Overboost Function

[swamp2]

ozinaldo:

I see no qualitative and little to no quantitative differences between the dyno I posted and the one you posted with regards to the 1M power roll off. In both plots the power simply stops increasing at around 5250 rpm and then actually decreases as rpms increase to redline. The curve is closest to the RED curve I posted in my cartoon-ish chart, except instead of having a positive slope past peak it actually has a negative slope (again it rolls off). A very high performance NA engine such as the S65 has an ENTIRELY different qualitative and quantitative nature showing almost a perfect linear curve up to redline. In fact the M3s curve looks most like the PURPLE curve I posted but even closer to slope of the RED curve continuing on another 3000+ rpm past the 1Ms roll off point.

This exactly explains the feeling and character of the cars above around 5250 rpm. The 1M feels in comparison to the M3 like it is dying. In some ways it is - it is entirely suffocating and just can't pump any more air.

Of course to each their own. As I've said the 1M is a very nice car. It is the character and performance of the engine in comparisom to the S65 that is the most compelling difference. As to chassis, handling, braking etc. there are minor differences and some advantages to the 1M, but the engines are simply like night and day.

[///ADMAN]

I like the M1. But, I didn't fit in it comfortably. So, the IS with overboost was the right choice (for me) until the M4 comes out.

I personally like the "surge" and typically drive in SPORT-SPORT. I've raced a lot of M3s so far and beaten most off the line.
Haven't gone too fast for their HP to get me. So, I'm a happy with my ///M2.5

Can't wait for the M4. Wish they would come out with the engine specs as well.

[jtvr4]

Originally Posted by ozinaldo

Peak hp was 294.2 hp and torque was 342.9; all three runs were with similar results and best hp number was attained at the last run. I saw the chart of a new stock 2012 M3 there (the car was there for a supercharger install) and it was 323 hp, merely 29-30 whp more and later I learned that it was pretty much what M3 was making on a Mustang dyno.
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It takes more then 30whp to trap 4 miles an hour faster... Seriously, it does and trap speeds don't lie.

Originally Posted by ///ADMAN

I've raced a lot of M3s so far and beaten most off the line.
Haven't gone too fast for their HP to get me. So, I'm a happy with my ///M2.5

An e9X M3 is faster 0-60 than an 335IS. More rubber and an LSD just to start. Real sports cars have an LSD in them.

[///ADMAN]

Um. Okay. I'll let the other iS owners pipe in on that one.

[ozinaldo]

Originally Posted by jtvr4

It takes more then 30whp to trap 4 miles an hour faster... Seriously, it does and trap speeds don't lie.




An e9X M3 is faster 0-60 than an 335IS. More rubber and an LSD just to start. Real sports cars have an LSD in them.

It is what it is, and you forget other factors like 1M's refrigerator like aero vs. M3. Is this 4 miles an hour difference you talk about is tested at the same time, by the same driver by the way? Where did you get it? M3 should trap faster, no doubt about it though.

It is not the last time you will be hearing that these two engines have around 30 whp difference by the way, it is indeed curious that you heard about it first time. BMW's advertised 80 hp crank difference is simply not true.

[ozinaldo]

Originally Posted by swamp2

ozinaldo:

I see no qualitative and little to no quantitative differences between the dyno I posted and the one you posted with regards to the 1M power roll off. In both plots the power simply stops increasing at around 5250 rpm and then actually decreases as rpms increase to redline. The curve is closest to the RED curve I posted in my cartoon-ish chart, except instead of having a positive slope past peak it actually has a negative slope (again it rolls off). A very high performance NA engine such as the S65 has an ENTIRELY different qualitative and quantitative nature showing almost a perfect linear curve up to redline. In fact the M3s curve looks most like the PURPLE curve I posted but even closer to slope of the RED curve continuing on another 3000+ rpm past the 1Ms roll off point.

This exactly explains the feeling and character of the cars above around 5250 rpm. The 1M feels in comparison to the M3 like it is dying. In some ways it is - it is entirely suffocating and just can't pump any more air.

Of course to each their own. As I've said the 1M is a very nice car. It is the character and performance of the engine in comparisom to the S65 that is the most compelling difference. As to chassis, handling, braking etc. there are minor differences and some advantages to the 1M, but the engines are simply like night and day.

I agree engines are night and day and it is good that we have these two available, or had at one point.

