Lateral-g Forums - Big problem with my power dyno numbers

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Quote:

Originally Posted by camcojb

you don't measure boost in the carb hat; you need to measure it in the intake, somewhere after the carb blades. My guess is you're not running anywhere near that boost level, at which point you'll need to figure out why.

A couple questions. What size air cleaner? Is it mounted directly to the blower or does it have some sort of intake tube? What pulley size? What blower? What timing at WOT? What A/F at WOT?

Don't panic yet, once we get it sorted out you'll be very happy with your choice.

Jody

Hey Jody. Ill need to pick your brain. The air cleaner is mounted on the supercharger itself, no intake tube. The size of the aircleaner was in the mid range due to clearence issues. It's a P1SC blower, not sure of the timing, but timing changes did nothing for power, and did not hurt power. I thought that was weird myself, but they advanced it 2/3's per pound after going down 1 degree per pound, or something like that. I'm not sure of the A/F. We took the carb hat off and it blows well into the engine, this is all I know.

Quote:

Originally Posted by streetfytr68

So it's getting air. Was it getting fuel? Were you monitoring A/F ratio? BSFC's? Post some numbers. Did you purchase a specialized blow thru carb?

Blow thru carb engines are among some of the hardest to tune as they violate the very principle that carburetors are based on: Signal. By signal, the engine sucks or pulls on the carburetor to draw air and fuel during the intake stroke. With a blow thru system, you are pushing instead of pulling. Be patient. Collect and analyze data on available air and fuel across the pull. Contact ProCharger and your custom carb builder to analyze the data. If you don't have a custom carb builder, get one. And get to know him on a first name basis.

All the numbers I left in the car. I know that as WOT we read 11.8 to 12.5 on the A/R meter though the rev range to 6k. On the freeway at cruise we had 14 to 14.5. We also had an issue after a long downhill sweep, I was on it pretty good in 2nd at a high RPM and when the straight away came, the car died. They checked the floats and it's a bit on the low side, but they figured it was not the carb that lead to the stall out. The carb is a holley, but was sent to the carb shop and rebuilt for blower power. The boost reference is below the carb height.

Quote:

Originally Posted by DJW32

Are you on the stock internals? 9 pounds of boost with no intercooler could wreak your day.

I'm sure you will get this figured out. :thumbsup:

The engine was rebuilt for blower power. Everything is forged.

You want to mount your boost refrence line for the fuel reg in the carb hat. If you mount it below the throttle blades it will see vaccum and lower your fuel pressure. This is how the guys set them up at turbomustangs.com. Do you have a msd btm? You want to retard timing with boost 1 deg to 1 psi. Or you can lock it out.

Quote:

Originally Posted by 69bird

They had the boost reference on the carb hat, and it was running too rich at WOT. When they moved it, that's when they saw better A/F readings. The timing is what you are referring too, spot on.

Just got off the phone with Jody, thanks again BTW, I should really pay you for your advice. We chatted about this problem, and got to the filter, which is mounted on the supercharger. We had to use a smaller one because the one that came with the kit, was hitting the master cylinder. So we got one half the size. Jody thinks this could possibly be a problem. I'm thinking Jody is on to something here. They are going to re dyno it in the morning without the filter on for a few runs. Just to ask, has anyone had similar problems with this before?

What size pulley do you have? What size cam are you running? Whats your compression?

Mike,

Chrs here. Sorry you are having trouble dialing in yor car. Hang in there man, it will get sorted out. And, you have a PM.

Take care,
Chris

Quote:

Originally Posted by 69bird

What size pulley do you have? What size cam are you running? Whats your compression?

1 1/8 pully, cam specs are the same as the zz430 cam. Not sure what they are, and the compression is 8.9-1.

My imediate thought was air cleaner. Also, do not under estimate drivetrain loss. I have seen many cars loose 25% on a RW dyno. So you may already be at 500HP before final tuning, which would not be that bad after all.