My Conversation w/ a BMW Test Driver about the M3/M4

[M3ryder55]

Spotted these test cars around my house back in November of last year-- 2 series hybrid and 3 x5m's.







Never bothered to post pics of anything because I figured I wasn't the first to spot these at the time. Regardless, I approached one of the drivers who was waiting on his colleagues and talked to him about the upcoming F8X, this was back in November. He was a cool guy and didn't really give me much information as to the questions I was asking, but here what I got out of him. I waited to long because i didn't want to get the guy in trouble or anything, and now that the guy is on its way i think now is the time to post.

1. The car is an animal. It is under rated. BMW has started under rating their cars since the transition to FI for one reason or another. And a lot of that has to do w/ the government/EPA. He said we got to tell them what they want to hear to make them happy. The car is rated at 430 crank hp, but with a carbon fiber drive shaft in addition to the power ratings being under rated, it is very plausible to believe these things will put out around 400 to the wheels. He said once the cars get produced and released, and the power is actually higher, say 460-475 crank, the government can't do anything about it haha. Something like that.

2. The E9X and F8X are two completely different animals. He said its amazing how different the cars are, but both amazing in their own ways. The I6TT will not come close to the V8 in terms of sound, but performance he said is night and day. The torque difference he said changes the dynamic of the car so much, and the car is much more fun to drive all around than the E9X.

3. The weight difference makes a significant difference all around. He said its amazing how noticeable the weight difference is despite being only a couple hundred pounds lighter.. well that was back than, and obviously the weight has gone up, but he said the responsiveness of the cars makes them a pleasure to drive.

So thats my story to share w/ my fellow patiently waiting M3/M4 enthusiasts.

Now only time will tell.

[soccer dad]

Great info and glad to hear that there is a "surprise" in store!

[M4TW]

Even though it starts with "hey guys, I had a conversation with a BMW test driver almost a half a year ago and here is some top secret information that told me on the down low" I sure want to believe it.

[ybbiz34]

So BMW is perpetrating a fraud upon the U.S. government?

For the record, OP, I believe what you're saying. I'm just skeptical of what the "test driver" told you regarding "underrating" the cars.

[M3ryder55]

Originally Posted by ybbiz34

So BMW is perpetrating a fraud upon the U.S. government?

For the record, OP, I believe what you're saying. I'm just skeptical of what the "test driver" told you regarding "underrating" the cars.

No they are not. Yes basically in a nut shell they are under rated. And basically what it comes down to is the wheel hp which is what matters.

E36 rated around 240 250bhp--- avg dynos stock 200-210 whp-- approx 18% loss

E46 rated at 333bhp-- average dynos around 270whp-- approx an 18% loss

E9x rated at 414bhp--- avg dynos stock around 340whp-- 18% again

Now F8x which is going to follow the same under rated trends like the f10 m5 where crank power is under rated and in addition a carbon fiber drive shaft translating to a less drive train loss to the wheels, u can pretty much bet these things will be putting down over 400whp. Previous generations have shown roughly a 70whp increase. So yes I think along with many others the cars are under rated and that was confirmed to me by a test driver. So take it how u want to I'm just sharing my experience with the driver along with my knowledge to the forums

[03Saleen]

Originally Posted by M3ryder55

No they are not. Yes basically in a nut shell they are under rated. And basically what it comes down to is the wheel hp which is what matters.

E36 rated around 240 250bhp--- avg dynos stock 200-210 whp-- approx 18% loss

E46 rated at 333bhp-- average dynos around 270whp-- approx an 18% loss

E9x rated at 414bhp--- avg dynos stock around 340whp-- 18% again

Now F8x which is going to follow the same under rated trends like the f10 m5 where crank power is under rated and in addition a carbon fiber drive shaft translating to a less drive train loss to the wheels, u can pretty much bet these things will be putting down over 400whp. Previous generations have shown roughly a 70whp increase. So yes I think along with many others the cars are under rated and that was confirmed to me by a test driver. So take it how u want to I'm just sharing my experience with the driver along with my knowledge to the forums

I think your right. So what do you estimate the crank HP to be?

[M3ryder55]

Originally Posted by 03Saleen

I think your right. So what do you estimate the crank HP to be?

going to be hard to judge, because we don't know what the drive train loss is going to be w/ that CF drive shaft.

