VW Mk4 Golf Estate 1.9SDI

[1.9SDI]

Good news Kingsway. I also change gears when most efficient to do so (around 1800-2000RPM in my car) so I'm in 5th at 30MPH and being so freewheeling I don't have to apply much power to maintain that speed.

I don't yet have energy saving tyres but I do get good part-worn tyres to replace the old ones. This save a huge amount of money over time as I treat them well and they last as long or longer than new ones if properly maintained and inflated.

It's been a comparatively mild winter so didn't go for the grill block. You'll have to tell me (or show me) how you did yours. I have a spare in the house somewhere that I can modify.

And you're right, the real number 1 fuel-saving method is driving style, it makes such a dramatic difference. Would be good to swap stories and mods. I bought replacement components for my entire suspension to fully adjustable coil-overs for less than the price of 1 original VAG shock!

[kingsway]

The 'stealers' do know how to charge for spares and service all right!

On my last MOT the cat-convertor was loose due to a broken bracket. Vindis wanted to supply a new cat and pipe for approx £1000.00 - I went to the local Kwik-fit who welded it up for me for £20.00 - job done!

I can't say I've seen much difference in FC since adding the grill block, but when the weather was at or around zero degrees C, the car would warm up in about 5 minutes instead of the usual 10+ minutes.

I used some black Correx and zip-ties for the lower grills. For the main grill I folded some foam sheet that had been used as packing in a parcel, and squeezed it between the slats. Looks a bit tatty.... but very quick and easy to remove! I also put the under-engine cover back on... which I was lazy enough to leave off after the previous oil-change.

BTW I think our car - or a TDI version at least - were marketed in the US as both 'Jetta' and 'Passat' at various times.

Richard

[paulgato]

Very interesting to find your postings 1.9SDi.

I have a 2002 Golf 1.9TDi Estate and I've been tweaking it over the past year or so for economy. So far I'm averaging about 75 mpg Imp overall with a mix of driving, and more on long journies.

(I found your post because I need to replace my rear shocks so I was looking at upgrading at the same time.)

My best ecomod so far has been modifying my driving style. I cruise on the motorway at 50mph and I find the mpg starts to drop off dramatically even at 55mph.

Next best thing was to keep the engine temperature nice and warm. I totally block the entire grille in winter and almost totally block it in summer. A thermostat change was also required but in winter the engine just doesn't get up to temperature, and that impacts mpg. (The 'idiot guage' on the dash is designed to show '90' at any temperature between about 75 and 107 degrees, but below 90 degrees it doesn't run efficiently.)

One tip I can give you is to replace the gearbox oil. VW say you never need to but after 150k miles I decided to do it anyway. I got the right stuff from VW, a small tube of Molyslip gearbox additive (from Halfords) and got my mechanic to do the change. Once up on the ramp it took him ten minutes and he charged me £15 labour. The difference was immediate and obvious. The car clearly rolled much better - especially when coasting in neutral - and mpg (as displayed on the dash) was up by a full 5%.

I use low rolling resistance tyres and pump them up to the maximum allowed on the side wall, which is 51 psi. I will probably drop the rears back down to 45 or so but keep the fronts at 51. I find the car handles way better: steering is lighter, the car doesn't 'wallow' into corners and I've also found that it maintains speed much better when going round roundabouts and so on. I use the stock alloys and 165/65 R15's.

I also use BP Ultimate and that helps mpg a lot - pays for itself anyway. I've never tried it but I suspect that using standard diesel and adding Miller's additive/cetane booster would produce similar mpg gains at a lower cost. Millers does not improve mpg when used with BP Ultimate, but using 1 part acetone to 1000 parts diesel improves mpg by a couple of percent.

Not sure what else to add right now but if I think of anything I'll post again. Did you ever get rid of the hydraulic steering gear? Having harder tyres is always going to help as steering is so much lighter, but Golfs have always been notorious for having heavy steering. Not sure I would want to do without. I had a N/A Astra 1.7 diesel with no power steering and that was fine, but Golfs, ...nooo...!

I'm currently experimenting with engine remapping but the results are not encouraging so far. My guess is that if you normally drive slowly anyway - drive for economy rather for speed - then the economy gains with remapping will not impress, but if you are frustrated with lack of power and so tend to thrash the engine regularly, a remap with more torque can result in a more relaxed driving style and so can save fuel. But that's just a theory. I'll persevere with remapping for a while and see if I can get some gains that way. It might be the first remap was not quite right and they need to do a bit of tweaking.

