before, but hopefully the problem will not come back.
Diver said 1 bar with ignition on engine off. You should see vacuum at idle (engine on). With standard chips anything much over 0.85 (1.85 in dash guage) and you will hit the overboost. Start going off the top of the guage with modded chips and you may run lean and detonate.
loose the boost line to the wastegate and you may hit overboost, you may find the exhaust pressure opens the wastegate anyway dependant on wastegate spring condition.
Tony
loose the boost line to the wastegate and you may hit overboost, you may find the exhaust pressure opens the wastegate anyway dependant on wastegate spring condition.
Tony
The car is going into Hartech next week while I am away on hols... its a 1991 on a J and has done 77k - I am tempted to get them to replace the wastegate anyway - although my insurance company will probably charge me liberally for such an "upgrade". Can't wait to have that conversation with their call centre girl:
"I just wanted to let you know that I have replaced the factory wastegate, you know how those springs go... I have replaced it with a dual port aftermarket part."
"Oh. Wastegate... thats nine letters... hmmm... your premium has gone up £400 sir."
Or should I just let them do their "Category C" Service (wallet trembles) and fit new vacuum lines and a new gate myself???
"I just wanted to let you know that I have replaced the factory wastegate, you know how those springs go... I have replaced it with a dual port aftermarket part."
"Oh. Wastegate... thats nine letters... hmmm... your premium has gone up £400 sir."
Or should I just let them do their "Category C" Service (wallet trembles) and fit new vacuum lines and a new gate myself???
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