Cylinder de-activation. will it work?

[Yostumpy]

At the mo I'm into 'hypermiling' and 'ecomodding' in all my vehicles. My avg in the 300tdi 110 has gone from a 5 year av of 26.5 mpg, to 30.6 mpg on the last tank, in 4 fill ups, and this is only a 10 mile urban commute. In swambo's 12 year old Toyboata yaris, we (I) drove from kent to brighton and back on 2 galls of petrol, 127miles avg 63.9mpg.So it def does work.

I see VW's new POLO has 'cylinder de-activation' This basically shuts off 2 of the cylinders during operation, and VW has quantified this in terms of mpg gain as ' de-activation of 2 cylinders at 31mph (on an already frugal polo) gives a net gain of 16mpg!!!!!!!!' Apparantly it does this by closing both valves in both cylinders. This I can't replicate , but

Now my question, can I fit a fuel cut off solonoid to each of the 2 inner ( or outer, or both sets as pairs to alternate) fuel lines from the bosch IP to the injector. I know these lines are under extreeme internal pressure, so would the solonoid work, or break up under pressure. How easy would it be to try this, and how do you think the engine would cope with only 1250cc, bearing in mind I am only thinking of highway driving at 50-55.mph. How would the turbo react and would it push the egt up. I'm already using a good % veg oil, and have fitted a kill switch, for engine delete at ' oppourtune moments' I would like to achieve 40mpg at some point in the future,

[zoltan]

Not teaching VW to such eggs but wouldn't shutting both the valves on the shut down cylinders increase the pumping losses in the engine? I'd have thought open valves will be more beneficial.

A 300 TDi on two cylinders would sound interesting/awful. Have you looked at running LPG with diesel?

[ballcock]

You would have to find a way to decompress the two cylinders as zoltan has said it would also cause an imbalance surely.

[Yostumpy]

Not teaching VW to such eggs but wouldn't shutting both the valves on the shut down cylinders increase the pumping losses in the engine? I'd have thought open valves will be more beneficial.

A 300 TDi on two cylinders would sound interesting/awful. Have you looked at running LPG with diesel?

Apparantly leaving the intake open would cause the pressure to go the wrong way in the induction system, and leaving the ex open would cause too much air in the exhaust and mess up the co2 meters (or something like that). That is on the polo. on the LR cant do any of this stuff. It would be balanced if the corect 2 were deactivated, but would sound like it was '8 stroking' I was thinking of the fuel cut offs as it would be cheap. LPG would NOT be a cheap option, with kit, installation costs, insurance etc. The cost would be prohibitive to the poss gains on the milage that I do. 7k pa . I've already made gains ( based on my last tankful of 30.6mpg ) of some 16%!!. ( excluding the veg oil saving), am still running a FULL roofrack at present, as I need it, but this will have its sides cut off and then segmented to achieve 2 smallrack pods of 3 double legs each, which will be easy to remove but still miuch more usefull than ladder racks. My latest tank will be a test as I have re-fitted the bonnet spare, in an attempt to improve aero. I read somewhere that when they road tested the series 3, the truck with the wheel on the bonnet consistently went faster than that without. Also at 50+mph , some effort is required to open the vent flaps due to the pressure build up at the base of the screen/bulkhead, whereas with the spare on bonnet, no effort req at 60. Will have to wait a few more days to find out yet tho.

Hopefully here's a link to the ecomod site. http://ecomodder.com/forum/showthread.php/vw-quantifies-mpg-gain-4-2-cylinder-deactivation-20943.html

[simonr]

What a great site! If you search for my name (simon Rafferty) - My DIY EV Charger gets a mention!

Tell us what mods you've made?

Si

[ian_s]

i expect it would fubar the IP pretty quickly, they arent designed to pump against an imovable object. if you could redirect the injection pulse back into the tank that might prolong it's life.

[Yostumpy]

What a great site! If you search for my name (simon Rafferty) - My DIY EV Charger gets a mention!

Tell us what mods you've made?

