Power spilt modification...

BAC5.2 · Post by **BAC5.2** » Wed Jul 07, 2004 11:57 pm

As I understand it, we've got a 50/50 even split in the 5MT Legacy Turbo's.

How would I go about getting a 40/60 (front/rear respectively) distribution?

WRX 1.1:1 center diff and rear end?

And does anyone know the center diff ratio of the new FXT? Is it a 1:1 or 1.1:1? I wouldn't mind a bit more neutral handling as opposed to slight under-steer around fast corners.

Plus the 40/60 would be hella fun in the rain

THAWA · Post by **THAWA** » Wed Jul 07, 2004 11:59 pm

I dont thnk te 1.1:1 does anything but modify the gear ratio.

vrg3 · Post by **vrg3** » Thu Jul 08, 2004 12:05 am

I don't see why switching to a WRX center and rear diff wouldn't work... you might have to switch in other parts of the WRX transmission in though, depending on where the 1.1:1 thing happens.

I don't understand how having the 1.1:1 center diff, the 3.900 front diff, and the 3.545 rear diff results in a torque split different from ours though... The gearing cancels itself out to keep the speed right, right?

evolutionmovement · Post by **evolutionmovement** » Thu Jul 08, 2004 12:22 am

I've wondered the same question, but the only thing I can think of without redesigning the center diff is to get a 6MT with DCCD.

I don't know how the WRX diff is supposed to split the torque differently, but from what I've heard it makes the car more front biased than rear.

I tend to wonder if it wasn't somehow cheaper to make a 3.545 rear instead of a 3.900 and that's the reason for the center diff ratio change.

Steve

THAWA · Post by **THAWA** » Thu Jul 08, 2004 12:24 am

but do you think the price difference in making a 3.545 vs 3.900 would offset making a 1.1:1 vs a 1:1?

vrg3 · Post by **vrg3** » Thu Jul 08, 2004 1:36 am

Yeah, I was thinking about that too...

I just found something else. I just fired up my TI-85, and it tells me that 1.1 times 3.545 is 3.8995.

Huh.

I wonder if the WRX setup makes the rear axle turn slightly faster than the front.

I wonder if that results in some interesting "preload" kind of effects in the viscous limited slip center differential.

Brat4by4 · Post by **Brat4by4** » Thu Jul 08, 2004 2:09 am

The WRX "stepped" setup makes it behave more FWD than RWD, the fronts turn slightly faster.

Since when did torque split change how the car HANDLES in a turn, Phil

. The answer you are looking for lies in your camber and toe settings. You could also mess with the rear sway bar rate, but we all know you are looking for these mystical roll center adjusters (even though the BC/GC chassis has the lowest rear roll center of any EJ equipped chassis) Boy, I'm on a roll tonight.

If you really want your car to oversteer, let off the gas mid corner... that'll do it. Otherwise I would get rear HD endlinks first. Then go ahead and put some rear toe-out in the alignment (and positive camber if you are really brave). My car actually has positive rear camber right now and I will attest to the fact that it will let the back end out around fast corners. Don't worry, I plan on getting the rear eccentric bolts to correct this... eventually.

91l-t · Post by **91l-t** » Thu Jul 08, 2004 2:51 am

you can use a jspec sti 5spd with dccd even without the controler it automaticly runs 35/65 split

rich

THAWA · Post by **THAWA** » Thu Jul 08, 2004 3:25 am

vrg3 wrote:Yeah, I was thinking about that too...

I just found something else. I just fired up my TI-85, and it tells me that 1.1 times 3.545 is 3.8995.

Huh.

I wonder if the WRX setup makes the rear axle turn slightly faster than the front.

I wonder if that results in some interesting "preload" kind of effects in the viscous limited slip center differential.

while it's true that 3.545*1.1=3.8995, that's not how the drivetrain works. Remember the engine powers the transmission, which sends power through the center differential which then does the stepping down, not the rear differential doing any stepping up to the centerdiff then tranny etc. So if you use the equation 3.9/1.1 it will equal 3.545 repeating.

Also by defination the rear axle has to turn slower if it's getting equal power yet has a taller (lower number) gear ratio.

Post by **Legacy777** » Thu Jul 08, 2004 4:07 am

As some have mentioned....the stepper is to make the WRX more FWD like.

The WRX MT has 50/50 split same as all the 5MT subie trannies.

The WRX auto trannies however have 40/60 split due to it being a VTD tranny.

vrg3 · Post by **vrg3** » Thu Jul 08, 2004 4:22 am

Brat4by4 - Wouldn't a 3.8995 ratio mean a higher speed than a 3.9 ratio?

THAWA - I don't follow. There are two gearing ratios that you multiply -- why does it matter where the gears are?

