BMW M3 M4 RPM Redline Visual, Finally

[CanAutM3]

Originally Posted by swamp2

Results are not at all as you predicted. Shift points are all well below redline. This is with the exact power curve, gear ratios and redline you have used.

Torque is simply falling too fast above ~5500 rpm to "have room" for the force curves not to cross!

IMO, this can only mean that some of the input assumptions in the CarTest simulation are wrong. The results go against basic physics.

I could understand a very slight difference due to parasitic losses in the gearbox, but not this much of a difference.

Let me explain.

Let's take the 2-3 shift for example. Wheel torque in 2nd gear at 7500RPM is 3004lb-ft (296 x 3.218 x 3.154) and in 3rd at 5600 is 3001lb-ft (395 x 2.402 x 3.154). If you do the math for any RPM shift below 7500, you will find that wheel torque in 3rd will be lower than in 2nd, this means that shifting before redline would not be optimal. The same also applies to all gears.

One element that my estimations does not consider, is a portion of the parasitic losses in the gearbox. The torque and power numbers are at the flywheel, so any losses upstream of the gearbox are already accounted for in the torque numbers. For a given road speed (shift point), the drivetrain losses downstream from the gearbox are the same for both gears (drivetrain is spinning at the same speed). The CarTest output suggest a 7200RPM optimal shift point from 2nd to 3rd. This implies that 2nd gear at 7200RPM has 25hp more loss in the gearbox compared to 3rd at 5375RPM. I don't buy it. Inside the gearbox, the losses caused by the higher engine RPM would be in the faster spinning clutches, input shaft, lay shafts and gears. IMO, not enough to make such a significant difference.

[CanAutM3]

Originally Posted by swamp2

By the way I don't think a (fixed) ratio between ratio is at all a standard transmission gear selection technique. It produces very odd shaped speed in gear curves compared to most similar BMWs. More typical is an even spacing on the rpm vs. vehicle speed plots. Below I've shown yours and the M3 M-DCT. The 1M 6MT is not too dissimilar from the M3.

Agreed, my gear selection is a bit odd compared to traditional gearboxes. However, there are not that many engines out there with such a broad power plateau. On the F8X, the power plateau is broad enough to cover all 7 gears over a vast road speed range, hence my equal gear spacing selection.

But BMW will likely stick with a more traditional spacing like they did on the M5. If it is the case, it is a shame, because it would not allow to fully exploit the capabilities of the S55 . I can only hope

[CanAutM3]

Originally Posted by Boss330

Thanks once again. No need to do the 320i

I am really looking forward to the first test drive reviews of the F8x What will the S55 feel like? Does it want to rev etc?

The day I drove the 428i I also drove a E36 M3 3,2. The intersting thing is that the 428i felt more spectacular and entertaining during acceleration. The 428i even had more/better engine noise inside the cabin during hard acceleration and definitely felt quicker. I'm a devoted fan of the BMW I6 engine, but the E36 M3 engine actually felt, dare I say it, uninspiring compared with the N20 in the 428i...

The E36 M3 just has a steady and "slow" rise in revs to redline. The 428i just felt meatier at every stage of the rev scale. I'm sure I still would choose the M3 engine for exhaust sound and smoothness, but that 428i engine just put a big smile on my face. Even though it's slower from 0-100km/h it just feels more spectacular!!

I NEVER thought I'd write what I just did. But that was before I drove the 428i. It felt fast, and it sounded like a sports car engine from the drivers seat, which probably also "helped" my perception of it

Probably active sound?

If I am not mistaken, you are in Europe, so that means it was the 321hp engine in the E36. Which makes your comments even more worth noting...

[swamp2]

Originally Posted by CanAutM3

IMO, this can only mean that some of the input assumptions in the CarTest simulation are wrong. The results go against basic physics.

Unless you have made a spreadsheet or written out the math yourself this is a bold and incorrect thing to say. In addition CarTest has been validated compared to real world test data time and time again, by myself and by others.

Originally Posted by CanAutM3

I could understand a very slight difference due to parasitic losses in the gearbox, but not this much of a difference.

