Can't put power down in corners.

[Rickybobby]

I race W2W in NASA Super Touring 4 and I am having trouble making my car competitive with the top tier in that class. After extensive testing we have found that my biggest problems is that I can’t put power down out corners (In some instances spinning the inside wheel out of corners) & Axle tramp when braking.

Current Mods include
Front: Custom MCS (1) Way Shock 750# Springs Ford Performance Bar BMR Tubular Arms w/ Poly Bushings Roll Center Ball Joint Bump Steer Toe Link 5.5° Deg Caster -3.7° Front Camber 14 3/8” Ride Height (Center Cap to Fender) 275/40-18 R7’s Ford Performance Race Spec Brembo Brakes

Rear: Custom MCS (1) Way Shock 250# Springs Steeda Race Upper Control Arm/Third Link 1° Pinion Ford Performance Aluminum Drive Shaft BMR Trailing Arms w/ Poly Bushings Steeda Lower Control Arm Relocation Brackets Ford Performance T2 Torsion Differential Ford Performance Bump Stop UMI Adjustable Pandhard w/ Poly Bushings 15 1/8” Ride Height (Center Cap to Fender) 275/40-18 R7’s GT500 Rear rotor w/ OEM Caliper

Other Notes Stock ABS Stock Crossmembers No Strut Baces Full Roll Cage 3,500 Comp Weight

 

[Duane Black]

Is it a T2, or a T2R? The T2 doesn't have the preload bearing and its torque multiplier orwhatever is lower, so if one tire is getting "light" in corners, you might essentially have an open differential.

 

[2012-Boss]

What are you using for your rear sway bar? The difference between your front and rear spring rates is wider than usual, so I am assuming you are running a fairly large / stiff rear sway bar to balance the vehicle front and rear grip.

What hole are you using on the Steeda rear UCA mount? What length did you adjust the Steeda UCA to?

 

[Rickybobby]

Is it a T2, or a T2R? The T2 doesn't have the preload bearing and its torque multiplier orwhatever is lower, so if one tire is getting "light" in corners, you might essentially have an open differential.

I believe it’s the T2. Is there a large difference in the T2 vs the T2R?
Thanks!

 

[Ewheels]

"In some instances spinning the inside wheel out of corners"
....this instantly tells me open diff. A good locking differential will allow you to power out of corners.

 

[Mad Hatter]

I gather you are already running with out a rear bar right?? Sounds like something is off with the Torsen, Looks like its worth opening up and taking a look.
About the braking issue, what angle do you have your rear control arms at? Can you change the angle in your class?

With out running a splitter up front, or any extra downforce, do you need such a hard front spring?? And with only 250# in the rear what are your rear shock settings?

 

[Rickybobby]

Thanks guys! Keep the questions coming some of which are over my head others I simply don’t know. I’m going to be talking to my race mechanic and hopefully get the answers.

 

[Rickybobby]

We are running a Ford Performance rear bar.

 

[2012-Boss]

I think Mad Hatter and I are thinking similar things. Your front spring rate is crazy, especially with only a 275 R7. I would seriously consider something more like 450 - 500 In the front and try keeping the 250s in the rear with no rear bar.

I doubt there is anything wrong with your Torsten - its a worm drive type configuration. If it breaks it basically destroys itself.

You probably have a number of things going on. Too much rear sway bar with too little rear spring rate. The soft rear spring will allow the car to roll but the bar will counter act this - but in doing so it unloads the inside rear tire.

You also need to look at the setup on your rear UCA and mount, where you have you lower control arms mounted in the relocation brackets, and consider ditching the poly bushings (bind). For the axle side UCA, I probably wouldn’t run Poly or a spherical with your tire size. I would use an OEM rubber bushing.

 

[Mad Hatter]

Totally agree about the torsen being indestructible. I guess I was being too polite and should have its worth making sure that there is a torsen is acutally installed!! You will probably find that most of the fast mustangs have a small 18mm rear bar or run without one. 500#/300# Springs are the usual setup.

But, if you take off the rear bar, with those very firm front springs, you have you will have some serious understeer.

 

[blacksheep-1]

try a stock GT500 center link in the rear, and 18mm or no sway bar and go light on the rear shocks.throw away the rear relocation brackets, the rear springs seem about right to me, what hot tire pressures are you running?

 

[Rickybobby]

try a stock GT500 center link in the rear, and 18mm or no sway bar and go light on the rear shocks.throw away the rear relocation brackets, the rear springs seem about right to me, what hot tire pressures are you running?

30-32 R7s

 

[SMGDHG]

As others have stated, try no rear bar, or a very small rear bar (stock GT rear bar or less).

A normal T2 diff has a bias ratio of around 2.5:1, as in, (oversimplified explanation) if the outside tire has 2.5x as much weight on it, the diff will be able to lock. Anything more than that, it will (in theory) behave like an open diff.

The big dog T2R has a bias ratio of 4:1.

