[Diy_efi] Jetronic - RFI

Ian Molton spyro
Sun Mar 5 15:25:52 UTC 2006

WSCowell at aol.com wrote:
> In a message dated 04/03/2006 10:22:47 GMT Standard Time, spyro at f2s.com 
> writes:
>     whats involved in retrofitting ABS to a vehicle ? Does anyone make kits?
> Hoo boy, where shall we start?

Thats never a good sign :-)

> Modify the wheel hubs to carry suitable reluctor rings, modify hub 
> carriers to hold sensors, modify the hydraulic pipework from the master 
> cylinder so as to include the pump piping, accumulator and valve block, 
> design & fit bracket for hydraulic pump for the high pressure lines, 

Ok, so it was probably obvious I know nothing about practical ABS 
implementations from my post (nevermind that we're straying far from efi 
here...). Suggestions for a place to read up on this would be most 

The theory is, AIUI, keep the wheels from locking up by pulsing the 
brake when lockup is detected. So, needing wheel sensors was obvious...

whats a reluctor ring?

I'd guessed already that pipework would need rto be re-done, but Im not 
familiar with how its done.

I know ABS systems must 'fail safe' so clearly theres some kind of 
allowance for that in the valve block.

My car currently has a 2-way split crossed front/rear setup with a 
balancing block in it and a vacuum assisted master cylinder.

I assume any ABS pump would typically be run off the fanbelt or a 
seperate line from the crank pulley.

What does the valve block and such *do* in an ABS setup (beyond the 
obvious). well, I guess I want to know more *how* it does it...

This is all a bit hypothetical right now because a) it'd need 
certification from the authorities here, and also affect my insurance, 
and b) I need to find some discs for the back end long before this is 
worth the bother.

are ABS computers often standalone devices ?

> In short it's do-able, but definitely not trivial!  :-)
> I think if you have to ask that particular question, don't attempt the 
> job, because of the danger involved in implementing a project that you 
> don't understand from top to bottom.

Oh, dont worry, Im not dumb enough to tinker with the braking system 
without the effort to fully understand it.

My dad once used his lathe to trim the discs on his fiat, not realising 
that the fiat system depended on a minimum wear not being exceeded, 
which resulted in the pad over-extending and jamming - you only need one 
graphic example of why not to do something like that ;-)

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