Fair enough everything you say, for a driver who got used to high rpm NA V8 1M must be a confusing experience, acceleration wise.

All I want to say is there are two facts which seem crystal clear to me:

1M's sweet spot is between 2000 to 6000 rpm, especially 2500 to 5500 is very strong. Contrary to this, M3's sweet spot is 6000 to 8400 where it redlines (corrrect me if I am wrong on this) and closer to redline is better.

As a result, my understanding and experience is whereever you have lights, traffic, speed limits, people, buildings etc. etc. whic I call the real world, driving with 1M is a more "utilitarian" experience because you simply can benefit from the sweet spot of the engine very frequently, as a matter of fact, all the time.

Are you telling me that other than track you can and you do keep the M3 over 6000 rpm all the time? I hope you don't, for the sake of public health and safety.

I never doubted the quality of the S65 as an engineering marvel but it always seemed to me that it has a much narrower window of enjoying it where it makes a difference vs. a more "work horse" type of FI engine, sad maybe but I feel that it is the truth. I actually was glad that 1M came with a tweaked N54 and not a detuned (or not) S65. I would go buy the E90 sedan instead of the 1M if that would be the case.

It is this engine which is explosive almost immediately after idle, mated to a basically shortened M3 chassis, that gives the 1M its terrier like agility and readiness. I find it loveable and don't care too much if it looses to cars like M3 on long straights. Likes dictate preferances as always.

[jtvr4]

Originally Posted by ///ADMAN

Um. Okay. I'll let the other iS owners pipe in on that one.

You really got me with your anecdotal facts. Bravo. Show me how a car that runs high 13's@ a lame 105mph is faster.

Originally Posted by ozinaldo

It is what it is, and you forget other factors like 1M's refrigerator like aero vs. M3. Is this 4 miles an hour difference you talk about is tested at the same time, by the same driver by the way? Where did you get it? M3 should trap faster, no doubt about it though.

It is not the last time you will be hearing that these two engines have around 30 whp difference by the way, it is indeed curious that you heard about it first time. BMW's advertised 80 hp crank difference is simply not true.

I'm only going to tell you this one more time. It takes more than 30whp for a car to trap 4 mph faster. How you choose to deal with this information is up to you. Also anecdotal facts are meaningless. It would take 414 crank horsepower for a car that is 3,576 pounds to trap 114 mph. BMW did not lie, this is high school math and I rounded the figures so you would not be further confused. You are talking about things you know very little about. It's obvious.

Low end torque is completely meaningless for a tarmac race car. You do not spend your time driving in the 2,500-3,800 rpm band and you do not own a rally car or a diesel. The 1M is over 250 pounds lighter and uses much of the same suspension/chassis bits from the M3. It should be much faster on the track than it is over the M3 but it's not. I have no doubt if it had an S65 like the racing Z4 it would be faster than it currently is.


http://www.motortrend.com/roadtests/...n/viewall.html


I'm starting to see a trend in this forum of people who should know more than they pretend to. We need a sub forum for anecdotal facts and TORQUES!. We can call it advanced tech.

[CanAutM3]

Originally Posted by swamp2

However, in choosing between possible options and comparing to the baseline (green) to a more torque same (peak) power option (red) or more peak power (purple) generally the higher peak power option (purple) will deliver more broad spectrum performance improvements. Yes, you will have to drive it at high rpm and if its rpms drop often and well below the plateau level of power from the turbo engine, it will make for a much closer contest. If it is indeed kept in the high rpm range, it will on average consistently produce more power and that is better for performance than making more torque.

I fully agree with the vast majority of the points you are bringing on this thread. Also with the point that as a single number, peak power is the best number to assess an engine performance potential .

Except for the point that I have quoted though. To fully assess a powertrain potential, the shape of the power curve as well as gearing are important considerations. When I mention the impact of gearing, it is not about multiplication of the torque to the drive wheels, but rather the RPM range used in each gear during a maximum acceleration run, which is dependent on the ratio that the gears have relative to each other.

Going back to your power curve cartoon, comparing the red and purple engines in the same car with the same transmission, assuming that the gearing would require both engines to use the RPM band defined by the black bars on my modified cartoon, both engines would have very similar performance because the average power produced in that range is very similar for both engines.

Furher, the car with the red engine would most likely pull ahead beacuse it is producing more power early on. The purple (edited) car would match the speed, but would stay behind.

This is all very theoretical, but I am sure you get the drift .

