: Vacuum readings



JFensty
03-05-12, 08:54 AM
What is everyone getting for vacuum readings at idle? I find it strange to be getting 50-55 in./hg. At idle. All of the other cars I have and have owned were always in the 20-30 range. This is an ls6 with 122k on the clock. Should I be worried or is this a good thing?

JFensty
03-05-12, 06:58 PM
Almost 100 views and no response? I pulled the heads to remove broken exhaust bolts and there was a layer of oil in the intake. Just curious if this amount if vacuum is normal for the ls motors or if there is an issue that I cam address while in the motor. A friend said the cam could be advanced a little too much but as far as I know everything is stock.

CancerJCC
03-06-12, 01:08 PM
Mine Idles around 35 with the Maggie and It was around 30 stock.

*Note I swapped to a 2 bar MAP so the difference could be sensor to sensor vice a change in actual MAP value.

Gus_Mahn
03-06-12, 09:21 PM
I don't think your gauges are correct, or you may be reading them wrong. 30 in HG is pretty much a perfect vacuum. Most engines run in the 16-20 in HG range. A LS6 with what is an aggressive camshaft for a stock car should be towards a lower end of that range perhaps lower.

rand49er
03-06-12, 11:37 PM
I don't think your gauges are correct, or you may be reading them wrong. 30 in HG is pretty much a perfect vacuum. ...Yeah that.

Unless, of course, you're on some other planet.

JFensty
03-07-12, 12:37 AM
I was using my bluetooth obd with the torque app. Used it on 5 different makes and years. Not sure how you can misread a digital gauge. All the other cars and trucks showed 20-26 at idle. Mine was 53. This is why I had some concern.

CancerJCC
03-07-12, 08:41 PM
I was using my bluetooth obd with the torque app. Used it on 5 different makes and years. Not sure how you can misread a digital gauge. All the other cars and trucks showed 20-26 at idle. Mine was 53. This is why I had some concern.

Your readings are probably in kilopascal and what I was referring to with my post. 50 kPa = 14.77 inHg so it seems maybe you are on point? Of course this doesn't explain why the other vehicles you scanned where 20-26. Are the units staying the same from scan to scan or is it loading parameters from the vehicles like HP Tuners does?

JFensty
03-07-12, 09:15 PM
I believe it was reading in/hg for all vehicles. I will check it again this weekend. Motor is apart right now for cam and light porting.
Although that may change things but even with the mileage there is still signs of a cross hatch pattern in the cylinders and no lip whatsoever.

JFensty
03-12-12, 09:15 AM
FWIW just git the car back together. Installed z+ cam for Scoggin dickey, lt, mild port on heads and a ls7 clutch. Still reading 48-52. Odd thing is it only drops to 28-30 at wot. Could some be wrong with the ecm causing it to read inaccurately? Reads great on all the others tested and since it is pulling numbers from the obd port makes me thing there is another issue.

AAIIIC
03-12-12, 09:34 AM
Odd thing is it only drops to 28-30 at wot. Could some be wrong with the ecm causing it to read inaccurately?
If it's showing that it's still pulling that strong a vacuum at WOT then YES, there is something reading inaccurately. Maybe time for a new MAP sensor?