Si

Si , how are you. we met about 6 years ago, I came up to your place , you showed me your electric bike etc, I had the ex mod Camel 110, that was stolen the next day!!!!

Any mods so far are very basic. pumped up the tyres to 48 rear and 40 front, although will try 55 rear and 45 front next. I removed the mudflaps, but then re fitted , as I fig the reduction in aero drag is not worth the loss of their usefull ness. I've refitted the bonnet spare (jury's out on this till mid week/weekend. Driving style, EOC, P+g, que busting, it all works. I've fitted a rad muff, and buttoned it closed. Then I cut out the section over the intercooler, and made a simple plastic diverter to direct spoilt ait from rad to IC. (grill blocking)

Then i closed the gap twixt bumper and front body, with some plastic conduit and an ally strip.

[Maverik]

Back to your original questions... could you use the glow plug port as a control for pressure relief in the cyclinder?

[simonr]

I remember you!

I'm less convinced that shutting off two cylinders will make that much difference as the mechanical loss per revolution will stay the same. The efficiency of the combustion will also stay the same - so the amount of energy needed to push you forwards, should also stay about the same? No?

I can see that if you could isolate two cylinders using a clutch in the crank shaft - you might be able to make a saving, but surely it would be more efficient to fit an overdrive? By shutting off two cylinders, you are halving the amount of fuel per revolution. By gearing up the transmission, you are reducing the fuel per rev, but also the mechanical losses in the engine by the same amount. So long as the efficiency of the overdrive is better than the saving in mechanical loss in the engine - it should give a better return.

I have found the biggest return is from running my tyres at their max rated pressure. This has resulted in a gain of about 25% in efficiency. OK, it will wear the tyres more quickly, but the cost saving in fuel would pay for a new set of tyres every six months if necessary!

Solidworks can run flow analysis - so if one had a good 3D model of a defender, you could simulate wind tunnel testing of different options?

Si

[Daan]

I would start by fitting the tallest transfer box ratio your engine can pull - probably 1.0 - and fit a 2wd conversion with freewheeling hubs at the same time. and ditch every kilo you can.

The switching off a cylinder thing is a non starter with a mechanical injection pump I reckon.

Daan

[vulcan bomber]

the injector pump will not care at all.

The ve pump when built to run a 6 cylinder engine will run a 4 cylinder engine fine with 2 ports blanked off.

[dirtyninety]

Im very interested to hear more about that plastic strip, gains?

a white strip would look a little odd on my alvaston red 90!

[CwazyWabbit]

Im very interested to hear more about that plastic strip, gains?

a white strip would look a little odd on my alvaston red 90!

You could simply repaint the 90 white

Or in the interim wrap the plastic strip in red insulating tape

[Yostumpy]

Im very interested to hear more about that plastic strip, gains?

a white strip would look a little odd on my alvaston red 90!

Do I detect a bit of mikey taking? The plastic stip acts as a 'flexfoil' to seal the gap, whilst the alloy strip, is riveted to the bumper to squash it tight in to shape. The idea being as air is forced on to the front panel, it is prevented from being forced down and mixing with the air flow under the car. This is all very much work in progress, but future plans could involve Moon Discs made out of pizza pans, paneling some ( or as much as I can) on the underside with coroplast, maybe some rear wheel spats, and if I lose the roof rack, maybe a demountable 'kammback'. But 16% gain so far is pretty good. for mostly urban driving.

I had a good look on the interweb last night for in-line fuel cut off solonoids, on the high pressure side, but without success. Yes I could fit an overdrive @ £1200, or change the t/box for 1.22 or even the v8 one, but I'm trying all I can without spending much, as yes it would be loverly to have a rocky mountain overdrive, but I couldn't justify the expense for, say 6-8mpg gain. You see I'm trying to look at this in a 'post appocoliptic' way , where fuel is rare and costly, so every mile covered is precious. Yes I could buy a 10 year old 3 cylinder Suzuki swift, and prob get up to 75mpg, with a few mods, but thats not the point. If I can source a couple of inline solonoids, that would stand the pressure, and if the pump would take it, then all I need is the solonoids, a switch, some wire, and two injector pipes to play with, then if it don't work \I've lost nowt.

