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I've had discussion with another forum member regarding horsepower, torque, shift points, etc, and from that I have seen many dyno sheets of tuned E63, with/without downpipes and it became evident to me that the factory shift points (6400 or 6500 rpm) is too high for most of our tuned vehicles. The power increase is mostly midrange and we lose to much relatively by 6000+rpm that we are better off in a higher gear even accounting for the drop in wheel torque that happens when you shift up.
With the gear ratios on our m157 transmission, each upshift results in approximately 30% reduction in rpm. So a shift at 6500 will result in drop in rpm to 4500. Every time you shift up a gear, your engine torque goes up but you lose about 30% torque to the wheels for every ftllb your engine is putting out, because of the gearing disadvantage. For some cars, its a different percentage for different gear shifts (eg. 20% for 1-2 vs 30% for 4-5) but the gears are spaced pretty evenly in the m157. To simplify things, and not need to do too many calculations, you must look at the horsepower curve. Not the torque curve. Horsepower curve accounts for the mechanical disadvantage of the higher gear AND the advantage of higher torque at lower rpm. Using the torque curve ignores the fact that you lose 30% force to the wheels at the next higher gear for any given rpm.
I have attached a dyno sheet for illustration purposes
If you don't follow whatI have said until now, just know this fact:
For maximum acceleration, you want the maximum area under the horsepower curve in the RPM range you will be at during WOT. For us that means 4400 rpm to 6400 rpm if we do not modify shift points (correct me if im wrong, it may be 6500 but I think its 6400). In the example dyno above, you can see that the area under the horsepower curve between 4500rpm and 6500rpm is less than the area under the curve between 4000rpm and 5700rpm. Shifting at 5700rpm would mean you start at ~4000rpm in your next gear. This will give better quarter mile trap and times vs 6400rpm shift point for the vehicle that was dynoed above.
If you look at a dyno of stock E63, you will see that 6400 rpm is a good shift point based on the horsepower curve.
What we need from our tuners, ideally is the ability to calculate area under the horsepower curve between two rpm values, to determine the ideal shift point for each gear (max area). If precise area under curve calculation is not possible with our software, careful eyeball of the horsepower curve over rpm values 30% apart (max rpm, and max rpm x 0.7). Different platform would have different gear ratios and something other than 30%.
If you use the paddle shifter to upshift while you are in wide open throttle will the E63 upshift or will it hold the lower gear. We all know that in part throttle it will usually upshift but what about wide open throttle?
'03 E55, Range Rover Sport Supercharged, Ducati 748R
Good luck trying to time the shifts to correspond with a target rpm. The lag time between a paddle depress and the actual initiation of a shift is a joke!
You would think that multiple tuners would have considered this... makes sense what he's saying though
consider a Diesel engine with much of its torque down low in the rpm band.... why wouldn't that car have low shift points at WOT? Seems like hp has something to do with it too
also the torque curve is different in each gear, torque and gear ratios will determine this as well
Last edited by PeterUbers; 03-27-2017 at 08:44 AM.
much when the car make shift ... put the car on dyno at 5000 rpm to the redline to see the graph is the same thing ... but i think the problem is probably the manifolf without a good flow its why the boost decrease at high rpm
I had this theory after running my car at the strip, but I didn't have all the data to back it up. Not only is it going to a higher RPM which isn't producing the most power, it's generating unnecessary heat in those ranges too only to result in timing being pulled from the car.
A car that puts more power to the wheels will go faster not slower. Area under the curve is the average wheel horsepower between 2 RPM points. Those points being the shift point and the RPM that the car drops to when it up shifts.
Good luck trying to time the shifts to correspond with a target rpm. The lag time between a paddle depress and the actual initiation of a shift is a joke!
Biggest problem with manual shifting right there.
So close to redline by the time you shift at 5700 the car is going to automatically get to it before your input does lol
The car will be slower if you shift by a dyno graph I can almost guarantee it
Why do you keep repeating this?
