Power steering issue with slicks?

[Davidss]

EDIT - way more info here: https://www.ft86club.com/forums/show....php?p=3486168

I'm bumping this thread because it is one of the top results on google and I have some new info and areas we can research.

Background:

I did a two day autocross this past weekend and had a lot of quick steering drop outs. I haven't run many events in the car and those I did were a few months ago. I don't remember this happening as often before. I tend to think it is related to putting a tiny cheap lithium battery in the car. I am pretty certain I overheated the battery the first day, this was a practice event and the car was racing and idling constantly for hours. The aftermarket radio started rebooting itself and the traction control turned itself back on. Years ago I had a similar issue in an ND Miata where an overheated lithium would cause glitches including the traction contol resetting.

Testing:

I attached a temp sensor to the power steering motor, and then logged voltage. I found a strip of grippy concrete pavement and rolled forwards at 1-2 mph while quickly moving the steering back and forth. After about 10 minutes of this my arms were sore. If I turned the steering literally as fast as I am capable I can get the steering to drop out, this is completely consistent whether the car is cold or warmed up. In the 10 minute test the steering motor only went from 65 (ambient) to 75 degrees F. Additionally occasionally there were about a half a volt drops but this is less than the voltage drop you get from headlights or hvac fan. The steering induced voltage drops seemed to occur after no steering input for a few seconds, however these voltage drops did NOT correlate to an actual loss of steering assist.

I would say it is somewhat conclusive that the power steering motor itself is not overheating.

Next I had the idea to test the temperature of the steering control module. When I went out to put the thermocouple on it immediately I could feel way some heat in the module where the motor always feels ambient. The car sat for 30 minutes between these tests but even after that rest time the back side of the module was 90 degrees. Repeating the steering test for 5 minutes got it up to 95 degrees.

Given this is a worst case torture test of constant steering input for a long time I tend to think that the module overheating is also not an issue.

From here I think what would be needed is for someone to log voltage on track, do a video overlay and call out on the video when you feel the steering lose power.

[RedReplicant]

I've logged voltage on track when it cuts and there is no correlating drop.

If you log the EPS CAN it outputs torque... you'll notice that the cut is when it touches 8nm.

My car has more or less has completely stopped doing it after getting the front end link geometry right.

[Davidss]

Originally Posted by RedReplicant

My car has more or less has completely stopped doing it after getting the front end link geometry right.

What was wrong and then corrected on your endlinks?

[RedReplicant]

Originally Posted by Davidss

What was wrong and then corrected on your endlinks?

It seems that it is very easy to induce endlink bind on these cars and a lot of off the shelf coilovers make contact with the endlink under certain circumstances.

I can't give you an exact blueprint but when I moved to Xidas I played with the endlink and shock length for unrelated reasons, when I got them in the right window I magically stopped having EPS cut at the same time.