3.5V8 - Dual Fuel Timing

garrycool , at the end of the day the optimised advance might gain you say 5% in power , ****all really . The reason Dual fuel setups are crap is the Dynamic compression ratio , unless you can change that from 9:1 to 11:1 (thats the difference in static,overlap will determine final dynamic)then everything else is just a compromise . I build either straight gas engines or staight ULP engines , never dual fuel !!

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Originally Posted by 400HPONGAS

garrycool , at the end of the day the optimised advance might gain you say 5% in power , ****all really . The reason Dual fuel setups are crap is the Dynamic compression ratio , unless you can change that from 9:1 to 11:1 then everything else is just a compromise . I build either straight gas engines or staight ULP engines , never dual fuel !!

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Yep, thats why dizzys suck - they're ok for all out power, tuned for either, but can't do the job properly if you're trying to setup for dual fuel.

I reckon it's worth the few hundred bucks and the mucking around with coilpack ignition + the dyno tuning, you'll get it back in fuel saved in no time.

you have to be committed though... do you really love your rover Gary? Show it you care. You'll both feel all warm and fuzzy after.

Regardless of how many coil packs you put on and how you manage them , they still wont to do as good a job as a proper specced MSD system , especailly for LPG .

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Originally Posted by garrycol

Thanks for that - I was amazed at the 30-50% improvement in fuel consumption from just changing to the GT 40R coil. I was surprised that the bosch dizzy did not have an oil O ring on its main shaft housing like the rover one has - as would have let out oil from the engine - silastic around the top of the clean housing fixed that. I will try about 6 degrees BTDC and see how we go.

I am also surprised at the complete lack of waterproofing on the bosch dizzy - will need to work on that one as the 101 will stop with just a little splash of H2O. The ignition amp seems well protected though.

Oh - and my tacho does not work with the electronic ignition. The needle flops around 1500rpm irrespective of engine speed and when the engine is at constant revs it settles back to indicate 1000rpm. Is there a special way to connect the tach or do I need one for electronic ignitions. I have it currently connected to the coil as per the previous arrangement.

Garry

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The dissy is probably sealed as in the Holden with a gasket under the clamp ring. Silastic will be fine.

I have rally driven P76's through quite deep water in the past, so long as the lead boots are tight and waterproof, the only extra protection needed is to stop water lifting the cap and getting under the edge. I found that a circle of electrical tape around the top of the distributor body helped, just carefully push the cap on over the tape. You might also consider a splash shield to protect the cap from direct impact of a load of water.

Sad to hear the tacho doesn't work here. It may be feasible to fit a series resistor in the tacho wire to reduce the pulse size, although I haven't tried this. The issue is that electronic switching is not quite to zreo volts, unlike points which do so. I have seen older VDO tacho's misbehave on electronic ignitions, I seem to remember some had adjustable triggering on a screw on the back.

Oh and I suggest you ignore anyone trying to make you spend $$$ on dual or otherwise fancy ignition systems. As suggested your gain will be minimal on the low comp engine. Talking efficiency and standard 101 in the same sentence isn't sensible.:)

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Originally Posted by 400HPONGAS

Regardless of how many coil packs you put on and how you manage them , they still wont to do as good a job as a proper specced MSD system , especailly for LPG .

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The coilpacks don't do the magic, Thats done by the little computer that works out the exact spark timing, based on rpm, air flow, intake air temp, engine temp, fuel type, manifold vacuum, throttle posistion..

for an every day engine that needs to run on dual fuel they run rings around a msd dizzy system. Even set for just one type of juice they would poo all over a dizzy. You bag the rover for been old design then bag new tech ecu ignition because old 1920's based crap is better :confused: It doesn't matter how fat a spark the msd spits out - if it's doing it at the wrong time whats the point? BTW stock coilpack pack a decent punch./