Finishing up Cobra 55...Coyotes are great!

[Wayne Presley]

Finishing up a cobra for a guy in Texas and broke the motor in this afternoon and then did some power pulls....386RWHP on a Mustang dyno!

[Olli]

I don't think that I have ever seen you wearing long pants....

Olli

[Wayne Presley]

I don't think that I have ever seen you wearing long pants....

Olli

Was cold this morning...

[BadAsp427]

That is cool... I've never had the opportunity to run a car on a dyno or even be there to watch a run for that matter... Could you please tell me, what gear do you run in for the pull?

[BEAR-AvHistory]

That is cool... I've never had the opportunity to run a car on a dyno or even be there to watch a run for that matter... Could you please tell me, what gear do you run in for the pull?

Should be the 1:1 gear.

[Wayne Presley]

I did the pull in 3rd gear, it shows about 1.5% less HP than 4th gear pulls. That 1.5% isn't worth the extra wear and tear on the dyno. The rollers are at 100 mph at the top of third and 125+ in 4th

[mike223]

I did the pull in 3rd gear, it shows about 1.5% less HP than 4th gear pulls.

I understand not wanting to spin everything up to 125mph+, but I'm really surprised that 3rd gear shows less hp than 4th.

I would have expected the mechanical advantage of 3rd to show more hp than 4th.


So I guess that lost/missing hp is being eaten as heat in the transmission gears / bearings / etc???

Just asking (very curious)...

[Jeff Kleiner]

I don't think that I have ever seen you wearing long pants....

Olli

I had EXACTLY the same thought Olli!

Jeff

[mike223]

So I guess that lost/missing hp is being eaten as heat in the transmission gears / bearings / etc???

Further thought:

I guess I shouldn't be surprised by that since I already knew the mechanical advantage of the rear end is getting "eaten" in the same manner.

[Wayne Presley]

Ok HP measurement isn't being affected by gear ratio, if it was then every car would have to have the same overall ratios in order for comparison. Now there is measured differences in doing a pull in 3rd vs 4th vs 5th gears on the same vehicle due to the tooth angle of the gears. Picture 4th which is usually 1:1 and how the gears mesh, they are meeting at exactly the same angle, and departing at the same angles. 1:1 gears are still eating HP due to friction and being converted into heat energy Picture a gear that is 4" in diameter meshed with a gear that is 2" in diameter and the tooth engagement is much different so there is extra friction being turned into heat which is causing the loss. It doesn't matter if it is under drive or over drive, the extra frictional losses are still there. The rear end is eating HP due to the friction of the gears meshing friction.

[mike223]

Ok HP measurement isn't being affected by gear ratio, if it was then every car would have to have the same overall ratios in order for comparison. Now there is measured differences in doing a pull in 3rd vs 4th vs 5th gears on the same vehicle due to the tooth angle of the gears. Picture 4th which is usually 1:1 and how the gears mesh, they are meeting at exactly the same angle, and departing at the same angles.

1:1 gears are still eating HP due to friction and being converted into heat energy Picture a gear that is 4" in diameter meshed with a gear that is 2" in diameter and the tooth engagement is much different so there is extra friction being turned into heat which is causing the loss. It doesn't matter if it is under drive or over drive, the extra frictional losses are still there. The rear end is eating HP due to the friction of the gears meshing friction.

I agree that any and all gears are eating hp and creating heat through friction.

I disagree on the 1:1 eating hp - typically no gears involved (in v8 RWD transmissions) : locking up the input shaft to the output shaft - where's the friction there? Not much I think...???... (except in the rearend, but that's happening in every gear)


I was just a little surprised to hear that third gear *typically* shows less hp than 4th (1.3~1.5:1 vs 1:1), but I understand how that could happen.


Thanks for your thoughts - I appreciate any further "things to think about"...