Essentially, the more grip your car makes, the more bias ratio you need, because the more force you are putting on that outside wheel (more G's in corners). You MAY be overwhelming your T2 diff on those 275 hoosiers.

T2R Link




In regards to "not being able to put power down": By this do you mean you one wheel peel, or the car oversteers immediately upon throttle application?

Axle tramp is usually related to the % of anti squat you are running in the rear of the car. The higher your anti squat percentage, the more likely you are to get axle tramp under braking. If your rear lower control arm relocation brackets have multiple holes, I would try running them one hole higher and see if the axle tramp under braking improves.

 

[Rickybobby]

As others have stated, try no rear bar, or a very small rear bar (stock GT rear bar or less).

A normal T2 diff has a bias ratio of around 2.5:1, as in, (oversimplified explanation) if the outside tire has 2.5x as much weight on it, the diff will be able to lock. Anything more than that, it will (in theory) behave like an open diff.

The big dog T2R has a bias ratio of 4:1.

Essentially, the more grip your car makes, the more bias ratio you need, because the more force you are putting on that outside wheel (more G's in corners). You MAY be overwhelming your T2 diff on those 275 hoosiers.

T2R Link

View attachment 81950


In regards to "not being able to put power down": By this do you mean you one wheel peel, or the car oversteers immediately upon throttle application?

Axle tramp is usually related to the % of anti squat you are running in the rear of the car. The higher your anti squat percentage, the more likely you are to get axle tramp under braking. If your rear lower control arm relocation brackets have multiple holes, I would try running them one hole higher and see if the axle tramp under braking improves.

Wheel spin, although it will oversteer if provoked with the throttle.

 

[2012-Boss]

try a stock GT500 center link in the rear

Axle tramp is usually related to the % of anti squat you are running in the rear of the car. The higher your anti squat percentage, the more likely you are to get axle tramp under braking. If your rear lower control arm relocation brackets have multiple holes, I would try running them one hole higher and see if the axle tramp under braking improves.

The axle tramp is why I was asking about your rear UCA setup and where you have your lower control arms set in the relocation brackets. It is likely you have too much anti-squat leading to the axle tramp under braking. Your Steeda arm is adjustable in length and the mount has two different holes. I suggest downloading the Steeda instructions, setting the arm to the longer length (approx. 9.5" center to center of the mouthing holes) and use the forward most hole to the passenger compartment / furthest away from the axle on the mount.

 

[Dave_W]

Good ideas from everyone so far. What lube are you using in the diff? A very "slippery" gear oil can lower the Torque Bias Ratio of the Torsen diff. So you could try changing to a basic non-synthetic oil in the same weight. It's probably not going to make a large change, but if you're trying to optimize everything it's worth a try.

 

[RodS197]

Being that you are running ST4, I would think you are running a semi stock 3V? What gearing are you running in the rear? With my old 3V I could only dream of power oversteer... with my Coyote now its the nightmare! 100 more lb/ft works wonders!

Does the car behave the same in right and left corners, slow vs fast corners? My car was loose (oversteer) in right handers and tight (understeer) in left. Turned out to be the thrust angle of the rear axle was off (not straight in the car). That helped to balance it out left to right.

What are your damping settings percentage wise? I would think you want to soften (speed up) the rear damping and go to a smaller sway bar as some have suggested (a V6 sway bar might do the trick). I personally don't like the feel of a no sway bar rear axle on my car, so I run the Watson 1/2" bar. You are somewhat limited with the single adjustable, but with a quality unit like the MCS you should be able to get it in the ball park for sure.

Softening up the rear will likely get you into oversteer territory, so you might consider balancing out the rear with some more mechanical grip up front, maybe a 650/600 lb spring, then stiffer damping in the front to control the weight transfer. Front bar on full stiff.

 

[blacksheep-1]

Once he sticks the back half of the car, we can work on the front.

 

[Rickybobby]

Being that you are running ST4, I would think you are running a semi stock 3V? What gearing are you running in the rear? With my old 3V I could only dream of power oversteer... with my Coyote now its the nightmare! 100 more lb/ft works wonders!

Does the car behave the same in right and left corners, slow vs fast corners? My car was loose (oversteer) in right handers and tight (understeer) in left. Turned out to be the thrust angle of the rear axle was off (not straight in the car). That helped to balance it out left to right.

What are your damping settings percentage wise? I would think you want to soften (speed up) the rear damping and go to a smaller sway bar as some have suggested (a V6 sway bar might do the trick). I personally don't like the feel of a no sway bar rear axle on my car, so I run the Watson 1/2" bar. You are somewhat limited with the single adjustable, but with a quality unit like the MCS you should be able to get it in the ball park for sure.

Softening up the rear will likely get you into oversteer territory, so you might consider balancing out the rear with some more mechanical grip up front, maybe a 650/600 lb spring, then stiffer damping in the front to control the weight transfer. Front bar on full stiff.

The engine has a few mods with a peak 311 RWHP. (305 average)

The car is better in slower corners but it’s both when I turn left and right.