BMW M3 M4 RPM Redline Visual, Finally

[Onurleft]

Just to point out a few things for comparison sake.

Most GTR guys (namely the guys setting the 1/4 mile records in stock form) are short shifting the cars in first gear only (6600RPM) then letting it wind out to the 6800 redline for 2nd gear and beyond. The built motor guys are revving beyond 9000 RPM...

A stock GTR peaks torque in the low 4000RPM range (roughly 420awtq) holds about 400awtq shortly after to about 5500 RPM then falls off to about 350 wheel torque at 6850 RPM (Avg. late model car on a dynojet).

To say "the torque falls off you will have to short shift way early" is not looking into the quantitative factors of this equation carefully.

As torque falls off (as it does in all cars), enough revolutions CAN keep the horsepower constant, or increase it and this applies to FI cars.... For our purposes, horsepower is the rate work that is done by a factor of time . More RPM = more work "can be done," assuming your torque doesn't plummet (Mazda Speed 3, 335i, E36 M3 U.S spec beyond 6800).

If you calculate horsepower using torque (with a rough estimate on the graph using increments of 2000 RPM)

@5700 RPM you are making 370ft/lbs which equates to 401 HP
@7300 RPM you are ONLY making (rough est. as it looks to drop 110ft/lbs in 1000 RPM)
about 290ft/lbs but that equates to 403 HP

As your M3/M4 needle swings past 7100, the car is still doing more work in the same amount of time despite the drop in torque Vs. a lower RPM and the rate of increased torque on the graph. As you go past 7300 RPM the H.P numbers have only dipped a slight percentage from 7100. At 7600 RPM though, it has gone down to roughly 391hp..
RPM and the fact that it looks as if the BMW will only loose about 110ft/lbs of torque from 5700-7600 RPM is to thank for that. Other, less important cars (haha) drop off torque much more harshly, hence the need for an early shift.
However, the trend with technologically advanced F.I cars (MP4, GTR, or any "built" Turbo car) is as long as you are spinning it fast enough, a slow drop off in torque could still mean more work being done. Once we have real dyno graph's we can calculate this with more accurate numbers and really see how much work is being done is at given RPM's

[A418t81]

Originally Posted by Onurleft

Just to point out a few things for comparison sake.

Most GTR guys (namely the guys setting the 1/4 mile records in stock form) are short shifting the cars in first gear only (6600RPM) then letting it wind out to the 6800 redline for 2nd gear and beyond. The built motor guys are revving beyond 9000 RPM...

Nah, that isn't true. In first gear they spin them as high as they will go. The stock motor/turbo guys usually run out to 7200 rpm or so (stock fuel cut is 7100 rpm on virgin ECU ROMs). There's absolutely no reason to short shift first as it runs out to 7k in literally 1 second after launch. Short shifting 4th into 5th at 6500 rpm is what it takes to get the best trap speeds on E85 as power falls off substantially after that when on the stock turbos with E85 tuning.

[ozinaldo]

Originally Posted by Carlos_Danger

I dont know where you pull off your opinion that the engine is a
"very well tuned 1M engine" when they have specifically talked about
building the engine FOR the new F8X M

but if it is thatd be great, according to Jeremy Clarkson the 1M
has one of the best engines he has ever driven in his life,
the episode is available on Netflix, it was an interesting episode

If you pay attention to what I posted you will see that I did not say S55 "is a very well tuned 1M", I said "like" as in someone estimating something, pointing out a similarity, it's there in my post, I believe it is not a confusing post at all. Just read the whole sentence.

I know very well the Clarkson episode like almost everybody else, thanks anyway.

N54T is a great engine imo, but of course, the S55 will be even better. That is the part of the F8X that I have no doubts about. I don't like to compare apples to oranges that's why I don't want to say that it will be better than the S65 also, because I don't feel like it is a meaningful thing to say, they are different, like N54 and S65 are different too. There are things that one makes better than the other and I have zero doubts that S65 will remain as the better engine in terms of revving, linearity, sound (engine not exhaust) and especially throttle response. The new engine will do other things better, way much better and there are no winners or loosers here, it is a shift or a new way of going fast. In fact, I need to hear more about the steering, manual transmission, clutch, standard brakes, ride (with passive suspension), exhaust, production car's final design inside/outside and the price tag which may kill it or make shine. Engine itself seems fine really.