The losses are primarily:

Transmission
Differential
Axles

Some of these move at road speed (rpm) whereas some move at engine rpm (well technically the tranny moves at both...). The total drivetrain loss I am using for these predictions is 11% which is over 40 hp. In addition to this 40 hp you must also account for the effects of drivetrain intertia. This also acts very similar to an actual loss (even though iti is not a truly dissipative loss which converts to heat, the energy is used up to angularly accelerate all rotating components) and is about the same size in peak value. Thus peak total "losses" can be as much as 80 hp. A typical time average total loss might be about 50 hp (for this M4).

I don't think I really need to respond to the rest of your post. Build a spreadsheet, run the numbers. You can also refer to Chapter 2 in "Fundamentals of Vehicle Dynamics" by Gillespie. He covers in detail the calculations required and points out the huge importance of losses and drivetrain intertia terms in the overall equations.

I don't only use CartTest, I've also written a complete detailed spreadsheet program to do the same calculation, it is about 5000 or so rows just to give you a feel for the size and complexity. Of course shift points can be calculated in a fraction of that.

Not to sound too condescending but it will significantly help your overall understanding to go through the exercise yourself. Or heck purchase CarTest. Cheers.

[CanAutM3]

Originally Posted by swamp2

Unless you have made a spreadsheet or written out the math yourself this is a bold and incorrect thing to say. In addition CarTest has been validated compared to real world test data time and time again, by myself and by others.

The losses are primarily:

Transmission
Differential
Axles

Some of these move at road speed (rpm) whereas some move at engine rpm (well technically the tranny moves at both...). The total drivetrain loss I am using for these predictions is 11% which is over 40 hp. In addition to this 40 hp you must also account for the effects of drivetrain intertia. This also acts very similar to an actual loss (even though iti is not a truly dissipative loss which converts to heat, the energy is used up to angularly accelerate all rotating components) and is about the same size in peak value. Thus peak total "losses" can be as much as 80 hp. A typical time average total loss might be about 50 hp (for this M4).

I don't think I really need to respond to the rest of your post. Build a spreadsheet, run the numbers. You can also refer to Chapter 2 in "Fundamentals of Vehicle Dynamics" by Gillespie. He covers in detail the calculations required and points out the huge importance of losses and drivetrain intertia terms in the overall equations.

I don't only use CartTest, I've also written a complete detailed spreadsheet program to do the same calculation, it is about 5000 or so rows just to give you a feel for the size and complexity. Of course shift points can be calculated in a fraction of that.

Not to sound too condescending but it will significantly help your overall understanding to go through the exercise yourself. Or heck purchase CarTest. Cheers.

I am not disputing the CarTest software itself, simply the results of the simulation you ran. As any analytical tool, the proper input assumptions/parameters need to be entered to obtain good results.

I do have a good enough understanding of physics and dynamics. I have done this type of calculation numerous times both professionally testing aircraft engines and personally developing track/race cars. And yes, I have built spreadsheets to calculate shift points on several occasions.

Chapter 2 - "Acceleration Performance" does provide a good overview of the losses and effects of drivetrain inertia. I am not disputing any of the principles exposed there.

However, when calculating shift points, as I explained in my previous post, only a small fraction of the total drivetrain friction and inertia losses have an impact. When the car travels at 94km/h (using my previous numbers), be it in 2nd at 7500RPM or in 3rd at 5600RPM, the losses downstream of the transmission (driveshaft, differential, axle shafts, wheels) will be identical. The only differences are the losses in the transmission and in the engine inertia generated by the 1900RPM difference in engine speed. I don't believe that this delta loss (not total loss) can equate to 25hp.

I still could be mistaken though and will keep an open mind, if you are able to precisely point where my logic is flawed.

[swamp2]

Originally Posted by CanAutM3

I am not disputing the CarTest software itself, simply the results of the simulation you ran. As any analytical tool, the proper input assumptions/parameters need to be entered to obtain good results.

For this calculation the only use adjustable parameters are the losses I mentioned previously. Drivetrain intertial "losses" are not user adjustable in CarTest. Other than that the torque curve, redline, gear and FD ratios are the only inputs required for this calculation.

Originally Posted by CanAutM3

I do have a good enough understanding of physics and dynamics. I have done this type of calculation numerous times both professionally testing aircraft engines and personally developing track/race cars. And yes, I have built spreadsheets to calculate shift points on several occasions.

