Is there any difference in the ABS Systems across the SW20 years?
I have a '90 driver with 290k on the clock & a '96 parts car with only 90k so I'm slowly upgrading the driver.
I know the master cylinder & booster have to be swapped if I use the later brakes but is the ABS actuator block & ECU the same or do they have to be swapped too?
Brian

Early revisions that had ABS were three channel - two in the front and the rear was a single channel.
 
Later revisions have the 4-ABS sticker on the rear window, with the newer system each wheel was independent. 
 
Beyond that i'd only be guessing about how many lines came out of the control block, do they look different?
 
There's a few guys who disable the abs system entirely, personally thats something I wouldn't do but they seem happy with the change. Early model SW's do have a problem with the ABS triggering at low speeds (as in 1~3kph) but when mine did that it didn't appear to affect the proper function of the ABS at higher speeds. 

Thanks for the reply - they look the same.
I walk past the back of the car maybe twice a day & haven't noticed the 4-ABS sticker before! Its an 07/90 car so they must have dumped the three channel very early in the run.
 
I agree with leaving it active. I have had my neck saved twice now by ABS in wet conditions thanks & it was the steer around feature that got me out of trouble.

Brianl
Thanks for the reply - they look the same.
I walk past the back of the car maybe twice a day & haven't noticed the 4-ABS sticker before! Its an 07/90 car so they must have dumped the three channel very early in the run.

 
I wouldn't rely solely on the sticker to identify if its a three or four channel ABS, the window could have been replaced or someone may have put the sticker on to look like the cool kids.

A few interesting comments about SW20 ABS:
https://www.mr2australia...mr2play/tm.aspx?m=56917

Hi Guys, done a rev3 brake upgrade to a 1991 turbo, booster, master cylinder, rotors and calipers.
 
I have the abs kicking in at low speed just as we come to a stop.
 
Any idea hoe to fix this one? Dudeman had the same issue?
 
Thanks

I don't know what booster you had before your upgrade, but I assume you know that early (pre 11/'91 build) SW20 boosters had the vacuum check valve on the booster body, while later boosters require one to be fitted in the engine bay.