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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
For referance, assunming about a 6500rpm shift point a stock 4 speed's shift points are about as follows:

1st to 2nd is a shift at about 53mph with about a 2700rpm rpm drop.

2nd to 3rd is a shift at about 94mph with about a 1900 rpm drop.

3rd to 4th is a shift at about 137 mph and about a 1800 rpm drop.

Red line at 197 mph.

It is fun to look at your dyno graph and plug in your HP numbers at the begining and end of each gear.

If one built a 930 motor that has a shift point of say 7200rpm this exadurates the rpm drops and the first to second shift is more like 3000rpm.

Not many builds including turbos have that wide of a power band. Most build make great power over about a 1500rpm to 2000rpm range.


IMO the large 1st to second rpm drop is the biggest problem with a 930. That drops the motor down to about 3800rpm at just under 60mph which is right in the middle of where most street wars are going to take place. On the track, this is probably going to kill ones speed right as they enter they leave the slowest corner that is right at the begining of the most important long straights on a track.

Even with a monster build that is going to see a greater needed drop in performance with the shift into second on a stock 930 box.

When doing a trans build I would first ask myself what I want first gear to look like. Stock, higher, lower.

Second question is, what do I want top speed to be.

Third, question if it is a street car is what rpm at cruse speed can I live with.

From there, 2nd and 3rd are best fit to keep the motor in its best power band depending on use. It could be near equal rpm drop spacings or lean toward better acceleration early or better acceleration down the longest straight.

Some street builds might end up with closer 1st, 2nd, & 3rd for max street racer acceleration and then a tallish 4th for cruse.
Old 05-15-2010, 03:37 PM
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