Chapter 2 - "Acceleration Performance" does provide a good overview of the losses and effects of drivetrain inertia. I am not disputing any of the principles exposed there.

However, when calculating shift points, as I explained in my previous post, only a small fraction of the total drivetrain friction and inertia losses have an impact. When the car travels at 94km/h (using my previous numbers), be it in 2nd at 7500RPM or in 3rd at 5600RPM, the losses downstream of the transmission (driveshaft, differential, axle shafts, wheels) will be identical. The only differences are the losses in the transmission and in the engine inertia generated by the 1900RPM difference in engine speed. I don't believe that this delta loss (not total loss) can equate to 25hp.

The above point of view is correct for true parasitic (->heat) losses ONLY. The inertial terms (which are different pre and post shift) involve engine inertia and transmission inertia and those terms are scaled by the square of the product of the FD and gear ratio (this product are particularly high in this hypothetical M4 and the M3 as well - the ratio of this term between your 1st and 2nd gears is 180%). The total inertial terms (those above plus those of the components at "road rpm" - driveshaft, axles and wheels) can cause the vehicle to perform as if it has 20% more mass (by the way parts of the table of sample mass factors in Gillespie are almost for sure way off for the cars we are discussing...). This also helps explain the obsession with low intertia drive train components in racing...

Originally Posted by CanAutM3

I still could be mistaken though and will keep an open mind, if you are able to precisely point where my logic is flawed.

Review mass factor and drive train inertia in greater detail and we can continue.

P.S. If the moment of inertia of the components of the entire drivetrain are known, mass factors are not required but except at the OEM these are rarely if ever known, hence the use of mass factor.

P.S.S. I got this whole topic wrong myself here on this forum long ago in a long debate. I was making more or less the same error you are - ignoring the inertial terms and how significant they are.

[CanAutM3]

Originally Posted by swamp2

For this calculation the only use adjustable parameters are the losses I mentioned previously. Drivetrain intertial "losses" are not user adjustable in CarTest. Other than that the torque curve, redline, gear and FD ratios are the only inputs required for this calculation.



The above point of view is correct for true parasitic (->heat) losses ONLY. The inertial terms (which are different pre and post shift) involve engine inertia and transmission inertia and those terms are scaled by the square of the product of the FD and gear ratio (this product are particularly high in this hypothetical M4 and the M3 as well - the ratio of this term between your 1st and 2nd gears is 180%). The total inertial terms (those above plus those of the components at "road rpm" - driveshaft, axles and wheels) can cause the vehicle to perform as if it has 20% more mass (by the way parts of the table of sample mass factors in Gillespie are almost for sure way off for the cars we are discussing...). This also helps explain the obsession with low intertia drive train components in racing...



Review mass factor and drive train inertia in greater detail and we can continue.

P.S. If the moment of inertia of the components of the entire drivetrain are known, mass factors are not required but except at the OEM these are rarely if ever known, hence the use of mass factor.

P.S.S. I got this whole topic wrong myself here on this forum long ago in a long debate. I was making more or less the same error you are - ignoring the inertial terms and how significant they are.

Yes, I am familiar with the "mass factor" to estimate resulting acceleration. It is well explained in Gillespie's book. The mass factor remains an approximation of the effects of inertia in a vehicle though. It assumes that the inertia of the various drivetrain components are directly proportional to the vehicle's weight, which is not the case in reality. Mass factor is only appropriate for rough calculations since it is a sort of "peanut butter" approach. A high RPM engine will usually be engineered with less moment of inertia compared with a low RPM high torque engine. For example, the mass factor formula would not take into account the benefit of the carbon torque shaft on the F8X.

Using "equivalent mass" for the different drivetrain components would be more precise. I would have thought that Cartest would be using various moments of inertia (engine/flywheel/transmission, transmission/driveshaft/diff and axleshafts/wheels) as input assumptions.

I stick with my view that all the inertias (as well as friction losses) downstream of the transmission (drive shaft, diff, axle shafts and wheels) do not have any impact on the shift points.

As I stated in my previous post, only engine and transmission inertia have an impact on optimal shift points. What I do realize though is that I may have underestimated their impact on optimal shift points; especially so in the lower gears. I need to go back to the text books and do some calculations .

