M3 Dynotest

[T Bone]

Originally Posted by GregW / Oregon

Why do you suppose peak power on the M3 was measured at 7,808 rpm vs. 8,300 as spec'd?

The S65 torque curve falls off fairly quickly at the high rpms. This only conclusion you can draw is the engine makes less torque at 8,300 than 7,800. Unlike the S85 (V10), the torque gets peakier with at high revs versus the S65's flatter torque curve (with faster drop off)

The S65 will be more "driveable" than the S85 but the S65 will be capable of deliver more power once a tuner provides a camshaft + ECU tuning to give more torque in the high rpms.

BTW, I think the M3's drivetrain is "less efficient" because it is driving bigger engine accessories (like a bigger waterpump) than the 335i

[swamp2]

Originally Posted by T Bone

BTW, I think the M3's drivetrain is "less efficient" because it is driving bigger engine accessories (like a bigger waterpump) than the 335i

Crank hp includes the effects from all accessories, right? The losses should be "apples to apples" comparable and should isolate just the effects from the clutch, tranny, driveline, rear end, axles and wheels.

If the tests from the manufacturer somehow did not include the effects of accessories the M3 would make up ground in losses comapared to the 335i by BER.

[swamp2]

Originally Posted by chonko

An AWD has more losses becuase of the number of lossy interfaces, gear interfaces and bearings, etc, as well as the larger rotating mass involved.

I was trying to make the distinction between using a fixed percentage of drive-train torque losses as opposed to a given torque loss number.

For the same coefficient of friction, the torque loss at 3000 rpm is the same as the torque loss at 6000 rpm, however your engine torque at both rpm is different. Since the enumerator is the same, with different denominator, it will erroneous to assume that your percentage losses are the same.
You can conversely use the fixed percentage loss and apply it to the various torques at the different rpm, which will give you different Parasitic torque loss. Unfortunately, your torque losses for a given coefficient of friction is not a variable loss, but fixed hence you will be liable to erroneous answers adopting this approach.

With regards to what I wrote as a the formula for frictional losses- it is what we use in the industry, and it forms the basis of managing torque losses.

Torque losses= side force * coefficient of friction*radius of the rotating mass

Side force barring external forces due to bending and curvature on the rotating mass= Normal reaction.
Normal reaction= Weight perpendicular to the plane
Weight perpendicular to the plane(horizontal plane)= Mass * Acceleration due to gravity. (Forgive me for using mass and force loosely didn't realise I was in a physics class: but a mass under the influence of gravity does exert force on a plane)
Side Force*radius = torque.

Torque generally speaking is not a function of rpm, but a function of Force and the radius arm.

Engine Torque does however rely on rpm only because the force generated by the engine is a function of rpm
The engine force= mean effective pressure*cross sectional area of the piston*effective strokes per second*number of cylinders
Torque= Force * Radius.

I can't remember stating Parasitic Power loss, I believe I said "Parasitic Torque losses.
Power represents the ability to do work per unit time.
Torque which I am sure you know very well represents the rotating action of force.



If you have two surfaces in contact, I believe you will have friction.
So like you rightly pointed out, the cumulative frictional coefficient across the drive-train is a lot more than a RWD system. And the rotating mass is more than what is applicable to a RWD system.

Yes your original formula had torqe on the LHS not power, the units still did not match (force x length is not equal to mass x length). Your corrected formula does at least have the correct units.

Even though this is not a physics class there is no escaping the physics. Physics describes our world - very accurately and your physics is still incorrect. There is no concept of "weight perpedicular to a plane". Weight is always mass x gravity which can have a direction if you consider gravity to be a vector bu then we typically call this a force, not a weight.

Next torque or power losses take two forms - inertial and frictional. Inertial losses are just those that arise from the mass and rotational inertia of drive train components. The "loss" here is because it takes more energy to spin up a heavy shaft than a light shaft. Frictional losses are fairly obvious the friction turns energy to heat irreversibly.

Your forumula accounts only for frictional losses not intertial.

