Brunoboy
Well-known member
Just wondering if the transition of Front and Rear is 50/50 or not?
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are our cars 50/50?
- Thread starterBrunoboy
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Brunoboy
Well-known member
does this include launching also?
Specter
Well-known member
MY friend is using a three bolt diff on his colt with a 1g 4g63t setup, its more like 40 front 60 back not 50/50
i know the 1gs are closer to 60/40, not sure about the galants, I'd assume the same.
And Colts are FWD, did your friend swap it all wheel? thats cool if he did
And Colts are FWD, did your friend swap it all wheel? thats cool if he did
GVR-4
Well-known member
The center diff is a limited slip viscous coupling, like the limited slips in the stock rears. The viscous fluid heats up and locks the two shafts together. As far as I know there is no way to make a viscous diff anything but 50/50. But they do sometimes do unusual things under very high torque loads. Check this out:
click
click
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Chad989of2000
Well-known member
^ awesome vid...interesting how the front and rear wheels really work together to lauch the car.
Specter
Well-known member
381gvr4
Well-known member
Yes 50-50. Drive it 50% of the time and fix it 50% of the time!!!!!!!
slugsgomoo
Well-known member
Front/Rear split is 50/50!
it's not 60/40 or 70/30 or 30/70 or 25/75 or 90/10 or any other stupid ratio that you were told on t00nerz
it's not 60/40 or 70/30 or 30/70 or 25/75 or 90/10 or any other stupid ratio that you were told on t00nerz
Specter
Well-known member
Oh and one more thing, we all have scene gvrs doing wheelies right? are they on the stock drive train or is it changed some how? because if they are on the stock drive train i dont think it would be 50/50 otherwise the front of the car wont lift in the air?
jepherz
Staff member
There's not even any way to make it anything other than 50/50 without some electrical/clutch assistance (which we don't have) is there?
slugsgomoo
Well-known member
No, you'd have to have some electro gadgetry to make the car not be 50/50.
The reason you'll see some galants (and early pre-gadgetry evos) with the front tires in the air briefly is simply due to the violence of a stupid hard launch on slicks, and the magical effects of weight transfer.
Look how far a gvr4 on stock suspension will throw the nose in the air on launch /ubbthreads/images/graemlins/wink.gif
yet most t00ners still think there's a FWD bias on these cars. /ubbthreads/images/graemlins/rofl.gif
The reason you'll see some galants (and early pre-gadgetry evos) with the front tires in the air briefly is simply due to the violence of a stupid hard launch on slicks, and the magical effects of weight transfer.
Look how far a gvr4 on stock suspension will throw the nose in the air on launch /ubbthreads/images/graemlins/wink.gif
yet most t00ners still think there's a FWD bias on these cars. /ubbthreads/images/graemlins/rofl.gif
Brunoboy
Well-known member
ok thanks, well all the center diffs are lsd on these cars? what about rear diff? My rear is NOT lsd.......
slugsgomoo
Well-known member
the center diff is from the factory. 1g dsm's with 3 bolts came with LSD or non-LSD, galants were non-LSD only. AFAIK all the 1g 4 bolts are LSD but there are supposedly some non LSD 4 bolts as well.
Dialcaliper
Well-known member
The center diff itself is 50/50, and the viscous coupling (once it heats up from speed differential) can bias a limited amount of torque towards the front or rear (the VCU plates never actually touch, and the silicone fluid that "seizes" up to transfer the torque can only handle so much before it is overcome). The torque bias is limited, and it has no scaling torque reaction like a torsen or the cams on a plate diff that keep increasing the more torque is applied to the body.
The nature of the VCU means that it will shift torque to the rear both in a corner (when the turned front wheels are traveling on a larger circle) or when a wheel spins, but in a straight line, it will be very slow to react. In short, without any shaft speed differential between front and rear, the car will remain 50/50 torque split until a wheel starts to spin.
For the WRX, there is an "STI Group A" VCU upgrade (originally for the older Japan only WRX), that has a higher torque capacity than the stock one, but apparently the heaviest version is so stiff at rest that it causes turning problems in tight turns similar to a spool/welded differential. Stock WRX coupling will transfer 10 kg-m or about 72 ft-lbs when tested at 100 RPM, the upgrades available are 12 kg-m (87 ft-lb) and 20 kg-m (145 ft-lb)
The mitsubishi vcu supposedly runs around 8-10 kg-m. As far as I can tell, no such upgrade replacement was made for the VR-4 or early Evos, as Mitsubishi elected to move directly to the ACD instead, which is claimed to handle "3 times the torque" of the VCU, and even higher in the Evo IX.