In principle, the engine inertia has much less impact in the higher gears. Yet, the Cartest results still show shift points around 7200RPM in all gears; I would have expected higher shift points in the higher gears. Any thoughts why?

[Kadema]

Really an interesting read, CanAutM3 and swamp2. Thank you! I have no deeper engineering knowledge and struggle to understand why engine inertia should have an impact at all. Isn't that already 'included' in power or torque charts?

Also, like CanAm, I do think that downstream of the transmission, there should be only speed dependent losses, no rpm dependent losses, hence no impact on shift points?

[CanAutM3]

Originally Posted by Kadema

Really an interesting read, CanAutM3 and swamp2. Thank you! I have no deeper engineering knowledge and struggle to understand why engine inertia should have an impact at all. Isn't that already 'included' in power or torque charts?

Not all dynos are created equal.

Bench dynos are brake dynos that measure engine output at the flywheel. These are the type of dynos used by car companies to develop engines and publish official engine outputs. Usually the numbers produced by such dynos are obtained in steady state and are much more precise and repeatable. Since the engine is not accelerating when the torque is measured, the engine inertia is not accounted for.

However, chassis inertia dynos have to be operated in transient mode. They calculate the engine output based on the capability of the drivetrain to accelerate a flywheel (the dyno drum). Numbers obtained from such dynos will include the losses created by the drivetrain inertia.

Any dyno operated in transient mode will include interia losses, what makes it complicated is the fact that the inertia losses vary depending on the acceleration rate. Combining results from steady state and/or different transient runs allows to back calculate the moment of inertia of the drivetrain components.

This begs another question regarding Cartest. When inputing the power/torque numbers, how does Cartest know if they were obtained in steady state (excluding inertia losses) or transient (including inertia losses)?

[Kadema]

Ah, I see, thanks again. Now I think I also understand why you said inertia losses have less impact at higher gears. But iirc the shift points swamp2 posted did get lower in higher gears. Isn't that contradictory?

[CanAutM3]

Originally Posted by Kadema

Ah, I see, thanks again. Now I think I also understand why you said inertia losses have less impact at higher gears. But iirc the shift points swamp2 posted did get lower in higher gears. Isn't that contradictory?

Yes it is. And this is why I am asking Swamp for his thoughts... there might be other parameters that have an impact.

[Kadema]

And here comes another question... Aren't engine inertia losses largely saved as the momentum is entrained (is this correct english?) when you shift up? I.e. if you shift early to avoid engine inertia losses you also have less momentum, thus short shifting didn't help that much? In other words: If you use force-at-the-wheels to road speed charts that include engine inertia losses but don't include engine inertia gains you'll find shift points that actually are too low? Then again, I might be completely wrong.

[CanAutM3]

Originally Posted by Kadema

And here comes another question... Aren't engine inertia losses largely saved as the momentum is entrained (is this correct english?) when you shift up? I.e. if you shift early to avoid engine inertia losses you also have less momentum, thus short shifting didn't help that much? In other words: If you use force-at-the-wheels to road speed charts that include engine inertia losses but don't include engine inertia gains you'll find shift points that actually are too low? Then again, I might be completely wrong.

I don't believe you are completely wrong. I guess it depends on how the shift is executed. A slow/lazy shift will let most of the inertia dissipate in engine pumping and friction losses. A power shift, were throttle is kept open during the shift, will recuperate a portion of the engine inertia while some is lost in clutch slip. The "surge" felt in an agressive DCT upshift is exactly that, a portion on the engine inertia being recuperates to provide forward thrust. I am not sure how Cartest takes this into account...

[swamp2]

Originally Posted by CanAutM3

This begs another question regarding Cartest. When inputing the power/torque numbers, how does Cartest know if they were obtained in steady state (excluding inertia losses) or transient (including inertia losses)?

There are multiple options and sub-options for inputting engine performance data into CarTest, they are:

1. Peaks
-Peak hp, rpm of peak
-Peak torque, rpm of peak torque
-redline
Then the software does a very good job of curve fitting to come up with a realistic curve. Although some refinement can improve performance prediction this method is generally pretty accurate.