I regularly drive in 5th gear at tickover speed in 30mph zones - i.e. 850 RPM and 26/27mph (traffic allowing). On the flat the engine is nice and smooth at that speed and the mpg meter goes way off the scale and pegs at 99.9mpg average. (Oh, but before I changed a failed alternator the engine was rougher at that speed and I was getting (showing on dash) more like 95mpg average at 27mph. Turned out the alternator pulley freewheel was stuck (didn't even know there was a freewheel pulley!) causing the rough idling and lower mpg at tickover.)

(By the way, my dash mpg gauge is about 7% optimistic. Useful for before-mod/after-mod comparisons though.)

I thought about ditching the spare wheel but decided against. I lost a tyre in a blizzard one dark night on a country lane a couple of years back, and without having a spare I would have been stuck. The RAC would have been 'snowed under' (ha ha) that night as it had just started snowing heavily and they would have taken hours to get to me. The tyre had ripped right away from the rim so tyreweld would have been useless. Nice idea but no, I'm going to stick with a proper spare (I also carry a breaker bar with wheel nut socket, a pair of wheel chocks, a jack, a foot pump and a can of diesel.) Every little helps but the maximum possible theoretical fuel saving from leaving a spare wheel out is the proportion of the total vehicle weight that the spare wheel represents. That's maybe 1%. But that saving would only apply to acceleration. At constant speed, friction and air resistance play a larger part than weight so ditching the spare tyre will save maybe 1/2% on fuel - or about a quarter of a mile per gallon. Now, running on a nearly empty tank most of the time could save a full 2% in fuel. My dilemma is that it is much easier to MEASURE mpg if I fill to the brim each time.

[1.9SDI]

Thanks for your interest and post Paul, it's always good to hear of others stories about a similar car.

I haven't done anything else to my car since these posts but I am still keen on at least a partial grill block (the lower vents under the bumper – I don't have fog lights in mine) and some sort of flexible dam under the front chin.

I've lowered my car by 5cm and I can honestly say it has improved the aerodynamic performance to the point that I can drive approx 10-15MPH faster for the same fuel usage. Long runs at 70MPH are at around 3.2–4 L/HK (88–70 MPG Imp) depending on route and weather conditions, as calculated by calibrated ScanGauge II. Fitting a front air dam will improve this slightly more. The problem with being so low is that I am affected by speed bumps grounding the car, so I have to be very careful.

I haven't investigated engine mapping or fuel additives but I did a test of the higher grade diesel but (for whatever reason) it didn't work out financially viable for me. Very minimal economy gains of >2% max.

The car is regularly serviced and lubricated and tyre pressures are checked monthly – it's about time I checked them now actually. Free-rolling is effortless to the point of having to apply brakes occasionally.

I did briefly look into more weight reduction a while ago, with a carbon fibre or fibreglass bonnet, racing perspex side window replacements, etc but the cost is prohibitive and would take many years to pay back. Everything I don't need is taken out – spare wheel included, so I carry a can of Holts and an air pump, which I hope will see me to a garage, except in a derimming or catastophic tyre failure. I also run with a half tank which easily returns me approx 400 miles.

Are you a steady accelerator or an instant one? I've been experimenting with both methods – using economic gear changing at minimal accelerator levels to gain speed and also just shooting up to speed limit and cruising. From initial testing (not exhaustive) getting up to the speed limit quickly, if it is 30-40MPH seems to be more economical, but this gain fades slightly if speed limits are higher, and disappears completely if it's to 70MPH. Have you tried this?

Cheers, Steve

[paulgato]

Hi Steve, so you still have the SDi then. I'm jealous. No turbo, no intercooler, no temptation to step on it and use more fuel. Less weight, more space in the engine bay. Less to go wrong. Nice. Not so many SDi's around in the UK.

Actually, since you don't have an intercooler, I think you can block off the lower grille completely - and I would suggest semi-permanently - with no issues at all. Mine is in fact blocked with plastic sheet secured by black PVC insulating tape (it's a black car so it looks fine) but I realise that it blocks the cold air from the intercooler, which might not be ideal. The way I drive though, I so seldom use the turbo that I think it probably makes very little difference in my case. (I blast the engine briefly once a week or so just to blow any soot out and to make sure the turbo parts (vanes?) don't seize up.)

