Rear Diff Options - Power Oversteer Found Here
I am coming to the end of my first year of tracking my Evo. I went to my first NASA event last weekend at CMP. I plan on working through the DE ranks of NASA and trying some TT action in a year or two.
One constant theme from the first track day I ever attended (March of this year) to this past weekend has been understeer. I started to find it at that first track event. After that, I was down for 3 months (tcase death whine) before I went to another event. As my driving has progressed, I have begun to bang my head against the wall on understeer. Nothing seems to bring out the understeer in my car more than low-medium speed sweepers. This past weekend at CMP it was the carousel and the turn 12-13 combo.
I've got one more event this coming weekend at RA. After that the car is done for the winter and the rear diff is coming out.
I am running the Bilstien/Spec R with AP RSB combo, 2deg camber front 1.5 rear, 0 toe all around. All this slightly helped the understeer, but has been far from any major improvement on the issue.
Here I am at CMP following a friend in a Silver WRX. I have an HP and Braking advantage, but watch him walk me in the carousel and 12-13. Hard to hear on the camera, but the outside front is squealing and chirping as I have to mamby-pamby the throttle or the thing just plows.
http://vimeo.com/16681942
One constant theme from the first track day I ever attended (March of this year) to this past weekend has been understeer. I started to find it at that first track event. After that, I was down for 3 months (tcase death whine) before I went to another event. As my driving has progressed, I have begun to bang my head against the wall on understeer. Nothing seems to bring out the understeer in my car more than low-medium speed sweepers. This past weekend at CMP it was the carousel and the turn 12-13 combo.
I've got one more event this coming weekend at RA. After that the car is done for the winter and the rear diff is coming out.
I am running the Bilstien/Spec R with AP RSB combo, 2deg camber front 1.5 rear, 0 toe all around. All this slightly helped the understeer, but has been far from any major improvement on the issue.
Here I am at CMP following a friend in a Silver WRX. I have an HP and Braking advantage, but watch him walk me in the carousel and 12-13. Hard to hear on the camera, but the outside front is squealing and chirping as I have to mamby-pamby the throttle or the thing just plows.
http://vimeo.com/16681942
hi Jim,
don't know if your car will survive it, but letting off and then getting into the throttle might get you out of those corners a bit better.
otherwise it sounded like you were saving gas between a few of those corner complexes.
make your brakes work harder and use them to close that gap to nothing.
don't know if your car will survive it, but letting off and then getting into the throttle might get you out of those corners a bit better.
otherwise it sounded like you were saving gas between a few of those corner complexes.
make your brakes work harder and use them to close that gap to nothing.
yes
Lift to rotate? Probably something I need to work on (lot of driving things I need to work on). I guess part of my problem is, I am a good deal older than most people on here, grew up driving American Iron (RWD) and adding throttle in that world usually brings the rear end around.
The usual behaviour I find now is I hit apex and start trying to feed in throttle to accelerate as I track out, but the front just starts plowing. I can lift and let it re-hook then ease back into it. I presume this is the same understeer issue most of you are talking about?
Also a few places in that vid I did not push braking beacuse I saw a traffic jam forming up and new I was going to just have to wait for the next passing area.
hi Jim,
don't know if your car will survive it, but letting off and then getting into the throttle might get you out of those corners a bit better.
otherwise it sounded like you were saving gas between a few of those corner complexes.
make your brakes work harder and use them to close that gap to nothing.
don't know if your car will survive it, but letting off and then getting into the throttle might get you out of those corners a bit better.
otherwise it sounded like you were saving gas between a few of those corner complexes.
make your brakes work harder and use them to close that gap to nothing.
The usual behaviour I find now is I hit apex and start trying to feed in throttle to accelerate as I track out, but the front just starts plowing. I can lift and let it re-hook then ease back into it. I presume this is the same understeer issue most of you are talking about?
Also a few places in that vid I did not push braking beacuse I saw a traffic jam forming up and new I was going to just have to wait for the next passing area.
