# Anti Blockage System (ABS) braking system : anything I'm missing?



## EV480lution (Oct 4, 2010)

Hi all,
Sorry for any duplication but the search engine was clueless. I would appreciate your views on what are the technical implications of keeping an ABS system in a conversion. I'm afraid I'm a bit caught in a mindf**k with my equipment provider. The state of play is:
- I've been trying to figure out how ABS generally works and basically, my understanding is that it is a closed system based on a electronic calculator connected to a brake fluid system (as on motorbikes) and sensors on each wheel. In such design, there is no vacuum pump, hence not the need of fitting a vacuum pump. I thought I had ticked that box. BUT:
- My provider now reckons I should devolve the ABS calculation management to the controller (huh?) and therefore need to install a vacuum pump as in a "classic" conversion to keep a physical control over the brakes.
Now, this is where it puzzles me. Reading between the lines, he's basically asking me to remove the ABS system and go for a standard vacuum pump + controller braking. I'm not sure I want to go down that route and I'm not sure about the need to purchase a vacuum pump... But there's a point I may be missing...
Is it a complete nonsense to keep the ABS system as such and have a controller braking alongside? Do you think my provider induces it would be feasible to connect the wheels sensors to the controller?
I'm a bit confused right now... 
Thanks


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## Woodsmith (Jun 5, 2008)

I can't help but would be interest in ABS for my trike if it were possible. I think I would look at motor bike systems but I don't know enough about what would be needed to ensure it worked properly.

It would be interesting to see why you would need to remove a system that, I suppose, would work for a more complex system with a vac pump.


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## piotrsko (Dec 9, 2007)

ABS as I understand it: there are wheel sensors that tell a computer that indeed wheels are spinning and at what rate. Transmission and some engine data is also used here, too. when the brakes are applied, there should be a gradual (relatively) slowing of the output from the wheel sensor. a locked wheel does not spin or provide rate data to the brake computer. the brake computer then releases pressure to the affected wheel brake cylinder until the wheel speed matches other data. Note this would be a mechanical energy dissapation system as used on most cars today.

Now unless someone has built a system unknown to me, vacuum is generally used for a pedal effort assist system in the master cylinder of the main braking system. Remove vacuum and the brake pedal becomes too hard for many to use.

Sounds fishy since I haven't had regen braking effectively demonstrated to me in this manner/ I have issues doing the final stop portion at very low speed.

You don't need ABS if you have a plain mechanical system but ABS is nicer and much harder to implement. 
Not sure how the controller would deal with wheel data

my $.02: your mileage can and will vary.


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## Guest (Dec 22, 2010)

Just let the computer keep control. You should not have to completely disregard the computer. The vehicle needs it. I bet most items work still if you keep the computer hooked up. I think the issue is how to shut things off that are no longer needed but still allow all other computer functions to operate as expected. 

Pete


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## rwaudio (May 22, 2008)

One thing to keep in mind, it's usually not legal to remove factory safety systems from a vehicle. Depends on your local laws as well but you might save yourself some hastle by keeping it. (keeping it might mean you need the vacuum pump)


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## Jimdear2 (Oct 12, 2008)

The vacuum boost or hydroboost systems on your brake system have *NOTHING TO DO WITH THE ABS SYSTEM*. If the brakes on the car were boosted then you should ensure they remain boosted after the conversion. 

There should be no conflict between an antilock system and regenerative braking. With the exception you would want to turn the regenerative system off or waaaay down when you were in a situation where ABS might be necessary. 

Ok, a stand alone ABS (Antilock Brakeing System) does exactly what it's name implies. It prevents the wheels from locking up (skidding) during braking thus allowing the maximum braking friction without loosing the the ability to steer and control the vehicle or prevents the rear wheels from locking and causing a skid. There are a couple of subtle side benifits we don't need to go into. 