2. Actual curves at the crank
-A full power OR torque curve at the engines crank
This captures a bit more subtlety of the shape of the curve. It is more important for non linear power curves (typical turbo) and less important for a typically linear power curve (E9X M3). Redline is also needed.

3. Wheel values
-Again power or torque by rpm and the other curve is computed. Redline is also needed.

[swamp2]

Originally Posted by Kadema

And here comes another question... Aren't engine inertia losses largely saved as the momentum is entrained (is this correct english?) when you shift up? I.e. if you shift early to avoid engine inertia losses you also have less momentum, thus short shifting didn't help that much? In other words: If you use force-at-the-wheels to road speed charts that include engine inertia losses but don't include engine inertia gains you'll find shift points that actually are too low? Then again, I might be completely wrong.

Inertial terms in the basic equations are not actually losses. Really they just behave fundamentally like extra vehicle mass but their mass is already accounted for in the weight of the car. The "extra" mass effect, i.e. rotational intertia comes into the force balance in the drive train. Parasitic losses from lubricated components such as transmission, differential and axles are truly LOSSES the power is turned into heat. The inertial terms just come from a basic application of F=ma (Newton's Law) or technically the torque balance.

Imagine this thought (or real) experiment. Let a block with simple wheel(s) attached slide down an inclined plane. Here the only work done is by gravity not an engine. If you compared the speed of the block/wheel assembly at the end of a certain height/length incline it will be going a different speed if the axle is locked or unlocked (of course assume no complicating friction effect whether or not axle is locked). When the axle is unlocked there is extra rotational energy stored in the wheels angular momentum. In both cases gravity did the exact same amount of work but again the final speeds will be different!

In each successive gear the flywheel, transmission shafts, driveshaft, differential axles (and wheels) all must be "spun" up over and over again (regardless of the small conservation of angular momentum effect depending on shifting style). Some of these terms depend on road speed and some depend on engine speed.

Again, in a typical sport road car, the car may actually accelerate as if it has as much as 15-25% more total gross mass than in weighs just from these inertial effects. The effects are made larger by high power/high redline engines (compared to low redline ones typically with lower gear ratios) because the terms have factors which are the square of the gear ratios. Again a 3000 lb vehicle accelerates much more like a 3600 lb one in first gear solely due to drive train interial effects. The effect is clearly not small. The thought experiment here is that if you could magically make all of the relevant spinning components have no mass, ones vehicle would accelerate just like it was ~600 lb lighter.

The engine (crank, pistons and flywheel) intertias are all important each time these components are accelerated. This is unrelated to the particular method that establishes the crank power of the engine. These terms are only in effect when the entire vehicle is accelerating. Steady state power measurement does basically eliminate these inertial effects from the power rating.

Bringing things full circle shift points depend on the actual dynamic force delivered to the wheels in each gear, which in turn depends on both parasitic losses and drivetrain inertia.

[EvenSteven]

Originally Posted by sebaflex

Seems the new M engines are tuned more towards midrange power. While fun on the street when driving 6/10ths and you dont want to stretch out each gear, at the track where you are flat out all the time, I would prefer a powerband shifted more towards the right.

7500-7700rpm is spot on with the predictions. But lets see, on most cars aftermarket software will increase the rev limiter, so hopefully we could se close to 8k rpm with an aftermarket tune?

Maybe not worth it for stock turbos since the powerband seems to be very strong in the midrange and drops at high rpms, but I imagine with a nice aftermarket turbo kit which develops power all the way up to redline. 8k would be great.

I agree with this sentiment. My view on the evolution of the M3 is that it is a track car that is increasingly focused on street driving. The E30 was a pure, raw gocart. The E36 added a few creature comforts, and the E46 added even more, but was still more track car than luxury cruiser. The E92, I think many will agree, hit the sweet spot of a 50/50 mix between track beast and comfy DD. The F80 seems to continue this evolution, and seems to me is more of a 40/60 or even 25/75 track/street split. The better fuel economy, new gadgets, and oodels of power down low will make this a much better car than the E92 for daily tasks, but won't be as thrilling when pushed to its limits (spool lag [however small], electronic steering, power concentrated in the middle of the power band, slightly bigger chassis [although a lighter one, so it's a wash], etc.).

