Mi16 pinking

[fergus]

Hi.

Got an Mi16 engined 205, which pinks heavily when the engine is under load. I've replaced the HT leads with Bosch OE items, but this hasn't helped.

The car is running standard distributorless ignition. It starts easily and idles evenly, so I'm guessing the crank sensor is OK. Any avenues to pursue would be great.

I am thinking of going to a mapped ignition and would welcome any suggestions for a suitable system. Omex seem to be the system of choice for the mi16 engine.

thanks

[Marlon]

I'm no expert (but I did used to have an Mi16 - great car) there's an interesting thread here;

www.pistonheads.com/gassing/topic.asp?t=156328&f=13&h=0&hw=pinking

Presumably the ECU is for the Mi16 engine (the bleedin' obvious), the injectors are OK and you're not running it on potato water, so could it be that intake airflow is the problem?

[dougc]

Practical Performance Car has got a big article on the Mi16 this month if you can find a copy, could be useful?

[annodomini2]

Is the engine designed to run on 95octane unleaded?

[deltafox]

Has the head been skimmed, thereby raising the CR?

[fergus]

Cheers guys

The engine is running the 16v ECU (not the 8v one off the 1.9 gti). The head has not been skimmed and the gasket is standard height, so the CR is fairly standard. The engine has just been built so there's no carbon buildup, etc.

I'm running the car on 95 octane, although I may try optimax to see if this cures the problem. On this note, I was wondering if anyone has had any problems with the knock sensors on these engines, thereby not allowing the ECU to retard the ignition a tad?

The car 'blips' well and has good throttle response, so I'm guesing the AFM is functioning correctly.

I may replace the knock sensor, then if that doesn't work, I think I'm moving over to a mapped ignition as there's too much p1ssing about involved with trying to isolate ECU problems with an ECU which isn't too great at fault logging (i.e. Bosch Motronic).

haven't checked the injectors for flow rate or spray pattern yet. Surely a problem with these would mean that the pick up would be poor and the idle rough as the atomisation would be poor at low inlet airflow speeds?

cheers chaps.

>> Edited by fergus on Wednesday 18th May 14:23

[Marlon]

Is the pinking only at high RPM, in a certain band, or everywhere?

[fergus]

The pinking only occurs when the engine is under load. For example, I can cruise on the m/way at 3500 rpm in 5th, then put my foot down slightly, which results in that familiar sound!!