Midnight F-117A

It's not avail on the LS1 V8 equipped. It's for V6's, the owners manual states "for a softer limited traction surfaces"

Midnight F-117A

The V6 f-bodies does. I do know I saw throttle by wire throttlebody on my uncle's '02 firebird (don't ask me why he's stupid to buy a V6)

JasonWW

iTrader: (2)

I don't pay attention to the firebirds at all, unless it's a formula. So it might be drive by wire. I don't know.

Nova5

when i hammer my LT1's pedal with ASR on it kicks the pedal back at me. the brakes have never activated that i can feel when i do that with ASR on.

TooSlow02

I've been called out. Ka-ching....ka-ching....ka-ching....DRAW!
Just kidding. Anyway, this is going to be kind of long, so if I put anyone to sleep I apologize beforehand. But here goes. Our fine automobiles are equipped with Bosch 5.3 anti-lock control, with traction control as an option (ASR acceleration slip regulation on Chevys, TCS traction control system on Pontiacs). These systems operate by controlling inlet and outlet solenoids for each brake circuit. The inlet solenoids are sprung open/powered closed, while the outlet solenoids are sprung closed/powered open. The EBCM/EBTCM runs the show (electronic brake control module/electronic brake and traction control module). On the driver's side of the engine compartment towards the front of the car is a BPMV brake pressure modulator valveblock. This houses the majority of the ABS and ASR/TCS hardware. It contains the following:

1.) Brake pressure circuit valves (inlet and outlet pairs). On cars without ASR/TCS, there are 3 pairs in a front/rear split, 1 for each front circuit, 1 for the single rear circuit; with ASR/TCS, there are 4 pairs, 1 each up front and 1 each in the rear. This is necessary for select high/select low torque split functions of the ASR/TCS.

2.) The brake fluid pump. On an ETM schematic this will show up as a motor. This pump is responsible for returning fluid that has been released via ABS operation through the outlet solenoids back to the master cylinder via compensation ports. On cars with ASR/TCS, this pump is also responsible for building brake pressure in the BPMV when a traction control event is commanded. This, along with the next items, are what applies the brakes even though your foot is not on the brake pedal.

3.) On ASR/TCS cars only, there are 2 additional solenoids in the BPMV. One is the master cylinder isolation valve, which controls the supply line coming from the master cylinder, and is sprung open/powered closed. It is closed when a traction control event is commanded to allow the return pump to build apply pressure within the BPMV. The other solenoid valve is the ASR/TCS prime valve, which allows fluid to backfeed from the master cylinder resevoir through the compensating ports (which normally allow fluid to return to the resevoir) back to the BPMV to supply the pump with the fluid volume necessary for brake application.

Also, wheels speeds are monitored by sensors. On a non-ASR/TCS car, there are three; one in each front wheel bearing, and one installed in the rear diff housing. On an ASR/TCS car, there's four; the rear diff sensor is deleted, and each rear hub has a speed sensor to monitor the rear wheels separately.
Now, during an ABS event, the EBTCM will detect impending lockup of a wheel or wheels via the wheel speed sensors. When this happens, the EBTCM will go on standby mode and monitor the wheel's deceleration rate as compared to the others. If it detects too sharp of a deceleration, the EBTCM commands the BPMV to go into "pressure hold/isolation" phase. To do this, the inlet solenoid valves of the locking wheels are ELECTRICALLY closed (the valves are not controlled by pressure) to stop you from increasing brake apply pressure by pressing the brake pedal harder. If the wheel locks anyway, the EBTCM will then command the "pressure release/regulation" phase, where the outlet valves are electrically opened to release fluid from the locking wheel circuits and lower the apply pressure of those circuits. When this happens, the fluid motor on the BPMV turns on to return the released fluid back to the master cylinder resevoir via the compensation ports of the master cylinder. If this didn't happen, fluid would "stack up" in the BPMV and the system would stop working. When the EBTCM detects that the locking wheel starts to rotate again, it goes back into "pressure hold/isolation" phase again. If it detects the wheel is turning freely again, it goes back into its normal operating mode. If it is starts to lock again, it will go back to "pressure release/regulation" phase. It continues this cycle until the EBTCM no longer detects any wheelspeed variance. It then goes out of standby and the car goes on its merry way.

Now, in a traction control event, if the EBTCM detects rear wheelspin, it goes into ASR/TCS standby mode, and sends a message to the PCM (powertrain control module) to reduce ignition timing. If the wheels continue to spin, the EBTCM then sends a message to the PCM to reduce throttle. The gas pedal will push back at your foot. If wheelspin is still detected, the EBTCM will command a "pressure build/apply phase", where the motor that the ABS uses to return fluid to the master is activated. At the same time, the front brake circuit inlet valves are closed to keep pressure away from the front calipers and the master cylinder isolation solenoid valve and ASR/TCS prime solenoid valve are both activated to allow the pump to draw fluid back out of the resevoir through the compensation ports and build pressure in the BPMV. Since the rear inlet valves are still open, the brake pressure in the BPMV applies the rear brakes to slow the spinning wheels. If the rear wheels happen to be spinning at different speeds, and require different pressures to control them, the rear inlet valves can used to modulate pressure side to side. Whew. I'm spent. Questions?