I don't know what industry you are in and where you use your formulae but if you are designing rotating equipment I don't want to be anywhere near that equipment.

Care to try again ?

[T Bone]

Originally Posted by swamp2

Crank hp includes the effects from all accessories, right? The losses should be "apples to apples" comparable and should isolate just the effects from the clutch, tranny, driveline, rear end, axles and wheels.

If the tests from the manufacturer somehow did not include the effects of accessories the M3 would make up ground in losses comapared to the 335i by BER.

SAE Net HP does this but the N54 engine declutches and disengages some of the accessories, so I am not sure if SAE HP is calculated with the accessories attached (but not working) or if it is measured with the accessories attached and working.

Does it take more HP to drive a LSD?

[swamp2]

Originally Posted by T Bone

SAE Net HP does this but the N54 engine declutches and disengages some of the accessories, so I am not sure if SAE HP is calculated with the accessories attached (but not working) or if it is measured with the accessories attached and working.

Does it take more HP to drive a LSD?

Both good questions, I don't know but would like to.

Aren't you a Canadian fellow? Have you seen the beast in person yet - plans to? Congrats on the 1k post mark (a bit late...).

[esquire]

Originally Posted by swamp2

I don't know what industry you are in and where you use your formulae but if you are designing rotating equipment I don't want to be anywhere near that equipment.

Care to try again ?

hilarious.

[chonko]

Originally Posted by swamp2

There is no concept of "weight perpedicular to a plane". Weight is always mass x gravity which can have a direction if you consider gravity to be a vector bu then we typically call this a force, not a weight.

You are kidding right? Weight is a force. For an inclined plane, there is a component of the weight that acts in the perpendicular direction which is the Sin(inc)* Weight. When you are standing on the flat surface, the inclination is 90 degrees:Sin(90)*weight= weight.

Originally Posted by swamp2

Next torque or power losses take two forms - inertial and frictional. Inertial losses are just those that arise from the mass and rotational inertia of drive train components. The "loss" here is because it takes more energy to spin up a heavy shaft than a light shaft. Frictional losses are fairly obvious the friction turns energy to heat irreversibly.

Your forumula accounts only for frictional losses not intertial.

Sorry, the formula accounts for both.
Torque losses= side force * coefficient of friction*radius of the rotating mass
Side force as I had mentioned earlier barring other forces is entirely due to weight acting perpendicular to the plane.

Originally Posted by swamp2

I don't know what industry you are in and where you use your formulae but if you are designing rotating equipment I don't want to be anywhere near that equipment.

Care to try again ?

We do design lots of rotating equipment,and yes we also design systems that minimizes torque loss, and the industry has been successful doing this for years.

Care to take the time to read carefully, and perhaps do a little bit of thinking as well?

[e36jakeo]

Originally Posted by southlight

Here's the full dynotest result of the new M3:
http://www.rri.se/popup/performanceg...p?ChartsID=768

JustMe mentioned the results some days ago. Not bad...

For comparison:
RS4: http://www.rri.se/popup/performanceg...p?ChartsID=769
M5: http://www.rri.se/popup/performanceg...p?ChartsID=153
335i: http://www.rri.se/popup/performanceg...p?ChartsID=647

Best regards, south

Did anyone check out the details section in each of these threads? Curb weight of each car was listed. We never fully figured out if the M3 was going to weigh 3650 or so or more like 3500 (which BMW originally led us to believe).

The weight of the each car is listed at

M3: 1611 KG = 3552 lbs
335i: 1621 KG = 3574 lbs (correct for 335i)
RS4: 1728 KG = 3810 lbs (about right for a Euro model - more in US)
M5: 1844 KG = 4065 lbs (about right for M5 with a couple options

Since the 335i has been weighed by multiple car mags right about 3575 lbs, I think the listed weight for the M3 might just be accurate. I think this is good news for those of us who thought the M3 was coming in well into the 3600s. They have managed to keep weight about 100 lbs more than the E46 M3!

