First off.. I have two boost gauges, the aftermarket reads well, i trust it and have tuned to it since i've had the car, ever since i fixed the switch valve, the stock boost gauge will jump up to 40 psi when i start spooling? whats up with this? i haven't looked far into it. but i have had this car apart several times and i don't know what i am missing.

2nd thing.. I want to say i need to rebuild my engine but i dont see much of a sign of a weak engine. A while back i checked the compression and it was 75psi on the rear rotor and 85psi on the front rotor(a month after purchased). The idle is a little flimsy, when the engine is up to temps, it will sit and idle at 650 or so. i can tap the gas, and it will sit at 1100rpms, and after about 30 seconds drops to about 850, and then i watch the vacuum go from 20 to 10 and it drops back to 650. I feel a little twitch on the brake pedal sitting still but i think that has to do with the rear rotor not having enough pressure for the master cylinder. The previous owner says the engine had 40k when i bought it(now about 55k), and he also said he had ceramic seals installed on it. No smoke comes out the car when i start it up. The only time i see smoke is at a 7k shift in first and 2nd, but its defenitly from the unburnt gas(open recurculating bov, tuned rich for interstate, stock turbo, 3"dp, gutted cat, boost creepin, need to bore wastegate). The car pulls very strong i feel. i ran a 14.2 on stock boost and crappy radials a while back, i still have room for improvement now that i have it tuned a little better.
Any ideas?

 

The stock guage is in hmg's or whatever though. That is kindof low compression for an engine though.

 

Is it an Autometer boost gauge?

What does the boost gauge read in vacuum when idling?
Idle RPM?


-Ted

 

I hear Autometer boost gauges are not accurate at all. My autometer reads a whole 2 psi higher than my Microtech hand controller reads...

 

i do believe its an autometer. i am not going outside this second to check, but the stock boost gauge is reading 40psi. what could that be?

i do believe its an autometer. which would mean time for upgrade if its problematic. I trust it better than the stock one atleast. seeing as its not hitting 40 psi ever.

 

No, it's not graduated in psi.
I believe the units are mmHg?


-Ted

 

Thats what it is mmhg's(not hmg's).

 

yes its an autometer and yes its in mmhg. which is what they are talking about in atmospheric pressure, 14.5? psi is the atmospheric pressure at sea level, the idea behind forced induction is increasing that atmospheric pressure.... point being this is not helping solving the origional two questions.

 

14.7 is atmospheric, I think, close enough

 

the factory guage will hit 400mmhg (or whatever it is) which is like 6psi, if you're boosting more than that, the guage will just be pegged.

2. i'm not sure what you're asking, it reads more like a statement.... but it sounds like the idle control system doesnt work right, and imo the engine seems a little suspect. i would suggest a compression test, but its pretty key that the engine runs well to get a good reading. you're looking for even bounces more than the actual number, as compression testers are pretty crappy.

 

If it has ceramic seals and the compression is that low after than many miles either the housings are scrap metal or the oil metering system is broken

 

It would've answered your question if you had answer my questions on idle vacuum and RPM...

Your first question was invalid since you were assuming the gauge read up to 40psi.


-Ted

 

point.

guess i never put the boost gauge mmhg into thought. I guess i will be searching for more problems when i get a chance to do a couple checks this weekend and buying a new boost gauge. while i also have to install a differential mount too.

 

oh yeah, those are fun..diff. mount.

:AA:

 

ok. i can understand where the housings could be scrap metal especially due to something such as overheating. but where does the oil metering system come into play with compression? im searching threads and not getting a whole lot of results and answers. The previous owner "removed" it and ive been running dehitsu rotary premix since i bought it.