If you're talking about autocross situations I've found that a couple simple things can help avoid the problem in a spot it occurs during a run.
One is roll off the gas a split second earlier in case your brake problem is a lack of vacuum in the booster.
Number two is to settle the car by straightening out a little right before you hit the brakes. This means changing your line slightly in that braking zone.
It sucks to have to drive around these problems but if there are no allowances in your class to make a hardware fix then, you have to. Otherwise, it kills your run.
Watch that short video clip. In both 180's I have a straight shot to slow in and I was on the ABS but the car is not making enough stopping power to make any tire noise. I'm pretty sure I can do better myself.
I will pull one rear wheel abs sensor and try it out. Thanks for the tip!!
As for the lack of vacuum in the booster. I asked around about that and everyone I asked said there should be enough vacum for atleast one stop stored in the booster. The first 180 was the first time I touched the brakes in that run and it was not stopping. So I'm thinking I'm fighting with the ABS and brake booster but might aswell try and solve one of them.
nah steve is right .. your check valve in the brake booster is sticking .. you have no vacuum cause you are going from gas to brake quickly and the check valve is not saving you any vacuum. If your ABS light comes on then you can be pretty certain that abs is kicking your ass but ill bet you it isn't. Try a set of rear tension struts ( the improved ones) and a new check valve.
nah steve is right .. your check valve in the brake booster is sticking .. you have no vacuum cause you are going from gas to brake quickly and the check valve is not saving you any vacuum. If your ABS light comes on then you can be pretty certain that abs is kicking your ass but ill bet you it isn't. Try a set of rear tension struts ( the improved ones) and a new check valve.
David
The improved ones? You are talking about the Mopar ones?
Is the pedal going soft or is it getting real hard?
If its soft it may be going into ice mode. You should feel the abs working but the pedal gets soft and the car does not seem to stop very well.
If its hard itmay be loosing vacuum removing any asist to the pedal.
I remember basically the same thing being discussed some time ago in this section but am feeling to lazy to search for it right now.
Im pretty sure it has been discussed in a bunch of forums here =] 'ice mode' is caused by a instantanious substantial difference in wheel speeds. If the ABS cannot correct this with modulation it figures we must be on ice, and starts to attempt to get the wheel speeds to match up. This tends to feel like a loss in braking preasure, pedal going to the floor ABS modulation and slowing at a sub optimal rate. Now the reason why is because if you brake in a turn inside rear lifts, (perhaps only minutely but none the less load has been near zeroed) and if the brakes are applied then the wheel stops. If the wheel stops there is little the car can do to modulate the pressures to the remaining grounded wheels to get wheel speeds to match until contact is restored to the light wheel. Meanwhile the ABS system goes into 'ohsh!t mode' it assumes that the airborne wheel is actually in a skid of some sort and the rest of the car must be on a extremely slippery surface and says to itself we may be on ice, overbraking is bad, so we may be able to save this from a full loss of control/traction/direction by excess modulation of brake pressure (think duty cycle here since the brakes are being modulated). Now this doesnt work well when we are on the conetrack cause there is a lot of time when being on 3 wheels is optimum for traction. SO best thing to do is drive around this issue as steve advises ( since getting a better ABS program is unlikely ) or set the rear of your car a bit softer to keep the wheels more equally loaded on tight trailbraked corners. OR go manual and remove the wheel speed sensor wire. Rear tension struts (yes the mopar ones) help a lot in straight line conditions where the braking areas are bumpy and you are coming in with a lot of speed and may help. I try to make sure I tip out and go to brakes with a slight pause between events (lift.2.3.brakes2.3maintenance.turn.unscrew.tip-in...repeat) you need a moment at high vacuum to replenish the booster. This will likely help.
well I'm going to try a check valve for the brake booster this week. Is there a plug in the ABS harness thats easy to reachat the rear of the car?
If I had to say one way or the other, I'm guessing I'm fighting vacum in the booster because the pedal is rock hard. I find myself pushing as hard as I can with my left foot and the car just will not slow.
The improved ones? You are talking about the Mopar ones?
I had looked at those as a possible upgrade for my car, but I don't believe they would be allowed in SCCA Stock Class - Would they? It's a Mopar direct replacement part, but would probably be considered a "performance part" (?)
I'm sure that disconnecting the ABS sensor would not be allowed in the Stock Class rules.
I haven't had any major problems with the ABS (yet), but am just crious about the legality of this part.
if it could be proven that the new part (mopar performance) superceeds the old one as a factory replacement (later 05s apparently came with them) then you should be able to use them on any year SRT-4.
No, you can't pull a fuse or disconnect a wheel speed sensor in stock class, unfortunately. I have had "ice mode" cost me before, not just cones and time, but money and parts, when I was on stock suspension. With coilovers and stiffer sways it's only happened maybe once, and that was on an oddly banked uphill decreasing radius 180. I would still rather disconnect the sensor and not have abs (but keep EBD) for autocross events, though.
if it could be proven that the new part (mopar performance) superceeds the old one as a factory replacement (later 05s apparently came with them) then you should be able to use them on any year SRT-4.
No, you can't pull a fuse or disconnect a wheel speed sensor in stock class, unfortunately. I have had "ice mode" cost me before, not just cones and time, but money and parts, when I was on stock suspension. With coilovers and stiffer sways it's only happened maybe once, and that was on an oddly banked uphill decreasing radius 180. I would still rather disconnect the sensor and not have abs (but keep EBD) for autocross events, though.
Is it against the rules in stock class to have a blowin fuse?
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ABS is killing me!!!!
Linear Mode
