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I was pondering what the best shift points would be for the Elise -- specifically, what speed would correspond to 6000 rpm and 8200 rpm in each gear, the range where the engine creates maximum power. My thought is, if I'm driving along at, say, 40 mph or 55 mph and want to downshift for max acceleration, what gear should I pick?

Well, I have a VibeGT with the same engine, tranny and axle ratio the Elise will have. Of course, the 16-inch wheels on my Vibe probably have a slightly different outside tire diameter, so I would need a conversion factor. But I rather guess that the 17-inch Elise rear Yokohama tires are lower profile than my Continental original equipment tires, so they might be pretty close.

Anyway, here's what I figured out, if anybody is curious. I checked my speed in each gear at 3000 rpm:

1st: 17 mph
2nd: 25
3rd: 34
4th: 43
5th: 53
6th: 67

Doubling that would give me the car speed at 6000 rpm, and mulitplying by 2.73 gives me the speed at 8200 rpm. Here are the ranges of car speed at 6000--8200 rpm:

1st: 34--46 mph
2nd: 50--68
3rd: 68--93
4th: 86--120
5th: 106--145
6th: 134--183

Of course, wind resistance inhibits speed at the top end, so the upper values are theoretical. But the answer to my original question is apparent. At 40. I could actually downshift to 1st for a quick boost, but I probably wouldn't, since I'd lose enough time just after that shifting into second. At 55, though, I would find the sweet range in 2nd gear.

Anyway, hitting 6000 rpm, my VibeGt noticably cranks up. The Elise will scream in those ranges. I think for common driving, or I guess for racing, it would be good to memorize those ranges, or whatever they correspond to in the Elise.

One other interesting point. I remember reading in this forum somewhere that the 1st to 2nd shift pulls the engine back to the lower valve cam setting. That looks to be the case, as you can't quite get to 50 in first gear.
 

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I understand that the revised Redline for the Elise is 8500 for short bursts, 8000 sustained. Also, while it goes on the high speed cam at 6200 it falls off the high speed cam at 5800. It is easy to rather than estimating based on the Vibe, use the tire size 225/45/17. The transmission ratios have been list previously on the forum.

I think with the new parameters, you will find it will stay on the high speed cam if you do your part.

Good Luck,
Greg
 

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OK, I have done the calculations and I wrong. Here is what I got.

Gear 5800 8500
1 30.5 44.7
2 46.4 68.0
3 64.4 94.2
4 81.6 119.6
5 103.8 152.2
6 116.7 171.1

Gear ratios I used:
1st: 3.116
2nd: 2.050
3rd: 1.481
4th: 1.166
5th: 0.916
6th: 0.815
Final: 4.529

So it does look like even with the higher rev limit and lower drop back off the cam, you still fall off on the 1-2 shift. The 2-3 shift will be tight (perfect shift) after that it should not be a problem.

I appears that the gear splits were not well designed for the VVT-Li engine. The Lotus tuning helps but does not cure the problem.


Greg
 
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