Lupo222

But I'm getting normal vacuum readings on my gauge. 15" at idle, 20" when I let off while in gear... I'm gonna spray carb start around it tomorrow while idling to see if it revs

turbo 2.8

what was the dyno numbers ?? does the car feel slow ? , is there a chance the gauge is defective. also is the bypass valve operating correctly ? id check the gauge with a air pump just to b sure , process of elimination

808muscle

Lots of guys with hotrods and detroit rocker cams with m90 blowers. Everything I have read says those cams are very similar. Is the saleen blower that much different from a m90? Seems weird that your cams are causing you to lose your boost.

moochman4life

Your boost/vac gauge is not always going to show a vacuum leak if there is one, believe it or not. A prime example: recently, two of my spark plugs found their way loose in their banks. Gradually they worked their way up and out and it was creating problems like hesitation during take-offs, loud exhaust popping noises, and exhaust was flooding the inside of the car from the engine compartment. She gradually starting feeling more "nervous". Now, because there was a "hole" in the engine because of some loose plugs, it created a vacuum suction back in when you let off the gas.

Guess what? Through every stage of it gradually getting worse until I couldn't take it any more and found out what it was, every reading on my wideband A/F gauge, my boost/vac gauge, and the gauges I have set up on my mounted Diablosport Trinity never varied by more than .2...everything from MAF to Knock Sensors. AND, the loose spark plugs never threw a code (because they were still firing...they were just loose).

moochman4life

I guess what I'm saying is, gauges are awesome tools, but they're not perfect for diagnosing every problem your vehicle could have.

Because of all the issues I've had with installing my own gauges until I became a "pro" through trial and error lol, I think you should take down and re-install your boost/vac gauge...and make absolutely sure that the rugged, hard plastic hose is not getting pinched anywhere, and that the seal on the back of the gauge is as tight as you can get it. I used teflon tape to seal the back end like you did...but I went a step further and electrical taped everything together on the back-side of the gauge. It might have been overkill, but it's worked ever since.

dmhines

You guys do realize he added the Boost Gauge yesterday AFTER he discovered that the S/C was not making any additional HP on his engine. The gauge is not causing a problem .. only verifying a problem.

moochman4life

Unless I missed it, I did not see that mentioned in that sequence at all. Maybe it was in his Hot Rod cam thread (looking)?

The only thing I got was he hooked up his boost/vac gauge and it's not providing him a good reading.

Lupo222

No, I dyno'd the car and got 333rwhp....which is just a couple more than I had N/A (I think it was 332rwhp n/a) and I got 280ft lbs of torque in a very nice, flat tq curve, but not anywhere near where it should be.

I've checked the boost actuator via the method explained to me on here (unplug vacuum line, lift plunger, place finger over vacuum nipple, let go of plunger...it stayed up which I've been told means its good). And the plunger on the actuator lifts and falls with RPMs.

So no one yet with a Saleen S/C and Hot Rod cams and what size pulley they're running?

SON OF 68

I don't have this particular car (09 GT) supercharged, yet However, I have supercharged mustangs in the past. I personally would not suspect the cams being an issue. Yes, they and the LT's together flow more exhaust, but I hardly feel it's enough to be blowing ALL of the boost out of the cylinders that quick. It's easier for a motor, or anything sealed for that matter, to release a vacuum than it is a small amount of pressure.

dmhines

Have you verified whether or not you have underdrive pulleys? I read that UD pulleys will remove a couple of PSI. With a 4" Pulley your PSI is gonna be pretty low already until the upper RPM's ..

The Saleen S/C with a 4" pulley is rated at 425 HP ... That is 360 at the rear wheels. Now add in the fact that you MAY have UD pulleys ... and your numbers make some sense ...