Enhance TRAC, ATRAC

There has been quite a bit of discussion as to the differences of TRAC vs ATRAC. I admit ATRAC seems to be a great feature and I wish my sport had it.

From what I understand the main mechanical difference between an ATRAC and a non ATRAC truck is how the brake system is boosted. The sport (TRAC) uses a vacuum assist, while the off road (ATRAC) uses a hydraulic assist. Here is my question, Can you increase the braking force on a non ATRAC truck to achieve performance closer to ATRAC? (I assume there is some different logic in the pcm as well but for now we will ignore that.)

The vacuum is automatically created when the gasoline engine is running, so we already have an ample supply of vacuum available. When you hit the brakes the vacuum pulls on a diaphragm inside the brake booster. What happens when you step on the gas? The plate in your throttle body opens and air rushes in to your engine (as it should) but this lowers your vacuum
level while you are on the gas. This is normally not a problem because you are not accelerating while braking. When you truck experiences a traction loss that triggers the TRAC system you are on the gas thus a lower vacuum available to boost the brakes. Are you with me?? (*we are assuming the truck is in 4hi)

How could we "boost" the vacuum system? Here is my stupid idea. . . Take and air tank similar to what is used on a semi for the air brake system and plumb it in line between the engine and the brake booster. You would also need a one way check valve between the engine and the tank. This would prevent the loss of vacuum in the tank when you do hit the gas. This would basically be a plenum storing vacuum for your brake system.

This may sound stupid or just a waste of time? This is why I am looking for your thoughts on the topic.

 

I highly doubt a system designed for vacuum forces could cope with forces that could be produced by a hydraulic system.

If it could, Toyota would leverage synergies rather than desgin, troubleshoot, manufacture, and install a hydraulic system for ATRAC.

 

Vacuum reservoirs are quite common -- the vacuum brake booster has one built in, essentialy, enough for one to two brake applications even if the engine is stopped. Vacuum servo cruise control systems often have separate reservoirs too.

Your idea has merit. It might or might not do anything useful in improving TRAC, but it will improve the amount of vacuum reserve available for the brakes.

You might also look into an electric vacuum pump as an accessory to help maintain vacuum in the reservoir. They are often used on muscle cars with really aggressive cams, because they develop very little vacuum at idle. Try the Jegs catalog.

 

I don't know how large the vacuum diaphragm is on the brake booster, but assuming it's about six inches across then there is a maximum of 415 pounds of force available from standard atmospheric pressure (14.7 pounds per square inch). In practice, drawing about 20 inches of vacuum, that would be about 300 pounds of force. That is then applied to the master cylinder, which provides some hydraulic multiplication at the wheel cylinders.

The hydraulic booster probably does not produce more hydraulic force than is normally found in the brake system. What it probably does is produce it for a longer period of time than can be maintained with a regular vacuum booster and reservoir.

 

Keep reading and you should do fine without making any changes other than performing the YELLOW WIRE MOD.

You have TRAC in H4 (and AUTO LSD in H2)... now they may not be as strong as they are for the Off Road TRDs... but they work. What you don't have is any traction control in L4... no A-TRAC. So, the yellow wire mod is available to give you TRAC in L4, and those who have done so rave about it.

 

Well, I would not expect more vacuum rather "peak" vacuum when TRAC kicks in. As apposed to the reduced vacuum available with the factory setup.

I admit it seems to be a lot of work for not much gain, so it will likely remain just and idea at this point.

 

The factory brake system should maintain a high vacuum level while the brakes are not being used, so long as the engine produces high vacuum once in a while. There is a check valve that maintains the vacuum.

 

What would be gained by adding a Separate Vacuum Booster?

 

You do realize this is a 7-year-old thread?

Maybe a point of discussion, but the 4WD Off Road TRDs have a HYDRAULIC BRAKE BOOSTER specifically for the A-TRAC to work at matching tire rotation across the axles (like lockers), and all other Tacomas have a VACUUM BRAKE BOOSTER.

 

Exactly, 2 completely different style Brake Boosters.