How much is recorded power affected by wheel wheight

[R1000]

Thanks cw2, the question was raised from discussions with a friend who dynoed his modified Busa and found the power reading was about 10 hp lower than estimated even though A/F readings are good. The bike in question gave 170+ rwhp instead of estimated 180 or a bit more, which it should do with the actual set-up. I know dynos can read (a lot) different, but in this case a well-reputed dyno was used, so we came to the conclusion there is a reason that is to be found on the bike. It is the Yellow Fever bike on BosseJensen.com - Art, cars and bikes

 

[GPW]

I suppose you would see that in the negative power test although I hardly ever use negative power feature that my dyno has. I have my system configured to auto brake at the end of each sweep so I can quickly perform another run. Therefore I'm never letting her spin down for 10 minutes just to collect those types of numbers.

The negative power test is done with the clutch pulled in on slow down, oil pressure stays up and the drive train free rolls to a stop........testing drag on the drive train.

 

[cwalker2]

The negative power test is done with the clutch pulled in on slow down, oil pressure stays up and the drive train free rolls to a stop........testing drag on the drive train.

I'm familiar with doing the negative power test - I just don't do them very often. I did find it useful on one particular dragbike to document the impending failure of the transmission. Its drag was increasing on that trany over time. Told us to go looking for a drive line failure and we (actually the trany manufacturer) found the excessive drag in 5th gear.

My point is my dyno uses the eddy brake to slow the run so I can get multiple runs in the time it takes to do a single pull and spin down on an inertia only dyno, or one with no means of braking the drum at the end of run. I would have to specifically set up the run for a negative hp test and since they are not often needed...

 

[GPW]

Good for you, this stuff ain't rocket science by any means. Some do more testing than others. Its a very nice tool to use your own imagination with, not necessarily doing what everyone else does.

 

[Mr Bogus]

This was one of many things that I pointed out in a certain pipe shoot out thread that used different bikes a while back. There is a big difference in tire changes on the dyno and other factors in the drive train.

I don't know the exact rate for rotation power calculations but you can figure a pound off a wheel is a little over 2lbs. off the bike. Dropping 5lbs. off a set of wheels is like dropping 10lbs. off the bike...

is one of the main reasons I never take dyno numbers all that serious.. Great tool for comparison testing but for absolute values? forget it...

Just will never work at some guys shop no matter how good he thinks his dyno cell is... Even if his is "right" you gotta take every other dyno out there and average them out.. Be a much better system if they could do a dual sprocket and chain drive the rollers..

my bike had some reading of I think it was 161rwhp.. I have run against some 180rwhp bikes and beat them... so the HP is only good for relative comparison testing and bragging rights....

now, you will have to excuse me... I am going to dyno drag racing school.. (hey no gear needed right? )

 

[cwalker2]

Good for you, this stuff ain't rocket science by any means. Some do more testing than others. Its a very nice tool to use your own imagination with, not necessarily doing what everyone else does.

Thank you, and I agree, using your imagination is probably the most important part of the tool. I don't think I've heard anyone say that yet, but it is very true. I was an engineering technician for many years, so I am used to looking at problems from many sides and attempting to figure out how to measure something and then how to collect data and prove or disprove what is supposed to have happened.

Cheers

 

[GPW]

Thank you, and I agree, using your imagination is probably the most important part of the tool. I don't think I've heard anyone say that yet, but it is very true. I was an engineering technician for many years, so I am used to looking at problems from many sides and attempting to figure out how to measure something and then how to collect data and prove or disprove what is supposed to have happened.

Cheers

I agree, thats why I try to think outside the box, sometimes I am right, sometimes I am wrong. But just following the line in the sand is too easy.

 

[BigRod1300]

I never did a dyno before the fat 330, but with Greg on his dyno it hit 154 with the OSD set up ( no jackshaft ). Thats +5 gain over when he did it when the Jackshafts was on. At 154hp ..Greg thinks with the performance mods that are on the MULLET..its about a 15 - 20 hp loss with the 330 vs what it should be making.

 

[GPW]

I never did a dyno before the fat 330, but with Greg on his dyno it hit 154 with the OSD set up ( no jackshaft ). Thats +5 gain over when he did it when the Jackshafts was on. At 154hp ..Greg thinks with the performance mods that are on the MULLET..its about a 15 - 20 hp loss with the 330 vs what it should be making.

Keep in mind the strongest 2006-2007 we have seen made 164 HP SAE. So at 154 you are about 10 HP under the max power curve. Is a thinner head gasket worth ten HP..doubt it but its a cheap mod to do which may get you some of the power back. I forget what your best MPH in the 1/4 mile was, since you are one of the few with a big tire bike who actually goes to the strip that would be another way to look at your drive train power loss.

 

[BigRod1300]

Keep in mind the strongest 2006-2007 we have seen made 164 HP SAE. So at 154 you are about 10 HP under the max power curve. Is a thinner head gasket worth ten HP..doubt it but its a cheap mod to do which may get you some of the power back. I forget what your best MPH in the 1/4 mile was, since you are one of the few with a big tire bike who actually goes to the strip that would be another way to look at your drive train power loss.

Best MPH was 143 @ 9.98....that was my ONE sweet launch. Ive backed up 10.23 @ 137mph. With a stretch fatty on air-ride it always spins or bougs off the line. PLUS..Im still learning the 1/4 on a bike.

And Greg..plan to come by this week to talk again!

 

[iride]

I sure would like a set of them carbon fiber wheels, But for 2000 bucks
I can go on a weight loss plan and have the same effect by losing 50 LBS..
Ok I will shut up now...
Mike

 

[Got-Busa?]

I sure would like a set of them carbon fiber wheels, But for 2000 bucks
I can go on a weight loss plan and have the same effect by losing 50 LBS..
Ok I will shut up now...
Mike

Try more like $3,500 bucks...