Good question. Since we're on the subject, I'd like to know if altered gearing affects dyno #'s. I'm scheduled to have a custom map made next week for my R1, and I'm wondering if I should install the new chains and sprockets before the dyno run.

Thanks!

Rene'

 

Does tire pressure, chain tension... affect dyno results. I was just thinking that if you had more or less tire pressure (Bigger vs. smaller contact patch) that this might affect dyno results.

What else can affect it.

B

I've never seen it affect the BHP (but I could be wrong), just the beauty of the graph. A loose chain will make the power/torque curve look eradict.

 

It stands to reason (can't document/prove) that one or all of the following could certainly have a minor effect by themselves or in combination.......

tire pressure, chain tension, and the tension applied to the nylon tie-down straps used on the rear subframe (or thereabouts) to secure the bike.
So when you take into accout these factors (especially the tie-down straps) its not very scientific. To be fair i would submit this is part of the 3-4% variance some refer to when speaking about dyno tests.

BD

 

Hmmm. Might have to try this out... What do you guys run for tire pressure anyways..
B

 

Hmmm. Might have to try this out... What do you guys run for tire pressure anyways..
B

36 in the rear and 34 in the front. I'm 170 lbs...........

 

It stands to reason (can't document/prove) that one or all of the following could certainly have a minor effect by themselves or in combination.......

tire pressure, chain tension, and the tension applied to the nylon tie-down straps used on the rear subframe (or thereabouts) to secure the bike.
So when you take into accout these factors (especially the tie-down straps) its not very scientific. To be fair i would submit this is part of the 3-4% variance some refer to when speaking about dyno tests.

BD

The tie down pressure will also affect the graph with either aiding or controlling wheel hop on the dyno.

 

YES, tire pressure can affect dyno results. Even different tires from different manufacturers can affect results. Could be as great as 2-3 hp.
Can't say what the results different gearing, chain tension, etc. would have but it stands to reason it would have some affect....even if just minor.

 

a loose chain will affect your graph certainly
but on the plus side of that you will know precisely where your chain deflection is
tighten your chain and check the graph
my stock 530 chain started deflecting at 6375 rpms and continued until 7185--i replaced the chain went back and ran again with new 520 chain-still had some deflectio but gain HP due to less reciprocating mass
changed gearing and it didnt change the graph much--just brought the torque curve on early and i reset my shift light accordingly
on when fat torque kiks in / off when torque is gone
course ive changed more since then and realy need to go back and recheck but im a lazy a$$ and will do so in the future
PS--i get free dyno time muaahahahahahahaha

 

Almost anything will effect it. I forget which mag did the test but they replaced a worn out chain and sprocket on a ZX and got another 7hp.

if you use a 180 rear instead of the 190 you should get better numbers. Same goes with a near worn out tire to a new one.

Fanatic, different gearing will effect your tq curve but not your HP curve.

 

Almost anything will effect it. I forget which mag did the test but they replaced a worn out chain and sprocket on a ZX and got another 7hp.

if you use a 180 rear instead of the 190 you should get better numbers. Same goes with a near worn out tire to a new one.

Fanatic, different gearing will effect your tq curve but not your HP curve.

Interesting. So I guess the real true numbers between each manufacturer would come from machines equipped with the same rubber/size/pressure, the same chain/sprocket/miles on chain manufacturer and size, and the same dyno with the same tie downs and tie down tautness.

 

These would be for an inertia dyno. Some of these can be eliminated on a brake dyno.

 

These would be for an inertia dyno. Some of these can be eliminated on a brake dyno.

Ah, gotcha. Thanks for clearing that up.

 

Interesting. So I guess the real true numbers between each manufacturer would come from machines equipped with the same rubber/size/pressure, the same chain/sprocket/miles on chain manufacturer and size, and the same dyno with the same tie downs and tie down tautness.

Almost makes you not want to bother with it.

Not sure what effects the tire pressure would have. If it's lower, then the radius of the rear tire will seem smaller causing an increase in tq but the extra flex may also provide more resistance than normal reading as a decrease in hp. Or it could provide more traction not allowing the rear tire to slip to provide better numbers.

There should be a perfect combo of tire pressure and force from the tie downs. Though it seems logical this would also change with the HP from the bike. For the same tire pressure wiht an increase of say 20hp you would need more force on the straps.

Does anyone already have a formula or want to develope one?

 

http://www.sportrider.com/features/146_0406_comp_dyno_clar/
This might help clear all these questions up. Look forward to reading it.

 

when i run on the dyno, they had my fill up my rear to 40psi. They said it helps out?

 

http://www.sportrider.com/features/146_0406_comp_dyno_clar/
This might help clear all these questions up. Look forward to reading it.

SR says:
"Other testing we have conducted has shown that dyno readings can vary as much as 3 percent with two different tires on the same bike."

Wow!! Up to three percent difference just from a different brand tire.

 

Hot Rod magazine did an article on dynos this month. They covered tire presure in there. Can't find the article on the website. I'll look for my copy of the issue that covers it.