Your focus on the redline seems misplaced, since the car's power curve seems to plateau after about 6500 and the demonstration videos I've seen had the driver shifting well before the redline.

Once we start considering aftermarket FI solutions, the S65 wins, so let's not go there.

Regardless, I'm holding out on making any final judgements until I drive the car myself. I would love to have the new M3 (love the new sedan's wide body) as a fun daily driver that I don't feel guilty putting 20s on and doesn't kill me on the gas, and then gut and supercharge my E92 to be a true monster. Plus, that way I avoid having that heathen 4 after the M. Savages.

[Boss330]

Originally Posted by EvenSteven

I agree with this sentiment. My view on the evolution of the M3 is that it is a track car that is increasingly focused on street driving. The E30 was a pure, raw gocart. The E36 added a few creature comforts, and the E46 added even more, but was still more track car than luxury cruiser. The E92, I think many will agree, hit the sweet spot of a 50/50 mix between track beast and comfy DD. The F80 seems to continue this evolution, and seems to me is more of a 40/60 or even 25/75 track/street split. The better fuel economy, new gadgets, and oodels of power down low will make this a much better car than the E92 for daily tasks, but won't be as thrilling when pushed to its limits (spool lag [however small], electronic steering, power concentrated in the middle of the power band, slightly bigger chassis [although a lighter one, so it's a wash], etc.).

I disagree a little with your view on the evolution of the M3.

The E30 M3 LOOKED like a "pure, raw gocart", but wasn't really that fast. Especially compared with the Ford Sierra RS Cosworth that was one of it's direct competitors. The three door Cosworth looked even more aggressive than the E30 with it's big (functional) rear wing, deep front spoiler and wide fenders. In reality the E30 M3 was a E30 with a body kit and a 2,3l engine that developed well under 100hp/liter. Very minor suspension upgrades to the front suspension, rear suspension was carried over from the E30. The street version of the E30 M3 had all the "creature comforts" available at the time, and was just as comfortable to drive as would be expected of a production vehicle. But E30 will always be considered a classic M3.

Then the E36 came, which possibly is the least special M3 so far. It has just a minor bodykit, no wide fenders etc. The engine and handling is good, but just like the E34 M5, it doesn't look like a special car. Seems like the M3 that is the least different from the std. production models. It even came as a 4 door and was much more likely to find use as a family carrier than the E30. Most likely to become the Ferrari 348 of the M3 range.

Then we have the E46, which returned to the E30 M3 legacy of special looks. But this time also backed up with a strong engine. The E46 was a return back to the original idea, and especially models like the CSL will ensure that the E46 will be remembered as a classic M3.

The E9X model is something between the E46 and the E36, but more towards the E46. It's got a wide body and crazy engine (I'm not a fan of a V8 M3, but the S65, like the S85, will probably be remembered as some of the great M engines). But you could get a 4 door and it became HEAVY...

With the F8x models it seems we will be getting the best handling M3 ever and probably the M3 that differs the most from the car it's based on. Wide body and mechanical differences in suspension beyond what has been seen before. And the engine is also based around a completely new block with different bore spacing etc from the N55, requiring new tooling and means that it's a M3/M4 specific engine, not just a tuned N55.

IMHO the F8x looks like it will have even more M specific development than any M3 before it, and I'm pretty sure BMW hasn't done all of that work with light weight components and suspension development just to create a car that isn't a better track car than it's predecessor...

Until we have read independent reviews, we have no way of knowing that the F8x won't be as thrilling to drive... I think many will be in for a surprise on how good the F8x actually will be (or at least i hope it will be that good )

[CanAutM3]

Originally Posted by swamp2

In each successive gear the flywheel, transmission shafts, driveshaft, differential axles (and wheels) all must be "spun" up over and over again (regardless of the small conservation of angular momentum effect depending on shifting style). Some of these terms depend on road speed and some depend on engine speed.

Not sure I follow you here. IMO, only the engine and part of the transmission need to be re-accelerated after each gearshift. For a given road speed, all rotating components downstream of the transmission rotate at the same speed regardless of the selected gear. These components need to be accelerated further, but not re-accelerated. However, since the engine needs to be decelerated before it can be re-accelerated, there is a possibility to recuperate a portion of the angular momentum.