[TheRecklessEngineer]

You'll be wanting 3 way solenoids to divert the fuel. The IP won't pump against a closed valve - it'll be game over with the first crank of the engine.

I agree with Simon - I don't think you'll get a gain.

[FridgeFreezer]

Plenty of engines already doing it, a few of the LS series V8's do it I think although it's mostly been petrol ones in big cars. Fairly sure Merc & BMW do it too.

I find that dropping down to <80 saves a few MPG, the TD4 is up to ~37mpg now.

What about some of those wind deflectors that trucks have on their front corners to smooth the airflow, they make a difference. As does leaving it a bit dirty, a matt surface has less resistance than a shiny one doncha know? Fitting a bigger intercooler, losing the viscous fan, unloading the alternator, pumping up the tyres, and not driving a car with the aerodynamics of a wardrobe can also help

[jbs]

On my 200 tdi 90 I recently(last Friday morning) got 105 miles to the 1/4 of a tank of Diesel doing 50 MPH maximum on the M4 going to Windsor-From Somerset where I live, This is after I changed my tyres to Good year wrangler MTR's and re-adjusted my valve clearances too, I do have a full width intercooler and also my injectors and fuel injection pump are in good order too

John

[discomikey]

shutting off 2 cylinders would not achieve much because of the compression inside these 2 cylinders resisting the power of the other 2 cylinders. you are effectively halving the output power, and doubling the compression resistance-power ratio.

and the turbo wouldnt work half as well either, as even if the 2 shut off cylinders are pumping air through (just like how a compressor works) this air is not expanding, therefore not enough air is going through the turbo exhaust to work efficiently

[cackshifter]

....and if I lose the roof rack....

Lose the roof rack!

[Yostumpy]

Lose the roof rack!

I will, but I'm refurbing a house at the mo, so use it quite a bit.

I filled up again today, and t'was only 28.6mpg with the spare on the bonnet, a drop on 2mpg!!! That did suprise me, as the truck seemed to coast better with it on. Oh well, life's one BIG experiment, then you think you've got the answer and............agh!!

[FridgeFreezer]

I really doubt the 2mpg drop is related to the spare wheel, it's probably well within the error bounds of this experiment. Are you logging the weather conditions, tyre pressures, routes driven, average speeds, etc...

[TheRecklessEngineer]

I agree with Fridge. 2/28 is about 7%. Probably on the margins of error.

Keep it there for 5 tankfuls and see what the difference averaged across the lot.

[Eightpot]

Would weather/temperature conditions have an overall effect on the calculations as well - do we get slightly better mpg on very cold days due to the denser air??

I don't think overdrive makes that much difference to mpg. on my rolling barn of a Range Rover ambulance, I've been experimenting with different tyre sizes, starting with 205, up to 235/85, and have now also added an overdrive. This has brought my rpm at 65 down from around 2750 to 1820 (perfect for my Isuzu diesel), and I would say at best, if I stick to cruising at 65mph, I maybe get 2mpg extra. On the plus side, at 90 it's only doing 2600 rpm

Surely the only way to make a serious dent in economy is to reduce weight and wind resistance. Maybe lower the springs, a smooth steering guard to improve airflow under the front, road biased tyres. Then remove the roof and sides, recline the seats, fold the screen down and wear a swimming cap.

[muddy]

In my experience tyres are a huge factor. I'm sad and enjoy watching the EGT gauge with different sets of tyres, you can see the engine working harder with muds, low pressures etc.

Do you have a deflector on the roof rack? how about shaping some foam to stick on the wing mirrors.

Will.

[FridgeFreezer]

Would weather/temperature conditions have an overall effect on the calculations as well - do we get slightly better mpg on very cold days due to the denser air??

Look at the number of extra sensors and things attached to modern engines - air temperature is almost universally measured, and certainly on petrols it makes a significant difference to the running. Then again, putting the engine under even basic closed-loop electronic control gains quite a lot too.