Vacuum Question
 

My boost gauge reads around 10-11 psi vacuum at idle. As I recall it used to read close to 20 at idle. Boost reads normal at around 12-8-12 with Efini twins. What kind of vacuum should I expect? Yes I searched before starting this thread. Thanks

need more info on motor! are you on stock ports? or is the motor ported? a healthy stock port motor should have 16-18 psi of vacuum at idle. but a lot of things can effect this reading so more info about the car and mods are needed.

Jeff

Sorry, stock motor all the way around. The only thing new are the '99 turbos.

Youve got a vacuum leak or low compression. For the most part, vacuum is not a perfect indicator of engine health, unless it changes drastically (as it seems to be in your case). I would suggest getting a compression check. If it turns out ok, then I would start looking for a vacuum leak.


BTW, who installed the new turbos?

Vacuum readings also vary widely with rpm and the accuracy/setup of the boost gauge, so basing anything on the vacuum reading at idle is a crapshoot at best.

BTW, vacuum markings on most boost gauges that read pressure in psi are in inHg (inches of mercury), not psi.

I had the turbos done at Alamo Rotary in San Antonio.

I have not personally had work performed at Alamo rotary, but just a quick search did not yield a lot of positive results. I didnt see any horror stories about f'ed up engines, but I only read through 4 threads. I am in no way saying that this shop caused any problems, but its something to think about. If the mechanic working on your car was inexperienced, or careless, who knows what kind of havoc it could wreak.



How is your car running now? Does it idle funny or have other problems? Did this vacuum reading change slowly over time, or suddenly? If it happened suddenly, where you driving the car hard? Besides the compression check, you may want to check your air pump to see if its working. IIRC, the A/C fuse is also the air pump fuse. Mine had blown a while back, and I noticed a drop in vacuum. Not as significant as yours, but its worth checking.

Alamo Rotary
 

Actually Alamo is pretty well known. Tito, the owner is very experienced but I have read on this forum that he is more expensive than others. He is one of the few shops that does an 3 rotor conversion and he did a beautiful 3 rotor RX8. The work I had done was quite awhile ago. It ran great when I got it back. At the time he did tell me that compression on one rotor was not great and the idle would suffer.

To be honest the engine is coming due for a rebuild I think. I just noticed awhile back that the vacuum had changed a bit. It is very driveable now but not fast by any means. The only problem I have with it is when I come off the highway and start driving stop and go traffic the engine idles down and tries to die if I goose the gas a bit and then take my foot off. Like it is flooding. The two problems may be related. Which hoses are prone to blowing off under boost?

Sorry you are correct. mmHG.