Prochargers N Boost..
 

Is it normal for Procharged engine to have less boost when it's warmer out ?

Was testing a prop yesterday, in the warmest weather I've run this engine in, (92°) and noticed I was down almost a pound of boost at 6000 RPM..

No signs of the belt slipping. Engine seemed to run strong. When I checked the fuel learn table, it had pulled almost 10% fuel out on the top end.
Checked the datalog and it made 9.1 LBS of boost at 6000 RPM where it normally makes a solid 10 Lbs...

SOO Close to triple digits.. :)



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Yes. Thats normal.

So, to hit 100 you need a cooler day or ask your passenger to jump.
Congrats, sounds like you are getting it dialed in and you will be at triple digits!

Padraig

Our mini Winnebago..
a Velocity 290sc..






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I could tell you how to make consistent boost but you may break that drive.

Let me throw out a couple of thoughts. You are reading the map sensor which reads the absolute KPA the intake is seeing. If the barometer changes, that number changes. You go up to high elevation and the kpa will read a lot lower and your data log would show a lot lower. However if you were looking at a boost gauge it would still read 10 psi boost, which is the amount of pressure above atmospheric you have. So, your data log will read something different every time, but it shouldn't be nearly as much as you are seeing. I also believe that with hotter, less dense air the boost will drop slightly, inlet air temp changes. Another thought, boost is created by load. If the load at a given rpm changes the boost will also change slightly. So weight, trim and water conditions can impact it, especially with a centrifugal as compared to a positive displacement supercharger.

Bob

Yes... Air Density or ADR , Aircraft stuff , higher numbers more lift . More Power
Lower number , less lift or less power.

are you running a AWIC?
on a turbocharged engine, yes, this is supercharged. The boost (impeller RPM) is directly related to engine RPM. output increases proportionally to the square of the rotation speed

LOL - aerodynamics ....

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That one ran 94.8 running 7lbs never went faster. 720 HP and 727 tq

Still trying to figure out why I'm stuck in the 90's, as I have 1000hp and a 290sc hull is supposed to be faster than a 280
Talked with Steve Stepp the other day and it would seem my prop is just too deep.. I'm Saving $$ for a -2 Imco now.. ;)

Save a little more and get a cat

I always have heard that the 290sc was slower then the 280. Heavier and taller deck. The 290 VR is supposed to be faster. I have no data and may be wrong but just what I have heard by being a Velocity owner since 1996.

Padraig

Mine was 4200 lbs dry. I ran a B-max 1.30 with a 28 labbed Bravo. I think I could have run better with a shorty. It was turn key though for 6 years and super quick. There were faster boats at the time they just didn't have near enough lake to catch me. Made 685 TQ at 2800 RPM.