[///ADMAN]

Originally Posted by jtvr4

Low end torque is completely meaningless for a tarmac race car.

...and means everything from stoplight to stoplight.






I love being the red car right now.

[swamp2]

Originally Posted by ozinaldo

It is what it is, and you forget other factors like 1M's refrigerator like aero vs. M3.

I don't think this is the case. Either my google-fu is a bit off or it is very hard to find but I could not find reliable Cd and frontal area for the 1M. At any rate the most physically meaningful thing is not Cd or frontal area but their product. Using the changes (ratio) from the 335i to M3 I have extrapolated reasonable values for both parameters for the 1M from the 135i. Although it probably has a worse Cd than the M3 is also likely has a smaller area that counters the effect of Cd. My estimates show the Cd x A to be identical to the M3 and thus power lost to drag between the cars as a function of speed is also identical.

Kind of an apologists point of view you have...

That being said should you provide solid numbers different than my estimates I'm willing to reconsider your point of view on the relevance of this to the power the 1M makes compared to the M3.

On a related point, all physics based performance simulations I have done and compared/validated a wide variety of published test results do not indicate the M3 is under not overrated on power. However, just like the 335i and F10 M5 the 1M is pretty clearly underrated to the tune of about 15-20 hp.

[swamp2]

Originally Posted by ozinaldo

As a result, my understanding and experience is whereever you have lights, traffic, speed limits, people, buildings etc. etc. whic I call the real world, driving with 1M is a more "utilitarian" experience because you simply can benefit from the sweet spot of the engine very frequently, as a matter of fact, all the time.

Are you telling me that other than track you can and you do keep the M3 over 6000 rpm all the time? I hope you don't, for the sake of public health and safety.

Rubbish. I completely disagree. The "unsafe" things we might do driving high performance vehicles on the street (in a straight line) have ABSOLUTELY nothing to do with rpm, only acceleration and velocity. The same amount of "unsafe-ness" will occur in a 1M or M3 regardless of engine rpm.

Yes of course the engines offer dramatically different characters. One takes a bit more volume and perhaps gear shifting to get the highest level of performance. For those unable or unwilling to do so the 1M is perhaps the better choice.

[swamp2]

Originally Posted by CanAutM3

Going back to your power curve cartoon, comparing the red and purple engines in the same car with the same transmission, assuming that the gearing would require both engines to use the RPM band defined by the black bars on my modified cartoon, both engines would have very similar performance because the average power produced in that range is very similar for both engines.

Ahh but yes with these power curves the cars would probably not use the same gearing! It depends a bit too on how close the slope of the purple curve is to the red or blue curves. But in general the purple car will win more performance contests. Perhaps not 0-60 but most others.

Originally Posted by CanAutM3

Furher, the car with the red engine would most likely pull ahead beacuse it is producing more power early on. The blue car would match the speed, but would stay behind.

No. Red would likely out launch blue but blue would catch up and punish pretty quickly by staying in the rpm range above red's redline.

Cheers.

[ozinaldo]

Originally Posted by jtvr4

You really got me with your anecdotal facts. Bravo. Show me how a car that runs high 13's@ a lame 105mph is faster.




I'm only going to tell you this one more time. It takes more than 30whp for a car to trap 4 mph faster. How you choose to deal with this information is up to you. Also anecdotal facts are meaningless. It would take 414 crank horsepower for a car that is 3,576 pounds to trap 114 mph. BMW did not lie, this is high school math and I rounded the figures so you would not be further confused. You are talking about things you know very little about. It's obvious.

Low end torque is completely meaningless for a tarmac race car. You do not spend your time driving in the 2,500-3,800 rpm band and you do not own a rally car or a diesel. The 1M is over 250 pounds lighter and uses much of the same suspension/chassis bits from the M3. It should be much faster on the track than it is over the M3 but it's not. I have no doubt if it had an S65 like the racing Z4 it would be faster than it currently is.


http://www.motortrend.com/roadtests/...n/viewall.html


I'm starting to see a trend in this forum of people who should know more than they pretend to. We need a sub forum for anecdotal facts and TORQUES!. We can call it advanced tech.

This post needs re-reading by its writer, but if he is underaged, then no problems for being juvenile.

[///ADMAN]

Originally Posted by swamp2

No. Red would likely out launch blue but blue would catch up and punish pretty quickly by staying in the rpm range above red's redline.

