Why can't the Evolution be rear wheel bias?
 

I remember reading somewhere that the Evolution can't be rear wheel biased in terms of power distribution due to the drivetrain layout. So I heard the Evolution can be 100/0 to 50/50, but nothing like 0/100. Can someone explain why?

Because of the way the engine is mounted, it makes it impossible to put more power to the rear wheels. I can't explain it very well, but it's something along those lines. Hopefully someone else will help me out.

biased in terms of power distribution due to the drivetrain layout>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>you said it!
turn the engine around!
beef up the shaft!
or beef up the transfer case and remove the fwd power supply!
it can work but not for too long!
i remember reading a sportcompact or modified mag where a, white wrx, guy tried the 0/100it but was braking sh!t let right and center so he put it back to awd!

because it's front engine based.

if you want rear engine biased, get an sti or Skyline. Those are the closest thing to EVolution that I know of.

That or Audi S4, pre v8 engine.

You know, I actually would like the rear drive based awd better than fwd like us.

the only advantage is that we get the cab forwarded interior layout and usually the front wheel based awd setup is a lot more stable at high speed than the rwd based awd setup.

It's easier to drive an evo than sti.

I thought our tq split was a constant 50/50?

It is but more weight is on the from resulting in Front Wheel Bias.

I was specifically looking for the answer dealing with the transfer case, gearbox, front axles and center diff position. I recalled someone had a great technical answer (I'm an engineer so I have a liking for mechanics) and would just like to remember it.

exactimundo

um... all the cars you mentioned are front engine based... that has nothing to do with it. As for cab forward layout or the engine/trans layout, that has nothing to do with it either.

The mechanical reason is because the rear output of the center diff has the adjustable clutch (acd) while the front output does not. So normal driving the acd is 100% open and all the torque is sent to the front wheels. As the acd starts to lock, torque starts to be transferred to the rear. So when the acd is 100% locked ,the torque split is even 50/50. There is no way for the center diff to 'let go' of the front wheels.

As for why mitsu used a system like this, I suspect that it was a combination of easier and safer to drive at the limit and faster corner exit speeds.

the Sti has a boxer engine that is horizontally opposed....the Skyline motor has a straight inline six that faces the fenders...its the the engine and tranny layout that makes the difference just like what wave said. My theory of why the evo used the front drive/ awd system is because there is no weight in the back, the car would break loose constantly until the awd kicked in....front drive has more traction because of the weight distribution and will be helped when the car understeers through a corner. It also helps exiting corners. I wish evos in the states had an option of AYC...something Acura Calls SH-AWD...Mitsu came out with it first :beer:

That's what I read as well. Mitsu did the non-rear bias on purpose. They could have set up the ACD any way they wanted to. By keeping the front bias layout, they gain cornering speed and stability, but gave up big burnouts and drifting (which to Mitsu warranty department is a GREAT thing).

PS. If anyone still thinks that the engine layout has anything to do with front/rear bias, look at the 3000GT. It had transversely mounted V6 and a 40/60 rear biased AWD system

3000GT have a 40/60 Rear Bias? Really? I thought they had a 50/50 because of the vicous center diff? I thought you had to have a clutch pack or gear based center diff to get a different bias other than 50/50.

Do you have any facts to prove that it is 40/60? That would be really awesome if it did.

tks

/<

This may not apply to the pre 05 USDM Evos, but here's a graph and a tech paper.

http://evo.open-aerospace.org/pix/AWD.jpg


ACD Paper http://evo.open-aerospace.org/tech/ACD.pdf

Choice quote from the paper:

"If an emphasis on cornering performance is required, the front/rear torque-distribution should be established at about 30:70."

"If an emphasis on traction performance and stability is required, the front/rear torque-distribution should be established at 50:50."

"In light of the factors described above, it was determined that the base front/rear ratio should be 50:50 (optimizes running performance and stability) and that directional response should be maximized by control of the center differential differential-limiting action."

The 50/50 split of the Evo is not a limitation, but a conscious design choice by :mitsu:. It gives you the best possible traction, and the ACD moves the split around that base line to achieve better turning response.

http://www.modernracer.com/history/m...r4history.html
http://www.internetautoguide.com/rev.../3000-gt/1999/


Sorry... 45/55. I knew it was slightly rear bias.

Remember torque split != difference in speed.