Rev-matched down shifts/SMG thoughts

erikmoeser · 5th January 2007, 19:56

Rev matching when downshifting, on the brakes or not, is an art and many of us do it routinely and well. The SMG ability to do that "automagically" is certainly cool, but not amazing, and in my experience at M School, was extremely consistent, although not (at least on "my" car) completely accurate, being about 200 or so rpm short as the clutch engages and completes the match. A good manual driver can do way better, but not perhaps as consistently.

One thing I noted yesterday on a balmy little top down drive in my S2000 (January? Wisconsin? You're joking, 007), a car for which a 6 speed manual is as "natural" (it comes no other way) as some members here think the SMG is natural for the M5, is that when braking hard into a corner, I typically choose my gear just at the turn in, and it may be going from 5th to 2nd at that point with no time in the intervening gears. SMG of course would require three shifts, however brief a time spent in the intervening gears, easy enough with flicks of the finger, but "different" than we manual types would typically do it. Yeah, I know some people work up and down through all the gears, but from a pracitcal standpoint it is usually unnecessary in either direction and just wears things out faster. And downshifting through the gears can't add any deceleration to what the brakes are doing because they already usually take the tires to the limits of adhesion.

rodman31 · 5th January 2007, 20:14

Ughhh???!! Downshifting as you are going into the corner?? Thats a new one to me, usually best to brake and downshift in a straight line. Hey, if it works for you great. The SMG will allow you to change more than one gear at a time as long as by doing so you do not exceed the rpm's, just as with a standard the same principal should apply! This is also one of the benefits of the SMG system as opposed to the newer double clutch systems which will only allow one gear at a time. I am a little confused at what speed you are traveling going from 5th to 2nd without any intervening gears??!

Anyway, the SMG is one smooth operation, barring the few failures!

Robert

Sebring NL · 5th January 2007, 20:42

Yep

This is where the left-foot braking comes in in manual transmission cars

I use it all the time on a local "racetrack" called the Mini Ring...The car I use for this is FWD and has no weight in the back, so I change the shift before the corner, using the rev-match sideflip, and use my right foot slightly on the accelerator to prevent the car from becoming unbalanced ( which would mean the back breaks loose because of the hard braking) .

With milliseconds between the braking and the correctional throttle use, the car remains stable. Took me a few spins to find that one out though!

Wout

MRichmond · 5th January 2007, 20:52

I think that is one of the most strained justifications for preferring the 6-speed over the SMG I have seen yet. "A good manual driver can do way better" rev-matching downshifts than the SMG? Please.

And as Robert said, every racing instructor will tell you that the downshift and braking should be done before the turn begins.

erikmoeser · 5th January 2007, 21:08

Perhaps I could have been clearer. My downshift is "at the point of turn in", meaning at the speed of the corner. Whether is is a second b4 that exact point is not of consequence, however. The point was that along the straight at say 120 mph in fourth or fifth , and the corner is to be taken at say 35, then it is hard on the brakes, and at the point of turn in, about 35 mph plus or minus, the shift is made directly to 2nd. Yes, before the car is turning very much at all so as not to inadvertantly break loose with a sloppy downshift rev match which can happen.

I am not using that to "justify" the 6 speed over the SMG. If I wanted to do that , which I don't (I have made my own choice) I would go to the areas of reliability and style and fun and whatever, not inability to skip gears,, which we have now learned can be done, unlike the DSG transmission, or the less than perfect rev matching I know I experienced with at least one car. I see the rev matching as a cool feature, but not anything we humans can't do JUST AS WELL, albeit with concentration and not as consistently, with a little practice. Speed of upshifting and downshifting is an entirely different matter. Some people, as you know, make no attempt to rev match, and so for them SMG rev matching must seem like the living end. My TL has perfect rev matched upshifts if you care to wait for the revs to drop.

Mr. Vroom · 5th January 2007, 21:32

Ironically, since I have had the M5, I have become better at rev matching and heel and toe downshifting in my 6 speed. I don't think the average driver will be able to beat the computer here. When the M was new this feature used to put smiles on my face; now I take it for granted. The smiles now happen on the odd ocasion when I nail a perfect downshift on the 6 speed.

T Bone · 5th January 2007, 21:41

Quote:

Originally Posted by erikmoeser

Perhaps I could have been clearer. My downshift is "at the point of turn in", meaning at the speed of the corner. Whether is is a second b4 that exact point is not of consequence, however. The point was that along the straight at say 120 mph in fourth or fifth , and the corner is to be taken at say 35, then it is hard on the brakes, and at the point of turn in, about 35 mph plus or minus, the shift is made directly to 2nd. Yes, before the car is turning very much at all so as not to inadvertantly break loose with a sloppy downshift rev match which can happen.

I am not using that to "justify" the 6 speed over the SMG. If I wanted to do that , which I don't (I have made my own choice) I would go to the areas of reliability and style and fun and whatever, not inability to skip gears,, which we have now learned can be done, unlike the DSG transmission, or the less than perfect rev matching I know I experienced with at least one car. I see the rev matching as a cool feature, but not anything we humans can't do JUST AS WELL, albeit with concentration and not as consistently, with a little practice. Speed of upshifting and downshifting is an entirely different matter. Some people, as you know, make no attempt to rev match, and so for them SMG rev matching must seem like the living end. My TL has perfect rev matched upshifts if you care to wait for the revs to drop.

I am not sure how much track experience you have but I don't know any living person that can consistently match the SMG (or Ferrari's F1) for downshifting in terms of rev matching and time for change.....it is just fallacy believing so.

People seem to believe SMG upsets a car's balance.... the time it takes for SMG to change gears, the car's dampeners and springs don't have time to see-saw like a car would with a manual box.

In addition to skipping over gears, you can actually blip the throttle with SMG on downshifts....that is if you think you are better than the computer.

Finally - what race course are you going from 120 mph to 35 mph?? I would like to see that one, must have a long run off area.

unfoundhorsepower · 5th January 2007, 22:34

Not talking bad at you....But maybe you need a driving course...your NOT shifting properly.......

Sebring NL · 5th January 2007, 22:45

Quote:

Originally Posted by T Bone

I am not sure how much track experience you have but I don't know any living person that can consistently match the SMG (or Ferrari's F1) for downshifting in terms of rev matching and time for change.....it is just fallacy believing so.

.

I have been out with drivers that 100% sure can match revs consistently.

I even dare to say that on my favourite forrest road, in one of my own cars, ( please don't take this wrong) mine are perfect. Note, I am not saying I am a perfect driver, but if I was to take the E60 M5 down that road with a manual for the same period ( some 3 years) , the rev matches would be spot-on with SMG.

rodman31 · 5th January 2007, 22:50

I used to "heel and toe" and was ok at it, sooooooo I spent the $3500 to attend the "M" driving school. We spent about a solid hour practicing "heel and toe" in the M3, this was a great help to getting a solid handle on the technique! Not to mention we spent the next 2 days going over and over the technique. However, I would never ever, ever kid myself into believing I could ever, ever match wits with the SMG computer, period.

By the way, at Summit Point Raceway in WV, they have a Shenandoah course and on turn 9, I believe, I was going around 140mph down to maybe 60-70 mph in 2nd gear. Lots of braking and quick downshifts. I think I have some video of this turn, maybe I will post!

Robert