Which is exactly why I said what I said:

Originally Posted by ///ADMAN

I've raced a lot of M3s so far and beaten most off the line.
Haven't gone too fast for their HP to get me.

[ozinaldo]

Originally Posted by swamp2

I don't think this is the case. Either my google-fu is a bit off or it is very hard to find but I could not find reliable Cd and frontal area for the 1M. At any rate the most physically meaningful thing is not Cd or frontal area but their product. Using the changes (ratio) from the 335i to M3 I have extrapolated reasonable values for both parameters for the 1M from the 135i. Although it probably has a worse Cd than the M3 is also likely has a smaller area that counters the effect of Cd. My estimates show the Cd x A to be identical to the M3 and thus power lost to drag between the cars as a function of speed is also identical.

Kind of an apologists point of view you have...

That being said should you provide solid numbers different than my estimates I'm willing to reconsider your point of view on the relevance of this to the power the 1M makes compared to the M3.

On a related point, all physics based performance simulations I have done and compared/validated a wide variety of published test results do not indicate the M3 is under not overrated on power. However, just like the 335i and F10 M5 the 1M is pretty clearly underrated to the tune of about 15-20 hp.

Sport Auto 1M super test. Issue 7/2011.

A: 2,18 m2
Cw 0,35
Cw x A : 0,77

Front down force: 5kg. (45 Newton)
Rear lift at 200 km/h: 37 kg. (359 Newton)

says the printed magazine.

French Le Moniteur Auto had a very detailed test on 1M back in June 2011 and there they mention the SCX as 0,80 which is worse than Sport Auto data, but I think Sport Auto is more careful about the data they provide plus there was no other details on aero in the French magazine.

By the way, it would be better if you don't start your posts in a friendly automotive forum by putting words like "rubbish", even if you are right you loose respect of others and for a good reason, so let's avoid that.

[CanAutM3]

Originally Posted by swamp2

Ahh but yes with these power curves the cars would probably not use the same gearing! It depends a bit too on how close the slope of the purple curve is to the red or blue curves. But in general the purple car will win more performance contests. Perhaps not 0-60 but most others.

I believe you are mistaken here. Red car can have the advantage over the purple one with same gearing in a good portion of performance contests (see explanation below), and no reason why they would use different gearing.

Originally Posted by swamp2

No. Red would likely out launch blue but blue would catch up and punish pretty quickly by staying in the rpm range above red's redline.

Cheers.

I had my colours confused in that last sentence, sorry about that. I was comparing the red and purple cars all along, not the blue car. With the same gearing, the red car will pull ahead. The purple car will eventually match the speed, but will stay behind.

Here's why: the red car accelerates faster until the power lines cross. All this time it will have more speed than the purple car, therefore traveling more distance than the purple car. Only when the power lines cross does the purple car start to out accelerate the red car, but even at this point, the red car is still traveling at a faster rate than the purple car. From that point on, the purple car out accelerates the red car until it matches the speed of the red car. So during the entire acceleration run, the red car has a higher velocity and therefore travels a greater distance. I know, a bit over simplified, but still explains the concept .

Again, this is theoretical. Considering aero drag and other factors, the outcome will be somewhat different, but the general concept remains true. My point is that it is not only peak power that counts, but rather the power produced over the rev range used by each gear.

If the cars were to have a CVT that holds the RPM constant at the power peak, then yes, the power peak is all that matters. The purple car would walk away. But not the case with finite ratio gearboxes .

Note: I understand that the purple car would pull away from the red car if the acceleration run is started where the purple car makes more power than the red car, but my example was limited to a single gear pull in the rev band limited by the two black lines.

[swamp2]

Originally Posted by ozinaldo

Sport Auto 1M super test. Issue 7/2011.

A: 2,18 m2
Cw 0,35
Cw x A : 0,77

Front down force: 5kg. (45 Newton)
Rear lift at 200 km/h: 37 kg. (359 Newton)

says the printed magazine.

Well my very simplistic prediction gave pretty darn good estimates. However, I completely typoed the part about that Cd X A being identical to the M3, it is in fact (with those guesses) identical to the 335i.

However, 2.18 x .35 is .76 with rounding not .77. And indeed with these values I agree that drag is a pretty reasonably large difference compared to the M3.

Originally Posted by ozinaldo

By the way, it would be better if you don't start your posts in a friendly automotive forum by putting words like "rubbish", even if you are right you loose respect of others and for a good reason, so let's avoid that.