Or are you just saying that 3.8995 is 3.900 if you're only using 4 significant figures? That I'd agree with.

But you guys (Brat4by4 and Josh) are saying that it is indeed a small speed difference that is responsible for the "non 50-50 split?"

91White-T · Post by **91White-T** » Thu Jul 08, 2004 5:34 am

2.5GT 5MTs are rear biased I believe 65/35.

THAWA · Post by **THAWA** » Thu Jul 08, 2004 6:29 am

yeah the sig figs is what i meant. I ws just trying to explain it how I think of it.

BAC5.2 · Post by **BAC5.2** » Thu Jul 08, 2004 9:17 am

William - I just like power-on oversteer in the rain. It's wicked fun, espically now that I'm faster

I didn't know the WRX was a front-biased setup.

Steve - DCCD = the devil. Fun feature, but the JDM NON-DCCD trannies are significantly stronger from everything I have heard.

WRXdan · Post by **WRXdan** » Thu Jul 08, 2004 3:45 pm

Can someone explain how less than 50% goes to the front. I'm assuming the MT is like the AT dues to not having a true transfer case. In the AT the planetary are directly linked to the front pinion drive. There is no way to disengage the front drive from the trans. Unlike the rears where you have a clutch assembly in the AT. So I don't know how anything less then 50/50 can be achieved to the front? I guess I don't understand it. That's why the WRX is geared 1/1:11 or whatever it is, right?. I would still rather have the same gearing but more power going to the rear. Kinda like having the transfer clutch connected to the front drive and solid to the rear.

In the rain the WRX does feel like FWD. I always spin the front right tire. I'm sure the back tires are pushing, but it have more power going to the front tires.

THAWA · Post by **THAWA** » Thu Jul 08, 2004 4:07 pm

I was under the imporession that the 5mt's used a differential in the center. That is considered the transfer case.

WRXdan · Post by **WRXdan** » Thu Jul 08, 2004 4:09 pm

THAWA wrote:I was under the imporession that the 5mt's used a differential in the center. That is considered the transfer case.

Oh...I thought it was in the tail section like the AT but not a clutch type like the AT

THAWA · Post by **THAWA** » Thu Jul 08, 2004 4:11 pm

right it's still in the tail section of the transmission, but it's a gear diffferential, instead of a clutch type like you were saying.

WRXdan · Post by **WRXdan** » Thu Jul 08, 2004 4:27 pm

One of my pet projects is to convert an 4EAT to RWD. Just for fun. It's really not that hard to do. Some plugs, a little welding. Not sure how to mount up the front brakes...maybe a cut half shaft. I think the VB may not like the RWD convertion.

THAWA · Post by **THAWA** » Thu Jul 08, 2004 4:51 pm

there shouldn't be any welding at all. just disconnect duty solenoid C and you shouldn't be getting any power to the front. Personally I'd just leave the front halfshafts, it shouldn't hurt anything with them there, and I doubt it'll cause that much extra power loss having to spin them. What is VB?

mTk · Post by **mTk** » Thu Jul 08, 2004 4:56 pm

I would remove the front axles if you are converting to rwd. Vb is valve body.

MK

WRXdan · Post by **WRXdan** » Thu Jul 08, 2004 4:57 pm

THAWA wrote:there shouldn't be any welding at all. just disconnect duty solenoid C and you shouldn't be getting any power to the front. Personally I'd just leave the front halfshafts, it shouldn't hurt anything with them there, and I doubt it'll cause that much extra power loss having to spin them. What is VB?

I don't think that would work because the it's a direct link to the front pinion in the AT. You have the drive gear (connected to the trans) and driven gear ( which is connect to the pinion). The easiest way would be to remove the front ring gear and leave the front diff in. The speedo is driven by the front diff so you need that in there. I would weld up the transfer unit, but leave the clutchs alone so the TCU thinks is activating the transfer clutches.

VB = valve body

WRXdan · Post by **WRXdan** » Thu Jul 08, 2004 5:11 pm

Okay I'm done thread jacking.....last comment. My ring gear removal would also delete the trans brake in park. I don't like that idea very much. This is why I'm searching for JATCO RWD trans for one that will work with the suby bell. No luck so far.

Edit: nevermind..the brake will still work.

THAWA · Post by **THAWA** » Thu Jul 08, 2004 5:16 pm

Oh yeah, forgot about the diff

Also I thought the MPT clutch system did all the power transfering?

vrg3 · Post by **vrg3** » Thu Jul 08, 2004 6:08 pm

THAWA - The MPT clutch doesn't transfer power from the front to the rear, exactly... Power's always going to the front; the MPT clutch just allows power to also go to the rear. With Duty Solenoid C disconnected, both front and rear axles spin together, driven by the output shaft of the transmission.

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Power spilt modification...

Power spilt modification...