Following the same 18% loss presumably as the other generations have shown, whp should be around ~360whp

However--- dynos have shown the F10 M5 rated at 560bhp, to put down around 510 (508) stock (at least the video I saw online)

598hp based on a 15% drive train loss (rear wheel drive) no carbon fiber drive shaft either ---> approx 40bhp more than reported

This is just one example, showing the output to be even higher than reported at the crank

So I'd say assume the F8X to put about 30-40 more bhp so around 460-470. At 460 w/ an 18% drive train loss (max) that puts you at about 380whp
My guess is this thing will put out approximately 70hp more to the wheels compared to the older generations and follow a similar trend-- e36, e46, e9x. Based on that thought, to achieve around 400-410 whp, drive train loss will be around 10-12% which seems extremely reasonably w/ the CF shaft. Or the car could be really at 430whp with even less of a drive train loss. I'm hoping, along with all of you, this thing puts out over 400 to the wheels, which seems very reasonable if you ask me. Look at the historical trends, along with the current numbers the FI bmw engines are putting out w/o cf drive shafts, and join my bandwagon.

[swamp2]

Originally Posted by M3ryder55

a carbon fiber drive shaft translating to a less drive train loss to the wheels

The inertia of the drive train components do not affect the parasitic loss. More inertia is basically like more mass, whereas losses are actually converting power to heat. If you took a car with a very heavy drive shaft and compared it one with a very light driveshaft on a true accurate hub dyno the power would not change. However, the acceleration performance on the road would show a small improvement.

Loss for the E92 M3 and F82 M4 are probably a lot closer to 11% rather than 18%. Have a look at rri.se, a very respected organization measuring power with very accurate equipment.

http://www.rototest.com/rototest-dynamometer.php
http://rototest-research.eu/popup/pe...p?ChartsID=793

Even given this, I also expect the S55 to output at least 445 crank hp.

[M3ryder55]

Originally Posted by swamp2

The inertia of the drive train components do not affect the parasitic loss. More inertia is basically like more mass, whereas losses are actually converting power to heat. If you took a car with a very heavy drive shaft and compared it one with a very light driveshaft on a true accurate hub dyno the power would not change. However, the acceleration performance on the road would show a small improvement.

Loss for the E92 M3 and F82 M4 are probably a lot closer to 11% rather than 18%. Have a look at rri.se, a very respected organization measuring power with very accurate equipment.

http://www.rototest.com/rototest-dynamometer.php
http://rototest-research.eu/popup/pe...p?ChartsID=793

Idk man, i was just shooting out the 340whp on the E9X because that look like the norm for most of us on here. That translates to an 18% loss. At an 11% loss, approximate whp is around 368-370 stock. And those high numbers where from gintani or eas dyno haha jk. well sort of at least.

Again, this isn't my field of expertise. There are plenty of wizards that are experts at this dyno/number craft that will put me to shame along with 99% of the people on here. I'm just stating what I believe is likely to be true. Lets hope over 400whp, yes? :thump:

At an 11% loss, lets say 12%, at 460bhp, that puts the F8X at around 400-405whp. At 11% loss at the rated 430bhp, puts it at around 380-385whp. Again, time will tell and these numbers don't really mean shit as of now, but its definitely something to keep in mind going forward.

[Ezio]

The m4 will be faster. But the e90 will sound better. Is what I gathered. I know people the I6 is the best sounding engine. I am just repeating what BMW said. Sorry don't flame me .

[ybbiz34]

Originally Posted by M3ryder55

No they are not. Yes basically in a nut shell they are under rated. And basically what it comes down to is the wheel hp which is what matters.

Man what does a guy have to do to convey sarcasm around here. People are running on the high-strung side here in the F80 section as of late.

My initial post was meant jokingly.

Guess I should've included one of these:

[M3ryder55]

Originally Posted by ybbiz34

Man what does a guy have to do to convey sarcasm around here. People are running on the high-strung side here in the F80 section as of late.

My initial post was meant jokingly.

Guess I should've included one of these:

lol i didn't mean to come off high strung at all lol I'm the least bit compared to most people. just sharing my convo, most of which is known now and then

[ybbiz34]

Originally Posted by M3ryder55

lol i didn't mean to come off high strung at all lol I'm the least bit compared to most people. just sharing my convo, most of which is known now and then

I know. I rather enjoyed reading it. Thanks for sharing.

[CanAutM3]

Originally Posted by M3ryder55

Idk man, i was just shooting out the 340whp on the E9X because that look like the norm for most of us on here. That translates to an 18% loss. At an 11% loss, approximate whp is around 368-370 stock. And those high numbers where from gintani or eas dyno haha jk. well sort of at least.

Again, this isn't my field of expertise. There are plenty of wizards that are experts at this dyno/number craft that will put me to shame along with 99% of the people on here. I'm just stating what I believe is likely to be true. Lets hope over 400whp, yes? :thump:

At an 11% loss, lets say 12%, at 460bhp, that puts the F8X at around 400-405whp. At 11% loss at the rated 430bhp, puts it at around 380-385whp. Again, time will tell and these numbers don't really mean shit as of now, but its definitely something to keep in mind going forward.

