Injector Pressure

[listeroil]

For the last 5 months 12 hours a day I have been running a genuine 8/1 engined 4.5 kw Start O Matic on unheated WVO. No dual fuel just the clear runny stuff from the top of the barrel filtered to 5 microns. I have not had to pull the head off yet. It starts ok but I have the benefit of electric start.

I have just had 2 injectors serviced and according to my Lister manual the pressure should be set at.

1323 psi for the 6/1  8/1 and 12/2 engines at 20 deg BTDC injection setting.
 
2205 psi for the 16/2 engine at 26 deg BTDC injection setting.

This got me thinking and asking questions off the man who was servicing my injectors. Why is the injector set higher for a 16/2 engine when a 16/2 is basically a twin cylinder version of the 8/1 engine they both run at the same speed 850 rpm. He couldn't tell me why but he did tell me that the higher pressure setting was why the timing had been advanced and that the actual injection point when the injector injects into the cylinder would be the same. Because of the increased pressure the pump had to start pumping earlier for injection to occur at the same point. In fact he said the actual timing occurred even later because the setting is for spill timing not when it actually injects.

I got him to set one injector to 1323 psi and the other to 2205 psi. My plan is to try the 2205 psi injector in my 8/1 engine with the timing set to 26 BTDC. I reckon this could be a good improvement for running on WVO. Higher pressure coming out of the injector sounds good to me. I don't intend to do this job immediately but will do when it gets a bit warmer.

Anybody else got any comments.

Mick

[Oilengines]

The 8/1 pressure should be the higher figure, NOT the lower one for the 5/1 etc.

There was some confusion in the injector manufacturer's data for the 8/1 engine, which a lot of injection company listings just carried over from the 6/1, but in fact there is a higher pressure setting, part of the process which allowed the cold start change-over device to be done away with.

Pare

[listerdiesel]

I checked the figures that Oilengines quoted, and there does seem to be an anomaly with the figures.

The 8/1, 16/2 and VA should all carry the same injection pressure (as they all use the same pump and injector) and nominally all produce the same HP, but on Lister Drg No: Inf Sheet 361 from the 1990's, the 8/1 is shown as the lower figure of 90 atm, while the others have 150 atm.

I'll see if there is any reason for that, it is possible that something changed in the pump and delivery valve, but to get 16hp out of a twin, implies 8hp from the single.....

Peter

[Ian]

Are there any significant downsides to increasing injection pop pressure ?

Regards,
Ian

[listeroil]