lowish vacuum

[E30godz]

I have been noticing lately that my engine vacuum has gone from 18-17 hg/inch to about 14 or 15 hg/inch. I assumed vaccum leak but checked the usual suspects and found nothing. The car also runs fine/idles fine. How much of a chance is there that i fucked a piston ring? car has 130k miles now and has just recently begin boosting about 5-6 psi for short instances. guess ill whip out the compression tester

also i could tell no difference between the numbers of the compression test when the throttle shut, or completely open. I also had all the spark plugs out.

[m42technic]

Uhh... youre running a turbo, wouldnt you inherently have less vacuum?

[E30godz]

well....not at idle....on further investigation, when the car warms up its only about 1 inch/hg less than it used to be.i may just not worry about it

[E30godz]

did a compression check today.

150, 142, 135, 141 150 147.

these were done on an engine that had beens sitting a around 2 hours probably?

TCD recommended that i switch to mobil 1 10W-30 instead of of staying with the 15W-50

car idles fine, vacuum is low on startup (about 11-12 hg/inch and when its warm its around 16 hg/inch.) the car is also happy to build 6-7 psi and spikes to 9, to 5000 rpm. since i had problems with the 30 lbers, i swapped in some 19's and dump fuel at WOT. pulls very very hard. Im not going to get over 5grand untill i work out the extra fuel problems. I also mounted my boost gauge right behind the steering wheel...looks great there.

[PeterCip]

did a compression check today.

150, 142, 135, 141 150 147.

these were done on an engine that had beens sitting a around 2 hours probably?

TCD recommended that i switch to mobil 1 10W-30 instead of of staying with the 15W-50

car idles fine, vacuum is low on startup (about 11-12 hg/inch and when its warm its around 16 hg/inch.) the car is also happy to build 6-7 psi and spikes to 9, to 5000 rpm. since i had problems with the 30 lbers, i swapped in some 19's and dump fuel at WOT. pulls very very hard. Im not going to get over 5grand untill i work out the extra fuel problems. I also mounted my boost gauge right behind the steering wheel...looks great there.

what to you mean it spikes to 9.. mine build to 11 almost instantly and holds there.. ther are no spikes what-so-ever. what turbo are you using? the only other person I heard about this spiking from was bimmerjim, and he seemed completly incompitant.
-p

[E30godz]

its a wastegate thing.

[E30godz]

all boost spiking is, is when the turbo builds boost faster than the wastegate can respond, usually only happens for a second or two and then settles down. Like ive im off the gas at 5 grand and then floor it, it spikes up to 9-10 PSI and then settles down...external wastegates have this problem less i believe.

[E30godz]

ok, Update....the problem mysteriously went away! and the vacuum and everything was back to normal...idling at 17-18 Hg/inch.....BUT i put in those turbo spark plugs (W5DC) and the fucking problem came back! now..what would you suppose this is? i have my thoughts but id rather hear some others

[DaN]

If you aren't noticing any performance problems, and there are no vacuum leaks, then don't sweat it dude. You'll live longer. ;)