[NFS]

Originally Posted by teknochild

i should just totally remove the auto stuff though, i only even posted that because all i had to do was change the #defines i used

This is my slight concern about using the dyno as the starting point.

If you wanted to compare both gearboxes you would need dyno's from both.

I still think the best bet would be to start with the engine torque then work forwards from their.

Anyway .. I think it's interesting that in theory the 335i should be short shifted (very slightly).

My 530d definitely benefited from short shifting and I proved this with a similar calc to the one you posted int his thread.

[BoostedBMW]

I don't know enough about automatic transmissions in general with torque converters and all to really make an informed post here, but what I have noticed is that AT BMW's have always had higher gearing then the same model with a MT. For example, I remember the E46 325ci with an AT had the most aggressive gearing of all the non-M 3'er. I don't know why they wouldn't put the more aggressive gearing in a car with the same exact engine platform, but there must be a reason why they always do it. Maybe they feel that you would have to shift too often with a manual? Too much wheel spin? I have no clue, but I have always seen that AT's always have more aggressive gearing then the same car with a MT. I don't think this post has informed anyone of anything, but I just figured that I would type what I was thinking no matter how useless it might be.

[teknochild]

Originally Posted by needforspeed

This is my slight concern about using the dyno as the starting point.

If you wanted to compare both gearboxes you would need dyno's from both.

thats true in a sense, but not in practice, the only thing that ACTUALLY effects results is the SHAPE of the torque curve, which is pretty much the same between manuals and autos

values dont matter at all they can be 10 300 or 3 million, the results will be the same if the shape of the curve is the same

Originally Posted by needforspeed

I still think the best bet would be to start with the engine torque then work forwards from their.

i actually did do that, i found a BMW released graph, it has abit different shape (again what is important) than the wheel dyno, i sculpted it into numbers and the results were a bit diffrent, redline first, short shift second (6800) WAY short shift third (6200)

i dont think this is acurate though because driveline loss changes the shape of the curve (not just the values)


again if i could get ahold of a proceede log file of 1st and second gear, full throttle from 1k all the way up to 7k in a straight line (without shifting) i could tell you with 100% certainty wether or not the car is putting out more torque all the way to redline then it is in the next gear (notice ive stopped saying "needs to be shifted", dont really want to deal with arguing with people at this point)

Originally Posted by BoostedBMW

I don't know enough about automatic transmissions in general with torque converters and all to really make an informed post here, but what I have noticed is that AT BMW's have always had higher gearing then the same model with a MT. For example, I remember the E46 325ci with an AT had the most aggressive gearing of all the non-M 3'er. I don't know why they wouldn't put the more aggressive gearing in a car with the same exact engine platform, but there must be a reason why they always do it. Maybe they feel that you would have to shift too often with a manual? Too much wheel spin? I have no clue, but I have always seen that AT's always have more aggressive gearing then the same car with a MT. I don't think this post has informed anyone of anything, but I just figured that I would type what I was thinking no matter how useless it might be.

i think its a combination of exactly that, to much torque to launch with, and shorter gears, not as big a problem with an AT