Keep in mind that the torque numbers are at the center diff, and so the engine torque applied after gearing and final drive is multiplied by somewhere between .68 to 3 depending on what gear you are in (final drive doesn't apply until the front or rear diff). In second gear for example (around 2:1), that puts the stock engine at about 400 ft-lbs applied to the center diff, which would give a torque bias ratio of about 1.45:1 with the center diff spinning at 100 RPM (essentially this would be a ~350 RPM difference in wheel speed - which is about 25mph for the car - serious wheelspin) net difference. Keep in mind the VCU does not have a static maximum torque bias because it reacts to speed differential, not torque. Also, the effective maximum torque bias drops with additional engine torque, since the torque transfer is fixed at a given RPM.
So yeah, our cars are pretty 50/50 because of the center diff, but there's a little bit of torque biasing (as much as 40/60 or 60/40) under very severe wheelspin. It's probably closer to 45/55 to 55/45 (~1.2:1 torque bias) in general usage. (Note: SWAG)
The important thing to remember with differentials is that weight distribution (60:40) does not matter, and it's usually where people pull erroneous "constant" 60/40 or 40/60 numbers from. Also, almost every aftermarket diff is default 50/50 with a torque bias capability. The only diff that is not is the open Cusco planetary "tarmac gear" which is 35/65. Only planetary open differentials or planetary LSD's (Torsen T-3) have an uneven torque split.
Understeering like a pig has more to do with the way the car's suspension is set up than just the AWD.
The nature of the VCU means that it will shift torque to the rear both in a corner (when the turned front wheels are traveling on a larger circle) or when a wheel spins, but in a straight line, it will be very slow to react. In short, without any shaft speed differential between front and rear, the car will remain 50/50 torque split until a wheel starts to spin.
For the WRX, there is an "STI Group A" VCU upgrade (originally for the older Japan only WRX), that has a higher torque capacity than the stock one, but apparently the heaviest version is so stiff at rest that it causes turning problems in tight turns similar to a spool/welded differential. Stock WRX coupling will transfer 10 kg-m or about 72 ft-lbs when tested at 100 RPM, the upgrades available are 12 kg-m (87 ft-lb) and 20 kg-m (145 ft-lb)
The mitsubishi vcu supposedly runs around 8-10 kg-m. As far as I can tell, no such upgrade replacement was made for the VR-4 or early Evos, as Mitsubishi elected to move directly to the ACD instead, which is claimed to handle "3 times the torque" of the VCU, and even higher in the Evo IX.
Keep in mind that the torque numbers are at the center diff, and so the engine torque applied after gearing and final drive is multiplied by somewhere between .68 to 3 depending on what gear you are in (final drive doesn't apply until the front or rear diff). In second gear for example (around 2:1), that puts the stock engine at about 400 ft-lbs applied to the center diff, which would give a torque bias ratio of about 1.45:1 with the center diff spinning at 100 RPM (essentially this would be a ~350 RPM difference in wheel speed - which is about 25mph for the car - serious wheelspin) net difference. Keep in mind the VCU does not have a static maximum torque bias because it reacts to speed differential, not torque. Also, the effective maximum torque bias drops with additional engine torque, since the torque transfer is fixed at a given RPM.
So yeah, our cars are pretty 50/50 because of the center diff, but there's a little bit of torque biasing (as much as 40/60 or 60/40) under very severe wheelspin. It's probably closer to 45/55 to 55/45 (~1.2:1 torque bias) in general usage. (Note: SWAG)
The important thing to remember with differentials is that weight distribution (60:40) does not matter, and it's usually where people pull erroneous "constant" 60/40 or 40/60 numbers from. Also, almost every aftermarket diff is default 50/50 with a torque bias capability. The only diff that is not is the open Cusco planetary "tarmac gear" which is 35/65. Only planetary open differentials or planetary LSD's (Torsen T-3) have an uneven torque split.
Understeering like a pig has more to do with the way the car's suspension is set up than just the AWD.
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GVR-4
Well-known member
^^ Thanks for that. Good info.
BTW, I had to Google this: SWAG => Scientific Wild Ass Guess
/ubbthreads/images/graemlins/rofl.gif
BTW, I had to Google this: SWAG => Scientific Wild Ass Guess
/ubbthreads/images/graemlins/rofl.gif
turbowop
Well-known member
I can't believe how many people in this thread think the our cars are something other than 50/50 and said so as if it were fact. /ubbthreads/images/graemlins/uhh.gif
