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Discussion Starter #1 (Edited)
OK, I've finished my Gtech runs with the Dinan 3.91 differential, and have some accurate comparisons with the stock setup. I calibrated the Gtech at our local dragstrip with the exact setup I used for these runs, so it should be pretty accurate. The conditions were very similar for all the runs, temperature varied from 58 deg to 62 deg. I did 9 runs, 2 aborted with the stock car, and 7 runs, 1 aborted with the 3.91 differential (I used the 60' and 0-60 times on the aborted runs).

There is a substantial difference in the acelleration. Here are the results, using average numbers:

------------------------Stock -----------------------Dinan ----------------------Difference

60 ft. time ---------2.229 sec------------------2.225 sec----------------0.004 sec

0-60 mph ---------4.56 sec---------------------4.40 sec------------------0.16 sec

Quarter Mile -----12.78 @ 115.59 ---------12.54 @ 118.24 -------0.24 sec, 2.65 mph

50 - 110 mph-----7.86 sec---------------------7.31sec-------------------0.55 sec


Interestingly, my 60' times were really not much better with the new diff - the traction was just not great, and with more torque, it's not really any easier to modulate the throttle. Also, with the Dinan I got a fair amount of wheelspin in second gear, and had to modulate the throttle slightly. With the stock car, I could just mash it once I hit second - a good chirp, but it didn't break traction.

These numbers don't really show how much harder the Dinan is pulling in gear. Some of my Dinan 0-60 times included a 2-3 shift at 59 mph if I didn't quite hit redline. All of the quarter mile times included a 4-5 shift at about 117 mph. If the rev limit was raised slightly (listening Dinan?) the car would have easily trapped over 120, and the times would come down .15 sec.

Note - I just edited the table to include the 50-110 mph times. These give a good indication of how hard the car is pulling in third and fourth gears. As a reference, Road and Track has the M5 running 50-110 mph in 8.0 sec, and the M6 at 7.6 sec.
 

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Thanks Mike! This is right in-line with I had expected from the 3.91 diff. It’s great to actually see it substantiated. The “butt-o-meter” is too often swayed by the sizable dent left in our wallets for each new tweak. Now, with a bit of software support (Steve, Simon...?), we will see some very solid improvements in real world performance from our beasts.

:wroom:
 

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Thanks for the detailed write up Wolverine.:)
 

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Ah yes, Im familiar with the difference in gear sets !!! I also found 1st and 2nd faster out of the hole then its basically the same !!!!

Right up to 175 mph.....
 

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Mike --

Many thanks for the detailed numbers. You have done a big service to all of us considering this part, not to mention to Dinan for providing objective customer-derived marketing.

Your results make perfect sense. Traction already is a significant limiting force at the start with this car, but the Diff slowly but surely makes a difference as traction is gained, time goes by, and speeds increase.

I, too, will be interested to see what further improvements are accomplished if and when Dinan optimizes the software.
 

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Discussion Starter #7 (Edited)
unfoundhorsepower said:
Ah yes, Im familiar with the difference in gear sets !!! I also found 1st and 2nd faster out of the hole then its basically the same !!!!

Right up to 175 mph.....
Actually, the car pulls harder in every gear, at every speed.

I've edited the above results to include the 50-100 mph times. These are good times to get an idea of how hard the car is acellerating, with the same number of shift points. That is, you are in 2nd gear at 50 mph, and 4th gear at 110. Most of the time, you're running through third and fourth gears. There is a big difference in the average times - stock is 7.86 sec, Dinan is 7.31. For reference, the Feb 2006 Road and Track has the 50-110 times for the M5 at 8.0 sec, and the M6 at 7.6 sec.
 

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Does anyone know if the they kept the diff the same for the 6speeds?? I am very interested in the Dinan diff, just want to make sure it will work fine and is the right ratio to switch to!
Evan
 

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Car & Driver and Road & Track got a 4.1 and 4.2, respectively in the 0-60 times with a stock M5. Was your 4.4 a median?
 

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Wolverine said:
All of the quarter mile times included a 4-5 shift at about 117 mph. If the rev limit was raised slightly (listening Dinan?) the car would have easily trapped over 120, and the times would come down .15 sec.
You shouldnt be finishing the quarter mile in 5th gear. The GPS'd (true land speed) at 8250 rpm while in 4th gear with the stock diff is 127 mph. Quarter should end in 4th with the stock diff. Not 5th.

Even with the Dinan 3.91 your top speed in 4th should be around 123 at 8250 rpm.
 

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KeithTa said:
You shouldnt be finishing the quarter mile in 5th gear. The GPS'd (true land speed) at 8250 rpm while in 4th gear with the stock diff is 127 mph. Quarter should end in 4th with the stock diff. Not 5th.

Even with the Dinan 3.91 your top speed in 4th should be around 123 at 8250 rpm.
I would love to meet up with you at some point to maybe snag a ride and hear your exhaust sytem! I am planning on doing a full supersprint into eisemann muffler exhaust system in the future to either the M5 or M6 and would like to hear yours first! Maybe you could shoot me a PM with your email and next time I am down in Lauderdale and you are available we could meet up!
Thanks!
Evan
 

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Discussion Starter #13
KeithTa said:
You shouldnt be finishing the quarter mile in 5th gear. The GPS'd (true land speed) at 8250 rpm while in 4th gear with the stock diff is 127 mph. Quarter should end in 4th with the stock diff. Not 5th.

