blown 87

And I hope that most understand that this is just us poking fun at Mark.

dcrasta

That guy sounds like one of the old school 2 speed powerglide racers. My father had friends like this back when I was about hubcap height.

I agree with you. Gearing (in motorcycle racing anyway) is often used to have enough speed for of the fastest section. Perfect gearing is your RPM peaking at the fastest section, and having drive for the corners. Of course a wide torque band helps for having less difficulty with the proper gear for your exit(corner). It is true a broad torque curve is easier to ride/drive fast than a peaky motor. Time shifting is time not on the gas..

Too high (numerically low) gear in the rear may end up with a car that cannot even pull redline in top gear.

Compromises, compromises. (this debate is strange.. )

mark kibort

There are no assumptions here. what you are failing to see is the conditions of the comparison. you are tossing around trade offs like they dont matter. settle down and think about this for a while and you will get it. trust me, my logic , math and physics are not flawed. just by your commment of using a longer gear, proves you are not really understanding the concepts.

So, one more time.

never said longer gearing is the winner, i said rear ends for differeent target speed ranges will have trade offs. over all they will be same using multiple speed ranges.

So, the object is to always stay as close to max hp as possible. so your silly comment regarding starting out in 5th has holes in it. (or 2nd and go to 80). remember, we are talking the same gear spacing, only rear end changes and we are not talking about top speed, we are talking target speeds of 120 to 150mph. for a target speed , a 2.75 gear box woud be optimal . for 150, the 2.2.

Here is why.

in 1st gear, the 2.75 has a 10% advantage torquewise over 2st in the 2.2 s4 box., however, it has a 10% less speed shift point, at which point the S4 would then have a 30% torque advantage for the longest time period of the acceleration time in that gear. after a shift, the s4 down 10% again unitl 2.75 shifts, and then it gains 30% on torque for a a short period of time. this 30% for a short period vs 10% for a longer period tends to cancel itself out over mutlple shifts and up through higher speeds. the net net of it all, is that if you were drag racing to 120mph, i would use the 2.75. very common speed for final velosity for most 12 second drag races. If i had more hp and my trap speeds were more like 150mph and in the 9 second ranges, i would choose a 2.2 (if i had only two 928 gear boxes to choose from) the gear spacing would be the same However, there would be an advantage of out of the hole gains, that is a big , hard to quantify , variable. so, for the sake of argument, lets leave that out.

Its all about HP-seconds. both cases would have their car in the narrowest area of the powerband, this is why skipping a gear or using 5th over all , is such a stupid thing to even mention. makes no sense if you understand the concepts of optimizing gearing to maximize HP utilization.

heck , dont even take my word for it, Carrol in his book , tune to win blasts all the knuckle heads that make more of this than there is. just take the power curves, look at the track data and find the gear box that allows for max hp application. exactly what im saying here. there are trade offs.

a 2.2 good for one track, might not be good for another where the 2.75 might work better. remembe, ive raced both, anderson has raced both, and this is a significant difference! if there was a big difference, dont you think someone like me, that has more races at laguna seca than any pro in the world over 10 years, might see a difference with the gear box change. Anderson saw no time improvement. i saw no time improvement driving a near identical race car with near identical HP , but one with 2.75 vs 2.2 as a gear box. As Anderson said as well, "I was just a little more busy with shifting in odd places on the track, but overall, it was just as fast". the proof was in our times too.

dont trust your feelings, your acceleration in each gear is greater, but at a SLOWER speed, and that is why it is so much fun. overall, dont think you have bought much of anything. the logic is solid here!

mark kibort

again, you have it backward. a flat torque curve is a peaky HP curve.
you want a broad HP curve so you are always at the engines max acceleration potential. you will always at the max acceleration out of turns as down the straights. peaky HP engines, (i.e.flat torque curves, ) are very critical for gear selection out of a turn, or required close ratio gear boxes to make sure the operational range of the engine is in the peak HP range.

acceleration = power/(mass x veloctiy)

mark kibort

no substitute for driving. you are talking about a 7hp difference! i race against cars with 100hp difference and hang, why? becuause of the jump at the flag, or the speed off the corner. so many factors, so little time.

why are you fighting it. want to learn something, re-read my post Mr Brian! common, havent i taught you anything young whippersnaper!

I got 150 hp less than this viper. why am I hanging??? your example is flawed with you getting a better jump off the line. the rest is subte differnces. look at the gear ratios that you have at the start. you might be more optimal as welll. ever think of that?? remember the Scot stories?? if we are at 60mph, scot is in 3rd, and Im in 2nd i could get a huge jump from 60 to 80mph and then hold him off when he has the advantage from 80 to 110mph.

all trade offs my boy! gearing doest make more HP, it just optimizes hp you have.

http://www.youtube.com/v/Sih48Dby9d0

Speedtoys

"dont trust your feelings, your acceleration in each gear is greater, but at a SLOWER speed"
---

And for those of us not racing..that's where we're at.


We're quicker, were not looking for a top speed or an overall time across a long distance where things like higher MPH over a longer distance would pay back.




2.2 rear end, it was pretty sad to go WOT at a stoplight..was very anticlimatic for passengers who..given the badge, engine, and sound, expected a lot more.

But hey, lets go find 5mi of "empty highway" and I'll show you something different...that only exists at the off-ramp the unicorn farm.

mark kibort

its not only 70 to 80mph as an advantage which is where i like to accelerate, but its also 40 to 50mph. now, if you are taking 1st gear redlining, from light to light as you say, then yes, the 2.54 or 2.72 is your gear box.

Charley B

FINALLY!!!! Quick Jeff, close the thread.

elgreco

thank you

Speedtoys

Ya Mark...thats where I started this thread.

It only took you 6 pages of redirection to wonder if that's what we were talking about.


In the famous words of Bill Engvall, "Here's your sign..."