SWAS Question/Idea
 

I've spent some time with the steering wheel angle sensor (SWAS) unplugged to keep the boost from being capped with the wheel turned. I've noticed that it adversely affects the steering feel. It's manageable, but it bugs me.

ztnedman1 described the effects well:
"[I]f you turn one way then the other the power steering will cut off for a second. If you push in clutch or gas, it kicks back in. This is the ONLY time this occurs, and IMO is not bad (steering just gets heavy but still easy to control)."

So, I had a thought. Most of us disable their SWAS by unplugging the sensor which keeps the signal from reaching any of the 3 modules it's supposed to go to: dynamic stability control (DSC), powertrain control module (PCM), and most importantly, electro-hydraulic power assist steering (EHPAS) module.

We want to keep the SWAS signal from reaching the PCM to keep the boost cap off and DSC to keep traction control from interfering. The problem is that the signal also no longer reaches the EHPAS module which relies on input from the SWAS to speed up or slow down the electric power steering pump in response to quick steering inputs.

So, what if we keep the SWAS sensor plugged in, and allowed the signal to reach the EHPAS module, but intercepted the signal before it reaches the DSC and PCM modules?

Here's a rudimentary wiring diagram of the CAN cables from the Workshop Manual. I'm thinking about unplugging M and J at the DSC, and 1AM and 1Al at the PCM, which are the respective CAN H and CAN L inputs to those modules.

http://i.imgur.com/cHohQPMl.png

I'm a little worried about cutting off the CAN connection to these modules from the BCM, since I don't know if the engine PCM will be able to communicate check engine lights to the instrument panel, and I don't know if the OBDII port would be able to reprogram the PCM anymore.

Can anyone with a wiring diagram verify, or send me a copy so I can verify?

Don't fuck with the CAN wires. The CAN wires are used for general communication between all the electronics and this information is key for running the car. The only thing you could do is basically create some hardware to act as a man in the middle and filter messages. By doing this you can block the SWAS messages from reaching the PCM. However, I personally wouldn't run the man in the middle setup on my PCM. if you really want to create something, have something on the canbus monitoring power steering and if the loss is detected, send a signal to the PCM to make it think the clutch was pushed in.

I like where you're going, but messing with canbus is opening a big can of worms.
There are other options such as intercepting the steering wheel angle input and inputting only the 'dead straight' voltage, assuming its a regular 0-5v sensor.

There are also tables in ATR..
Beta Tables > DBW Throttle compensation > Set all to 100%. This revents the throttle closing but not the rich condition.

I personally use a momentary switch to disable SWAS/ DSC / TC, it needs to be pressed after starting the car each time.

Thank you both for your excellent advice. I won't sever the connection.

I've seen the threads where people disable the SWAS with a switch (like a switch that accomplishes the same thing as unplugging), is that what you're talking about? In that case, I'd still have the same steering feel problem.

On this note: I think I'm going to try buying a second SWAS and plugging that in instead of the one mounted on the wheel. Then, I can trick the BCM into thinking the wheel is always straight. The downside is that the EHPAS unit won't register that the wheel is turning, and so it might respond the same way that it already is; by delivering poor steering feel in a slalom. On the other hand, the poor steering feel might be the result of some software glitch when the EHPAS unit doesn't have any input at all, in which case, this could fix the issue.

Any thoughts?

Just bought a second SWAS sensor on eBay. We'll see how this goes.

So can you answer me this. When I was buying my E85 Flash Tune, I had the option to disable EGR CEL (like always), and interestingly it gave me the option to also disable SWAS. I chose both, given this information, instead of doing all this hard work, can't you just disable SWAS from ATR?

Perhaps I'm oversimplifying shit, and I don't use ATR much at all, so there's that. It's a Stratified E85 Flash Tune FWIW. I'm not sure I can confirm that it's off/disabled, nor do I want to test it out now that it's slippery outside. If there's another method to test it out let me know, maybe I can try it and it would be of some use.

Not sure if that's available with an accessport. Versatune allows you to disable SWAS via their software, so that could be what Stratified is referencing.



n/m apparently cobb added that as well. Interesting.

From what I've read on here the SWAS disable function in ATR does pretty much nothing.
And they sure made it complicated by adding several tables where you can input values from 0 to 100. Stupid way to do it IMO.

Versatuner has one checkbox, check it and it's gone. Simple

When you disable a CEL, it doesn't usually disable the device, it just tricks the BCM into keeping it perpetually in "incomplete" mode so the CEL is never tripped. When you disabled the EGR CEL in ATR, it didn't disable the EGR, it just meant the light won't show up on your dash if your EGR wasn't functional. So, disabling the SWAS CEL will just keep the light from showing up if you disable the SWAS, but does nothing to actually disable the SWAS. Please tell me if I'm wrong here... I haven't had a chance to actually look at the ATR interface, so I'm basing this on research.

Can you circumvent the SWAS boost limitations in 1 and 2 via tuning? The Cobb rep replied to this question in a thread somewhere... He said that there is some way to alter the table that's activated with the wheel turned, but I don't remember which table it is, and I don't know what values to change. As SpeedRebirth said, it's a bit of a headache, especially for someone like me who's new to tuning, and who doesn't use windows (ATR only runs on windows).

More importantly, I bought my car to run it in G street Autocross so I'm not allowed to touch the tune, but I can disable/trick traction control and sensors.

I'm interested what you achieve with the spare SWAS unit :)

The momentary switch I use (on a Gen1) cuts the ground connection to swas just for a second. Once it's logged a 'SWAS not ready' state, the ECU doesn't attempt to use the SWAS input again until the car is restarted.
On Gen 2 it would still cause power steering problems if you choose to press the switch.

We have only shown that Cobb's SWAS 'fix' doesn't work in Gen1's and MS6's. We found this out only in the extremes at autocross where we don't have gen2's running as regularly or as modified as we are. That just means we don't know for sure if the SWAS fix in gen2's actually works or if it is lessening the effect at low speeds or who knows what.

Start reading about it here: http://www.mazdaspeedforums.org/foru...ml#post2825321

I regret to say that the secondary SWAS is not the answer; no dash lights were illuminated, but Dsc did some weird stuff, and steering feel was not improved.