Switching between gas and fuel

[Baggy]

Hi all

Ive been driving the 92 classic with fuel / gas conversion for several months now.

OK for those who have done the conversion when you run through a tank of LPG how long do you run your vehicle on fuel to keep the injectors and other ancillaries running OK.

Appreciate your thoughts,

Cheers

Baggy

[bee utey]

A few thoughts:

1. It's petrol, you're running on dual fuel.

2. Do your regular petrol run before you run out of LPG or one day you'll find it doesn't go when you need it. Ancient EFI pumps can die at any moment.

3. Drive a minute or two each day on petrol with the engine warmed up, between 1% and 5% of total running on petrol is quite adequate. Cold running on petrol tends to foul up plugs chosen to be best on LPG.

4. Never let your petrol get old and stale, three months maximum between petrol refills is optimal. As an absolute minimum let the low fuel warning light come on and then add 20 litres. Winter petrol is often different to summer petrol.

[Baggy]

Bee utey - thanks for the information.

Whats your thoughts on petrol octane .....I normally run 98% or does it really not make a lot of difference in a engine of this age.

Baggy

[Homestar]

The Rover 8's are low compression engines, in general no advantage will be had running it on 98. The exception I've found is that if you run a lot of advance (which these engines can take well - I've got one of mine at 14 degrees - from the 6 the factory recommends) then on a really hot day when heavily loaded or towing, the 98 can help stop the pre ignition I sometimes get.

Apart from that, you're wasting your dollars IMO.

[bee utey]

The only reason to buy 98 octane is because the only other alternative is E10, which attracts too much moisture to be safe in a dual fuel vehicle. Straight regular 91 is fine for most of the time but in summer you could top up with a bit of 98 occasionally. Even 95 octane would be plenty if that is available in your area.

[bikeman]

I am about to do a 4.6 to replace my 3.9. I run duel fuel, Haltec ecu, bosch ignition. So would there be any need to run 98, or there is no difference between 4.6 or 3.9 as far as octane is concerned. Thanks.
Phil

[bee utey]

The needed octane rating of a pair of similar engines mainly depends on the compression ratio and then the specific tune. At 9:1 I'd run 95 and 10:1 I'd run 98. If it's 8.2:1 I would be seriously considering some higher comp pistons unless you only have 91 available. Designing a dual fuel engine around 98 octane and high compression will mean your advance map would be similar, so even a distributor is OK. Of course if you can have dual timing maps you can use whatever fuel you like.

[Baggy]

Thanks bee utey and Homestar,

I'll start using 91 from the next 20 litre fill with the occasional 95 octane thrown into the mix.
Don't like to keep fuel in tank too long and that reminds me I have to drain the fuel in the 2 door Rangie which is sitting idle at the moment.

One further question ....if and when the fuel pump (in tank) does go is it best to buy a genuine Land rover replacement or are aftermarket unit OK or is there a cheaper modification that people do.
The reason I ask is that my 2 door has an external electric fuel pump which seems such as simpler (and easier) method though I understand that carbie and fuel injection systems are two different animals

Baggy

[TheTree]

I was about to ask a similar question.

My installer said it's better to run 98 RON because there is less difference when the switchover to LPG occurs, therefore the engine ECU has less adjustments to make

Do people think there is merit in this or am I wasting money on 98 RON?

Brc/impco sequential injection on a P38 4.6 litre engine

Thanks
Steve

[bee utey]

I was about to ask a similar question.

My installer said it's better to run 98 RON because there is less difference when the switchover to LPG occurs, therefore the engine ECU has less adjustments to make

Do people think there is merit in this or am I wasting money on 98 RON?

Brc/impco sequential injection on a P38 4.6 litre engine

Thanks
Steve

While mixtures won't change noticeably between 91 and 98 octane petrol, the timing map is the only part of the ECU that could be affected. And that would depend on how much the knock sensors are hit after changing back to petrol. If your engine is stock low compression I highly doubt that it would ping changing off LPG to 91. At least I've never experienced any pinging on any low comp P38 I've driven. A high comp engine is a different matter and 95 or 98 could be a noticeable benefit.