NoRotors.com - RX7 Engine Swap Forum

Technical Information => Electronics => Topic started by: rx7lee on February 20, 2015, 10:43:21 PM

Title: abs used to run speedometer
Post by: rx7lee on February 20, 2015, 10:43:21 PM

Can one of the front wheel abs sensors be used with a Dakota sgi-5 box to run the speedometer on a fd?

Title: Re: abs used to run speedometer
Post by: Skeltic on February 21, 2015, 04:22:13 PM

That sounds like something that would work

Title: Re: abs used to run speedometer
Post by: rx7lee on February 21, 2015, 05:52:47 PM

I'm thinking it would I just need to figure out how to find out how many pulse  pre mile the stock abs sensors are

Title: Re: abs used to run speedometer
Post by: gc3 on February 21, 2015, 07:21:04 PM

Quote from: rx7lee on February 21, 2015, 05:52:47 PM

I'm thinking it would I just need to figure out how to find out how many pulse  pre mile the stock abs sensors are

count the tone ring and multiply it by tire circumference speed

Title: Re: abs used to run speedometer
Post by: mdickw on February 23, 2015, 02:45:50 PM

Looks like the ABS wheels are 44 teeth (from looking at pics). That would work out to about 34k ppm for a stockish size. According to the manual, the SGI-5 should be able to accommodate that, though it does explicitly say not to connect to ABS sensors. I think that's more for liability than technical reasons. If you're still running ABS, though, it would be a bad idea to use one of the wheel speed sensors. The SGI-5 might sink too much current (but probably not), distorting the signal from the sensor. The additional wiring to get the SGI-5 onto the circuit could also introduce a lot of noise. That said, it would probably work fine.

Why do you want to use the wheel speed sensors? Too much extra mileage from spinning your tires?

Title: Re: abs used to run speedometer
Post by: rx7lee on February 24, 2015, 10:11:15 AM

Thanks guys. I want to use the abs sensor cuz I don't run abs and my transmission don't have a speed sensor

Title: Re: abs used to run speedometer
Post by: mdickw on February 24, 2015, 10:31:32 AM

Cool, let us know if it works..

Title: Re: abs used to run speedometer
Post by: Jordan Innovations on February 24, 2015, 02:12:30 PM

Generally the wheelspeed sensors aren't great places to pull speed from - the output is very low voltage, very fast, has to travel a hellishly long distance in the car, usually along with high-amp wires (battery, fuel pump, etc), and needs some filtering to be accurate or consistent.  The Dakota Digital boxes should have settings to bring the speed down enough, but I don't know if the output will be what you're used to seeing on a speedo.

My recommendation would be a mag sensor that reads the driveshaft nuts where they enter the diff - high-res, better speed (~16 pulses per wheel rev, vs 40), and less noise.

Title: Re: abs used to run speedometer
Post by: rx7lee on February 24, 2015, 03:24:05 PM

I was trying to keep from having to do that as it would have me trying to fab some kind of a bracket to hold the sensor but I think that is the best way to do it . I was hoping if I used a shielded wire from the and sensor to the box and used the sensor ground on the box that it would help with noise

Quote from: Jordan Innovations on February 24, 2015, 02:12:30 PM

Generally the wheelspeed sensors aren't great places to pull speed from - the output is very low voltage, very fast, has to travel a hellishly long distance in the car, usually along with high-amp wires (battery, fuel pump, etc), and needs some filtering to be accurate or consistent.  The Dakota Digital boxes should have settings to bring the speed down enough, but I don't know if the output will be what you're used to seeing on a speedo.

My recommendation would be a mag sensor that reads the driveshaft nuts where they enter the diff - high-res, better speed (~16 pulses per wheel rev, vs 40), and less noise.

Title: Re: abs used to run speedometer
Post by: stbrn19 on March 16, 2015, 02:52:18 AM

Any progress with this project?