I wouldn't say they are weak, I am sure they are 525hp at the crank. I am willing to bet between the drive and everything hooked up it just drains power, IF IT DOES THAT TO A 525 IMAGINE WHAT IT DOES TO OLD 454mpi:eek:

Thanks for the clarification Bobl.. Your comment to the motor being weak and missing would explain that it was down.. I am curious about the sensors not being hooked up though.. I have a set of CMI tailpipes that have O2 bungs on them, and I know that the sensors do not like water, but does the cam have such overlap that you are having reversion enough to wet the O2 sensor..? Is it possible to configure the setup to place an O2 sensor from a good meter like a Horiba in the exhaust..?

I am also curious about the 10-11% XR HP comment.. Are you saying that the drive takes 55-60 HP to turn it, and then you got the 10% figure? Or that it will take 10% of the rated power output of the engine to turn the drive? (If the motor was putting out a rated 1000 HP, then it should not take 100 HP to turn a drive that eats 60 HP, it should take the same 60HP, no..?)

I have been also thinking about having a modified dry pipe setup with a revised muffler design to help with noise, and to be able to run in closed loop.. An idea I got from some guys at the local road race track Laguna Seca near my home..

I have been told it's crazy, and will not work, but I wanted to try and run the system in closed loop...

Thanks..

50 H.P. loss threw an XR seems like alot. Might make a good thread in it self. Doug

Your experience matches mine (and mostly falls in line with shp ratings insurance companies use for our boats - 500 for this engine new)

Your dyno run is about what these engines put out after a season of running.

Everyone is acting completely surprised?!??!

Bill Aubernell from x power paid to spin dyno pretty much everyones drive and claimed it takes about 44hp to spin an xr 5500rpm.

Thanks for the informative post!

Uncle Dave

I usually add 02 bungs in the tailpipes so I can measure A/F, and connect my fuel transducer. I wasn't looking for that data. Just curios about the power. This engine did not have a miss. The previous 525 I dyno'd was the one with a miss, hence only pulling to 4900 RPM. I've run some engines in closed loop for a while, but eventually the moisture will kill the sensor.

I have only had the opportunity to test a few engines back to back on the engine and prop shaft dyno. In every case the loss was 10%+.

I'm just sharing data with everyone as I accumulate it. Hope it is of use to someone.

Bobl,

Thanks for sharing, I appreciate it, and try to do the same when I can. Again on the 10%, were any of the engines more than 550HP that you tested..?

I am curious, beause 10% of the 550HP is 55HP, but 10% of 900 HP will be 90HP, and if a drive takes 55HP to turn it, then it should take the same 55HP to turn it from another motor... Whereas, if most of the engines you test are in the 500-550HP range, then it would make sense that you observed 10% loss or about 55HP..

I got the missing engine mixed up with the current one, thx for clarifying..

R

Bob,

This stuff is extremely informative.
Thanks for all the hard work.

Chris

I think they were all different...Ask Reggie.

I tested a stock 496 HO. 387 at the prop, 431 at the flywheel. That's 10% with an X drive. I've never tried more than 550 HP.