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RX7 Traction Control


AlexLSX7

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I want to setup traction control on my FD. Previous owner removed ABS and the ABS rings and sensors from the front hub, as well as the sensors from the rear hub, although if i remember rightly, the rings are still at the rear.

I have seen people using the stock sensors and rings OK for traction control, but have read that using a hall effect or similar type sensor with the stock ABS ring will not work well due to the amount of teeth. I have had a look around and new sensors are about £200+, used are £50+ but you never know what state they will be in. I cant find any ABS Rings New or Used!

So my question is - Is there any aftermarket ring/sensor or other solutions i can use to run traction control?

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The teeth count was only a "limitation" in the G4+, and only really applicable if you had a really "busy" ECU, such as a V8 with sequential ignition & injection, quad cam VVT, dual bank knock monitoring etc, the speed calculation would tend to top out at around 500Hz. On something less "busy", then higher frequencies may work but generally aren't guaranteed.

With the G4X, though, the processor is much faster, and it doesn't have the same kind of limitations - all digital inputs are capable of over 10,000Hz, so a 43 tooth ABS ring won't be an issue.

That said, as someone has unfortunately already butchered your car removing rings & sensors, there are other options.

On my Ford Anglia, I'm picking up rear speed from the diff -> propshaft joint, where there's 4 bolts, so I get 4 x Diff Ratio pulses per revolution.

For the front, I was picking up on the 4 bolts that hold the brake disc to the hub, but I found that the mismatch in ~16 vs 4 pulses per revolution caused a bit of an issue with it calculating the "slip" percentage, so I added some extra bolt heads to increase the number of pulses up to 12, and with a change in diff ratio at the same time (from 3.96 to 3.69) means it's now 15 vs 12, which works much better :) 

front-wheel-speed-sensor-etb.thumb.JPG.68167da2ca485bdcc49e3884cc11399e.JPGfront-wheel-pickup.thumb.JPG.93d3fa401654f5121d6a0e4ae2408a59.JPG

 

This snip from a log file shows the issue I was having, the "staircase" effect on the front wheel speeds with only having 4 pulses compared to 16 for the rear. Certainly on the G4+, each time either sensor has a pulse, it recalculates the Slip % (difference between Driven and Non Driven speeds), and as I had the Driven speed ticking up more regularly, the Slip % was calculating based upon the last known speed from the Non Driven wheel, so the slip % kept going up & down, which meant I needed bigger values in my Slip Tolerance table, otherwise it was activating too easily. 

image.thumb.png.708087904db5994cdb4731853afaefe0.png

Since adding the extra bolts, this has become much smoother, and track much closer together during acceleration, and the traction control can be tuned a bit better now :)

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On 11/29/2022 at 8:18 AM, AlexLSX7 said:

I want to setup traction control on my FD. Previous owner removed ABS and the ABS rings and sensors from the front hub, as well as the sensors from the rear hub, although if i remember rightly, the rings are still at the rear.

I have seen people using the stock sensors and rings OK for traction control, but have read that using a hall effect or similar type sensor with the stock ABS ring will not work well due to the amount of teeth. I have had a look around and new sensors are about £200+, used are £50+ but you never know what state they will be in. I cant find any ABS Rings New or Used!

So my question is - Is there any aftermarket ring/sensor or other solutions i can use to run traction control?

^Are those prices for the OEM Mazda sensors? The OEM sensor is a VR type sensor, and I think the sensors are still available new from Mazda. You might try searching for set of used OEM rings & sensors on the marketplace section of the RX7 Forum - http://www.rx7club.com/ Often times the same knuckleheads that hack up their FDs to delete ABS end up selling the left over parts on the forum. Also, the VR sensors themselves are typically very reliable - my biggest concern with buying a used one from an FD would be if it was removed properly without any incidental damage. Sometimes they get rusted into the spindles, and removal may take a bit of extra "persuasion" to get them out - though that kind of damage is normally visible in pictures of the harvested used part.

 

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