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      07-27-2012, 04:42 PM   #111
pbonsalb
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The newer BMW M cars like the 1M, M5, X5M and X6M have a pretty good torque to horsepower ratio and offer very good performance. The new M3 will probably be comparable and likely outperform the previous M3.
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      07-27-2012, 07:16 PM   #112
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Exactly!

Swamp, you and I have had some good banter on here, and I respect your posts highly since you are one of the few that actually add value to the forums.
Right back at you!

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Please corroborate the message that I am trying to deliver by reiterating the statement of mine that horsepower can't exist without torque.
Yes absolutely (for rotating engines). Then to extrapolate you can know the performance of any given vehicle with said engine by knowing either the torque curve + gearing or simply by knowing peak hp. You get a darn good estimate with peak hp alone but of course knowing the full hp curve is better.
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      07-27-2012, 07:19 PM   #113
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My view on this is that the 4:10 gear is probably better suited for the "range" in which you are using the car. Same would hold true for the GT4. On a race track, you would rarely use the full range of the 6th gear with the taller gearing. Using the 4:10 gear allows maximizing torque at the wheel (the total area under the curve for all gears) in the desired speed "range" required at the track.
Agreed. Also in contrast to drag racing which is always across multiple gears. There are track sections which from corner to corner will can rely on a single gear without getting to redline requiring a shift. A FD modification can have a good impact on the time through such a section.
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      07-28-2012, 07:59 AM   #114
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Originally Posted by CanAutM3
The reason it is best to use a 1:1 ratio, is that on most gearboxes, this ratio is a direct drive (doesn't go through gears), so there is less drivtrain loss due to loaded gear meshing.
I think the 1:1 gear ratio thing is mostly myth. I can assure you that all 1:1 ratios are not direct drive, and do not bypass the gears. They have just as much mechanical loss (if not more) than the other gears in the gear box, and they still go through the final drive -- which has its own set of mechanical losses as well. The mechanical losses of our gear box was posted on this forum years ago, and on the 6MT, the 1:1 gear turns out to be the second least efficient gear in the transmission -- and has the second most loss in it. This has been recorded and verified on a hub dynos like Dynapack many times as well. Go dyno in 1:1 on a Dynapack, and you'll get much worse numbers than any other gear.
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      07-28-2012, 12:27 PM   #115
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Quote:
Originally Posted by img View Post
I think the 1:1 gear ratio thing is mostly myth. I can assure you that all 1:1 ratios are not direct drive, and do not bypass the gears. They have just as much mechanical loss (if not more) than the other gears in the gear box, and they still go through the final drive -- which has its own set of mechanical losses as well. The mechanical losses of our gear box was posted on this forum years ago, and on the 6MT, the 1:1 gear turns out to be the second least efficient gear in the transmission -- and has the second most loss in it. This has been recorded and verified on a hub dynos like Dynapack many times as well. Go dyno in 1:1 on a Dynapack, and you'll get much worse numbers than any other gear.
Well, yes and no...

I believe there are quite a few transmissions out there that connect the input shaft directly to the output shaft for the 1:1 ratio, therefore letting the layshaft spin the gears without any power transmitted through them. However I agree, there are plenty of other transmissions that use gears for the 1:1 ratio. I do not know how the M3 6MT is laid out...

Even in a transmission that has a direct drive 1:1 ratio, I agree that the 1:1 ratio might not be the most efficient overall, as the faster you spin the drivetrain, the more losses you will have, thus partially or totally negating the benefit of the 1:1 ratio. Every gearbox/drivetrain setup is different.

Last edited by CanAutM3; 07-28-2012 at 12:48 PM.
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      07-29-2012, 10:27 PM   #116
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Quote:
Originally Posted by CanAutM3
I believe there are quite a few transmissions out there that connect the input shaft directly to the output shaft for the 1:1 ratio, therefore letting the layshaft spin the gears without any power transmitted through them. However I agree, there are plenty of other transmissions that use gears for the 1:1 ratio. I do not know how the M3 6MT is laid out...
Think you can find a picture to post of one of those types of trannies? Maybe post cut-away picture, or even a make/model number? That would be pretty sick if one could be built that way and I'd love to see how that could be done.

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Even in a transmission that has a direct drive 1:1 ratio, I agree that the 1:1 ratio might not be the most efficient overall, as the faster you spin the drivetrain, the more losses you will have, thus partially or totally negating the benefit of the 1:1 ratio. Every gearbox/drivetrain setup is different.
You sure shaft speed is in the physics equation for a gear's mechanical efficiency? I don't think it is. But if you're talking about the inertia of the wheels, then yes you lose more the faster you spin.
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      07-30-2012, 11:47 PM   #117
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Many great points and very informative. I stated plenty of times why I went with those gears (the feel - nobody can argue that away), but here is a quick question, why did BMW chose to equip the M3 GT4 with the 4:10 gears? We all know there is no free lunch, and that gearing has its disadvantages, yet they still went with. Any ideas?

Best question asked so far. If BMW used 4:10 in this setup, then.......
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      07-31-2012, 08:31 PM   #118
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Buy a supercharger ....
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      07-31-2012, 09:47 PM   #119
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Quote:
Originally Posted by img View Post
You sure shaft speed is in the physics equation for a gear's mechanical efficiency? I don't think it is. But if you're talking about the inertia of the wheels, then yes you lose more the faster you spin.
Inertia has an impact and so do the shear forces of the oil in the transmission and diff. Power to overcome drag is proportional to the cube of speed...

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Think you can find a picture to post of one of those types of trannies? Maybe post cut-away picture, or even a make/model number? That would be pretty sick if one could be built that way and I'd love to see how that could be done.
This is the best illustration I could find quickly . The concept is actually quite commonly used... this is a big reason why we often see 1:1 ratios in gearboxes as it eliminates the need for a set of gears.

In this example, for gears 1,2 and 3 the power is transmitted from the input shaft to the lay shaft through the set of fixed pinion gears (left most gears in the illustration); then from the lay shaft to the output shaft through the selected gears. The gears are free to spin on the output shaft unless they are connected to it by the dog collar when a gear is selected.

In fourth gear, the dog collar directly connects the input shaft to the output shaft. The fixed pinion gears will still spin the lay shaft and all the other gears, but since none of the other gears are connected to the output shaft, no power is transmitted through the them.

In reverse, the power is routed through an additional idler gear to reverse the rotation.

Typically a 3 shaft design is used on RWD cars to keep the input and output shafts on the same axis, while FWD may use a 2 shaft design.
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Last edited by CanAutM3; 09-14-2012 at 07:02 AM.
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