4thGenTuner

iTrader: (1)

I was wondering what the normal vac. readings on my boost gauge should be. At the moment I have roughly 21 inHg showing on my gauge at idle. As I rev the motor slowly, the gauge seems travel to about 8 inHg all the way to redline then settle back to 19-20ish inHg as the car hits the limiter.


I was under the impression that a suitable souce for the gauge would be any vac line directly attached to the manifold. I used the one associated with the FMU. Shouldn't I be seeing positive pressure (boost) somewhere in the RPM range? Does that only happen under load? Is the 3.66in pully too weaksause? Im pretty sure the blower is making positive pressure.


I haven't been able to install all my gauges, EMU, wideband, injectors, etc in a permenent sense as of yet. I have most of these things, just not enough time to install them. I was puttering around the garage and decided to hook up the boost guage in a temporary sense. Hence my n00b questions.


My setup is;

110k mi. DE-K, Stillin 5th gen charge piping, V2 S-trim, vortech 8:1 FMU, and aux fuel pump. 3.66in 6psi? pully. Basically all the original stillin kit parts. Stillin lightweight flywheel, ACT 6 puck, etc,etc. Gauges are glowshift.


I have a 3.125in and a 2.87in pully and intend to get one of those in as soon as I can. I would like to have the walboro 255, EMU, injectors, and wideband up and working before I do away with the FMU and start to up the boost. Then eventually get a professional tune.


I dont drive this car much, it sits most of the time in the garage or under a cover when Im wrenching on somthing else. I will say that the damn thing is pretty fast. Faster than the I/H/E, 00VI, and street tuned 4th gens I have put together. This is all subjective, because I have never had it on a dyno. However, I would like to see this thing reach its max potential.


Thanks for reading and sorry for the paragraph.

Kevlo911

iTrader: (36)

I am around 20-22 at idle and then around 1-8 under a load

can't help with redline since im under boost by then

4thGenTuner

iTrader: (1)

Ok, seems 20-22 is normal.

Not seeing any boost through out the RPM range is sorta weird, guess I'll do some reading.

Thanks.

MaximaSpd85

iTrader: (14)

IdK, ive used some vacuum sources on the mani that didnt give me any readings before. I switch it back to my previous source and i get the readings again. I say try to find another source, and if possible not feeding anything else.

4thGenTuner

iTrader: (1)

Well, after reading for a few hours I wasnt able to figure this out.

I did solve my problem after I noticed a restrictor in the little plastic tee which came with the gauge. The thing would show inHg perfectly just no positive pressure. I also tried various vac lines and got the same results.

So, after seeing the restrictor in the tee I decided to ditch it. I then connected a 1/16" brass one I had laying around from some pneumatic HVAC controls I demo'd a while back.

Worked like a charm. Starts building boost at around 2800 rpms and pegs out at 9psi at redline (6800ish).

Hopefully this doesnt trash the gauge, if it does I'll just buy a better one. I only paid $42 for this one so no big loss.

In conclusion, if you are using a glowshift brand boost gauge, throw the tee included with the kit away.