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Do we need speed input - Manual


BeerTurbo

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Howdy 

Ive recently changed my ba+t from a t5z with a t5 rear housing and speedo drive to a t56 setup. The t56 does not have a speedo drive output.

the chassis is the base model, so it has no ABS or Wheel speed sensors..so this leaves me without speed input.

will the ECU care? if it does, what can i change to make it happy?

its not a road car so i cant road test it first and id rather not rock up to the track to find out ive got a limp mode due to speed source.

seciondarly, the speedo drive has a three wire plug...can i install a 2 pin wheel speed sensor and then wire it through this gearbox input. to get something ?

 

cheers

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Yes you need a wheel speed input for things to function properly. Your best option would be to add a speed sensor to the tailshaft, lots of people do this in the conversion world but it is an added cost.

You can also tune out the wheel speed input but I can't tell you what is required, there are lots of limp modes that kick in, some only occur 10-15 minutes after starting the car. Quite a few of the conversion guys fix this but I can't share what they do obviously as its their bread and butter. You could try Brett Hogno here, he might be able to assist.

https://www.facebook.com/Custom-Machine-Works-856789001022313/

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2 hours ago, Roland@pcmtec said:

Yes you need a wheel speed input for things to function properly. Your best option would be to add a speed sensor to the tailshaft, lots of people do this in the conversion world but it is an added cost.

You can also tune out the wheel speed input but I can't tell you what is required, there are lots of limp modes that kick in, some only occur 10-15 minutes after starting the car. Quite a few of the conversion guys fix this but I can't share what they do obviously as its their bread and butter. You could try Brett Hogno here, he might be able to assist.

https://www.facebook.com/Custom-Machine-Works-856789001022313/

do you know if the two speed sensor types output the same type of output? voltage or frequencies?

i was hoping i could just connect one of the wheel speed sensors, inline with a jaycar speed converter back into the std loom and adjust till vaguely accurate.

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1 hour ago, BeerTurbo said:

do you know if the two speed sensor types output the same type of output? voltage or frequencies?

i was hoping i could just connect one of the wheel speed sensors, inline with a jaycar speed converter back into the std loom and adjust till vaguely accurate.

You can just change the pulse count scalar in the editor to suit the new sensor. As long as it generates a square wave of some form with the same voltage it should work, it is a very primitive frequency counter, nothing special. I think a lot of people use a VT commodore hall affect sensor from memory but the ABS wheel sensor would also work, you should be able to piggy back off this. If the car doesn't have ABS I didn't think there would be any wheel speed sensors though? Where are they being wired to currently?

image.png.8d5601974818b82da3b397af4bfb0a72.png

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cheers, 

the front has the ABS rings and mounts - possibly because i replaced the hubs with new ones and the arms , so there is a level of convenience to use them now.

I'm finding out the abs sensors output is not linear square wave 5v output like the original sensor,  so ill need to look for an alternative option or converter to boost the signal from them.

the tail-shaft mounts look good, but i have the turbo diff flange that the premade kit wont bolt to.

 

 

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  • 2 weeks later...

I ended up solving this, but not myself...

I spoke with ShiftKitsAus about there tail-shaft sensor, but he said he could knock me up a custom converter to use the AC style output from ABS sensor to DC square-wave input the Barra ecu required.

He knocked this up with a divisor of 4, as the abs ring had 50 teeth...he said this will give me close to std output.

This is all working , but i cant test gps to output speed reading as my yards not that big ahahaha

This weekend on the track ill be able to see how accurate it is, if its out ill be able to use AUF0393 to fine tune it.

cheers

 

 

 

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  • 5 months later...

the ecu will actually accept a vr style sine wave input from a wheel speed sensor on b7, you just change the pulse/rev to suit the different tone wheel. 

some abs systems will throw a code and disable when piggybacking off an existing sensor which is something to keep in mind. 

Edited by misk
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