Power assist brakes, Has anyone done it? Options

[theer]

I Race an LS2 powered 914 and an LS1 powered 944 with a bunch of other guys. The 944 has a Ford hydro-boost system in place of the stock vacuum booster (no room with the v8). Works great, if maybe a little touchy for my taste.

The 914 has upgraded Boxster brakes, but no power assist. I like it better, but everyone else prefers the assist.

Has anyone figured out a way to get power assist for 914 brakes? We are pursuing an idea to use a Tesla brake module in the front trunk, with a stock MC (cap off all but one brake line) driving a slave cylinder which activates Tesla master. Even Better would be a electro brake module that’s hydraulically activated directly from the master…

We are still brainstorming, so any ideas are welcome!

Thanks!

[technicalninja]

I'd look into a dedicated "race" type dual master cylinder set up.

Seriously adjustable, good units have a balance bar to help with front to rear balance.

Some units come with adjustable pedal ratios.

Like this
https://www.summitracing.com/parts/wil-340-15078



I'd be VERY careful trying to adapt a can-bus operated system (Telsa) out of a modern car.

One of the members here had a serious accident racing a Honda with 3rd or 4th gen ABS which had the ability to individually operate a caliper for "stability control".

The video of his accident almost looks like CGI.
He goes into a corner and the car spins the WRONG direction.

I'm not sure a non-abs car could ever spin like his did without hitting something solid first.

I'd bet Ken Brock wouldn't have been able to save it...

Serious "due diligence" needs to be done if you're trying to adapt OG to modern.

[JeffBowlsby]

Maybe Ken Brock will respond to this thread? Maybe not….not that we would not want him to respond. :wink:

[Chris914n6]

What he said ^^

Way easier to do the 'race' pedals. Plus you can do brake balancing. We tend to favor the Tilton over the Wilwood here but they are practically the same. The Tilton cylinders fit better.

[theer]

Thanks guys- the objective is to reduce the pedal pressure. We’re team of Oldtimers and everyone is used to power brakes in DD and the other race car.

Does a dual pedal system make the brake pedal “easier”?

[Superhawk996]

The proposal to use the stock master cylinder, the slave cylinder, and the Tesla system in series is a death wish. (IMG:style_emoticons/default/screwy.gif)

There is no braking redundancy - all braking is dependent on one line. A failure of the master or the slave cylinder means you have zero brakes.

There would also be outrageous lag time and hysteresis.

Stick with something that is tried and true like the typical dual master and bias bar racing set ups mentioned above. There is absolutely no need for assist on a vehicle as light as a 914. Vacuum boost has its own weakness on track due to lack of vacuum from the engine. I have set up much heavier race cars (ie Viper) with the Tilton set up and there is no need for vacuum boost.

[Superhawk996]

Thanks guys- the objective is to reduce the pedal pressure. We’re team of Oldtimers and everyone is used to power brakes in DD and the other race car.

Does a dual pedal system make the brake pedal “easier”?

Hydraulics - size the master cylinders appropriately.

[Chris914n6]

Does a dual pedal system make the brake pedal “easier”?

It can. Size the masters for full pedal travel and max out the pedal pad position for max leverage.
Tilton can do the math for you after you fill out their form.

One option would be mount an overhead pedal and bolt the booster/master directly to it. Stock gas tank would be in the way. Your idea has too many possible failure points.

[Larry.Hubby]

I did add vacuum assisted brakes to my 914-6 conversion car. The link is:

http://www.914world.com/bbs2/index.php?sho...hl=power+brakes

It was a fair amount of work, as you can see, but the result has been good and solid.

Larry

[Vicious]

I did add vacuum assisted brakes to my 914-6 conversion car. The link is:

http://www.914world.com/bbs2/index.php?sho...hl=power+brakes

It was a fair amount of work, as you can see, but the result has been good and solid.

Larry

Incredible write up and engineering

[Artfrombama]

I did add vacuum assisted brakes to my 914-6 conversion car. The link is:

http://www.914world.com/bbs2/index.php?sho...hl=power+brakes

It was a fair amount of work, as you can see, but the result has been good and solid.

Larry

Outstanding engineering and equally impressive write up. Have you considered a remote booster? I know the universal units are single circuit.

[technicalninja]

Impressive fitting of a vacuum booster!

Make sure something like that will pass 'Safety/Technical inspection" for your class of racing.

There is another problem with a vacuum booster that you will have to overcome.

It's distant from your main vacuum source. I would use aluminum line for most of the run back to front.

On an application of forced induction, you will need a fail proof check valve to keep boost out of the booster.
Arnold Schwarzenegger couldn't depress the pedal under full boost.

And, in both ITB and forced induction the vacuum source can be whimpy.

I'd also install an "assistance" vacuum pump. Lots of options here. Many front drive 90s GM vehicles had a very workable electric vacuum pump assembly specifically for the brake booster.

I'd still try the "old school" way that most posters have suggested first.

You like that better anyway. What you like is the "feel" of a simple, non-assisted hydraulic system as it has more feedback. That Hydro boost in the 944 deadens this aspect a bit.

If the car was "mine" I wouldn't provision it for others.

Properly set up, the dual master set up should stop the car every bit as fast as a boosted set up and have less complexity making it more reliable.

[technicalninja]

Two more thoughts...

I too, prefer Tilton over Wilwood.

I just found something quickly as a demonstration piece.



And this is the more telling, I've seen boosters REMOVED for competition use, this is a common mod.

I cannot say I've seen a booster system added for competition.

[Superhawk996]

And this is the more telling, I've seen boosters REMOVED for competition use, this is a common mod.

I cannot say I've seen a booster system added for competition.

Cause’ if you have even been WOT down a long straight, late braking into the 1st corner and jump over to the brake quickly, you’ll get a surprise you’ll never forget.

The fix is adding the electric vacuum pump that ninja references. More weight, more wiring, and a brake failure mode that you don’t want to experience. Adding weight and complexity to a race car is rarely a good thing.

[gnomefabtech]

https://powerbrakes.com/pb900-universal/

https://mpbrakes.com/product/bs1011k-dual-d...-brake-booster/

https://www.amazon.com/Remote-Electric-Boos...r/dp/B07B8V7H34

https://thejeepsterman.com/products/remote-...willys-and-jeep

These are a few options for hydraulically activated remote boosters. These things are used in vans and things like that where the engine compartment is tight. For the "single system" ones like the Jeep unit, you'd use two, one for the front and one for the rear. Mount anywhere the hoses can go.

The double system could still be used in conjunction with a balance bar style master if you want perfect bias adjustment. Or just use a rear proportioning valve.

As for the vacuum source, I used to have a motorcycle powered race car and I used the little GM vacuum pump for a vacuum source and it was totally good. But honestly, you could just use engine vacuum with a check valve (like all factory setups). Even on a race track, you'll add plenty of vacuum when engine braking and it's stored for the next time you brake. Unless you "never lift" of course, then yeah, get the pump lol.

[Chris914n6]

It actually wasn't said but they are referring to a vacuum canister with a check valve to store vacuum, so it's there when needed.

But honestly, I'd tell the wimps to start doing squats and calf raises lol.

[Root_Werks]

Larry's adaption is truly impressive!

I thought I remember years back someone adapting a 911 booster to a 914? Both have pedals that come up from the floor. Wish I could find where I read that....

[Ron914]

It actually wasn't said but they are referring to a vacuum canister with a check valve to store vacuum, so it's there when needed.

But honestly, I'd tell the wimps to start doing squats and calf raises lol.

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