TVR Speedo Interface Box wiring

[Kensaunders]

Hello all

Anyone able to confirm the following wiring setup on the Speedo interface black / sometimes green box behind the dash?

5 wires:
1. Blue/Yellow = SIGNAL. (to speedo) (True Road Speed?)
2. Green = LIVE POWER. (to speedo) (from Ignition Live)
3. Black = Negative EARTH. (to speedo)
4. Grey = SENDER – to the speedo sensor
5. Green/Yellow = ECU – direct to ECU Pin No.6 – Note pick up for this is PIN 2 in white/clear 8 flat pin plug TVR engine loom.

and also how those wires fit into the connector that attaches into the box.. I think it is this:

starting at the top row on the connector and working left to right on wiring:
1st row: Black, Blue/Yellow, Grey
2nd Row: Green/Yellow, Blank, Green

any thoughts, comments, photos appreciated..

thanks

Ken

[SILICONEKID345HP]

Kensaunders said:

Hello all

Anyone able to confirm the following wiring setup on the Speedo interface black / sometimes green box behind the dash?

5 wires:
1. Blue/Yellow = SIGNAL. (to speedo) (True Road Speed?)
2. Green = LIVE POWER. (to speedo) (from Ignition Live)
3. Black = Negative EARTH. (to speedo)
4. Grey = SENDER – to the speedo sensor
5. Green/Yellow = ECU – direct to ECU Pin No.6 – Note pick up for this is PIN 2 in white/clear 8 flat pin plug TVR engine loom.

and also how those wires fit into the connector that attaches into the box.. I think it is this:

starting at the top row on the connector and working left to right on wiring:
1st row: Black, Blue/Yellow, Grey
2nd Row: Green/Yellow, Blank, Green

any thoughts, comments, photos appreciated..

thanks

That box can be ripped out if you have an after market ECU

Ken

[Hoofa]

Oh no you cannot be rip it out !!! It's a speedo not a Rev counter

[Kensaunders]

if I don't have it wired in the engine stalls..hence need to wire it in correctly unless there is a work around without changing the normal ecu setup...

[SILICONEKID345HP]

[quote=Hoofa]Oh no you cannot be rip it out !!! It's a speedo not a Rev counter [/quote

I thought the box was for the 14cux ! i spoke to Caerbount they said there is no box needed for after market ECU`s

[Kensaunders]

yes this is to connect into the ECU - probably should have been clearer in my wording - from what i understand the box, made by TVR is quite crude but effective, it gives a false max speed reading to the ECU to allow you to go faster than i think 90mph which was the original limit on the LR ECU to fit with LR tyres which had a speed rating maximum. it also I think gives some sort of reaading to the stepper motor to help or may be not on the idle.. certainily without it plugged in my engine is stalling and after an overall of electrics I'm trying to sort out how it is plumbed in correctly.. if anyone has their dash off and can post a pic of the wires in situ that would help confirm the positioning..

[ianwayne]

I don't believe it has anything to do with speed limiting. It provides a signal to the ECU that you are moving so that the idle speed is elevated. The speed isn't really relevant, so once you're doing a few mph, the ECU gets a signal.

Fuller thread here:

http://www.pistonheads.com/gassing/topic.asp?t=128...

[spend]

Kensaunders said:

yes this is to connect into the ECU - probably should have been clearer in my wording - from what i understand the box, made by TVR is quite crude but effective, it gives a false max speed reading to the ECU to allow you to go faster than i think 90mph which was the original limit on the LR ECU to fit with LR tyres which had a speed rating maximum. it also I think gives some sort of reaading to the stepper motor to help or may be not on the idle.. certainily without it plugged in my engine is stalling and after an overall of electrics I'm trying to sort out how it is plumbed in correctly.. if anyone has their dash off and can post a pic of the wires in situ that would help confirm the positioning..

Max speed limit is removed in the ECU, speed feed to ecu is just for idle ~ calibration is woolly to say the least

[SILICONEKID345HP]

spend said:

Max speed limit is removed in the ECU, speed feed to ecu is just for idle ~ calibration is woolly to say the least

Would there be any benefits when bypass it when on an after market ECU . The speedometer might be more accurate.

[Kensaunders]

Ok so really now needing to confirm the wiring on this box - whether the debate is to have it is not I've chosen to keep it on my engine but need help to confirm what the connections are for the wires and where they go to..

[blitzracing]

It appears the units main purpose is to read the variable signal level generated by the speedo transducer, and turn it into some sort of square wave signal the ECU can deal with. There are a pair of inputs from the speed transducer, and a 5 volt supply, plus a fixed pulse signal output to the ECU that the box generates at over 3mph to let the ECU know the car is moving - anything over 3mph generates a fixed pulse train of between 30 and 55mph, so the ECU does not get a true reading- just a stopped or moving signal. This changes the way the ECU uses the stepper motor, by raising the tick over to aid gear changes. If you lift the lid on the unit, you will find 4 wires- red 12 volt supply- black ground-(chassis ground and one side of the speed transducer)- yellow 2nd transducer wire and white fixed output signal output to the ECU. Ive still not worked out how the speedo signal itself is generated, unless the speedo has the required electronics to read the variable signal level from the transducer directly, and the speedo interface box is simply in parallel. You may find if you examine the connections that you simply have a connection bridged on the back of the socket to join the transducer output to the direct speedo input (?)

Edited by blitzracing on Wednesday 15th April 22:08

[SILICONEKID345HP]

blitzracing said:

It appears the units main purpose is to read the variable signal level generated by the speedo transducer, and turn it into some sort of square wave signal the ECU can deal with. There are a pair of inputs from the speed transducer, and a 5 volt supply, plus a fixed pulse signal output to the ECU that the box generates at over 3mph to let the ECU know the car is moving - anything over 3mph generates a fixed pulse train of between 30 and 55mph, so the ECU does not get a true reading- just a stopped or moving signal. This changes the way the ECU uses the stepper motor, by raising the tick over to aid gear changes. If you lift the lid on the unit, you will find 4 wires- red 12 volt supply- black ground-(chassis ground and one side of the speed transducer)- yellow 2nd transducer wire and white fixed output signal output to the ECU. Ive still not worked out how the speedo signal itself is generated, unless the speedo has the required electronics to read the variable signal level from the transducer directly, and the speedo interface box is simply in parallel.

I spoke to Caerbont , he said the speedometer can work straight from the transducer ,no box needed .

[blitzracing]

That makes a lot of sense then- so the box should be renamed to "ECU speed recalibration" then and be done with it.