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R_SAN_NI
11-26-2006, 05:23 PM
I was looking through the forums for solutions to the S15 speed signal that a few people have already dealt with. I found alot of great info, but because I am kind of a retard when it comes to electronics talk, I got lost in some of it (probably most of it).

I am putting an RB26 into an S15 as soon as I get back from Iraq and buy the car. Anyways, as I understand the diff sensor puts out a voltage signal to the speedo which feeds into the ABS and the ABS feeds back into the speedo.

My problem comes in that I intend to use an aftermarket speed gauge (not autometer) that reads a digital signal with 1,274 - 16 thousand something pulses/km (and is suitable for a 2 pulse - 26 pulse system). I have no idea what that actually means. I am wondering if the sensor produces that signal which would enable me to wire it into the speed sensor interface on the gauge and be displayed correctly. OR would I have to somehow convert this signal to something else to have it read correctly??? (i.e. dakota digital signal converter) I have been searching and googling my A** off and have a basic understanding of how it all works but am still lacking a bit. The FSM is a little vague but can someone tell me if I am on the right track??

Thanks in advance
Brian

thedman
11-26-2006, 11:32 PM
I was looking through the forums for solutions to the S15 speed signal that a few people have already dealt with. I found alot of great info, but because I am kind of a retard when it comes to electronics talk, I got lost in some of it (probably most of it).

I am putting an RB26 into an S15 as soon as I get back from Iraq and buy the car. Anyways, as I understand the diff sensor puts out a voltage signal to the speedo which feeds into the ABS and the ABS feeds back into the speedo.

My problem comes in that I intend to use an aftermarket speed gauge (not autometer) that reads a digital signal with 1,274 - 16 thousand something pulses/km (and is suitable for a 2 pulse - 26 pulse system). I have no idea what that actually means. I am wondering if the sensor produces that signal which would enable me to wire it into the speed sensor interface on the gauge and be displayed correctly. OR would I have to somehow convert this signal to something else to have it read correctly??? (i.e. dakota digital signal converter) I have been searching and googling my A** off and have a basic understanding of how it all works but am still lacking a bit. The FSM is a little vague but can someone tell me if I am on the right track??

Thanks in advance
Brian

From my post which can be found in "Best of 240SX":

"The S15 VSS located in the diff sends an AC signal (400Hz, at 30km/h, equivalent to 533Hz at 40 km/h = 25mph) to the ABS C/U [ABS Computer]pins 8,20 (ref. pg BR-39 in FSM p/n A008022). [BTW- One Hz = One cycle/sec] The ABS C/U conditions the signal into a 0-10v square wave at that same frequency and this goes out on pin 14 to gauge cluster pin 14 (ref. pg EL-24, EL-26 in FSM). If you want to run an S15 gauge cluster, you need to mimic this signal, or better yet, multiply the frequency by 0.62 to get the kph speedo to read in mph! The gauge cluster converts ABS C/U signal to a 0-5v square wave with a frequency of 14 Hz at 40km/h and sends it from pin 31 to ECM pin 32(ref. pg EC-27). I believe this signal is also referred to as 2-pulse."

Basically what this means is that the VSS in the diff puts out an analog voltage that continuously oscillates through one positive and negative voltage cycle 400 times per second at 30 km/h. At 30 km/h it takes 120 sec to go 1 km, so (400cycles/sec)x(120sec/km) = 48,000 cycles/km. If your speedo can handle an analog AC signal, then it should work since the frequency is within the range you state. If it requires a square wave input, then you'll need to either maintain the ABS Control Unit, and take the VSS signal from the pins I reference above, or try a converter such as the Dakota Digital device. You need to consult with the speedo vendor, and perhaps even read this post to the tech, who should then be able to advise you if their speedo is compatible.
-Ted

R_SAN_NI
11-27-2006, 09:13 AM
From my post which can be found in "Best of 240SX":

"The S15 VSS located in the diff sends an AC signal (400Hz, at 30km/h, equivalent to 533Hz at 40 km/h = 25mph) to the ABS C/U [ABS Computer]pins 8,20 (ref. pg BR-39 in FSM p/n A008022). [BTW- One Hz = One cycle/sec] The ABS C/U conditions the signal into a 0-10v square wave at that same frequency and this goes out on pin 14 to gauge cluster pin 14 (ref. pg EL-24, EL-26 in FSM). If you want to run an S15 gauge cluster, you need to mimic this signal, or better yet, multiply the frequency by 0.62 to get the kph speedo to read in mph! The gauge cluster converts ABS C/U signal to a 0-5v square wave with a frequency of 14 Hz at 40km/h and sends it from pin 31 to ECM pin 32(ref. pg EC-27). I believe this signal is also referred to as 2-pulse."

Basically what this means is that the VSS in the diff puts out an analog voltage that continuously oscillates through one positive and negative voltage cycle 400 times per second at 30 km/h. At 30 km/h it takes 120 sec to go 1 km, so (400cycles/sec)x(120sec/km) = 48,000 cycles/km. If your speedo can handle an analog AC signal, then it should work since the frequency is within the range you state. If it requires a square wave input, then you'll need to either maintain the ABS Control Unit, and take the VSS signal from the pins I reference above, or try a converter such as the Dakota Digital device. You need to consult with the speedo vendor, and perhaps even read this post to the tech, who should then be able to advise you if their speedo is compatible.
-Ted

Thanks alot man, I read your post and it was the one that I got lost in as I just didn't understand the difference between different types of signals as in what made it digital or analog. Thanks for clarifying it a bit for me. I have the S15 FSM right now so I saved your post to read it along with going through the FSM so I have a better understanding of what is going on. it is too bad the installation Manual for the speedo I want to use is in Japanese so it looks like I will be spending sometime on altavista to make sure I know what I am asking when I ask it.

Brian

Kingtal0n
11-27-2006, 10:41 AM
I wouldnt bother screwing with all that crap, honestly.

If your putting an RB26 into the S15, then you should already know you cant (easilly) run the RB26 trans. I bet you will use an RB25 Trans.

The RB25 trans has a speed sensor in it. Your autometer gauge configures dynamically, so this speed sensor will work fine for the job, and you can forget about the ABS if you wanted to, or not worry about the sine wave coming off the differential.

R_SAN_NI
11-27-2006, 02:23 PM
I wouldnt bother screwing with all that crap, honestly.

If your putting an RB26 into the S15, then you should already know you cant (easilly) run the RB26 trans. I bet you will use an RB25 Trans.

The RB25 trans has a speed sensor in it. Your autometer gauge configures dynamically, so this speed sensor will work fine for the job, and you can forget about the ABS if you wanted to, or not worry about the sine wave coming off the differential.

I know the RB26 tranny is not the easy option but it might be the best option I have f I find the same deals I did before I left for Iraq. I do not want to use a stock RB25DET tranny for my application as I don't feel it would be the right choice. That leaves me with OS gear kit for it or PPG dog kit for it. If the pennies are spent right, I can buy a rebuilt trust sequential or even a used Holinger for about the same price when it is all added up. Modifying a transfer case and widening a tranny tunnel a little would be worth it to save a couple grand.

The Rb25 Tranny has the speed sensor in it but I do not intend to use an autometer speedo. I figure it best to learn something so I can use what I want and keep other options open as well.

xsparc
02-06-2008, 02:05 PM
i got a s13 to s15 speed sig converter made if you need any more details on this.