Change of cam timing = need a remap?

[Rob Thomson]

Long story which I'll try to keep short...

3.5 years ago I bought my 172 Cup. It needed a cambelt change so took it to a Renault Sport specialist to do that and to re-re-map the engine because the existing re-map was awful (lumpy, flat-spots everywhere, and all the throttle action in the top 10mm of pedal travel). Car came back transformed, much nicer to drive and much quicker with reports that the cam timing had been a mile out. Since then I've done loads of hillclimbing and sprinting and the car seems quick compared with other 172/182s.

Over the last couple of weeks I've pulled out the engine to do 101 jobs around the front of the car. The cambelt wasn't due for another 18 months but with the engine on the stand it seemed stupid to ignore. I bought the proper tools, read the manual, and got stuck-in. I was surprised to find that the existing timing was a long way out (inlet cam was retarded, probably 5-10 degrees though measurement by eye rather than anything scientific). With the engine on the stand it was fairly easy to get the timing perfect; all tensioned properly and the alignment tools slot in nicely at TDC. I've put the car back together over the weekend and she seems to run better than ever.

However, I'm a bit nervous that the map was optimised for the previous cam timing. My understanding is that normally the engine management runs closed loop so should look after itself, at least to a degree, but at full throttle the engine runs open-loop and an incorrect map may be a more serious concern.

Any views?

Thanks, Rob.

 

[bloke]

Map will be miles out.

 

[Vaughan]

Was it group n timing?

 

[Rob Thomson]

That was my first thought too, but I don't think so. I didn't ask for Gp.N. Both cams were mis-timed but the inlet was retarded rather than advanced which I'd expect for Gp.N.

 

[Rob Thomson]

Next question... any recommendations for a decent remap in the South-West?

 

[robzracing]

It's possible that the timing had slipped since the car was mapped in which case it should be fine now and the fact that the car is running nicely may indicate this. There is a knock sensor on the block which may also help safeguard the engine. BUT, as already said above if you can stretch to it get it checked on some rollers with someone who knows what they're doing. They'll know after 10 minutes if it needs remapping.

 

[Mr Underhill]

Map will be miles out.

I've dropped you a message on Facebook regarding getting mine done Carl a few days ago

 

[Martin_172]

name and shame ??