General How are people feeding VSS to aftermarket ECUs in a 1g car?

[bling5tatus]

Is there a good solution for adding an aftermarket VSS to a 1g?

I tried searching various threads and all I could figure out is that it's a signal come from the cluster. Pin #18 appears to be the reed switch/vss from the cluster.

Anyone that has logged this signal before knows it garbage, so how is it possible to get a good clean/accurate VSS (possibly skipping all the stock stuff)?

GPS units - I would imagine the delay in their response would not be great for accuracy.

Can't find a TerraTrip T007 to save my life.

1G ABS sensor maybe?

Do people running standalone ecu's just not care about VSS or what?

 

[Spleen8urLSX]

I know of a few people using 2g speed sensors in 1g’s on Link g4+, I’m sure that applies to others but someone with some hands on may chime in.

 

[biglady112]

Is there a good solution for adding an aftermarket VSS to a 1g?

I tried searching various threads and all I could figure out is that it's a signal come from the cluster. Pin #18 appears to be the reed switch/vss from the cluster.

Anyone that has logged this signal before knows it garbage, so how is it possible to get a good clean/accurate VSS (possibly skipping all the stock stuff)?

GPS units - I would imagine the delay in their response would not be great for accuracy.

Can't find a TerraTrip T007 to save my life.

1G ABS sensor maybe?

Do people running standalone ecu's just not care about VSS or what?

The answer is easy. Install a 2G sensor and wire your three wires in. That is how we did it with FuelTech.

 

[DSMPT]

Can't find a TerraTrip T007 to save my life.

1G VSS signal is kinda erratic. Doesn't work well with some standalone or device.
You can probably still find an alternative of the TerraTrip T007 if you want to keep using the 1g factory cable-driven speedometer. Search with "Japanese gear box probe" or so.
If you don't care about the factory speedometer, then there are several options like 2g, 3000gt etc.

 

[bastarddsm]

The reed switch in the cluster works great for me. Super stable. Resolution at low speeds isn't super. The crappy logged signal is just because the stock ECU doesn't read that with an interrupt so it's not a good measure.

 

[jdxnc]

2g VSS works perfect, few of my friends and I as well use it.

 

[bling5tatus]

the reed switch in the cluster works great for me. Super stable. Resolution at low speeds isn't super. The crapy logged signal is just because the stock ecu doesn't read that with an interrupt so it's not a good meausre.

Thank you everyone for the responses.

Bastard, I think what you're saying here makes the most sense. I'll just take pin #18 and run that to the EMS for VSS. That will retain my cable driven speedo and allow me to still get a VSS signal. I don't know why I didn't consider that the speed signal is choppy on the OEM ECU because it's not interrupt driven.

NOT Interrupt driven means that the ECU can NOT stop other processes and ask for a VSS reading at any time in the control loop, right? The choppy signal on the logger comes from the ECU just being dumped that data on a timed interval?

What about the ABS sensors on a car that is equipped? Are those reliable for a VSS output?

I also like the option of a 2g sensor if I'm going to replace the stock cluster.

 

[biglady112]

Thank you everyone for the responses.

Bastard, I think what you're saying here makes the most sense. I'll just take pin #18 and run that to the ems for VSS. That will retain my cable driven speedo and allow me to still get a VSS signal. I don't know why I didn't consider that the speed signal is choppy on the OEM ecu because it's not interrupt driven.

NOT Interrupt driven means that the ecu can NOT stop other processes and ask for a VSS reading at any time in the control loop, right? The choppy signal on the logger comes from the ecu just being dumped that data on a timed interval?

What about the ABS sensors on a car that is equipped? Are those reliable for a VSS output?

I also like the option of a 2g sensor if I'm going to replace the stock cluster.

Depending on the ECU and sensor, you can indeed run an ABS ring. I run a FuelTech on my race car as well. The front of my car is a Chevy S10. I just both front and rear wheel speed for traction control. I use the front 52 tooth S10 ABS sensor and it is a fantastic signal. It is a 2 wire VR sensor so I have to run a small VR to Hall converter.

On the rear I use nuts welded to the inside of my rotor. It is only 16 teeth. And being home made it is a choppier signal. I have to smooth it out in the software. I don’t use smoothing for the 52 tooth ABS sensor though.

 

[DSMPT]

Thank you everyone for the responses.

Bastard, I think what you're saying here makes the most sense. I'll just take pin #18 and run that to the EMS for VSS. That will retain my cable driven speedo and allow me to still get a VSS signal. I don't know why I didn't consider that the speed signal is choppy on the OEM ECU because it's not interrupt driven.

NOT Interrupt driven means that the ECU can NOT stop other processes and ask for a VSS reading at any time in the control loop, right? The choppy signal on the logger comes from the ECU just being dumped that data on a timed interval?

What about the ABS sensors on a car that is equipped? Are those reliable for a VSS output?

I also like the option of a 2g sensor if I'm going to replace the stock cluster.

I think you were not sure what you were asking.
That's what you have to do even with the terra trip t007 style VSS that you remove the pin 18 and connect to the terra trip t007 and leave the 1g VSS on the transmission. (If you still want to use the pin 18 for a VSS like the stock) It's just the terra trip style VSS would allow you to keep the factory speedometer, you can just sandwich between the speedo cable and the VSS.
It doesn't matter what VSS you use as long as your ECU works with it. But if you would like to keep the factory cable-driven speedometer working, you can't go with some sensors that requires to replace the 1g VSS like the 2g's.

