ABS from LS1 - it's all in the details

[64skylarkls1]

I've been conversing with some of the members about adapting the ABS to my 64 Skylark ragtop along with the entire LS1 transplant. I thought it might be best to start a new thread because the other thread was more about ABS in general.

The help from other members had been amazing and I think I'm on the right track for success. I bought a totalled 02 SS Camaro with the LS1 6 speed which is now sitting in the Skylark. I've adapted the steering column and pedal set up from the donor as well. My plan is to have all the luxuries that came in the Camaro, cruise, ABS, traction control.....

The system is a four channel and has the sensors at the rear wheels. To use it, I'm adapting the whole rear brake set up to a 9" with the reluctor rings pressed on the axles. For the front I'm using ATS AFX spindles with sensors and ordered a front C5 brake package from Kore 3 but without the calipers. I will use the calipers from the donor car to keep the piston sizes correct for the front and rear.

So.. here is the next hurtle. I wanted to go with a little taller tire than what the Camaro had. I know that the tire diameters front to rear need to stay close for the ABS to work properly. I had planned on adjusting my rear axle gear ratio to compensate for the larger tires, that way I could keep the speedo correct and stay close to what the factory RPM ranges were for the LS1. But if I do that, the wheel sensors will be traveling at a different speed then the trans speed sensor.

The question is does the ABS or traction control set up look at the trans speed sensor as well as the rear wheel sensors or are they completely independant of each other? If they do look at the trans sensor, then I would need to stay with the LS1 diameter wheels and gear ratio correct?

This is a great site and the help has been great. Thanks to all.

[CamaroAJ]

you can have the speedo adjusted with a tune. the EBCM doesn't look at the trans speed sensor.

you can change the tire size to what. the camaro had 275/40-17 stock, so they were 811 revs per mile. now you need to stay within 3% max front to rear. from searching what tires sizes people are running and playing with different sizes on my vette it worked out just fine. i am running 295 fronts (798 rpm) and 335 rears (802 rpm) so we are talking 4 rpm different. that difference could be the same as a new 275 vs a worn out 275. also i am running a 9" with the reluctor wheels on the axles and ats spindles.

[64skylarkls1]

Excellent! That's what I was hoping for - that the ABS sensors and trans speed sensor don't pay attention to each other. Since I need to build a rear anyway, I will first decide on wheel / tire size and then set gearing ratio to make up any difference. That way I will have the motor rpms close to the LS1 stock arrangement. Who knows, I may not even have to do a tune for the speedo.

Thanks again.

[CamaroAJ]

you won't like it if you run it so its close to stock gearing. a lot of people complain that 6th isn't usable and bucks or surges. i had 3.50 gears in my '67 and it was the same way. common gear for ls1/t56 is 3.90 or 4.11, with a 27" tall tire in 6th @ 70mph thats still around 2300 rpm.

[64skylarkls1]

you won't like it if you run it so its close to stock gearing. a lot of people complain that 6th isn't usable and bucks or surges. i had 3.50 gears in my '67 and it was the same way. common gear for ls1/t56 is 3.90 or 4.11, with a 27" tall tire in 6th @ 70mph thats still around 2300 rpm.


If that's the case, I may be sitting just fine. I have a posi 3.70 9" center that I can use and due to the way the rear wells are in the Skylark, I can't go much larger than 26" on the dia.

[MiDave]

One other thing you may want to consider is the size of your brake calipers and the displacement of your brakes. The isolation and dump valves have different sized orifices. There are also different sized pumps and accumulators for different applications. I would think if you were running a different size brake setup then what would be stock for your donor car the unit would have a hard time finding the sweet spot it is looking for when you enter an ABS event. It would either be dumping too much brake pressure to fast or not enough fast enough. Same with when it tries to reapply the brakes.

Good luck

[68sixspeed]

If that's the case, I may be sitting just fine. I have a posi 3.70 9" center that I can use and due to the way the rear wells are in the Skylark, I can't go much larger than 26" on the dia.

You will be fine on gears, I run 3.70s with a 0.50 overdrive and I love it. 6th is useful from 50mph on up and the rims aren't bad on the highway.

[MonzaRacer]

ABS, in what I call first generation, has no traction control, or any other use but to stop the wheel lock up upon braking by looking at wheel speed and car speed and brake switch/on or off.
Remember your speed sensors are NOT critical as long as what ever system you use can be read by a scanner and your tire sizes are within 1% t o3%(general rule of thumb as tire sizes between manufacturers can cause issues).
biggest tthing I have found is if wheels say 55 and trans says 35 your gonna have issues in most GM/Ford based units.
As for sizes of tires use rimsntires.com tire comparer to make sure your computed tires match like a ZR1 Vette used 274/40 and 315/35 17 in tires and are dang close in height.
Going off half cocked on gear ratios and demanding higher and higher numerically is NOT the way. most people forget to look at first gear time final drive AND forget to tune 6th gear, they only tune for 1 to 1 and WOT.
Most FI systems dont allow for what the engine WANTS, be it more fuel, less fuel, more timing less timing and if you havent got good timing control or knock control you get buck and shudder.
Then every one wants to patch with gearing. tuning flat road cruise for best performance NOT highest AF/R.
Got a guy who runs 14.0 to 1 FR, he thinks it should be 14.7,,, but old style aluminum BBC heads wont handle leaning it out more. Generally high gear hijinks comes from lean misfires.
Rule of thumb is KISS, LOOK at what your system sees and think like it does. All basic ABS does is unlock and cycle the "channel" that is affected.
Also dont forget matching tire compounds are critical too.
As for drag racing and road courses add in a double pole/double throw switch and kill one front and one rear wheels speed signal OR a gang relay or power transistor switch setup to defeat the signals. ABS is fairly dangerous in competitive situations. Ask me how I know. As for a three or four channel set up on the car, live axles generally handle as well or sometimes even better in three channel. Last system I helped build up used controller from a 2001 Chevy Silverado.

[tlillard23]

I got my abs tcs working, hows yours coming along?