Combine this with a lot more HP to the wheels than the RS4 and you have yourself a very quick car.

[GregW / Oregon]

Originally Posted by e36jakeo

Did anyone check out the details section in each of these threads? Curb weight of each car was listed. We never fully figured out if the M3 was going to weigh 3650 or so or more like 3500 (which BMW originally led us to believe).

The weight of the each car is listed at

M3: 1611 KG = 3552 lbs
335i: 1621 KG = 3574 lbs (correct for 335i)
RS4: 1728 KG = 3810 lbs (about right for a Euro model - more in US)
M5: 1844 KG = 4065 lbs (about right for M5 with a couple options

Since the 335i has been weighed by multiple car mags right about 3575 lbs, I think the listed weight for the M3 might just be accurate. I think this is good news for those of us who thought the M3 was coming in well into the 3600s. They have managed to keep weight about 100 lbs more than the E46 M3!

Combine this with a lot more HP to the wheels than the RS4 and you have yourself a very quick car.

Yes, that's interesting. The weight specs begtween Euro ones and the US "unladen" weights has been confusing. BMWUSA lists the 335i at 3,571 lbs. Given the slightly heavier engine in the M3, larger brakes and tires, etc., combined with the weight savings of CF roof, plastiv fenders and lighter suspension, that sounds about right for the M3. However, unless it comes in at 3,541 or less I've lost a $100 bet over on Biimmerfest!

[Romo]

EU specs;

335i 1610kg

M3 1655kg

[2002 Tii]

http://www.rri.se/popup/performanceg...p?ChartsID=768

[swamp2]

Originally Posted by e36jakeo

Did anyone check out the details section in each of these threads? Curb weight of each car was listed. We never fully figured out if the M3 was going to weigh 3650 or so or more like 3500 (which BMW originally led us to believe).

The weight of the each car is listed at

M3: 1611 KG = 3552 lbs
335i: 1621 KG = 3574 lbs (correct for 335i)
RS4: 1728 KG = 3810 lbs (about right for a Euro model - more in US)
M5: 1844 KG = 4065 lbs (about right for M5 with a couple options

Since the 335i has been weighed by multiple car mags right about 3575 lbs, I think the listed weight for the M3 might just be accurate. I think this is good news for those of us who thought the M3 was coming in well into the 3600s. They have managed to keep weight about 100 lbs more than the E46 M3!

Combine this with a lot more HP to the wheels than the RS4 and you have yourself a very quick car.

I was excited the minute I saw this weight which was actually measured. Nothing wrong with a bit lighter than spec! The may be trying to account for the heavier sunroof model and the added weight M-DCT will bring. <3600 and less than the 335i is an accomplishment. I think this topic deserves it's own new thread!

[lucid]

Originally Posted by swamp2

<3600 and less than the 335i is an accomplishment.

If that turns out to be true, then things are much better than I thought in the weight department!

[swamp2]

Originally Posted by chonko

You are kidding right? Weight is a force. For an inclined plane, there is a component of the weight that acts in the perpendicular direction which is the Sin(inc)* Weight. When you are standing on the flat surface, the inclination is 90 degrees:Sin(90)*weight= weight.





Sorry, the formula accounts for both.
Torque losses= side force * coefficient of friction*radius of the rotating mass
Side force as I had mentioned earlier barring other forces is entirely due to weight acting perpendicular to the plane.



We do design lots of rotating equipment,and yes we also design systems that minimizes torque loss, and the industry has been successful doing this for years.

Care to take the time to read carefully, and perhaps do a little bit of thinking as well?

OK, I owe you an apology.

We were both wrong here. Your initial formulae were totally wrong but my comments about inertial losses were incorrect as well, that was sloppy thinking about the physics. I hope to post some more useful formulae soon that shows the difference - but here is the crux:

Torqe losses are indeed mostly frictional. Larger drivetrain mass is not an inertial loss but simply an impedement to acceleration - they DO NOT lower the actual torque applied to the wheels. It is just like the simple F=ma for linear motion, a lossy process lowers the force which lowers the acceleration. Just as well a larger mass lowers the acceleration for a given force. Same things applies to T=I*alpha where T=torque, I=moment of inertia (say of all drive train components) and alpha is angular acceleration.