[bplewis24]

Originally Posted by ScarecrowBoat

Yeah it's pretty hilarious really. People are touting the old M3's engine for it's "hard pull to redline". The new motor produces the maximum hp the m3 slowly built up to over 8400 rpm FOR over 1000 RPM. The build up is quicker, and it produces a substantially higher amount of torque throughout the rev range. Yet we're complaining?

If you had two career paths, both on a 10 year contract, both starting with $100k in pay. One gave you a 21% raise the first five years, but none after that (pay after 5 years being $259k) while the other gave you a 10% raise every year (pay after 10 years being $259k). Are you going to take the first job or are you going to complain that you wouldn't get a raise every year and take the second?!

Originally Posted by Jonjt

This engine is going to feel and drive differently than anything that has come before. I think some of the complaining owners are afraid of change, more than anything.

Quoted for posterity. They are remnants of antiquity. They'd rather drive slower, longer, so that they can feel the rush of speed at a taboo threshold accompanied by a audible cue, rather than, you know, be a driving enthusiast.

[rzm3]

Forget about dynos and gear ratios!

The best way to determine the optimal shift points is to look at real data, that is, longitudinal G.

You would simply shift up if the longitudinal G in the next gear at the respective RPM is greater than the longitudinal G in the current gear at current RPM.

See below. (from lapfaster.com, or what used to be there)

[Stratus650]

I hate where it says READY on the tacho, makes me feel im in a hybrid car or sumthin lol

[MCHL]

Originally Posted by SoCalS2k

3 and 4 series have HUD so I'm sure we'll see it as standard on M3 and M4, and with M mode like on M5/M6.

love the new dashboard! are those red and orange lines are LED illuminated?!

[pkimM3r]

Originally Posted by MCHL

love the new dashboard! are those red and orange lines are LED illuminated?!

Compared to the e9xM or the new m5/6 you think the dashboard looks better?

It looks like a noline 3 series dash.

[MCHL]

Originally Posted by SoCalS2k

3 and 4 series have HUD so I'm sure we'll see it as standard on M3 and M4, and with M mode like on M5/M6.

Originally Posted by pkim1079

Compared to the e9xM or the new m5/6 you think the dashboard looks better?

It looks like a noline 3 series dash.

of coz the m5/6 ones are better

[Jonjt]

Originally Posted by rzm3

Forget about dynos and gear ratios!

The best way to determine the optimal shift points is to look at real data, that is, longitudinal G.

You would simply shift up if the longitudinal G in the next gear at the respective RPM is greater than the longitudinal G in the current gear at current RPM.

See below. (from lapfaster.com, or what used to be there)

Attachment 918804

Indeed. But, you gotta start somewhere.

[John Tanglewood]

The tach looks passive. Needs to be more aggressive.

[b33g33]

Originally Posted by Carl L

Last time I saw a 1M was just two nights ago. The stance, and especially fenders, can't help but make one smile. I've never had chance to drive one, but by the stats and reports it must be a riot.

If you're ever in the ATL area, PM me beforehand and I'd be happy to give you some seat time.

[swamp2]

Originally Posted by Jonjt

A decent analysis, aside from one big issue.

Thanks for your blessing, unfortunately yours is not...

Originally Posted by Jonjt

Torque does not perform work, it doesn't propel the car forward.

Positively 100% incorrect.

Originally Posted by Jonjt

This torque roll off you are speaking of might be inconsequential only because the fall off seems slower than the corresponding increase in engine speed.

Correct, I did not say otherwise.

Originally Posted by Jonjt

You should be concerning yourself with the shape of the power curve, only.

Maybe you should, but I shouldn't be. More on that point of view below.

Originally Posted by Jonjt

Your own analysis demonstrates this because you've plotted tractive effort versus wheel speed. With some units manipulation (change the abscissa units from km/h to m/s and the ordinate values to newtons without the multiplier), that becomes power, not torque.

100% wrong again. Yes there are other way to plot this but the plot you describe would tell the exact same thing as mine but the plot would not be power vs. speed, it would still be force vs. speed.