TooSlow02

Yes, pulling the ASR/TCS fuse does deactivate the traction control and leave the ABS unaffected. But, if you'll refer back to WhtLT1's post, he mentioned unplugging then unit, not pulling a fuse. However, since GM was smart enough to install a button that turns the system off without having to pull a fuse and without setting system faults, why not use it?

TooSlow02

The motor is part of the BPMV (Brake Pressure Modulator Valvebock) and is not separately serviceable. The whole block has to be replaced. And you did feel the brakes apply.

TooSlow02

Solenoids are by definition a "coil of wire usually in cylindrical form that when carrying a current acts like a magnet so that a movable core is drawn into the coil when a current flows and that is used especially as a switch or control for a mechanical device (as a valve)". They do not respond to pressure. The motor is used as a brake fluid return and to build system pressure (ASR/TCS only). The newer, high end cars are not the only ones that have stability control. Minis have it too. It's also an option on Corvettes. But, before these systems were capable of stability control, they were ABS with traction control, exactly like ours. They just had it a long time ago. By the time GM decided to bless the F-cars with it, the higher end cars already had stability control added to theirs. The only additions were a yaw sensor, a lateral acceleration sensor, a steering angle sensor, and software. The hardware is the same. These systems are all made by Bosch.

TooSlow02

Yeah, BMW, Mercedes, Jaguar and others have this system. It uses a radar sensor in the front to measure distance between you and the car in front of you. It can apply the brakes to decelerate the car up to 3m/s2. After that, it shuts down and makes you brake. Kind of scary. I drove a few cars with this system, and it made me kind of nervous. After a while I shut it off so I could relax.

TooSlow02

Second gear start is a feature of the six-banger cars with automatics. It let you start off in second gear, so you could get some traction in the snow and ice. It was discontinued after GM began to offer ASR/TCS as an option on V6 cars.

TooSlow02

You're right, the Vette's gas pedal does not puch back. The only thing the pedal is connected to is a sensor that is monitored by the throttle body electronics so it knows how much throttle you want.

The torque management feature of the automatic cars is also trickle-down technology from high-end cars. It backs down ignition timing to reduce engine torque just as the transmission shifts. It does this so you don't feel the shift as much, and to reduce wear on the clutches in the trans. It works so well that some manufacturers no longer recommend a transmission fluid change, ever. It doesn't have anything to do with the ASR/TCS system, other than reducing the timing the same way the traction control does.

Midnight F-117A

JasonWW just got
by TooSlow02

TooSlow02

Yeah, it's a poor man's traction control for automatic V6's.

TooSlow02

1999 was the first major update for the L36 3.8L engine, which included a drive-by-wire throttle system. This was implemented across the board for this engine. The LS1 F-cars never had it. Even the new GTO doesn't have it.

TooSlow02

JasonWW

iTrader: (2)

I was giving him and others a much better and more elegant solution for turning the TCS system off. You make it sound as if it is going to "set a system fault". Are you implying that pulling the fuse will cause a trouble code light to come on? That is not the case. It simply prevents the ECM from seeing the TCS circuit once the throttle is engaged at which point the ECM turns off the TCS system just as if you had pushed that little button in the console.

JasonWW

iTrader: (2)

No, I didn't get own3d, as you put it. The conversation is still afoot and I'm just getting started.

(Pulls 50cal Desert Eagle) Bang! bang!

JasonWW

iTrader: (2)

Well, 2 things stand out to me in your explanation.

Does the motor have enough power to apply the very high pressures needed to activate the rear braking circuit, keeping in mind the vacuum power assist at the MC can not be used?

Where does the electronic front/rear bias circuit (porportioning valve or EBD) come into play?

JasonWW

iTrader: (2)

I was told by GM techs that the ABS motor was a kind of assist device to keep the solenoids from sticking. Made sense to me, I mean the brake pressures are several hundred pounds which seems like it would require massive solenoids to be able to open against that kind of pressure.

I guess they told me wrong. Maybe I need to go higher up than the techs at my dealership.

TooSlow02, were are you getting your info from? You sound like a brake system engineer.

TooSlow02

Yes. The motor is more than capable of producing the brake pressure needed to actuate the rear brakes. Bosch ABS 5.3 is the same system that is installed in a great number of cars (Corvette, Catera, Deville, Bonneville, Grand Prix, Aztec, Intrigue, Legacy, Camry, Contour, Mustang, Cougar, Mystique, Villager, 626, MPV van, Altima, Quest, Frontier, Sentra, Porche 911. BMW uses ABS 5.7 in their AWD vehicles, which is the same hardware, but weighs less and has four-wheel traction control. There are others, as well). The motor is powerful enough to apply all four wheel brakes to the point where ABS activates. The hardware is the same on all cars, it just uses software to enable or disable certain features. So, this is the same EBTCM/BPMV assembly that a car with stability control would have. It's up to the manufacturer to decide what features they want. In the case of the F-body, GM wanted ABS and EBD standard, with Traction control as an option.
Stability control was reserved for the Corvette, with Cadillacs getting it later.

The EBD electronic brakeforce distribution comes into play whenever you step on the brakes. It is designed to use the rear brakes to the fullest extent possible. It varies rear wheel circuit pressure constantly in order to maximize rear brake usage, so the car feels more stable during stops, and shorter stopping distances are assured, since the rear is not constantly underbraked as it would be with a mechanical proportioning valve.