The V8 Owners Forum -

Guys, just finishing the MG RV8 conversion and need to install a speed sensor for manual box into 14CUX, engine's relatively standard Griffith 4.0[3.9]. Can anyone give best recommendation as to which sensor to use and ideal location? Specifically I'm needing to know how many pulses per second the 14CUX needs to register that the car is still moving [decelerating towards standstill] in order to ensure smooth deceleration when coming to a stop.

Have searched forum but can't find answer. Any/all help greatly received.

Edited to add: I'm running electronic gauges which means the speedo cable drive on the R380 is free. Are there any LT77/R380 driven speed sensor that could run from the speedo drive + converted to the two-wire connection as per TVR/RR?

Do a search on EBay for AMR3386, it is the correct Rover part, should get it for about £40.
I used one of these when I converted to Hotwire injection.

There are different gears on the speedo drive, according to the rear axle ratio.
So you'd need a drive to suit the internal gear in the box. IIRC, there are three for the SD1 alone. So basically you'd need to know exactly which model the gearbox came from.

I don't think you need it to be exactly right for the Hotwire ECU. I believe it only uses it for lifting the idle speed when the car is moving and small details like that.
I am not entirely sure you need it at all?

Chris.

Guys, thanks for your quick replies...but have cracked it. And here's some background info' for those boys and girls who complete future V8 conversions...

My set-up's quite simple TVR 4.0 with some interesting trick bits for extra fun, Smith Classic Flight electronic speedo' & tacho'. I've installed the speedo' sensor 1mm front the front propshaft bolts [position the bolt face so it's flat when rotating past the sensor]; it's a CAI EMP34-1 sensor with standard three wires [sensor pulse o/p, 12v and ground. http://www.caigauge.com/documents/pdfs/ ... it-388.pdf These wires connect to the wiring harness supplied with the speedo'. I've spurred an additional yellow wire from the EMP34-1 o/p wire to pin.6 on the 14CUX. The on/off volt characteristic[ECU requirement] will give the correct i/p to the ECU 0-2V off/10.5-13V on pulse. There are 4no bolts on the propshaft, these will give the correct number of pulses @ circa' 6/second through to 8000/minute for the ECU to register a manual gearbox. Have wired this in this morning.

In addition, I had a real good chat with Mark Adams yesterday. Previously I had thought through changing/upgrading injectors, updating to a Tornado chip and a Bosch AFM...followed by a rolling road set up with Mark later this year. In discussion we covered the need for a speed sensor/is it really necessary? For my set up Mark's answer is yes. And one thing I would not want is the irritation of erratic running when coming to a halt, I always like my cars to run flawlessly.

One added advantage of sharing the speedo' o/p signal is that there's one less component to fail and having a separate road speed sensor can throw up spurious faults that could be attributed elsewhere. I'm aware that many a TVR owner has experience this erratic running and spending many many hours tracking down the fault :. if my sensor fails, the speedo' fails too and combined there's only one component to cause this

The car's due for firing up up very soon. I'll run with the new injectors and the existing 14CUX chip. Complete shakedown and then change chips and AFM prior to the rolling road session. I'll update this which should be end October. Hope this has helped others still using the 14CUX.

Must admit to wondering just why anyone would use such an ancient ECU?

I know, I know...stop embarrassing me Though may plan an upgrade with different engine once I've proven this B. Plus, keep getting urges for a BGT V8 with JE x-over intake & Jenvey throttle bodies...which I know will cost a kings ransom.