i have a HD take off, stock upper and 4lbs lower, the weird thing is when i was on the dyno i saw 12lbs of bost from 5K RPM on up, they pluged the dyno into my boost gauge line, most i saw was 12.2 lbs at 5700 RPM

 

Remember that the twin screws don't keep increasing boost like a turbo, for instance. You'll top out at a certain value with a given pulley combo.

Lee

 

yep that is what makes it weird, i kept building boost they whole RPM range, on the dyno we let off at 5700 RPM and it was still building boost

 

From what you described, it sounds like you topped out at ~12 lbs. of boost from 5000rpm up. It's my undertstanding that twin screws don't have a logarithmic boost curve like turbos.

Regardless, it seems that you've got one hell of a strong truck!

Lee

 

it will be once i get the tuning issues fixed i am losing tons of horsepower due to it being way way to rich

 

Perhaps it's just me, but is 5700rpm healthy for these long-stroke 5.4 motors?

 

My truck is set for 5750 RPM max from Troyer, so I guess it is safe at that RPM or he wouldnt have set it up that way.

 

I absolutely would not be turning it to 5750, for two reasons. First with stock heads and cams, you will see that the power curve is falling off rapidly above 5000 so you are better off in the next gear where you are back in the torque band. Second, with the OE glass rods and pistons, you're inviting disaster. Troyer tune or not. Every tuner I know sets the shift point at 52-5300 rpm.

I turn my 4V to 6000 and even though my HP curve is still climbing I am still better off in the next gear where the torque gives me greater acceleration, plus I have a built bottom end.

 

OOPS double post.

 

on a dyno for datalogging perposes it is safe to run it to 5700 RPM tho correct?

 

as long as you watch the A/F

 

thats what i thought thanks

 

dont see that...if he is getting 12 w/a 4 lb pulley, then obviously i should be higher with a 6 lb pulley. we both have the same ebay supercharger.

 

That is why he's pig rich, there is no way he's seeing 12psi in this weather!!!! Unless he's got some restrictions somewhere. Do the math. I'm suspect to the dyno gauge being off. It's about the ratio not the "name"! You would may possibly see 12 psi given everything else is virtually stock on a very cool night.

 

NO, why would you want to do that? A loaded dyno would simulate real world conditions better. 5200 will tell you EVERYTHING you need to know.