Personally... I think the car demands a bigger spread on the front and rear camber than you mentioned Jim.. Even if you are running FPS, you can still toss on camber plates to the front, possibly get -3 if you are going to stay with -1.5 in the rear, other option is to go -1.0 in the rear, to promote oversteer. Yes I know the whole arguement about removing grip... but that would allow for earlier throttle application for our powerful turbo cars.
The rear 1.5 way LSD also allows earlier throttle application, and I have noticed an incredible change in when the car is at apex (now on throttle) and it tracks out without the front washing out/pushing as it did before the LSD. Just something else to consider.
The rear 1.5 way LSD also allows earlier throttle application, and I have noticed an incredible change in when the car is at apex (now on throttle) and it tracks out without the front washing out/pushing as it did before the LSD. Just something else to consider.
Personally... I think the car demands a bigger spread on the front and rear camber than you mentioned Jim.. Even if you are running FPS, you can still toss on camber plates to the front, possibly get -3 if you are going to stay with -1.5 in the rear, other option is to go -1.0 in the rear, to promote oversteer. Yes I know the whole arguement about removing grip... but that would allow for earlier throttle application for our powerful turbo cars.
The rear 1.5 way LSD also allows earlier throttle application, and I have noticed an incredible change in when the car is at apex (now on throttle) and it tracks out without the front washing out/pushing as it did before the LSD. Just something else to consider.
The rear 1.5 way LSD also allows earlier throttle application, and I have noticed an incredible change in when the car is at apex (now on throttle) and it tracks out without the front washing out/pushing as it did before the LSD. Just something else to consider.
I started tracking with bone stock suspension, as many suggest. Then after a few events opted for the 'mild' upgrade with the Bilsteins/SpecR's and RSB.
However, I am ready to move a little further along and knock down some of the understeer.
If you can only tolerat 1.5-2* camber in front then balancing the rear at ~.75-1* is the best way to go IMO.
Dallas - I was definitely not arguing to increase rear grip, just to be clear. 
Jim- it sounds like camber plates in the front may be a great start. I would suggest for nothing more than as a starting point, to keep your rear camber roughly half of your front camber. i.e. -3/-1.5, -2/-1, etc. Personally I would start out even less than half on the rear camber without the Shep/TRE worked rear diff.
Simply my opinion, but I feel the car drives like a FWD car (I mean when pushed and at speed), unless the rear diff is working WELL, in which case it becomes more neutral to RWD biased.
Jim- it sounds like camber plates in the front may be a great start. I would suggest for nothing more than as a starting point, to keep your rear camber roughly half of your front camber. i.e. -3/-1.5, -2/-1, etc. Personally I would start out even less than half on the rear camber without the Shep/TRE worked rear diff.
Simply my opinion, but I feel the car drives like a FWD car (I mean when pushed and at speed), unless the rear diff is working WELL, in which case it becomes more neutral to RWD biased.
Last edited by Bassicfun; Nov 15, 2010 at 12:51 PM.
I am coming to the end of my first year of tracking my Evo. I went to my first NASA event last weekend at CMP. I plan on working through the DE ranks of NASA and trying some TT action in a year or two.
One constant theme from the first track day I ever attended (March of this year) to this past weekend has been understeer. I started to find it at that first track event. After that, I was down for 3 months (tcase death whine) before I went to another event. As my driving has progressed, I have begun to bang my head against the wall on understeer. Nothing seems to bring out the understeer in my car more than low-medium speed sweepers. This past weekend at CMP it was the carousel and the turn 12-13 combo.
I've got one more event this coming weekend at RA. After that the car is done for the winter and the rear diff is coming out.
I am running the Bilstien/Spec R with AP RSB combo, 2deg camber front 1.5 rear, 0 toe all around. All this slightly helped the understeer, but has been far from any major improvement on the issue.
Here I am at CMP following a friend in a Silver WRX. I have an HP and Braking advantage, but watch him walk me in the carousel and 12-13. Hard to hear on the camera, but the outside front is squealing and chirping as I have to mamby-pamby the throttle or the thing just plows.
http://vimeo.com/16681942
One constant theme from the first track day I ever attended (March of this year) to this past weekend has been understeer. I started to find it at that first track event. After that, I was down for 3 months (tcase death whine) before I went to another event. As my driving has progressed, I have begun to bang my head against the wall on understeer. Nothing seems to bring out the understeer in my car more than low-medium speed sweepers. This past weekend at CMP it was the carousel and the turn 12-13 combo.
