July 16, 2007

M3 Vs MCoupe at the Glen Part II, The Revenge!

Almost exactly a year ago we compared two laps form AC's and Stee's cars at Watkins Glen. Back then the M3 bested the MCoupe by 2/10th of a second with both cars in the 2:16s.
A year later and with different tires, things have changed a bit...

It's amazing to me how evenly matched the E46 M3 and the S54 Z3M Coupe can be. For the past few years AC and I have been having a blast lapping together at local tracks at HPDEs. Now that we have data acquisition (Traqmate) and in car video, we can do a post session analysis, compare our differences and similarities and find areas AC and I to improve. Some of the differences could be chalked up to driving style, others to car capabilities. Sometimes it gets hard to differentiate, but at the end of the day all you can do is give an educated guess based on the data recorded.

First, some info on our cars.

  • Both cars have the same stock S54 engine, the M Coupe is limited to 7600 RPM while the M3 revs to 8k. The engines are not chipped.
  • The M Coupe weighs in at ~3,000 lbs, 400 lbs lighter than the M3's ~3,400 lbs.
  • The M3 has SMG, the Coupe has a standard 5 speed but with a 3.46 final drive.
  • Both cars are on Kuhmo's magical V710 tires, which have enough grip to rip your face off. The MCoupe 245/45/17 and 275/40/17 while the M3 has a square 285/30/18 set.
  • The M3 benefits from newer suspension technology. Both cars have aftermarket shocks, springs and camber plates. Nicely set up but nothing extravagant or exotic.
  • The M3 has 4 wheel Brembo set, The MCoupe has stock BMW brakes with Performance Friction rotors in front. Both cars use Performance Friction pads.
  • Both cars retain full interior, air conditioning, radio etc.
Below is a comparison of AC and my fastest laps from our recent visit to the Glen with Group 52. AC in the M Coupe (affectionately known as "The Shoe") was able to cross the line first with a 2:12.3 and I was just behind in the M3 with a 2:12.7. Let's take a closer look:

The main thing to follow here is the graph at the bottom of each picture, the Velocity vs Distance plot. It's important because it shows who was going faster at which parts of the track. On the top right we show which car is leading overall, and by how much. The spreadsheet in the middle shows other interesting stats like time through that segment, min speed, max speed, max g forces and more.

Click on the images to enlarge them. Let's start the lap.

Through Turn 1 we are pretty much identical. Our minimum speeds are within a few tenths, we brake at the same time, and get back on the gas at almost exactly the time. Our net time difference at this point is negligible.

Through turn 2 we lift exactly the same amount, up the Esses we are dead even up to the shift to 5th in the back straight. This is where SMG shows its advantage with a nearly undetectable blip in the graph whereas the M Coupe's standard tranny shift is clearly evident. This extra shift time nets out to a .15 second advantage through that section for the M3.

Segment 3 is interesting. Both cars brake on the back straight at almost exactly the same point, the M3 brakes a little less and carries slightly more speed through the bus stop but the M Coupe carries more speed around turn 5, "the outer loop". The net difference in that segment is a .05 second advantage for the Coupe, which cuts the M3's overall lead down to .1 seconds.

Turn 8, "the Laces", is the first segment where the two cars show an appreciable difference. In the M3 I'm able to brake 1/2 a second later and get back to full throttle slightly sooner than AC in the M Coupe (thank you Brembo and PF-01 :) ), which nets a .6 second gain in that segment. I'm now ahead by .7 seconds overall.

But, AC brings it back in 7, "the toe". He uses a lot of trail braking, and carries 4 mph more minimum speed through the toe.

Then he's able to storm up the hill and pull harder than the M3 in 3rd gear (this probably has something to do with the 400 lbs weight difference). Overall, AC is able to gain back .5 seconds in that segment and cuts my lead to .2 seconds.

Coming up to 8, "the heel", I brake a fraction of a second later, we go through the turn at nearly the same speed, but AC gets on the gas a fraction of a second sooner, and again, the M Coupe out-pulls the M3 in 3rd gear. AC gains another .1 seconds in that segment and cuts my lead down to just .1 seconds.

For the off camber turn 9, I brake slightly less but I only gain .05 seconds. My lead is only .15 seconds.

Through the fast left turn 10, we are both identical with identical segment times.

In turn 11, AC gets on the gas a fraction of a second sooner than I do and again is able to out pull me in 3rd gear. That seemingly tiny difference nets out to a .45 second advantage through that segment and gives AC the faster lap time by .35 seconds.

Here is a side by side video of the above laps. It is a 33 meg download. If you want to hear the individual engines just pan the audio to one side or the other.


As always, we recommend downloading the higher resolution version above...but if you are in a hurry here is a fuzzier flash version:

M3 vs MCoupe Part II from Axis on Vimeo.


  1. Brilliant, brilliant!!! Great analysis!

    Why can AC often get on the gas sooner, if you are the left-foot braker? What gives?

  2. My guess is that the Coupe's tighter ability to rotate allows AC to be confident and lined up for the exit and get on the gas slightly sooner. This really only happens in the Heel (Turn 8) and Turn 11, where a fair amount of rotation is required early in the turn. In the laces though, I'm at full throttle sooner, even with braking later. I think this is because it's a much longer sweeper thats less about initial rotation. Most of the other turns we are pretty much identical. Remember, we are talking about fractions of a second, so the differences here are tiny.

    That's really just an educated guess though.

  3. Ithink it's more a simple matter of execution, I have laps where the data show a different tactic in turn 6 which results in a much earlier throttle application and significantly higher apex speed, I just did not get it done on that particular lap. I do remember doing some thinking during that lap...I just did not do enough of it! :o)

  4. I found the lap your talking about. Basically, you brake .8 seconds earlier (1.3 seconds earlier than me), but you brake a lot less, and carry a minimum speed a relatively huge 5 mph higher than any other lap. But, again, it appears you hold balance throttle through the turn and then full throttle slightly earlier than your other lap (slightly later than me).

    Your line on entry is much tighter in that lap and you hold the inside line. Your exit line is the same.

    Bottom line, you run a shorter line, and have a higher minimum speed, but you brake much earlier.

    It's all a give and take. The net effect of that radically different approach to turn 6 is .4 seconds faster than your other lap and .2 seconds slower than my lap.

  5. .4 sec is HUGE! Everything else being equal that alone would have made my final lap time 2:11.9!!!

    our bad was not studying this stuff closely enough at the track...

  6. Studying it at the track? What fun would that be!?

  7. A lot of fun when you can go out the next session and execute what you learn!

    AC, 2:11 is there! That's mind blowing to me, but its def there.

  8. Amazing times you guys run. Great analysis as well. I was told by a Speed Touring Team that their full course WGI qualifying laps were in the 2:02 range.

    Come on guys...YOU CAN DO EEET

  9. Remember that what matters mostly is the total time of corner + next straight.
    It always pays to give up some corner speed if you are much earlier on the throttle and much faster on the next straight.
    That was basically my conclusion from my analysis of last years laps. It was pretty clear you guys were giving a lot of time on corner exit and it showed on the empty 45 degrees of the g-plots. Now the friction circle is nicey filled and voila it shows in MUCH better lap times.
    Would be cool if you could run different tires now that you are consistent and see whta the real difference of the V710s is.

  10. "...Would be cool if you could run different tires now that you are consistent and see whta the real difference of the V710s is...."

    Maybe Tire Rack will step up! :O)


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