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Old 05-05-2007, 04:16 AM   #1
Alpine White
Join Date: Apr 2007
Location: Downtown Toronto
Posts: 1,297
what RPM should I change my gear in order to have max. accel and power?

I have e46 323ci with auto+tip tronic

previous owner of this car showed me what RMP should I change my

gear in order to have max accel and power.

I guess it was 5500 or 6000. that time I could feel car is really different

compare to normal "D". feels like someone is pushing my back.

do you know what RPM will produce max accel and power?

Displacement 2.50 L | 152.6 cu in. | 2501.1 cc.
Horsepower 170.00 HP (125.1 KW) @ 5500.00 RPM
Torque 181.00 Ft-Lbs (245.4 NM) @ 3500.00 RPM

is this mean I will have max HP @ 5500? and max torque @ 3500 ?
what does torque do? sorry for noob question. just want to clear myself.
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Old 05-05-2007, 04:28 AM   #2
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Just put it in "D"...or get a stick, and know how to use it! If you cant feel it, then your results will be better in auto...
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Old 05-05-2007, 05:21 AM   #3
Alpine White
Join Date: Apr 2007
Location: Downtown Toronto
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i forgot to mention that please don't tell me to get a manual or other things because I just bought my car and will stay for at least 2 years.

btw I tried to take a look at ur website but url does't work.
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Old 05-05-2007, 08:02 AM   #4
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Location: Milton
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Due to the significant difference in gearing between one gear and the next. Even though your car will have less torque at the redline then it would when you shift at say 5500 rpm, it WILL actually accelerate faster when you shift it at redline. This is due to the gearing of the transmission and how wide the gears are spaced appart.

I hope this is quite clear. In other words, the gearing on your transmission contributes MORE to acceleration the the engines' given torque at a specific RPM

That is why race transmissions have gearing that is extrememly close to one another and allows the driver the benefit of staying closer to the peak torque numbers.


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Old 05-05-2007, 09:37 AM   #5
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Location: Bradford, ON
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This is something I've actually spent some time on figuring out with my car. The easiest way to figure out: go to a dyno and do a run. From the torque graph and transmission gearing you can figure out at what speed and rpm to shift at. The goal is to keep as much torque transferred to the drive wheels throughout every shift. There is a lot of fine tuning to do, I find it a lot easier to do with an excel spreadsheet. Punch in a few formulas for the gearing, torque values and speed and you eventually have something to work with.

For example with my car, my optimal shift points are:
1-2nd shift - 7000rpm - 57.5km/h
2-3rd shift - 6900rpm - 95.5km/h
3-4th shift - 6700rpm - 138.5km/h
4-5th shift - 6400rpm - 178km/h
5-6th shift - 6500rpm - 224.5km/h (if I had a 6spd transmission)

Gearing matters, but only in the transmission, the final drive (differential) gear ratio and wheel circumference wouldn't change these shift points, just the speed they were made at.

It's different with every motor depending on torque and where the motor's power band is.

By the way, notice horsepower is never mentioned in how to figure out shift points and make your car accelerate faster? Because it's a useless number!!
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Old 05-05-2007, 10:28 AM   #6
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What these guys said, plus:

An M52TUB25 (which is what you have) has a just about flat torque band, moderately spaced gearing, and a pretty low 6500 limiter. With these specific traits of your car, just leave it in D (or S) and floor it. If the car had software with a 7000rpm limiter, then shifting prior to redline would help.
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