I stand by my choice of words. Trying to "shame" someone into the belief that their liberal use of the full range of a high rpm engine is somehow more dangerous than accelerating the same way to the same speed is just that, utter rubbish. It is not an insult, just a very firm disagreement.

[swamp2]

Originally Posted by CanAutM3

I believe you are mistaken here. Red car can have the advantage over the purple one with same gearing in a good portion of performance contests (see explanation below), and no reason why they would use different gearing.

OK, let's try it using my favorite physics based performance prediction tool, CarTest.

Consider two modified M3. One with 414 hp at 8400 rpm but actually revs a bit higher to 8500 rpm with completely linear power vs. rpm (i.e. a bit more than 414 peak hp). Otherwise this is a standard M-DCT E92 M3. This will be our "purple car". Next we have an identical car with a peak hp of 330 hp at 5000 rpm and also 330 hp up to 8500 rpm (the red car).

Purple wins:

• quarter mile, time and trap
• 50-70
• 60-130 (by a lot)
• 0-80 and all 0-XX above (by increasing margins)
• top speed

Red wins:

1. 0-50
2. 0-60 (basically a tie)
3. 30-50
4. stays ahead for about 1000' feet in a drag race

Purple will also win all tracks except the tightest ones with corner exit speeds at 30 mph and below.

Basically comes down to an 1/8th mi stop light drag race winner vs. everything else...

Also to be fair from a drag racing perspective the cars are down to being a drivers race. 0-100, 50-70 or 60-130 absolutely are NOT drivers races though...

Increasing the final drive will provide a win for "purple" in 0-60 and cut down the distance "red" is ahead in the 1/4 drag race substantially to about 600-700 feet. FD mods for "red" does more or less nothing...

However, this is all a bit unrealistic because no BMW turbo will rev to 8500 for some time (if ever) and also because the new M4 will have a lot more than 330 peak hp...

[///ADMAN]

Originally Posted by jtvr4

You really got me with your anecdotal facts. Bravo. Show me how a car that runs high 13's@ a lame 105mph is faster.

Here you go...

Originally Posted by swamp2

Red wins:

1. 0-50
2. 0-60 (basically a tie)
3. 30-50
4. stays ahead for about 1000' feet in a drag race

[CanAutM3]

Originally Posted by swamp2

OK, let's try it using my favorite physics based performance prediction tool, CarTest...

Don't get blinded by trying to win the argument, you are missing the point I am trying to make .

The power graph cartoon you drafted is just that, a cartoon; let's leave it at that. Inputing it in your advanced simulation tools requires a multitude of assumptions that go well beyond the point of this discussion. Let's just focus on the physics concepts.

I fully agree that as a single number, the power peak is the best number to assess the performance capabilities of an engines. I have argued that point myself multiple times in various threads. We are on the same page here.

However, my point is that to go to the next level to fully understand the capabilities of a powertrain, the power produced over the entire critical RPM range needs to be considered. The critical RPM range being the RPM band used in each gear during a max acceleration run. Arguing that only peak power matters for an engine is a mistake.

Going back to the cartoon, the red and purple cars (with the same gearing that uses the RPM band between the two black lines) will have very similar performance. Sometimes the red car at an advantage and sometime the purple car at an advantage despite the purple car having a much higher peak power output (and I am talking all out performance here, not lazy acceleration). This is because they produce the same average power in the critical RPM band (defined by the two vertical black lines on my edited cartoon).

Increasing the average power produced in the crtical RPM range will improve all out performance, even if it is done at the expense of reducing the power peak. That is a physics fact.

Going back to the overboost discussion, increasing torque below the critical RPM band will not improve ultimate performance, only lazy acceleration. However, if the overboost increases torque/power within the critical RPM band, it will improve ultimate performance. This even if peak power is not increased.

[RMB]

I really enjoy getting everyone's perspective on the upcoming M3/M4 and the comparison to existing M products. It's clear that everybody has a lot of passion for their positions and experiences. I can't wait till the next week or so and to see if we get some more concrete details about the M3/M4. Given what information comes out it will be interesting to see how BMW has approached this new vehicle. I believe in the M division and I think we will all be pleasantly surprised by what they have in store for us. Oh, the anticipation!

[04cobra]

My overboost will come in the form of an aftermarket tune. Turbo charged M should hopefully have some nice potential...similar to the n54/n55