A functioning ABS is even of more value in a EV because of skinny LRR tires, high tire pressures and higher average vehicle weight. All of which cause a tire to skid easier. 

The standard ABS systems I worked with were usually stand alone and *self contained*. ABS systems on vehicles that used the ABS pump and valve system for traction and stability control are a different story. (Maybe)

The standard systems work as follows.

Your normal vacuum boosted or hydroboosted brakeing sustem is ported *to and through* the ABS valve and pump body that is operated by the ABS control unit.* With the system functioning, until a wheel locks up or has a radically different speed during braking this unit does nothing and the brake system works normally*.* If control system fails, the ABS unit does nothing and brakes will continue to function normally*.

in a four wheel antilock system each wheel has a speed sensor and cog wheel that sends pulses to the ABS control unit. 

In it's simplest form, when the control, unit sees a pulse difference from the speed sensor in one or more wheels it will release the pressure from the normal brake system to those wheels, then through a system of valves uses the antilock pump to pulse pressure to those wheel until the pulses from the wheel speed sensor again match. 

There are multiple algorithms in the controller programming to handle 4 wheel lock up and many other different conditions. We don't really need to go into those.


Simply speaking, *leave it alone when doing a conversion*, if it requires a CAN buss or other connection to engine, traction, stability or transmission controllers it will just stop functioning and will work just like a normal non ABS system. If it works then you will find your vehicle safer.

I think I've covered the basics, but I've been away from it for a while, so any body with more information PLEASE jump in.

Hope this helps,
Jim


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## ewert (Sep 5, 2009)

ABS is gooooood (safety). Leave it intact unless your batteries/motor/controller can handle good regen braking.

Regen braking is inherently "ABS" (wheel stops, no regen = no braking force, wheel restarts moving).

Having both does not conflict in any way I can see. Regen braking is faster since it is "instant" braking force reduction from wheel lock. Regen braking is actually the perfect ABS due to the instant feedback system. A good setup of regen braking + normal braking does not need ABS really, but still the ABS is a safety feature, and don't see much use in removing it.


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## EV480lution (Oct 4, 2010)

Thanks guys. All of your views kind of merge to a final conclusion : I got some principles mixed up : 
1) I just figured out a vacuum pump is generally needed to replace what the engine used to do for the power brakes (wasn't too sure of what that was exactly) but now I realize this is what allows you to prevent needing to stand straight on your braking pedal whenever you need to brake. So no vacuum pump and you have a pedal as hard as damn brick. So my supplier is right in saying I still need one (I didn't want to insult his intelligence but I like to understand things whenever I'm told "that's how things go, don't ask" ). Mine should be vacuum-based, I'll double-check in the mechanics' guide.
2) I concur with what you said about the ABS as a security feature. I definitely want to keep it. The TIM 600 should only focus on regen and ABS comes as an emergency braking system that will prevent me from a little trip in the road sides (I can tell it is very effective in the snow )
I'll still need to check what data it computes but I would be happy if it only checked if wheels are spinning or not, whatever the speed of vehicle.



> Your normal vacuum boosted or hydroboosted brakeing sustem is ported *to and through* the ABS valve and pump body that is operated by the ABS control unit.


So to sum up : I'll always need a vacuum pump, irrespective of having ABS or not. Right?


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## Thaniel (May 25, 2008)

EV480lution said:


> So to sum up : I'll always need a vacuum pump, irrespective of having ABS or not. Right?


Yes if your car has a vacume brake booster. If it has a hydrolic brake boster it will need hydrolic pressure (most are vaccume brake boost). What car are you working on?

P.S. My car has the ABS intact.


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## EV480lution (Oct 4, 2010)

Hi Thaniel,
I'm working on a Volvo 480. My model has vacuum but her turbo sister has hydraulic (wtf?). It was worth checking. Thanks to you all 
Speaking of which, it appears my ABS module has connections to the aux battery and to the alternator. Apparently it can suck a bit of amps. Do you concur?


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