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Old 03-17-2004, 02:32 AM   #1
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Shifting points in a race! All read its interesting!

Ok so. Me and Vamz are debating with these 2 other guys, that...what they are saying is that in a straight line 1/4 mile street race/track whatever.


Here is the scenario:

2 E46 2004 M3's

One driver shifts at max torque, which is ~6500 RPM on the M3.
The other driver shifts at redline ~7900-8500 RPM on the other M3.

The other guys say the max torque shift will accel faster in the 1/4 mile and win. whereas me and vamz say redline man will win.


What do you think? This is assuming the shift time is exactly the same. They don't believe me that when you shift that low in a race, you lose your powerband. But they say the RPMS will "quickly go back up."

What do you think?
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Old 03-17-2004, 02:43 AM   #2
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does the torque drop off after 6500 or is it a flat curve all the way to redline...
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Old 03-17-2004, 02:56 AM   #3
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http://www.turnermotorsport.com/imag...dyno_s54m3.jpg


link to E46 M3 dyno.
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Old 03-17-2004, 03:00 AM   #4
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Rev to redline will be faster. Remember, the lower the gears, the higher the ratio is. Thats all that matters. In theory, if first gear has a 3.5:1 ratio, I guess it could mean that the car is putting 274 to the wheels, first gear will multiply power by 3.5 to the wheels = 959 to the wheels. I dont know how to really explain this but I got it in my head.

Thats why when you dyno cars, you dyno them on the gears that is in a 1:1 ratio.
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Old 03-17-2004, 03:03 AM   #5
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yea i know what you mean.
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Old 03-17-2004, 03:06 AM   #6
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Quote:
Originally Posted by Tuscan
yea i know what you mean.
One of the very few times where people understood that concept.
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Old 03-17-2004, 03:08 AM   #7
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Quote:
Originally Posted by TeKNiC330
One of the very few times where people understood that concept.

cause it multiplies it, from the crank, so like the M3 i think has a 1:1 ratio in 5th, so they dyno that puppy in 5 if it was...
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Old 03-17-2004, 03:12 AM   #8
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Originally Posted by Tuscan
cause it multiplies it, from the crank, so like the M3 i think has a 1:1 ratio in 5th, so they dyno that puppy in 5 if it was...

the tranny ratio is but the differential ratio isn't.

but the truth be told, it wont show up on a dyno. you can dyno in 3rd or 4th and you will never be able to tell the difference from looking at the dyno chart.
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Old 03-17-2004, 03:27 AM   #9
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yea i was counting out the diff.
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Old 03-17-2004, 03:38 AM   #10
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Quote:
Originally Posted by Tuscan
yea i was counting out the diff.

and i'm saying the tranny gear ratio or the differential ratio wont make a difference on the dyno chart.
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Old 03-17-2004, 03:39 AM   #11
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and i'm saying the tranny gear ratio or the differential ratio wont make a difference on the dyno chart.
really? news to me.
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Old 03-17-2004, 04:38 AM   #12
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really? news to me.

had my m coupe dynoed in 2nd 3rd and 4th

the variation was about 3-4hp which can happen between dyno runs using the same gear.
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Old 03-17-2004, 06:49 AM   #13
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i heard from bimmerforum guys

they say to shift at the lower rpm or the high point of the torq. point. to go threw more gears to get a extra boost from a extra gear than red line the motor in a 1/4 mile race. trick is always catch the rpm's at the right time so
when you shift car will accerate at full force. excuse my spelling on this post
lollllllllllll
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