If you have Scanguage (I don't at present) then you will know what temperature your engine coolant gets to. Does it stay up at the correct temperature (90+ degrees) with the grille open? I guess it might do in the summer. Over last winter I had the grille completely blocked (apart from the engine air intake of course!) and that worked fine for me. I did experiment with keeping the 100% grille block in the heat of the summer, and although the engine coolant temperature never rose above 100 degrees even when it was 30 degrees outside (I use VagCom to measure) the air temperature in the engine bay rose to over 50 degrees at times and I decided to unblock just the uppermost row in the main, central, upper grille, just for the summer. Come the autumn, it will get wrapped up warm again until late spring. Maybe different engines behave in different ways but for me that's the only way to get - and keep - the engine up to proper temperature in winter. And that makes a quite marked difference to fuel economy. (And no, there's nothing wrong with my thermostat - the engine simply doesn't create much heat!)

Your mpg for a steady 70mph, by the way, sounds astounding. My mpg is great up to 50mph and then drops off markedly even at 55mph. Sounds like the lowering really did work. It occurs to me that the new suspension components might just work better, and create fewer momentum losses, simply because they're new - or that may be a part of it - but 70-88mpg at 70mph is very impressive. Fortunately for me, I am entirely happy to drive slowly most of the time and 50mph is a perfect motorway cruising speed for me. For that reason - and for the reasons of both cost and comfort over speed bumps - I think I won't lower my suspension, but for most people it seems it would make a huge difference to economy. Whatever happened to those Citroën cars with the active suspension that you could lower and raise at will? That would be ideal.

As for the 'gentle-acceleration-vs-brisk-acceleration' question, well yes, I have tested that. I have a 50mph circular route that I use for testing the effect of mods on mpg. It's about 10 miles total: a rolling start at 50mph on a local dual carriageway. I zero the mpg meter as I pass the start location, drive the 5 miles at an indicated 50mph using cruise control, then slow down for the roundabout at the end, stopping for at least one of the three sets of lights on the roundabout, accelerate up to 50mph again for the return leg and maintain that until I pass the start point again, at which point I note the reported mpg average for the circuit. (I use the car's normal mpg display. Not accurate I know, but consistent enough for an A/B, before-and-after test of percentage difference in mpg following a mod. The display will read between 95 and 99.9 mpg these days. Less in winter. (The display seems to be about 6% or 7% over-optimistic overall. On my next really long journey I'm going to check exactly how optimistic it is at 50mph. I suspect it is less optimistic than at slower, city speeds.))

Obviously a significant part of the fuel used in that loop is for accelerating up to 50mph again after stopping, and I have experimented with different accelerating styles, including letting the cruise control get up to its set speed again on its own. My conclusion is that very gentle creeping up of speed is not good because even gentle acceleration uses far more fuel than steady cruising, and creeping up the speed just prolongs the extra fuel use. Aggressive acceleration, or even very positive acceleration (difficult to describe exactly what I mean but I hope you get the gist) is TERRIBLE for fuel economy - the average goes right down and doesn't recover. What works best is fairly gentle but positive acceleration, and getting into top gear as soon as possible consistent with that definite acceleration. In fact, kind of 'normal' acceleration works best. (Think typical minicab driver style?)

At present my engine is in a remapped state - having had it remapped on a 'like-it-or-money-back-and-your-original-map-restored' basis. I did explain that I was interested only in mpg improvements. Disappointingly, it has increased my fuel consumption slightly. Slightly but definitely. Even on a steady 50mph or 55mph route on a flat road, the fuel consumption is significantly up, and overall, tank-to-tank consumption is up by a good few mpg. A shame. I had put a lot of hope in getting a remap. The car drives better of course - much more torque, to the point where 5th gear feels like 4th gear used to feel - but for me that doesn't help much and actually makes it harder to drive economically. I will get it put back to standard as soon as I can arrange it.

Just to be clear, did you change your gear oil? If not, I can highly recommend it. A bit unscientific in that I put the Molyslip in at the same time as renewing the ten-year-old gear oil, but wow, what a difference it made!

[1.9SDI]

Thanks for the tips!

The scangauge is very handy in many ways, not only for fuel monitoring. As you asked, my temperature never gets above 74 degC, except in summer in stalled traffic. I think it got to around 85 degC on one occasion. If this is correct, a grill block would be very handy indeed.

Another good use for the scangauge is the throttle position sensor. Except in rare situations, like overtaking or up hills for example, I never go above 65% of my throttle. This is one of the reasons I attain high MPG at speed. Another is that I follow other traffic, however fast they are going. In a former life I used to be a competitive cyclist and one of the things you learn is that by tailing another rider you can conserve 30% of your energy by letting them push through the air while you follow in the slipstream.

I haven't yet changed my gear oil but based on your experience I will request it next service in November. I'm looking forward to see any results and as it will be up on the ramp anyway it should prove to be minimal cost too. Thanks for the heads up on that.

