Not making top speed

[74Nitro]

I did a pressure test on both sleds and found that if I pressure up to 15 lbs and stop, I lose 1 lb every 2 seconds, so I lose 5 lbs in 10 seconds. That doesn't seem like a lot to me ... am I wrong? Is losing 5 lbs in 10 seconds excessive? Seems like any loss is made up at the wastegate and so boost would stay the same.

Bill

It is normal to lose some pressure as there is no engine position where all the valves are closed at the same time. So there will be leakage through the ring gaps on whatever cylinder doesn't have the valves closed.
However if both sleds lose leakdown at the same rate, it doesn't explain the speed difference.

 

[Bill Hooper]

but is the faster sled running at the ideal RPM and the slower is over reving? loading it heaver would make it work hard to make speed if it has the HP to pull it.

The faster sled is running at 8300 rpm at 112mph. I am informed that the ideal RPM is 8800 RPM, leaving room for additional top speed. Given it has Thunder Products clutch kit, it should be pulling 8800 rpm and it isn't. This is why I think there is a problem.

Bill

 

[Motorhead]

Stock 8 JP belts! Asking because the xs825 aftermarket belt will bring your revs down!

 

[1nc 2000]

Have you checked clutch temps between the 2 sleds?
Belt slippage could be your issue on the slower machine.

 

[NYTurbo]

If faster sled is turning less rpm than the slower sled turning more rpm either your gearing or drivers are different or you have clutch issues IMHO .
Or speedo is off

 

[STAIN]

Do a clutch assembly swap sled to sled. Primaries, then secondaries. See if the problem follows either clutch.

 

[fatchance]

Should hold 20 lbs of pressure and have a very slow bleed. Same exhaust in both sleds? Guys use the stock shields over a non stock exhaust. Sled hitting 112 @ 8200 RPM is way too heavy and needs weight taken out of the primary. Other sled isn't getting fuel or not making boost.