vacuum readings
04-30-2007, 10:44 AM
#1
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ok, someone said you can see if you have an intake leak if your vaccuum readings are off. i think i may have one but not sure, i 'think' i hear more noise when i am under boost than normal.
so what is normal vacuum at idle and say 80 mph.
Thanks
so what is normal vacuum at idle and say 80 mph.
Thanks
05-03-2007, 04:55 PM
#3
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Is your car not running right? A vacuum leak WILL show up in low manifold vacuum if it's bad enough.
That said, I think what is "normal" will vary depending on the mileage and any porting. IIRC factory idle is ~750 rpm and 16 to 18 in hg is called for. But many cars either don't idle exactly at 750 (w/o AC, fan or electrical load) and/or have slightly lower vac readings due to age but still run just fine. Still other things like significant elevation above sea-level and even synthetic oil give lower vac readings.
That said, I think what is "normal" will vary depending on the mileage and any porting. IIRC factory idle is ~750 rpm and 16 to 18 in hg is called for. But many cars either don't idle exactly at 750 (w/o AC, fan or electrical load) and/or have slightly lower vac readings due to age but still run just fine. Still other things like significant elevation above sea-level and even synthetic oil give lower vac readings.
05-05-2007, 08:17 PM
#4
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Originally Posted by Signal 2' post='870343' date='May 3 2007, 02:55 PM
Is your car not running right? A vacuum leak WILL show up in low manifold vacuum if it's bad enough.
That said, I think what is "normal" will vary depending on the mileage and any porting. IIRC factory idle is ~750 rpm and 16 to 18 in hg is called for. But many cars either don't idle exactly at 750 (w/o AC, fan or electrical load) and/or have slightly lower vac readings due to age but still run just fine. Still other things like significant elevation above sea-level and even synthetic oil give lower vac readings.
well i think i hear a leak under boost and while my boost hits hard on the need it takes a while for the car to react, meaning i see boost then wait 2 seconds for the HP to hit. i think it is fine on idle, but someone who had a FD thought my vacuumm is near zero at 80. it is a factory engine still but BNR seqentials and a PFC and some intake stuff, but the operation is still the same. Just thought i would ask
05-05-2007, 10:07 PM
#5
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Not a guru, maybe someone else will chime in....
The first thing that comes to mind is not a vacumm leak per se, but just leaking boost. Have you checked all your intake couplings. If you have BNR stage II's , then you should have an efini 'Y' pipe, which would eliminate that coupling. If not, the coupling at the top of the Y pipe leading to your cross-over (the pipe going into the bottom of your IC) is the first suspect. It fails frequently due to all the turbo heat. Leaking there might give some of the symtoms you have. Do you have a boost gauge? What pattern are you seeing under wide open throttle (WOT)?
The first thing that comes to mind is not a vacumm leak per se, but just leaking boost. Have you checked all your intake couplings. If you have BNR stage II's , then you should have an efini 'Y' pipe, which would eliminate that coupling. If not, the coupling at the top of the Y pipe leading to your cross-over (the pipe going into the bottom of your IC) is the first suspect. It fails frequently due to all the turbo heat. Leaking there might give some of the symtoms you have. Do you have a boost gauge? What pattern are you seeing under wide open throttle (WOT)?
05-06-2007, 01:00 AM
#6
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Originally Posted by Razerx' post='870580' date='May 5 2007, 05:17 PM
well i think i hear a leak under boost and while my boost hits hard on the need it takes a while for the car to react, meaning i see boost then wait 2 seconds for the HP to hit. i think it is fine on idle, but someone who had a FD thought my vacuumm is near zero at 80. it is a factory engine still but BNR seqentials and a PFC and some intake stuff, but the operation is still the same. Just thought i would ask
Yikes! I don't even know where to start with this one..
So you hit targetted boost but takes 2 seconds to feel it?? And you hear leaking but you think thats vacuum leak but when you are hitting boost? And your vacuum is at zero at 80MPH?? I am so lost on this one..
05-29-2007, 05:26 PM
#9
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Originally Posted by herblenny' post='870637' date='May 5 2007, 11:50 PM
which BNRs do you have??
Your problem just puzzles me.. Makes no sense how you are boosting fine but lack HP?? Did this problem occur before or after BNR?
well the leak has been track down to either the primary injector seals, or a vacuum line in the rats next. So some weekend when i have a ton of time....
D
06-01-2007, 03:03 PM
#10
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You can disregard your vacuum readings at 80mph. Vacuum/boost is a load indicator, so at 80mph, your can have readings anywhere from 20"hg to 10psi of boost without problem.
What boost gauge are you using? Check to make sure the line isn't pinched.
What boost gauge are you using? Check to make sure the line isn't pinched.