Thread: 3.5V8 - Dual Fuel Timing

Having a fair bit of experience of dual fuel I suggest you try the static timing on 6-10 degrees. I imagine your driving would not be often at the high end of the RPM range. The use of premium petrol should be able to cope with this amount of advance without problems, especially if you are running 8.13:1 compression. If there is uneven (jerky) running at light throttle you may be able to run without vacuum advance. As far as switching to petrol for hills work is concerned, I don't think you need to do this as the Rover V8 has always been good on gas, I have not seen one with a burnt valve from lpg.
As far as dual timing is concerned, this is only needed in a high comp engine or with low quality petrol. In your case I don't think there will be a problem just optimising for lpg and running good petrol. The distributor you have is specifically built for a carby 3.5 so should work well in the 101. Most of your economy increase will be from the decent spark fully igniting the mixture for the first time in years.

Originally Posted by garrycol

Can Megajolt run two separate ignition maps that are switchable when LPG is switched on and vice versa?

Originally Posted by garrycol

Garry

Pretty sure, ive got the megasquirt which does - its been a few years since i looked at the jolt and they were working on dual tables way back then.

Slight hijack but related
I run a 3.5 9.35:1 but am using the electronic distributor from a 1999 Discovery 3.9.
Was at the point of sending the dissy to Performance Ignition Services to get them to change the advance curve.
As the dissy was originally from a 3.9 injected motor should I change the curve?
FYI I have used this dissy for the last 5 years and have had nothing but perfect running on LPG if I advance the timing on LPG its great but I figure I shouldnt really run 12 degrees all the time particularly on ULP.

What alot of rooting around, Easy fix , Crane -HI-6 with TRC-2 in dash retarder . will do exactly what you need . Plus or minus 10 degrees of advance / retard adjusted on the Fly . Pick em up Egay for $150 US , wouldnt never run LPG without a Multiple spark Discharge system .

Originally Posted by 400HPONGAS

What alot of rooting around, Easy fix , Crane -HI-6 with TRC-2 in dash retarder . will do exactly what you need . Plus or minus 10 degrees of advance / retard adjusted on the Fly . Pick em up Egay for $150 US , wouldnt never run LPG without a Multiple spark Discharge system .

the trc retard unit looks like a good setup for a soopped up engine where performance or economy at part throttle aren't issues - but i reckon its way too basic for anything else. Still left with limited range crappy vac advance, springs and weights, sloppy gear driven shafts controlling a pretty important aspect of engine tune. None of that matters though if you drive with the right foot planted to the floor - and with 400hp on gas who wouldn't

Originally Posted by bee utey

Having a fair bit of experience of dual fuel I suggest you try the static timing on 6-10 degrees. I imagine your driving would not be often at the high end of the RPM range. The use of premium petrol should be able to cope with this amount of advance without problems, especially if you are running 8.13:1 compression. If there is uneven (jerky) running at light throttle you may be able to run without vacuum advance. As far as switching to petrol for hills work is concerned, I don't think you need to do this as the Rover V8 has always been good on gas, I have not seen one with a burnt valve from lpg.
As far as dual timing is concerned, this is only needed in a high comp engine or with low quality petrol. In your case I don't think there will be a problem just optimising for lpg and running good petrol. The distributor you have is specifically built for a carby 3.5 so should work well in the 101. Most of your economy increase will be from the decent spark fully igniting the mixture for the first time in years.

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

Originally Posted by Hardchina

None of that matters though if you drive with the right foot planted to the floor - and with 400hp on gas who wouldn't

Driving a 101 on the highway is with right foot planted to the floor with the massive 90kw V8 nudging 100kph with 2800rpm on the dial. 400hp would be nice though.

Garry

Originally Posted by garrycol

Driving a 101 on the highway is with right foot planted to the floor with the massive 90kw V8 nudging 100kph with 2800rpm on the dial. 400hp would be nice though.

Garry

I'm just cracking the butterfly at 100kph - 2500rpm (ish) in fifth

why do you want dual fuel? you could mount 10,000L worth of lpg tanks around the 101?