Possible economy tip, or daft?

[Yostumpy]

Whilst trying to eek out more mpg from the 110 (best so far is 35.4mpg) I was wondering about the turbo and the xtra fuelling. Suppose, (just humour me) one was to fit a solonoid valve type thing to the vacum pipe ? that goes from the turbo to the FIP,(the one that increses fuelling on boost) so that once up and running at speed , one could flick the switch and switch off the vacum line, so that you still had boost, but no additional fuelling. Then when needed it could be switched on again. Similar sort of thing to the cylinder deactivation on some new vWs ie if you dont need the power, switch it off. Now would this work, I mean the turbo boost on without the xtra fuel, would it give ANY xtra power, over 'no turbo' and would it cause it to run lean. Any reason not to. ok , you can laugh now.

[landroversforever]

I don't know much, but I thought running too lean was bad for any engine? or is that just petrols?

[CwazyWabbit]

It's a pressure pipe not a vacuum pipe, not that it makes a difference to what you are talking about.

When I lost the banjo bolt that connects the boost pipe to the injector pump the power was really poor...... Fairly similar to how poor it was when the manifold gasket was split and a couple of bolts missing from the exhaust manifold (I bought the car like it btw). So in my experience no extra fueling or no boost both give really poor performance (which in my mind each was as poor as the other)

[CwazyWabbit]

I don't know much, but I thought running too lean was bad for any engine? or is that just petrols?

That is just petrols Ross, diesels run lean by design. There is no variable restricton in the air intake

[landroversforever]

That is just petrols Ross, diesels run lean by design. There is no variable restricton in the air intake

Thanks for that

Although I did read something about adding more fuel can reduce EGTs? No idea how true that is, mind.

[CwazyWabbit]

Thanks for that

Although I did read something about adding more fuel can reduce EGTs? No idea how true that is, mind.

That would be for petrol as well, normally extra fuel in a diesel raises temperatures.

[Disco1tdi]

Surely it's the fuel being burnt that produces the given amount of power to hold you at a certain speed, with friction and wind resistance trying to slow you down?

If you backed the fuel off, at a particular speed, wouldn't you just slow down, in the same way you would if you back the accelerator off?

[Aragorn]

Surely it's the fuel being burnt that produces the given amount of power to hold you at a certain speed, with friction and wind resistance trying to slow you down?

If you backed the fuel off, at a particular speed, wouldn't you just slow down, in the same way you would if you back the accelerator off?

This.

You'll find if you install a boost guage that when your cruising on the motorway your not generating much in the way of boost anyway, so doing what you suggest would basically do nothing.

The cylinder deactivation works on petrol engines, because running 4 cylinders with a very small throttle angle creates lots of inefficiency, by shutting two cylinders down and running on the remaining two, you end up with a larger throttle opening, and the engine runs more efficiently and thus uses less fuel.

[ian_s]

all you would be doing with this is limiting the maximum amount of fuel the FIP will try and inject. at cruise i dont think it would make much difference. just using less throttle would have the same result.

i've considered this in the past for the tdi in my Series 3, not for economy but to try and make it safer to drive for SWMBO

rear wheel drive + 1st or 2nd gear + turbo coming on boost == lots of wheel spin

i thought that by disabling the boost sensing gubbins, it would reduce the power spike that comes when the turbo spools. i never actually tried it though

[Off Road Toad]

I had this pipe break off on my old 300 tdi, the result was very slow truck, no smoke (it had been tuned as far as it could be) but absolutely astounding fuel economy that I could never hope to match driving normally (ish) Steve

[Yostumpy]

Go on then do tell..... How astounding.>>> sounds good.

[CwazyWabbit]

The fuel savings will be from the extremely slow acceleration rather than the cruising.

[kshurey]

You could just leave it in the garage and buy a Prius !

[Yostumpy]

You could just leave it in the garage and buy a Prius !

There is ALWAYS one isn't there.

Now then. Last week I looked into Nissan NV200 van. 54mpg, £9k +vat. OOOO! thats good isn't it. BUT WAIT

Avg 7k miles a year. £6.58gal

@ 30mpg = 233g x £6.58 = £1533

@ 53mpg = 132g x £6.58 = £868

Saving of £664 pa.

£9000 - £4000 (sell landrover) = 5000 + vat difference, would take nearly 8 years to pay for itself not including the vat, by which time the nissan would be worth bugga all. So If you don't ming I'll keep the LR and try to think of ways to reach my goal of 40mpg. 35.3 mpg is my best so far in Feb and it was V.cold.