On the weight thing, yes weight is a vector and a force, however, most folks refer to weight as a scalar quantity (no direction).

Again, my apologies for the sarcasm and my sloppy thinking. Again when I can find a few minutes I will post some useful formulae.

[swamp2]

Originally Posted by lucid

If that turns out to be true, then things are much better than I thought in the weight department!

AFAIK that was an actual measurement. Should be rock solid. I thought I saw another actual measurement in another of the reviews as well.

[lucid]

Originally Posted by swamp2

AFAIK that was an actual measurement. Should be rock solid. I thought I saw another actual measurement in another of the reviews as well.

Okay then. I really did not expect the M3 to weigh less than the 335i.

[southlight]

But I think it says curb weight. Means without driver but full tank, subtract 10% fuel, add 75 kg and the result is the real weight compared to the maufacturer claim of 1655kg.
335i was with AT...

Best regards, south

[lucid]

The only thing that makes sense to me is curb weight. The rest is just regulatory nonsense that seems to confuse people more than anything else. Two basic questions I want to be able to answer are: what is the weight difference between the E46 M3 and the E92 M3; what is the weight difference between the 335i and the E92 M3? Since these are relative differences, it doesn't matter what measurement scheme is being used as long as the same damn scheme is used consistently.

So, does someone know the curb weight for the 335i without AT then? (as independently measured and not stated although South's calculation seems to show that in this measurement, they agree.)

And, can we all agree that the curb weight of the manual E46 M3 is 3415lbs? [Edmunds.com]

That would mean the E92 M3 is 137lbs heavier than the E92 M3 according to the reported measurement on this thread...

[GregW / Oregon]

Originally Posted by lucid

So, does someone know the curb weight for the 335i without AT then? (as independently measured and not stated although South's calculation seems to show that in this measurement, they agree.)

As I stated in my post above, BMWUSA says 3,571 with MT, 3,582 with AT. Not exactly an independent measurement, I guess.

[chonko]

Originally Posted by swamp2

OK, I owe you an apology.

We were both wrong here. Your initial formulae were totally wrong but my comments about inertial losses were incorrect as well, that was sloppy thinking about the physics. I hope to post some more useful formulae soon that shows the difference - but here is the crux:

Torqe losses are indeed mostly frictional. Larger drivetrain mass is not an inertial loss but simply an impedement to acceleration - they DO NOT lower the actual torque applied to the wheels. It is just like the simple F=ma for linear motion, a lossy process lowers the force which lowers the acceleration. Just as well a larger mass lowers the acceleration for a given force. Same things applies to T=I*alpha where T=torque, I=moment of inertia (say of all drive train components) and alpha is angular acceleration.

On the weight thing, yes weight is a vector and a force, however, most folks refer to weight as a scalar quantity (no direction).

Again, my apologies for the sarcasm and my sloppy thinking. Again when I can find a few minutes I will post some useful formulae.

Just trying to share knowledge thats all.

[lucid]

Originally Posted by GregW / Oregon

As I stated in my post above, BMWUSA says 3,571 with MT, 3,582 with AT. Not exactly an independent measurement, I guess.

OK. Comparing the official 335i number with the reported M3 number yields the M3 being 19lbs lighter than the 335i then.

[swamp2]

Originally Posted by lucid

OK. Comparing the official 335i number with the reported M3 number yields the M3 being 19lbs lighter than the 335i then.

Well if that ain't apples to oranges I don't know what it (even if it is close to correct for an apples to apples comparo). If we don't have an actual measurement for a MT 335i I say the best estimate is measured weight with AT - (BMW official weight difference between MT and AT). This gives 3574-11=3563, making the measured M3 MT 11 lbs lighter than 335i MT. Close enough to call it a wash.