Originally Posted by Jonjt

The intersection of those curves you plotted occurs at the point where the power (not torque) available with engine speed increases is less than that available with an upshift. Since induction performance is not gear dependent, this point occurs at the same engine speed, no matter how fast or slow you are going.

100% incorrect. Because you are missing parasitic losses which are speed dependent.

Either way, due to both the math (the actual way you calculate from crank torque to wheel torque) and the fact that rpm does not "bias" torque the same way it does hp (at high rpms). I maintain that

Originally Posted by Jonjt

However, I'm confident that BMW is far more aware of the math behind picking shift points than you and I. As such, the car will favor higher shift points than is currently believed. After all, short shifting is not in keeping with the ///M aesthetic. That's reserved for the N series drivers.

I'm confident they will pick different gears and FD ratio than I have for the M4 and are more knowledgeable as to the very broad impacts of such decisions (such as fuel efficiency, noise, gear costs, wear, etc.) However, I am also confident that I can compute a shift point just as accurately as they can and infinitely more accurate than you can.

[ixse]

too many "smart people" here lol.. go to actual track w some corners.. and do your shit talking with your lap times.. nobody gives a crap on if you shifted 500 rpm too early..

[swamp2]

Originally Posted by ixse

too many "smart people" here lol.. go to actual track w some corners.. and do your shit talking with your lap times.. nobody gives a crap on if you shifted 500 rpm too early..

The discussion is only distantly related to the talent of individual forum members here. What a stretch really. We are talking about the redline and characteristics of an engine. Certainly engines that must be shifted well shy of redline vs those that can be consistently shifted at redline have a different character. This character is as important to many as their lap times.

P.S. Just to satisfy your potential curiosity I do take my car to the strip and to the track as well.

[swamp2]

Originally Posted by rzm3

Forget about dynos and gear ratios!

The best way to determine the optimal shift points is to look at real data, that is, longitudinal G.

You would simply shift up if the longitudinal G in the next gear at the respective RPM is greater than the longitudinal G in the current gear at current RPM.

This won't be appreciably different than the relatively simple method I've provided (of course assuming the shape and peak of the torque curve is reasonably accurately known). Since "my" method is using the net force at the wheels that is different from the acceleration or "g force" only by the constant of the vehicles mass! Now that being said the method you posted is much more costly, requires data acquisition, testing (and hell even post processing) and will be a bit obtuse to all but the most serious racers...

Oh well to each their own I guess.

[Bimmer4John]

Originally Posted by swamp2

This won't be appreciably different than the relatively simple method I've provided (of course assuming the shape and peak of the torque curve is reasonably accurately known). Since "my" method is using the net force at the wheels that is different from the acceleration or "g force" only by the constant of the vehicles mass! Now that being said the method you posted is much more costly, requires data acquisition, testing (and hell even post processing) and will be a bit obtuse to all but the most serious racers...

Oh well to each their own I guess.

His method (test) is what would be used to validate your method (analysis) as accurate.

Unless someone fully understands all the intricacies of your analysis then they may not be confident in the results. It may be more costly, but the results are easy to understand. You need to keep acceleration as high as possible and you can test to see what shift paradigm works best.

Me personally, I'm struggling to reconcile the fact that max power is held pretty much to redline but your analysis shows short shifting (sub 7k RPM) to be beneficial. I guess, as you mentioned, that losses increase as RPM increases so even though the engine power is constant the effective delivered power may be going down with RPM as well.

Since the M5/M6 engines have similar power delivery, I would be interested to get an owner's (or someone who's driven it) impressions about what kind of shifting worked best for them.

[swamp2]

Originally Posted by johns

Me personally, I'm struggling to reconcile the fact that max power is held pretty much to redline but your analysis shows short shifting (sub 7k RPM) to be beneficial. I guess, as you mentioned, that losses increase as RPM increases so even though the engine power is constant the effective delivered power may be going down with RPM as well.

It sort of comes down to reconciling these two facts:

1. Peak acceleration in any gear occurs at the point(s) where the engine crank torque is peak*. As a result the acceleration curve basically mirrors the torque curve NOT the power curve.