This is the same reason I think that only the engine and part of the transmission inertia have an effect on optimal shift points. I still need to take some time and do the math .

BTW, any thoughts as to why CarTest recommends similar shift point (7200RPM) in every gear in our previous simulation?

[CanAutM3]

Originally Posted by Boss330

I disagree a little with your view on the evolution of the M3...

Good analysis.

What are you thoughts on the E36 engines? I thought folks in Europe were pretty pampered with the 286ps and 321ps engines compared to the lowly 240hp we had here in North America. I had the opportunity to drive the 286ps 3.0L and found it pretty awesome. I think the 3.2L variant was the first ///M street engine to achieve 100ps/l...

[swamp2]

Originally Posted by CanAutM3

Not sure I follow you here. IMO, only the engine and part of the transmission need to be re-accelerated after each gearshift. For a given road speed, all rotating components downstream of the transmission rotate at the same speed regardless of the selected gear. These components need to be accelerated further, but not re-accelerated. However, since the engine needs to be decelerated before it can be re-accelerated, there is a possibility to recuperate a portion of the angular momentum.

I think there is a combination of a slight lack of clarity on my behalf and you assuming the worst about my comments. Without identifying each individual component of the entire drivetrain some must be re-accelerated after each shift and some do not. However, during acceleration the entire drivetrain must be accelerated (angularly obviously). Anyone who knows anything about how a car works can tell the difference between which component fits which description.

Originally Posted by CanAutM3

This is the same reason I think that only the engine and part of the transmission inertia have an effect on optimal shift points. I still need to take some time and do the math .

The devil is in the details. A force (torque) balance through the entire drivetrain also involves I's for the driveshaft, axles and wheels. The I's for those components affect the actual acceleration force delivered to the wheels and thus the shift points. Perhaps think of it this way. We all know lighter wheels are great because they essentially act like more power. No they are not actually more power but it is VERY similar as the car has more acclerative force. Different forces affect when the curves cross and hence shift points. Place massively heavy wheels on your vehicle and ideal shift points would change.

Originally Posted by CanAutM3

BTW, any thoughts as to why CarTest recommends similar shift point (7200RPM) in every gear in our previous simulation?

I do not recall any simulations I provided that showed a vehicle shifting always at or around 7200 rpm. We talked about and older 5er here in this thread as well as the M4. Both share the trend of a at or near redline shift in the first gear (or two) followed by an ever decreasing ideal shift point.

[Boss330]

Originally Posted by CanAutM3

Good analysis.

What are you thoughts on the E36 engines? I thought folks in Europe were pretty pampered with the 286ps and 321ps engines compared to the lowly 240hp we had here in North America. I had the opportunity to drive the 286ps 3.0L and found it pretty awesome. I think the 3.2L variant was the first ///M street engine to achieve 100ps/l...

The E36 3l and 3,2l are good engines, but lack punch compared to todays engines. As I wrote previously, I drove a 3,2l M3 and a 428i on the same day. The 428i feels faster and stronger, but doesn't have the charisma of the M3 engine (even though the active sound makes it sound awesome inside the cabin...).

I drive a F10 with the N53 NA 3l engine. And even though the 3,2l M3 has more top end power, the 3l only has 14hp more... (272 vs 286). And frankly they aren't that different. At the time the engine was great, but today it really doesn't feel that special IMHO.

[CanAutM3]

Originally Posted by Boss330

The E36 3l and 3,2l are good engines, but lack punch compared to todays engines. As I wrote previously, I drove a 3,2l M3 and a 428i on the same day. The 428i feels faster and stronger, but doesn't have the charisma of the M3 engine (even though the active sound makes it sound awesome inside the cabin...).

I drive a F10 with the N53 NA 3l engine. And even though the 3,2l M3 has more top end power, the 3l only has 14hp more... (272 vs 286). And frankly they aren't that different. At the time the engine was great, but today it really doesn't feel that special IMHO.

Agreed, compared to today's engines they are not that extraordinary. Just shows how much engine technology has evolved in the last decades. However, I still think they were pretty exciting engines at the time they came out in the mid/late nineties .