 

[bling5tatus]

I think you were not sure what you were asking.
That's what you have to do even with the terra trip t007 style VSS that you remove the pin 18 and connect to the terra trip t007 and leave the 1g VSS on the transmission. (If you still want to use the pin 18 for a VSS like the stock) It's just the terra trip style VSS would allow you to keep the factory speedometer, you can just sandwich between the speedo cable and the VSS.
It doesn't matter what VSS you use as long as your ECU works with it. But if you would like to keep the factory cable-driven speedometer working, you can't go with some sensors that requires to replace the 1g VSS like the 2g's.

Thank you for the thorough explanation but I wasn't confused about this much. My intent w/ a t007 was going to be to simply run that signal to the flying lead wire that is coming off the harness on my ECU marked "VSS".

I just needed somewhere to jack that digital signal from. It was either going to come from a:

* gearbox probe inline w/ my speedo cable on the transmission and retain my factory cluster/speedo
* 2g sensor and delete factory speedo (requiring me to also buy a digital dash)
* OEM pin #18 (on the cluster side -NOT- ECU side)
* ABS sensor completely skipping any modification to the OEM VSS stuff.

 

[DSMPT]

There is no difference between the Terra trip T007 and other VS Sensors. It's just the Terra trip T007 style allows you to keep the stock speedometer. Technically what you would need to do is the same between all the sensors. I still don't know why you need to do this, if you wan't to keep the stock speedometer or not and what ECU and harness you have etc. So technically what I am telling you is just the general basic thing. But did you try the factory 1g signal already? As far as I know, the 1g signal from the reed switch would probably work unless your ECU is AEM EMS series 2 or EMS-4. Those ECUs are the ones that possibly don't work well with the 1g VSS signal.

* oem pin #18 (on the cluster side -NOT- ecu side)

It's the same. That goes to the ECU #18.

 

[bling5tatus]

What is the same? The way I said it was to signify that it was the cluster sending a signal to the ecu on pin 18 and not the ecu sending a signal anywhere..... for others that would be reading that maybe didn't understand how it worked.

I understand what a terratrip probe is.... and why you'd want to use one. Maybe someone here knew where you could find them still. It was a stretch, but it's ok, I'm not bent on any certain solution.

The things I've gleaned from this thread are that a 2g VSS is a good replacement that provides a digital signal at the expense of being able to drive your mechanical cluster and that the low sample rate of the signal on stock ecu logs is because it's not gathered using an interrupt.... as opposed to it being a problem with a "choppy sensor".

Reasons to have VSS on an ecu:

* Launch control
* Boost by gear
* Traction control

etc.... my reason for "why" is the same reason anyone wanting a VSS on their aftermarket ecu is (I would imagine).

 

[DSMPT]

What is the same? The way I said it was to signify that it was the cluster sending a signal to the ecu on pin 18 and not the ecu sending a signal anywhere..... for others that would be reading that maybe didn't understand how it worked.

Yeah that's why I said the same. And it seems you missed I said "that goes to ECU", so no need to tell me how the 1g VSS work. I said it's the same which side you connect VSS signal to the wire on the cluster side or ECU side as long as if you cut the signal from the reed switch. It's on the same wire. Hope you get this point.

Reasons to have VSS on an ecu:

* Launch control
* Boost by gear
* Traction control

etc.... my reason for "why" is the same reason anyone wanting a VSS on their aftermarket ecu is (I would imagine).

I think you make yourself confused. That is actually I am telling you. And yeah that's the common reason why people replace the VSS. But where did you mention that in this post? How can I know that's also your reason? You don't even specify what ECU. That's why I said I think you were not sure what you were asking. Because the answer for your question would depend what ECU you have, if you want to keep the factory speedo or not etc etc. But you didn't specify. That's why I was telling you the common things.
And I am the person who always recommend the terra trip t007 to someone who has choppy signal on their 1g and who wants to keep the factory speedometer in this forum or facebook groups since AEM forum has been gone. You probably got the part number from one of my posts in somewhere. Because people who use AEM EMS series 2 have an issue with the 1g VSS signal from reed switch. It's a known issue.

 

[bling5tatus]

Why are you explaining yourself?

 

[DSMPT]

If you ask something here, specify about your case/question more and respond if someone who is trying to help you ask something. That is to help you. Somehow you don't wanna mention about what ECU you have. It seems finally you don't understand what I was asking you or just want to hear only something you are expecting. Please learn how to use the forum before posting. This is not a facebook private group.

 

[bastarddsm]

Interrupt means exactly that. They basically are for time critical stuff that needs to happen within a couple clock cycles or so. For example a very basic explanation of like the CAS interrupt, When the TDC signal goes high or low the ECU stops what it's doing and runs to the TDC interrupt handler. The this takes a timestamp, and goes RPM = (new time - old time)/crank angle moved. It also sets crank angle to 0, 90, 180, ect. It finishes that and then goes back to where it left off on the main loop. There is another one like this for the CAM, and MAF. Then there is like a timer overflow interrupt that does injector and coil energizing. Most MCU are limited in the number of interrupts they have, so you needed to prioritize.

The VSS is basically for the ECU to have some idea what's happening - the exact speed isn't critical so it doesn't need the precision of a interrupt. So it just samples the digital input every loop through the main loop ~800hz. basically it's like VSS ~ number of loops per edge/800. The reed sensor only changes state like 1 time every 5 rev's of the tire, so even at high speed several loops go by per edge, and it basically gets the job done. The problem is that at high processor loads the main loop can slow down, but not too much. Watch dog timer. Anyway that skews accuracy, and then at high speed when there is only a a few loops per edge so a change of 1 edge is a lot of speed.

On a real ECU with modern hardware there are plenty of interrupts, and or a much faster handler for sampling digital inputs. The only real issue is that at low speeds resolution is poor because the ECU will have a hard time playing is it 0 or not since time between edges will be so much. So it can be troublesome if you try to use speed only for turning off launch control.