2. Comparing two vehicles identical in all aspects except engines, at a given speed the car that can produce more power will out accelerate the other (WOT of course). Engine torque is truly 100% irrelevant in this point. No not 95% or 99% irrelevant, 100% irrelevant.

(* not counting corrections for drag and tire losses)

Unless you can convince yourself that both of these are correct, you'll probably continue to believe that constant power delivery means don't ever upshift until redline.

Even without losses (no drag, aero nor drive train losses) short shifting may still be required to obtain maximum performance. One does not obtain constant acceleration even with constant power. With constant power acceleration decreases with increasing velocity. This is more or less the definition of power. Constant torque in fact delivers constant acceleration.

So again the reason to shift is not the loss of power but the loss of torque.

Also, it is not just "my analysis". Yes, I have done the entire calculation by spreadsheet manually and it agrees with the software I use for this calculation, CarTest, which has been very extensively validated by me and by others, on this forum and in other places.

Originally Posted by johns

Since the M5/M6 engines have similar power delivery, I would be interested to get an owner's (or someone who's driven it) impressions about what kind of shifting worked best for them.

Both my analysis and anecdotal evidence over at m5board.com indicates the exact same phenomena for the F10 M5.

Hope all of that helps.

[Bimmer4John]

Originally Posted by swamp2

It sort of comes down to reconciling these two facts:

1. Peak acceleration in any gear occurs at the point(s) where the engine crank torque is peak*. As a result the acceleration curve basically mirrors the torque curve NOT the power curve.

2. Comparing two vehicles identical in all aspects except engines, at a given speed the car that can produce more power will out accelerate the other (WOT of course). Engine torque is truly 100% irrelevant in this point. No not 95% or 99% irrelevant, 100% irrelevant.

(* not counting corrections for drag and tire losses)

Thanks for the explanation.

I guess I'm still having a little trouble reconciling those two points above because they don't seem to be mutually inclusive.

For example, at a given speed, if car 1 had more HP than car 2 but less torque then according to your second point car 1 should out accelerate car 2. But your first point says the car with the higher torque should have a higher acceleration. They seem to be contradicting each other. What am I missing?

[Nang Vann]

Nice! Can't wait to buy me one of these!

[pkimM3r]

Originally Posted by swamp2

P.S. Just to satisfy your potential curiosity I do take my car to the strip and to the track as well.

I hope youre not one of those guys who talk scientific at the track though. I cant stand those guys.

Or more specifically just a couple people.

[Boss330]

Originally Posted by swamp2

It sort of comes down to reconciling these two facts:

1. Peak acceleration in any gear occurs at the point(s) where the engine crank torque is peak*. As a result the acceleration curve basically mirrors the torque curve NOT the power curve.

2. Comparing two vehicles identical in all aspects except engines, at a given speed the car that can produce more power will out accelerate the other (WOT of course). Engine torque is truly 100% irrelevant in this point. No not 95% or 99% irrelevant, 100% irrelevant.

(* not counting corrections for drag and tire losses)

Unless you can convince yourself that both of these are correct, you'll probably continue to believe that constant power delivery means don't ever upshift until redline.

Even without losses (no drag, aero nor drive train losses) short shifting may still be required to obtain maximum performance. One does not obtain constant acceleration even with constant power. With constant power acceleration decreases with increasing velocity. This is more or less the definition of power. Constant torque in fact delivers constant acceleration.

So again the reason to shift is not the loss of power but the loss of torque.

Also, it is not just "my analysis". Yes, I have done the entire calculation by spreadsheet manually and it agrees with the software I use for this calculation, CarTest, which has been very extensively validated by me and by others, on this forum and in other places.



Both my analysis and anecdotal evidence over at m5board.com indicates the exact same phenomena for the F10 M5.

Hope all of that helps.

Your knowledge on these subjects are really impressive!!! Thanks for your input and sharing your knowledge with us!

Would this BMW 523i have a "optimum shiftpoint" at around 4250rpm for max acceleration?

http://www.ultimatespecs.com/car-spe...ries-523i.html

And this one at 4800?

http://www.ultimatespecs.com/car-spe...-528i-Aut.html

Or am I missing something here?

Because the auto trans certainly doesn't shift that low at wot acceleration...