Thread: BRC IMPCO Install on 96 GEMS P38

Originally Posted by Scouse

Sorry to butt in on your thread Steve but what sort of difference is there in having the injectors a fair distance from the original petrol injectors?


It's just that I recently helped work on a GEMS engine with the LPG injectors right near the petrol ones & now I'm helping (sort of) with Thor V8.
The guy with the Thor has fitted the LPG injectors just below the upper/lower manifold joint &, IMO, it seems to defeat the point of having sequential injection when they're so far away.

Having spent numerous hours attempting to fit injected LPG to a single plane manifold on a P76 engine, I can say that if the LPG is injected too close to the top of the runners you will lose mixture to adjacent cylinders with intake resonance. I fitted 100mm nylon extension tubes to the nozzles to try and keep the gas in the short runners, that was reasonably successful. If I had the job again I'd fit a proper injection manifold with spacer plates.

In an injection manifold the runners are clearly long enough to contain the injected gas if the nozzles are somewhere near the petrol injectors. Move away from the head and the possibility rises that some gas is stolen by adjacent cylinders. Based on my limited experience (compared to a fleet lpg installer say) nozzles drilled up to around 1/3 of the total length of the runners away from the inlet valve are OK. A Mitsubishi 380 BRC kit I purchased second hand had the nozzles just above the manifold upper/lower join and probably ran perfectly that way.

Oh and the placement of liquid injectors (petrol or LPG) is quite critical to ensure atomisation, evaporation etc. whereas vapour injection is much less critical as gas and air mix quite quickly and don't suffer from wall sticking or any problems from droplet size.

Just found this picture on my camera showing where I finally ended up plumbing the return line from the converter. For some reason the engine thermostat would fully close the heater circuit and cause the converter to ice up. Hasn't had a problem since this modification. (Oh and before anyone wants to comment on what looks like a leak to the passenger side of the water pump, yes, I spilt some coolant while playing with the hoses).



Access to the w/pump inlet for drilling and tapping a 1/8 bsp nipple is easy with either the fan or the alternator removed.