E65 is likely right, and if tuners would pay attention and adjust the shift point at 5700 rpm that will keep it more in its peak power on each gear shift on a tuned m157 which runs out of breath on top end.
So close to redline by the time you shift at 5700 the car is going to automatically get to it before your input does lol
Hit the paddle earlier, one can't expect instant shifts. I would guess hitting it when you see 5400 will net a 5700 shift factoring human and mechanical delay.
Manual runs were about .2 -.3 seconds off the pace versus S+ when I was at the strip. Like someone else mentioned here, the delay in up-shifts when using the paddles negates any benefits of a selecting your own higher shift points.
E65 is likely right, and if tuners would pay attention and adjust the shift point at 5700 rpm that will keep it more in its peak power on each gear shift on a tuned m157 which runs out of breath on top end.
Because I've tried it and your just guessing! the car just loses momentum
Why do you think none of the biggest tuners who tune gtr porsches etc where mapping is much more well known when tuning the transmission they spend months researching what's best and none of them tune for this it doesn't work in fact I'm going to go out and race my friends big hp Subaru tonight I can guarantee myself I will lose horribly if I shift at 5k compared to letting the gearbox do it's work
Maybe its just me but my car has never shifted at 6400 rpm highest I think I saw was 6100 if that but I agree the powerband compared to gearing is pretty jacked up. There must be some reason Mercedes did it. It just cant be to go faster. My opinion is to make things last much longer. I've brought this up before all things aside without getting mathematical and complicated lets keep it simple...
Most Dyno's are done or should be done in 5th gear which is 1:1. That is the gear the most "true" hp will be transferred to the wheels. From what I've experienced the 4-5 shift happens around 126-130 or so depending on what the car shifts at as well as tire size.. That is ridiculous lol so we arent seeing what these dynos are showing until that mph.
Shift points can make a difference especially on the 4-5 shift. I try to shift around 5 thousand. Here are a couple visuals to kind of help make sense of the issue. These are based on the stock 7 speed mct, 2.65 gear and 26" tire.
If you want to go faster the goal is to get to whatever your 1:1 is as quick as possible and finish the Race at around redline. The 2.65 gear seems to be the biggest issue. If someone were able to put say a 3.08-3.23 gear in one of our cars I guarantee it would outrun cars with much more power. The downside would be the torque multiplication and breaking stuff lol
Why do you think none of the biggest tuners who tune gtr porsches etc where mapping is much more well known when tuning the transmission they spend months researching what's best and none of them tune for this it doesn't work in fact I'm going to go out and race my friends big hp Subaru tonight I can guarantee myself I will lose horribly if I shift at 5k compared to letting the gearbox do it's work
Good luck tonight take the GoPro! And yes you're correct! I would try on the 4-5 shift and see how that feels though. I roll race a bunch and from my experience it does help but I also dont have a tune so might be different result for you.
I'm going on basis of the tachometer it's possible the tachometer is off by a little bit. The factory shift point works well for factory tune that's why Mercedes did it that way. Aftermarket tune adds way more mid-range power but doesn't add much after 6000 RPM.
ideally the shift points would be adjusted on the tune. I think it's a lot more difficult to get the exact shiftpoint using the paddle shifters
'03 E55, Range Rover Sport Supercharged, Ducati 748R
Originally Posted by PurpleHeartAMG
Everyone on about the delay from paddle to shift... Really, how hard is it to just shift a split second sooner? Cmon now
Can you do it from 1-2? NOPE! Is the lag time between the paddle depress and actual shift always the same? NOPE! Why should anyone have to "time" the shift on a transmission that brags about 100ms shifts.
Can you do it from 1-2? NOPE! Is the lag time between the paddle depress and actual shift always the same? NOPE! Why should anyone have to "time" the shift on a transmission that brags about 100ms shifts.
Thats the problem when it has no consistency you can never get it right each time
03-26-2017, 11:42 PM
The proof is on the paper though.
