Yellow Renault 5 TX Crank Sensor Lead

[malcolm]

@mr-reno-139 or anyone else with a good memory -

Someone mentioned that the crank sensors were often replaced when unleaded petrol came into use, and the new sensor had a yellow lead and retarded the ignition.

Now my Renault 5 TX has a yellow lead and has the symptoms of overly retarded ignition - it's not quite as quick as it should be and has a slightly boomy exhaust noise both on part and full throttle. I'm wondering if it might have been retarded from the factory setting.

I'm planning to mess around a bit but wanted to check out if the yellow lead on the crank sensor has any significance.

 

[mr-reno-139]

Original sensor would of been black and sat in middle of fixing point
Yellow was replacement factory part to shift timing 4 degrees retarded and sensor moulded different place
Timing control by renix unit which hopefully correct one for car
It is possible to drill plastic moulded sensor through small holes and then slide across to another position and glue elsewhere after road test

 

[malcolm]

Thanks, good to know the yellow lead isn't a red herring.

I think it should feel a lot better with another 4 degrees advance. I'll have a fiddle with the sensor. I think the Renix is original.

 

[mr-reno-139]

http://www.registrostoricoitalianor5turbo.it/nuova_pagina_65.htm
This list renix as 031

 

[malcolm]

Thanks Paul, you are a genius! After carefully drilling out the holes (in a pillar drill with a limiter to stop drilling right through the sensor), the plastic body could be tapped along the mounting with a hammer. It is a tight fit so probably won't need glue. Before and after photos attached.

What a transformation! The engine has much more power, is more responsive, smoother, less boomy, and it is fun now! I've been driving around much too quickly this afternoon. It might well take one or two more degrees of advance as there are no ill effects and there is still a very slight boom. The Renix is the 031 - the curve seems to be a good match for the engine.

 

[mr-reno-139]

Think the yellow lead idea was a precaution taken by renault and a good will gesture as st the time it was a free modification carried out by main dealers

 

[malcolm]

Retarding the ignition would reduce cylinder temperatures which would be safer for valve seat recession. I guess nobody at the time really knew how unleaded petrol would work out in every single model, and you wouldn't expect manufactures to do all the testing again on cars they didn't make any more.

Retarding ignition also increases exhaust temperatures which I think is what caused the boom - the wavelength of sounds increases with temperature so you need a longer silencer to take out the low frequencies. The length of silencer in the Mk1 R5 is constrained by the space between the axle and bumper and is too short to start with.

 

[mr-reno-139]

Ha ha i am a genius
High praise indeed from the boss
My likes count is going up again I see
We are all still learning me included

 

[malcolm]

4 degrees is as far as it would go without the sensor hitting the edge of the hole in the bell housing. Boo hiss -I wanted to try another couple of degrees. I might file the hole out a bit when I fit the higher ratio gearbox.