Convert 12 valve to 24 valve. Idle musing......

[Geert]

I have a 12v auto, 33" tires and 2.5" OME lift
I get 18MPG, so, nothing abnormal I guess
I do have 33x12.5. I think more narrow tires would also make a difference in fuel consumption

 

[Jon Wildsmith]

One of the best back to back comparisons I have done was a trip to Libya with Toby. He was in a 12v auto and I was in a 24v manual. We had very similar loads and were running identical tyres. Because we were travelling together we were obviously going similar speeds and distance. Over the 3 week trip the 24v manual used 10% less fuel than the 12v auto. The gap would have been smaller, in my opinion, if the 12v was a manual.

Had you removed the electric valves and what not from the injection pump on yours and done the usual pump tweaks?

 

[Ian Rubie]

Had you removed the electric valves and what not from the injection pump on yours and done the usual pump tweaks?

At that stage the pump had been tweaked by JV, he freely admits he is much better at the tweaking now. Nothing else had been done to the pump. I cannot remember if the egr had been bypassed. If it was then it was nothing more fancy than disconnecting the vac pipe and looping it back on itself.

Ian

 

[Jon Wildsmith]

ok, seems like the electronics do some useful things if you have a bit of a fiddle, so it boosts the fueling under acceleration and drops it back on a steady throttle, just not sure what that's worth and how much of a factor it is in the consumption I'm getting. If yours still had the electronic bits then probably not making much difference based on your findings. State of tune is probably the key.

 

[Toby]

I'd agree with you Jon, state of tune matters, perhaps second only to weight of right foot... Lorin, if you're willing to take the comparison Ian came up with between his manual 24v and my auto 12v on a heavily laden & relatively high speed trip as any sort of real-world guide, then don't spend a fortune on a conversion: If your planned trips add up to 13500 miles and you use the car a bit more anyway in the next few years you might clock up, for the sake of argument, 20,000 miles before you need a minibus for all the children ;-) 20000 miles at 20 mpg is 1000 gallons or 4546 litres at say £1.45 per litre gives a fuel cost of £6591.70. Improving this by 10% will save you around £660 which probably won't go that far towards a 24v conversion?

All the best,
Toby
1994 HDJ80
1990 HDJ80 (sold)

 

[Lorin]

Have no fear Toby, conversion idea is well and truly binned! Portals however........