I'm going to have to find another set of those lower grills to cover up and replace the ones I have. Air in the wheel wells is a major source of front-end drag, so short of cutting exit vents in the bodywork it's best not to let it in to begin with – or as little as possible. I'm also trying to find a suitable flexible material for a front air dam. Being such a low car, any extension below the bodyline is going to be tested to destruction on our roads!

[paulgato]

So if your thermostat is working, your radiator is not being used at all, ...ever! You could remove the radiator and the fan to save weight! Ha ha.

The themostat should only begin to open at 87 degrees and should maintain a temperature of about 92, using the radiator to regulate things. (Anything up to about 105 is absolutely fine and normal. The dash guage will show '90' between 75 and about 107 I believe. The radiator fan cuts in at a certain temperature... About 102 perhaps? I forget.) When I changed my thermostat last year I tested both the old one and the new one with a pan of hot water and a thermometer. The old one was beginning to open at 65 degrees (!) and the new one at spot-on 87 degrees.

Once I'd changed the thermostat, things warmed up very appreciably, and I did see a rise in fuel economy (it was November I believe) but looking at the actual coolant temperature via VagCom, it still wasn't getting up to temperature, and the thermostat was never opening and never sending heat to the radiator. So I started gradually blocking the radiator grille, monitoring the temperature at every stage, until it was 100% blocked and all was well.

One other thing I notice with the grille blocked is that the engine loses much less heat when parked up for an hour or two. If I go somewhere in winter and park the car for an hour or so, when I come to drive it away the engine is still pretty much up to normal temperature. Well, 75 degrees at least, as the temperature needle shoots straight up to '90' on the gauge and the heater works straight away.

I've been thinking of ways of improving fuel economy in winter. Been looking at small 240v self-adhesive pad pre-heaters on oil sump and gearbox for early morning starts.

[euromodder]

Originally Posted by 1.9SDI

I'm also trying to find a suitable flexible material for a front air dam. Being such a low car, any extension below the bodyline is going to be tested to destruction on our roads!

Many people have used garden liner.
Cheap and fairly sturdy.
You'll grind it down to where it needs to be.

[euromodder]

Originally Posted by paulgato

I've been thinking of ways of improving fuel economy in winter. Been looking at small 240v self-adhesive pad pre-heaters on oil sump and gearbox for early morning starts.

Lower (cold) weight oil definitely helps in the first miles.
Engine uses notably less fuel and is less noisy.

Once warm, the effects are small though, so the effect on your overall FC depends on the length of the average drive.

[paulgato]

Lower (cold) weight oil definitely helps in the first miles.
Engine uses notably less fuel and is less noisy.

Once warm, the effects are small though, so the effect on your overall FC depends on the length of the average drive.

Thanks Euromodder. In winter most of my journies are short, local, work-related ones.

Using cheap mains electricty to warm the engine up rather than using expensive diesel to do that job makes sense to me. I also notice that on a long journey, the mpg goes up and is at its maximum after about two hours' cruising. I'm guessing this is not engine-related (the engine should be pretty-much heat-soaked after half an hour?) but related to other parts of the drivechain warming up, e.g. the gearbox, axles, CV joints, wheel bearings, tyres, etc. Hence wanting a heater on the gearbox as well.

Ultimately it would be very cool to use solar-charged auxilliary battery power to run the heaters. They could be on a timer to come on a couple of hours before drive-time.

Ultimately, ultimately, it would be super-cool to use that auxilliary battery (charged either by solar or by mains) to also replace or supplement the alternator. I.e. to use the aux battery to run a voltage-regulated 'charger' for the main battery so that the alternator 'sees' a high voltage most of the time and doesn't bother generating amps. For daily short journies, or for longer trips with lots of rest time, the solar regeneration might be enough, and when it isn't, the car can be plugged into the mains to top up the aux battery. And with that kind of arrangement, even if the solar isn't enough, or the mains charge doesn't completely negate the need for alternator charging on longer journies, any solar/mains power you can put in WILL save you a corresponding amount of fuel. Mild hybridisation.

That all would need a bit of electrical/electronic design/calculation, plus some investment of course. I think it should be feasible but first I'll try with a couple of pad heaters. (Maybe 12 volt ones so they can be used in any future solar/aux battery arrangement.)

Sorry - thinking aloud, ...kind of. I've been thinking about this over the last couple of days. My feeling is it would work. Probably cost-neutral at best, but you get the added benefit of quicker, more comfortable winter morning starts where the cabin heater kicks in much sooner.