List
Since we like to share info and speed secrets more than any other group of
racers (and I think LSR is better for it). I got his info from one of my
NASCAR buddies. He's building a belly tank too. He's slow and methodical,
but may make it to the Salt in a year or two. Anyway, didn't get all the
answers I was looking for, because there was some information he really
didn't have an answer for. However this info was derived from an actual Rear
End Dyno and Transmission Dyno as well as Engine Dyno vs Chassis Dyno
results.
Non-broken in gear sets (rear ends and transmissions) can rob 2 to 3% HP.
That's 22 HP to the rear wheels on a 750 HP NASCAR piece. Each gear set.
That's 44 HP Trans and rear together. Significant.
It takes 1.5 to 2 hours of run in time to break in a ring and pinion for
maximum efficiency. Hmmm, how many years is it gonna take running at
Bonneville to get 2 hours of running time on the rear or Trans? Lets see at
1.7 min per run...
4-speed transmissions are very efficient running in non-overdrive top gear.
98%. Overdrive kills efficiency significantly. The amount depends on the OD
ratio. A .96od ain't any where near as bad as a .86od, (both available).
Planetary gear sets from an Automatic or Lenco are very inefficient, but
doesn't have numbers to offer. From what I have heard and read a T-400, as
an example, would be about 89% to 90% without the torque converter.
The hypoid gear sets of a 9" Ford hover in the 92% to 93% range for the gear
sets (2.80 to 3.25) we run at Bonneville. A 6.50 is 89%. QC's are a little
worse than the 9" (2%) due to the 4.11 R&P, and the extra spur gears added.
He's not tested a 12 bolt Chevy but due to gear angles and what he has read
would estimate about 1% better than the Ford.
Suggested using the #1350 wherever possible for its efficiency and strength.
Yes u-joints can rob HP too.
Also said, for whatever its worth, that a Chassis Dyno is a good and helpful
tool, but does not take the place of an Engine Dyno, rather compliments it.
Application and cost are other factors to be considered. A NASCAR team can
afford to have 35+ gear sets on the shelf broken in and ready to race. I
don't have that luxury so a QC makes more sense for my pocket book, and I
don't have to haul a 1000 lbs. of extra gears around.
Hope this help some of you.
John Beckett, LSR Comp Coupe #79
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