cap671 Posted September 28, 2014 Share Posted September 28, 2014 Hi I am looking at a 3.5 v8 in a 110. What can be done to better fuel economy, or is it a diesel swap. Or log. Thanks guy's. Quote Link to comment Share on other sites More sharing options...
Tanuki Posted September 28, 2014 Share Posted September 28, 2014 Replacing the 3.5 [assuming it's a low-compression one still running on carbs and has a clockwork ignition system] with a modern high-compression electronically-managed version of the V8 [closed-loop injection, proper load/speed-mapped ignition] will gain you at least 25% and probably nearer 50% reduction in fuel consumption for a start. After that, it's a LPG conversion [again, has to be multipoint electronically mapped - preferably you go LPG-only and increase the compression-ratio to benefit from the higher effective-octane of LPG] or a TD5/TDV6/TDV8 and modern autobox. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 29, 2014 Share Posted September 29, 2014 Depends very much on what you want to achieve. An EFI V8 in good nick driven with a bit of restraint can see 20mpg but you're never going to get stellar mpg from a V8, if you want 25-35mpg then really you're best off putting a diesel in. Quote Link to comment Share on other sites More sharing options...
V8Pete Posted September 29, 2014 Share Posted September 29, 2014 I currently get about 18mpg (which includes towing a 1 ton trailer). Only change so far has been putting a Discovery transfer box in to increase the high-range gear ratios. I'm thinking about swapping the viscous fan for an electric one and I need to get the carbs tuned properly. I'm hoping this will get me to about 20mpg. A new and/or better camshaft can increase efficiency - so more power or better fuel economy depending on how you drive it. Ensure timing is as advanced as possible without pinking. Don't assume the crankshaft TDC indicator is right as they can be out by a few degrees. Make sure distributor advance works properly and that the leads and plugs are good quality. So generally make sure it is all properly tuned. No single change will make a dramatic improvement in mpg but it all helps. And when you're driving a well set up V8 you tend to forget the issue of economy Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 29, 2014 Share Posted September 29, 2014 No single change will make a dramatic improvement in mpg but it all helps. Going to closed-loop EFI, as in hotwire with lambda sensors or even better Megasquirt doing away with the dirstributor, will gain you a lot over carbs or open-loop (no lambdas) as it will constantly fine-tune as you cruise along. Quote Link to comment Share on other sites More sharing options...
Raggylad Posted September 29, 2014 Share Posted September 29, 2014 I was getting about 17mpg (and 20 on long motorway runs) from my old 15G-prefix 3.5 unit on Strombergs. As V8Pete says, improvement is a combination of things. In my case, the following all helped: - Fitting an overdrive to the LT95 gearbox (doesn't apply, really, if you have a 5 speed box) - Replacing the Strombergs (which were worn & knackered) with brand new SU HIF 44s and setting them up correctly - Don't drive long road distances with tyre pressures too soft - Take the roof rack off - Move the spare from the bonnet to the back door or, better still, inside - Resist the urge to boot it with your right foot (hard with a V8 !) Above all else, I converted to LPG. When you take into account the price differential with diesel, I am actually getting about the same fuel economy in terms of ££ per mile driven. This only applies, of course, once you have amortised the capital cost of installing the LPG system; in my case, that was after about nine months. Quote Link to comment Share on other sites More sharing options...
James NZ Posted September 30, 2014 Share Posted September 30, 2014 Hi guys, can I wade in on this discussion please? FridgeFreezer you mentioned "Going to closed-loop EFI, as in hotwire with lambda sensors", is this the standard Lucas 14cux system you are talking about or something different? The reason I ask is that my 95 Disco v8 used to have cats but now doesn't (a rock in a river took them out) however the lambda sensor are still fitted. I can't find any suggestion of which tune resistor to use. The usual replies are either white, which is fitted, or to go green and forget the lambda's. This seems like a backward suggestion or am I missing something? Cheers, James NZ Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 30, 2014 Share Posted September 30, 2014 FridgeFreezer you mentioned "Going to closed-loop EFI, as in hotwire with lambda sensors", is this the standard Lucas 14cux system you are talking about or something different? 14CUX usually works closed-loop with lambdas & the correct tune resistor, whatever that may be. My strong preference is Megasquirt for numerous reasons (not least of which is doing away with the distributor), have a peek at the Megasquirt sub-forum for other's installs etc. Quote Link to comment Share on other sites More sharing options...
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