Yes I understand - just like on a launch, blow the tires away and your time will not be too good. About 10 - 15% wheel spin usually results in better time.
I said under certain conditions it is possible to stop better. Of course if you setup the test to creat funny traction conditions the ABS will do better - I think I sort of agreed that was the case already.
It is easy to feel the stress in the car in the car/tires UNDER CERTAIN CONDITIONS and when you are ready for it.
Oh brother, Rick I just read more of your rant and saw the part about under accident conditions - I SAID THAT!
What type of scan tool are you using, for what and why? just curious.
It is the one supplied by my company (not a generic) I think it is made by autodiagnois.(sp?) On some model year cars I have access to data stream from ABS. however when accessing the data stream, the ABS goes into standby so while I can observe both individual wheel G loads + - , individual wheel speeds, as well as over all g force and speed all without ABS operating. Gives you an idea of what ABS is looking at.
I didn’t mean to sound like I was ranting. I just went back and reread what you posted, and we agree more than I first thought. It’s been a bad day and if I came across too strong I am truely sorry.
Cool Man. It sounds like there is a lot more to ABS than I thought. It seems like the pumping starts fron the master cylinder and the pressure is distributed through the lines via the pre set proportioning valve and on to the brakes. I know each wheel has a sensor but individual pressure control to each wheel - wow! I have not been keeping up much with the new cars for a few years - saving for a house.
Sounds like your scan tool is far more sophisticated than the one my friends and I use for test and tuning. Of course 85% of the time it is used to test 0 to 60 foot times and about 70 to 120 MPH top gear (well trans in 1:1 anyway) blasts.
Hope you are having a great day! This is not the time of year for bad days. Now go for a blast on the track - it will make you forget the bad day things.
As mentioned, the purpose of ABS is to prevent skidding and allow steering control when braking, particularly with hard braking and/or low-traction conditions. ABS is short for Anti Blockier System, which is German for “anti skid system.” (Not wishing to explain this to the average American driver, auto manufacturers came up with the phrase “Anti-lock Braking System,” which reasonably well describes what it does–but rest assured it’s a back-formation.) The whole point of it is to maintain control. If it results in a shorter stopping distance, that’s a nice plus, but it’s not the main goal.
A particularly skilled driver can usually achieve a shorter stop without ABS. The other 99.99% percent of drivers cannot, other than in some snow or gravel conditions previously noted. The overwhelming majority of us will benefit from using the ABS.
If you’re going to rely on ABS to help, don’t try to out-think or short-circuit the system. Stomp on the brake and stay stomped. Playing with it will only hinder its effectiveness. Let it do its job.
B&I,
I’ll try to describe the hydrulic circuit on the cars I teach on. Other cars may be plumbed diffenently. YMMV. Picture a normal dual master cylinder, and 4 wheel disc brakes. In the line from the master cylinder to the wheels is the ABS hydraulic unit. When ABS is not being used, the hydraulic unit acts like a very large junction block. In other words it doesn’t do anything. Inside the unit are two valves for each circuit for a total of 8. For each wheel, one valve is normally open, and one is normally closed. The normally open valve is between the master and the caliper. The other is between the open valve and the pump.
The ABS control module is constantly reading the speed, acceleration and decelleration of each wheel. As long as all four are near equal, and within the programed limits ABS is just watching and waiting. If one or more wheels start to slow abnormally, this indicates that it is starting to lock. ABS will first close the normally open valve to prevent any further pressure increase at the wheel. (a pressure increase from the driver pressing the brake harder, would make the wheel want to lock more, this being a bad thing.) This phase is called hold. If this action is enough to keep the wheel from locking then this is all the system will do. This action is not detectable by the driver. If however the wheel continues to lock, the the normally open valve stays closed and the normally closed valve opens which will allow some fluid to flow out of the caliper and the pump will then start to push fluid back against the pressure side of the master cylinder. This pahse is called return. This causes the brake pedal to vibrate or pulse. This pulsation acts as a warning to the driver that they are using ABS. This action of open (normal braking), hold, return continues until either the brakes are released, the risk of skidding is gone (driver hit a patch of sand, and is now back on clean pavement) or the car gets below about 3 MPH when the system disconnects. Each of these valves can cycle up to about 15 times per second, and each wheel is controlled individually.
Oh and Gary, I had a service manager back in '88 who insisted on calling ABS the automatic braking system. Drove me nuts.