Engine testing and dynos are my field of expertise. What Swamp is saying is correct. I was about to post it myslef but he beat me to it .

[CSBM5]

The carbon fiber driveshaft, while interesting and all, is really not going to be a major reduction in total drivetrain inertia. Mass is only part of the equation. What you must also measure to have any clue about the gains/losses in inertia is the radius of gyration of the steel shaft and the carbon shaft. Now you can make a comparison once you know the total moment of inertia of each shaft; however, it then needs to be taken a step further.

You then need to know the total drivetrain inertia...everything that rotates all the way out to the rear wheels/tires. Now you can compare the above inertia change in perspective to the total. More than likely, it will be insignificant at that level.

Finally, one should understand that the effects of drivetrain inertia are not static but are a function of acceleration only. Hence they show the most effect when acceleration is the highest (meaning their effect drops continually with speed since acceleration drops with speed).

[CanAutM3]

Originally Posted by CSBM5

The carbon fiber driveshaft, while interesting and all, is really not going to be a major reduction in total drivetrain inertia. Mass is only part of the equation. What you must also measure to have any clue about the gains/losses in inertia is the radius of gyration of the steel shaft and the carbon shaft. Now you can make a comparison once you know the total moment of inertia of each shaft; however, it then needs to be taken a step further.

You then need to know the total drivetrain inertia...everything that rotates all the way out to the rear wheels/tires. Now you can compare the above inertia change in perspective to the total. More than likely, it will be insignificant at that level.

Finally, one should understand that the effects of drivetrain inertia are not static but are a function of acceleration only. Hence they show the most effect when acceleration is the highest (meaning their effect drops continually with speed since acceleration drops with speed).

What is missing in your post is the impact of gearing. Since the drive shaft is spinning faster than the rear wheels (by a factor equal to the final drive ratio), any increase in the driveshaft inertia will be multiplied by that increased speed. The impact on the equivalent mass of a rotating component is proportional to the square of the gear ratio.

[GOLFFRR]

These guys come by our store all the time (we are located right next to the port) and never say one word to anyone about anything ever. I don't ask them anything when I see them and neither do any of the staff. They stop in talk to our service director for various things and than head out on their way.

Thats pretty cool that you were able to get some info out of them.

There is a coffee shop near my house that they all go for coffee everyday and there seems to be 2 f80 M3's in full camo that they are still driving, I wonder if its some sort of LCI or something they are working on. Either way what a cool a job!

[CSBM5]

Originally Posted by CanAutM3

What is missing in your post is the impact of gearing. Since the drive shaft is spinning faster than the rear wheels (by a factor equal to the final drive ratio), any increase in the driveshaft inertia will be multiplied by that increased speed. The impact on the equivalent mass of a rotating component is proportional to the square of the gear ratio.

Yep, all of that is factored into the overall drivetrain inertia value and each component's individual contribution.

[freeman727]

The weight has gone up? So is the weight really up or is the BMW website flawed? I hope its the later.

BTW, having an e90 M3, I'll have to drive it before I believe the hype. It has to feel at least 20% better to make up for the V8.

[MrCsquared]

Cool news, thanks for the post OP! Excited to hear the reviews regarding the nimbleness of the car (or if it's been grossly exaggerated).

I think many of us familiar with BMW's FI motors have already factored in the underrated power.

[Black Gold]

Originally Posted by freeman727

The weight has gone up? So is the weight really up or is the BMW website flawed? I hope its the later.

BTW, having an e90 M3, I'll have to drive it before I believe the hype. It has to feel at least 20% better to make up for the V8.

no. there is another thread in this section that talks about this

[catpat8000]

Originally Posted by M3ryder55

1. The car is an animal. It is under rated. BMW has started under rating their cars since the transition to FI for one reason or another. And a lot of that has to do w/ the government/EPA. He said we got to tell them what they want to hear to make them happy. The car is rated at 430 crank hp, but with a carbon fiber drive shaft in addition to the power ratings being under rated, it is very plausible to believe these things will put out around 400 to the wheels. He said once the cars get produced and released, and the power is actually higher, say 460-475 crank, the government can't do anything about it haha. Something like that.

These paranoid dreams about under-rating "because government" are downright comical. What government? Does he think all the governments on earth have conspired together to force BMW to under-rate their cars? And how would he explain the fact that you can buy a car with almost any power rating up to 1000 hp from an OEM? M5s are rated up to 575 hp. Does the government only clamp down on M3s?

Judging by BMW's past, the car probably will be under-rated but his reasoning is ridiculous.