I've got one more event this coming weekend at RA. After that the car is done for the winter and the rear diff is coming out.
I am running the Bilstien/Spec R with AP RSB combo, 2deg camber front 1.5 rear, 0 toe all around. All this slightly helped the understeer, but has been far from any major improvement on the issue.
Here I am at CMP following a friend in a Silver WRX. I have an HP and Braking advantage, but watch him walk me in the carousel and 12-13. Hard to hear on the camera, but the outside front is squealing and chirping as I have to mamby-pamby the throttle or the thing just plows.
http://vimeo.com/16681942
yes, bone stock rear diff at the moment.
This was my first season running an Evo. When I bought the car it had a TRE 1 way upgrade already done to it.
The diff definately works (I can hear it working), but I still fought slight understeer all season long from turn in to mid corner when getting back into the gas.
It seems that most people are running the 1.5 way for road coarse applications.
Has anyone ran both a 1 way and a 1.5 way to give some feedback on how the difference between the two impacts the handling of the car?
The diff definately works (I can hear it working), but I still fought slight understeer all season long from turn in to mid corner when getting back into the gas.
It seems that most people are running the 1.5 way for road coarse applications.
Has anyone ran both a 1 way and a 1.5 way to give some feedback on how the difference between the two impacts the handling of the car?
J,
An easy way to make your stock diff perform is to use the Redline 75/140 NS (non slip) Fluid. NO ADDITIVES. Try that out first.
I also second... the most amount of negative camber in the front as possible and between -1 and -1.5 degrees of camber in the rear.
Finding what rear camber works best will be a result of how much front grip you can generate.
An easy way to make your stock diff perform is to use the Redline 75/140 NS (non slip) Fluid. NO ADDITIVES. Try that out first.
I also second... the most amount of negative camber in the front as possible and between -1 and -1.5 degrees of camber in the rear.
Finding what rear camber works best will be a result of how much front grip you can generate.
If you still have ABS then I think a 1 way rear diff should be fine. The ABS/EBD will keep the inside rear tire from locking up if you are braking and turning at the same time (as in trail braking). If you did NOT have ABS then I would think that you would want a 1.5 way rear diff so that you have some amount of biasing under decel to help keep the inside rear from locking up. . .
From my understanding, a 1-way should allow you to initiate the turn easier while a 2-way will resist turning until you slip the tires (a la drift cars). 1.5 way falls in between. . .
From my understanding, a 1-way should allow you to initiate the turn easier while a 2-way will resist turning until you slip the tires (a la drift cars). 1.5 way falls in between. . .
Last edited by EVOlutionary; Nov 16, 2010 at 07:13 PM.
The alignment setup and hardware is pretty much the 'Smikeevo' setup including the cambers.
I started tracking with bone stock suspension, as many suggest. Then after a few events opted for the 'mild' upgrade with the Bilsteins/SpecR's and RSB.
However, I am ready to move a little further along and knock down some of the understeer.
I started tracking with bone stock suspension, as many suggest. Then after a few events opted for the 'mild' upgrade with the Bilsteins/SpecR's and RSB.
However, I am ready to move a little further along and knock down some of the understeer.
Have you also tried installing Whiteline's Roll Center Adjust Kit especially since you lowered your front end by 1.4"?
Key Feature and Benefit:
"KCA395 is designed to raise the front roll-centre geometry by using specially engineered ball-joints & tie rod ends while still maintaining original steering geometry. Front roll geometry actually encourages roll the lower you go. Testing proves that raising the front roll-centre resulted in a substantial increase to front roll resistance & a significant reduction in suspension compression of the outside front wheel during cornering (less roll). This improves weight distribution & maintains a better camber angle which ultimately improves front grip. The overall outcome is significantly reduced understeer through reduced front wheel compression as well as improved steering precision & vehicle stability."