[Off Road Toad]

Go on then do tell..... How astounding.>>> sounds good.

Thing is, it was 8 years ago and since then i've had two 3.9 v8's, a 4.6 and now a td5 engine in the same truck so memory seems distant. But as an example, my journey at the time usually used just over 1/4 tank (45liter 90 side tank) but on the journey with the broken pipe, the guage barely registered any movement (journey was from croyden to godalming, so about 40 odd miles? It was only astounding compared to normal considering the engine was tuned to within an inch of its life It was however veeery slow! to get to 50 took minutes rather than seconds, i say 50 because 60 wasn't possible!

Probably nothing constructive here for you i'm afraid.

Steve

[Adam001]

Just to add, Boost is dictated by exhaust gas velocity, if you cut the fuelling, you cut the exhaust gas speed and the boost would drop away anyway. For steady state you won't see a change, the load point will just move.

In short, doing the mod will not improve your economy through theory, in practice it will however purely because you cannot use 70 odd % of the engines power.

This.

You'll find if you install a boost guage that when your cruising on the motorway your not generating much in the way of boost anyway, so doing what you suggest would basically do nothing.

The cylinder deactivation works on petrol engines, because running 4 cylinders with a very small throttle angle creates lots of inefficiency, by shutting two cylinders down and running on the remaining two, you end up with a larger throttle opening, and the engine runs more efficiently and thus uses less fuel.

Just one addition on the deactivation, you got the theory but the major increase in economy comes from the reduction in pumping losses from isolating the cylinders (turning the valves off completely), throttle opening is part of pumping losses, but not as great as the effect of pumping the air through the cylinder.

[Retroanaconda]

Thing is, it was 8 years ago and since then i've had two 3.9 v8's, a 4.6 and now a td5 engine in the same truck so memory seems distant. But as an example, my journey at the time usually used just over 1/4 tank (45liter 90 side tank) but on the journey with the broken pipe, the guage barely registered any movement (journey was from croyden to godalming, so about 40 odd miles? It was only astounding compared to normal considering the engine was tuned to within an inch of its life It was however veeery slow! to get to 50 took minutes rather than seconds, i say 50 because 60 wasn't possible!

Probably nothing constructive here for you i'm afraid.

Steve

According to that Steve it was only doing 14mpg before the pipe came off (40 miles, 3 gallons of fuel), so it could well be that it just brought you back up to 'normal' levels as you say.

[Off Road Toad]

Indeed Retro, it was the hideous fuel consumption and black smoke that drove me to the dark side in search of more power! I'd inter cooled and boosted the poor thing to death, to the point that when I installed the high compression 3.9 I was disappointed! Only the 4.6 was better (and then td5 more so) Back to topic, Jeremy Fearn told me once that the best place to spend money on a tdi is the injection system. He was referring to its general health and the best gains and benefits are often as simple as things like good working injectors etc ie: everything in tip top working order, so maybe this is where the OP could seek further improvements in economy? Steve

[Retroanaconda]

I would suggest he also looks into air resistance some way. Particularly underneath the car. If off-road use isn't likely to be severe/often then you may be able to rig some kind of lightweight belly pans/deflectors to help smooth out the airflow under the vehicle. Big beam axles and the lack of undertrays won't be helping - you look under modern cars and it's all a relatively smooth single surface. If you're taking it off-road often then it's probably not worth doing as anything strong enough to take heavy bangs and knocks is going to add a whole lot of weight you don't need. But I'm sure there are savings to be had there.

Maybe also look at the weight of oils used and whether you can get away with lighter weight ones that will sap less energy from the drivetrain. And while on that train of thought, I suppose you could even look at converting to part-time 4-wheel-drive. Why waste energy in the front axle when with a conversion kit for the LT230 and if you wanted a set of free-wheeling-hubs you could save that too?

I'd be impressed if you managed a sustained 40mpg (by that I mean hitting that on several consecutive fill-ups), but I'm sure with enough fiddling it could be done. Personally I wouldn't go messing about with the engine too much, it's not exactly a powerful lump to start with, so I'd be looking to reduce the power needed to shift the thing along (i.e. rolling resistance, wind resistance) rather than try and increase the combustive efficiency of the engine itself and risk losing power.

[Yostumpy]

Ah, I didn't think you could fit free wheeling hubs to a 110, seem them for sale now and again, AVM or AVH or somesuch. Something to do with the lubing of the swivels etc.

