USIM/JWT ECU vs MEVI/JWT ECU using Cartest
10-25-2003, 10:15 PM
#1
Not DAVEB the parts guy
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Join Date: Aug 2000
Posts: 8,555
USIM/JWT ECU vs MEVI/JWT ECU using Cartest
Since one has really never compared their runs between a USIM/JWT ECU vs MEVI/ECU, I requested some help from our Cartest gurus to run some numbers. I was very curious to see whether or not the USIM/JWT was better for the 1/4 mile (0-100mph) acceleration. As many of us know, the USIM/JWT is quite a torquey setup with about 15fwhp/tq from 3500-5000rpms over the MEVI. Of course with the MEVI, after 5400rpms the MEVI owns with almost 40fwhp/fwtq over the USIM. However good topend rpms don't always own in 1/4 mile. Torque and strong HP is what wins the 1/4 mile. Much thanks to Nismo87 and SteVTEC for helping me out with this. According Cartest, the MEVI/JWT ECU is a couple tenths and ~2mph in the 1/4 mile. After that the MEVI is pretty brutal.
From Nismo87:
From SteVtec:
Dave
From Nismo87:
I have Jeff K's dyno plot and I've already played with cartest too. The MEVI would run away from the USIM in the 1/4, the results are 0.2sec and 2mph in favor of the MEVI. However at the 1/8 the results are simular, the main reason the USIM is slower is the 3-4 shift. Looking at the drive power curve (torque curve x gear ratio) the USIM loses to the MEVI after 70mph everywhere. For example the MEVI has more drive torque at 6800rpm in 3rd gear vs the peak torque of the USIM at 4500rpm in 4th gear.
Just for kicks I ran the same test with a MEVI given 205/50-15 tires. The results is it beats the USIM at every point in the powerband. Now these tires will cause a 3-4 shift in the 1/4 however with the smaller tires and the new effective 4.0 final gear makes more drive torque in each gear vs the USIM with stock 3.82 gears. There is alot more area under the curve and I'm sure the car will feel more responsive during daily driving. Also the 1/4 ET/trap don't seem to be any different with the gearing change. I believe the 3-4 shift is affecting the ET/trap otherwise it would have a lower ET.
So now all you have to do is find some nice lightweight 15in wheels and throw some 205/50-15 tires on them. That will give you more drive torque at all rpm than the USIM would prove at its peak! The car will look crazy with small tires in front but its all good .
Just for kicks I ran the same test with a MEVI given 205/50-15 tires. The results is it beats the USIM at every point in the powerband. Now these tires will cause a 3-4 shift in the 1/4 however with the smaller tires and the new effective 4.0 final gear makes more drive torque in each gear vs the USIM with stock 3.82 gears. There is alot more area under the curve and I'm sure the car will feel more responsive during daily driving. Also the 1/4 ET/trap don't seem to be any different with the gearing change. I believe the 3-4 shift is affecting the ET/trap otherwise it would have a lower ET.
So now all you have to do is find some nice lightweight 15in wheels and throw some 205/50-15 tires on them. That will give you more drive torque at all rpm than the USIM would prove at its peak! The car will look crazy with small tires in front but its all good .
Dave,
Keep your MEVI on.
I did the same stuff that Ari did with CarTest and got the same results. Mine actually showed the USIM to have a slight advantage on 60' but after that it was all MEVI.
JWT/USIM: 14.29 @ 96.73 w/2.22 60'
JWT/MEVI: 14.21 @ 98.56 w/2.24 60' (6800 rev limit)
JWT/MEVI: 14.14 @ 98.79 w/2.24 60' (7200 rev limit)
As far as passing times and around town tractability, yeah, the USIM is slightly better, but with this much power to the ground in an already light car I really don't think you're missing anything anymore. So I'd keep the MEVI
It looks like you could definitely pick up a tenth by getting your ECU properly programmed at 7200 rpm. The high rev-limit is of no use at all to the USIM since it still chokes after 6k anyways. It did no better with the raised rev limit than with the higher rev limits.
Keep your MEVI on.
I did the same stuff that Ari did with CarTest and got the same results. Mine actually showed the USIM to have a slight advantage on 60' but after that it was all MEVI.
JWT/USIM: 14.29 @ 96.73 w/2.22 60'
JWT/MEVI: 14.21 @ 98.56 w/2.24 60' (6800 rev limit)
JWT/MEVI: 14.14 @ 98.79 w/2.24 60' (7200 rev limit)
As far as passing times and around town tractability, yeah, the USIM is slightly better, but with this much power to the ground in an already light car I really don't think you're missing anything anymore. So I'd keep the MEVI
It looks like you could definitely pick up a tenth by getting your ECU properly programmed at 7200 rpm. The high rev-limit is of no use at all to the USIM since it still chokes after 6k anyways. It did no better with the raised rev limit than with the higher rev limits.
Dave
10-26-2003, 07:51 AM
#5
Originally Posted by I30tMikeD
Looks good on paper, but my best so far has been a 14.60 @ 95.94 w/ 2.22 60'.
10-26-2003, 07:54 AM
#6
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MEVI is definately better for the auto. I had my ecu before the MEVI and the best I could do was a 14.9. After the MEVI I was able to run a 14.6, and then a 14.4 with some weight reduction. I have gone from a best of 92.xxmph to a best of 98.xxmph with the MEVI being the only major mod. (also added underdrive pulley, minor weight reduction). I have not been to the track yet since I swapped out the Gforce ecu for the JWT. 
10-26-2003, 08:33 AM
#7
Moderator who thinks he is better than us with his I30
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Originally Posted by BEJAY1
Not to change the topic but is there any data regarding VLSD power vs open diff's? Does viscous create any drag or friction?
I think it may be similar to wheel weight. I know the axel for the VSLD is bigger, so maybe more rotaional mass???
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