Even with the Dinan 3.91 your top speed in 4th should be around 123 at 8250 rpm.
Not according to the specs, or my testing. R&T Feb '06 lists the gears and max speeds. The stock car is 126mph in 4th at 8250 rpm. This gives a top speed in 4th of 116.7 mph with the Dinan Diff. If the rev limit was increased to 8500 rpm, you'de be able to hit just over 120 mph with the Dinan diff.
 

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Wolverine said:
Not according to the specs, or my testing. R&T Feb '06 lists the gears and max speeds. The stock car is 126mph in 4th at 8250 rpm. This gives a top speed in 4th of 116.7 mph with the Dinan Diff. If the rev limit was increased to 8500 rpm, you'de be able to hit just over 120 mph with the Dinan diff.
You are right. I did some research after the I posted my reply of 123 mph with Dinan Diff......I tested my car and I hit right about 120 with the diff in 4th.....couldnt really tell exactly cause I was watching the road....

Anyhow, even if the speedo shows 120, actual speed might be 116 or so...so you are likely correct.

Once my car has the Kelleners cams installed..coupled with the ECU, Headers, Cats, Dinan 3.91 diff, I will REALLY need the rev limiter raised to hold out 4th to cross the traps in the 120s. If I have to shift into 5th.....I have no idea what mph I will pull.

I asked Active about cracking the rev limiter, they said they have not done so yet. When I bring my car to them for the cam install or post cam ECU tuning, I will ask them to take a stab at raising the rev limiter again.

Once done, cracked rev limiter or not...I am slapping on a new set of rear Michellin Pilot Sport 2s and going to the Moroso Motorsports Track for quarter mile runs.

I hope to turn an 11.99 @ 120 or better. You think its possible?
 

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Discussion Starter #16
KeithTa said:
You are right. I did some research after the I posted my reply of 123 mph with Dinan Diff......I tested my car and I hit right about 120 with the diff in 4th.....couldnt really tell exactly cause I was watching the road....

Anyhow, even if the speedo shows 120, actual speed might be 116 or so...so you are likely correct.

Once my car has the Kelleners cams installed..coupled with the ECU, Headers, Cats, Dinan 3.91 diff, I will REALLY need the rev limiter raised to hold out 4th to cross the traps in the 120s. If I have to shift into 5th.....I have no idea what mph I will pull.

I asked Active about cracking the rev limiter, they said they have not done so yet. When I bring my car to them for the cam install or post cam ECU tuning, I will ask them to take a stab at raising the rev limiter again.

Once done, cracked rev limiter or not...I am slapping on a new set of rear Michellin Pilot Sport 2s and going to the Moroso Motorsports Track for quarter mile runs.

I hope to turn an 11.99 @ 120 or better. You think its possible?
I hit over 119 mph on one of my runs with a shift at 116 mph. If the rev limiter had been raised to 8500, I would have trapped over 120. You will definitely be able to trap over 120. If you have all your mods and get a great launch, I think you'll easily break into the 11's.
 

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Wolverine, just curious, did you run the quarter mile in manuel mode or drive? Also, was DSC on or off? Lastly, off the line, did you bury the gas to the floor?

Just curious, I was looking at MOTORtrends article on the Z06 vs. Viper vs.Gt500. The GT500's numbers look very close to the beasts, and if I ever come across one I will have to be careful. Particularly, most guys load them with after market performance upgrades. Would be an interesting race.
 

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Discussion Starter #18
06M5777 said:
Wolverine, just curious, did you run the quarter mile in manuel mode or drive? Also, was DSC on or off? Lastly, off the line, did you bury the gas to the floor?

Just curious, I was looking at MOTORtrends article on the Z06 vs. Viper vs.Gt500. The GT500's numbers look very close to the beasts, and if I ever come across one I will have to be careful. Particularly, most guys load them with after market performance upgrades. Would be an interesting race.
All my runs used for comparison were done in manual mode, P500S, S6, EDC sport. My launch technique was to stab the throttle to get the revs up to 4,000 then let off and modulate the throttle as the clutch grabbed. I found later (somebody mentioned it here) that you could improve the modulation by choosing P500 instead of P500S - so I would use P500.

Using manual S6, you'll save .1 sec per shift, which is .4 sec with the Dinan diff in a quarter mile. Manual mode S6 takes .15 sec per shift, D mode S5 takes .25 sec.

Yeah, I'd watch out for the modded GT500's, but you should take a stock model without too much trouble.
 

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Hey thanks for the insight, I wonder what the result would have been if you had used the U.S. watered down launch control version (1500 RPM manual mode shift)
In the European model, I believe it was in Road & Tracks feb. 06 test came out 0-60 sprints at 4.2 secs. and those were with launch control. THe car's seems to be capable with the right set up. However, our hands are tied at the moment.
 

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I know this thread is historic, however, have you done these testings lately to see how the differential has worn in at all?
 
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