Sustainable 40mpg? I doubt it but to get close on a run would be nice. ive gone from a 5 year avg of 26.4mpg to a 30+ tank fill up avg of nearly 30mpg, a lot of these journeys are only 1-2 miles etc My 35.3 mpg was a run back from dorset with a side wind. Taking off the roof rack has given me 3-4 mpg gains.

[simonr]

Personally, I would just look at the way you drive!

There is a competition for getting the most mpg out of a standard car and until a few years ago, the MPG record was held by a Range Rover! I don't know if it was modified at all - but if you can do it in a Rangey - anything is possible!

My Electric Freelander has taught me a lot about economical driving. Because you have an instantaneous of voltage, current and power going in to the motor - you can immediately see what makes the biggest difference.

The freelander is capable of spinning the wheels at pretty much any speed - so has loads of power for accelerating and a top speed of 93 or so.

In general, I've found that driving as slowly as you possibly can and minimising acceleration are the biggest contributors. You are better off slowly building up speed on the flat, then using some of your momentum to climb hills - let it slow down on hills.

The other biggy is tyre pressures. If you run them at the max rated pressure, you can reduce consumption by about 25%. OK, you wear out the tyres faster - but this is more than compensated for by the fuel saving.

Keep your windows closed! Open windows seem (at least on Freelander) to add about 5% to the consumption.

By upping my tyre pressures in my 110, I now seem to average 30mpg in a Td5 instead of my previous 25mpg. Not quite 25%, but I guess it has a lot more drag than Freelander. On a long journey I seem to get about 35mpg - which is not bad considering. I use cruise control to keep it at 55mph, but let it slow down a bit on hills.

Lastly, electric versus viscose fan? Makes no measurable difference - contrary to what most people think! Kenlowe claim it will save you 10% - and I guess it might under ideal conditions such as replacing a series style direct driven fan rather than viscose and where the fan has been specified for hot countries.

I'd be interested to see if a belly pan made a difference. I saw one once made from the plastic barrels that chemicals are supplied in. Unrolled and screwed to the chassis rails front to back. They are flexible enough to deform round the sump & gearbox. This was on a trialer - and just acted as a huge mud-trap!

Si

[zoltan]

Lastly, electric versus viscose fan? Makes no measurable difference - contrary to what most people think! Kenlowe claim it will save you 10% - and I guess it might under ideal conditions such as replacing a series style direct driven fan rather than viscose and where the fan has been specified for hot countries.

Not wishing to start a fight but I beg to differ on this point.

I know it is a different engine but we measured (before and after) a 20 bhp loss running a standard A series Mini water pump and 11 blade plastic fan over an electric water pump on a 1460cc Mini racing engine. This was measured before and after on an engine dyno which has excellent repeatability. That is a considerable loss. Churning a big fan on the front of a diesel lump or V8 will similarly use power which requires an expenditure of fuel

Anyone on Facebook, the test results are here

http://www.facebook.com/photo.php?fbid=10151093867976734&set=a.408751951733.176640.293351166733&type=1

[TheRecklessEngineer]

In general, I've found that driving as slowly as you possibly can and minimising acceleration are the biggest contributors. You are better off slowly building up speed on the flat, then using some of your momentum to climb hills - let it slow down on hills.

I'd perhaps question this as well. I'm sure it's valid for an electric vehicle, but a diesel will gain maximum efficiency at around 70-80% of full load.

Something like this (shamelessly ripped from another site, but google will turn up many such graphs):

The result is that you should accelerate moderately hard in a low gear to get to your cruising speed - and repeat the same going up hills.

[Bowie69]

Is that with a fixed fan rather than viscous?

[Aragorn]

Not wishing to start a fight but I beg to differ on this point.

I know it is a different engine but we measured (before and after) a 20 bhp loss running a standard A series Mini water pump and 11 blade plastic fan over an electric water pump on a 1460cc Mini racing engine. This was measured before and after on an engine dyno which has excellent repeatability. That is a considerable loss. Churning a big fan on the front of a diesel lump or V8 will similarly use power which requires an expenditure of fuel

Anyone on Facebook, the test results are here

http://www.facebook.com/photo.php?fbid=10151093867976734&set=a.408751951733.176640.293351166733&type=1

Its worth remembering though, that 20hp was at 8000rpm...

If you look at the low end of the graph below 4000rpm, you find the difference is pretty small!