Some TDI's will wop some VRS's..... YOU HAVE BEEN WARNED

Seriously though I sometimes get this and have found it can be like a vapour lock in the tank vent. Remove the fuel cap and press the vent in. Also check what rev's you using, you could be just below youre opitmum, usually around 2500.

I tried again tonight, gave it a fair stab in 3rd and 4th gears at around 30-35 and surprisingly 4th is slightly more economical it seems, even though its about 1400 rpm in 4th gear at 30 mph, which is slightly on the low side, but it seems to work. Maybe I was wrong about it after all. I feel like a tit now!

Hi,

I have a 110bhp TDi Octavia and have tried the 2500 rev idea but I have found sticking it in a higher gear gives better consumption.

I will generally cruise at 30mph in 4th and anything over 40mph in 5th.

My old 2.0 petrol Octavia happily sat in 5th at 30mph but the TDi does seem to labour at this speed.

My current avg is 49.28 mpg for 5826 miles.

Regards

Diesel combustion works by the increase in temperature and pressure by compressing the air...so if the compressed air is warmer' date=' it will combust better. Warm air is less dense though, so you don't get as much expansion as you do with cold air.

So the ideal situation is warm cylinders but a cold air charge...however, diesel engines take a lot longer to warm up, hence you'll get relative innefficieny for longer (especially while the cold oil is warming up).

Once up to speed, you should see better instantaneous MPG, but your average will probably be down...

Rob.[/quote']

Well stemming from the ORIGINAL diesel engine design from Mr Diesel himself... the IDEAL situation is cold, dense intake air with PREHEATED diesel fuel! in the ORIGINAL engine design (that could use much lower pistion compression ratios and hence cause less engine stress) The fuel was heated to combustion temperature before being injected into the cylinders meaning that a higher percentage of the fuel was burnt... it was actually more efficient then the design that evolved commercially to what we have today! Two different inventors copied his design but to do this (Mr Diesel wasent that good a business man and dident effectively commercialise his design) they had to change it for patent and copyright reasons and so used compression to cause diesel combustion... and this is where we are today!

I thought of somehow preheating the diesel before it was injected, but i'm not sure if it would damage the new electronic injection systems in use now, such as the PD injectors in question now???

Anyone have any ideas on this>???

Cheers

Matt

Colin has a 5-speed so it may well be different. I tend to agree with his findings though' date=' although I have noticed that if you drive at 30mph in 5th, and the revs

drop below 1k rpm, the car has some kind of anti-stall mechanism which sharply accelerates the car until it's above 1k rpm. Bit of a shock the first time that happened! :eek:

Chris[/quote']

I drive a transit van at the mo and if you leave it in first it will keep going without touching any pedals at 5mph without stalling... is it just diesels that do this, because ive never had it in a petrol car??

I drive a transit van at the mo and if you leave it in first it will keep going without touching any pedals at 5mph without stalling... is it just diesels that do this, because ive never had it in a petrol car??

Every car I've owned does this. And I've only owned petrol cars.

Every car I've owned does this. And I've only owned petrol cars.

None of my previous petrol cars has done this! My Land Rover Discovery TDi did, but then it also "walked" up 45 deg inclines with all feet off the pedals too :eek:

Chris

I drive a transit van at the mo and if you leave it in first it will keep going without touching any pedals at 5mph without stalling... is it just diesels that do this, because ive never had it in a petrol car??

Yes the torque of a diesel keeps it from stalling. Great fun and does it in every gear but has not to be recommened. It probably isn't too good for the car.

I'm surprised Q has it in petrols unless they were automatics Every petrol car that I've driven like that has just shuddered then stalled. Mind you I have very little petrol car experience

Opel (Vauxhall) Omega - did it

Hyundai Coupe - did it

Austin Maestro - did it

Renault Laguna - did it

RS - does it.

None of these are automatic and all are/were petrol. Revs are around idle and will keep the car moving once it has been put into motion.

I'm with Q on this one...every car I've driven (with the exception of a G-reg Peugeot 405) did this...

Rob.

Could it actually pull away from standing start like that Q? I tried it in Dad's old A4 and Honda sport and both would simply die. :( Especially the Honda which would sometimes die even if I was giving it a good 1500rpm headstart.

Just to cheer you all up our average mpg for the cannonball was 23.6 :eek:

Could it actually pull away from standing start like that Q? I tried it in Dad's old A4 and Honda sport and both would simply die. :( Especially the Honda which would sometimes die even if I was giving it a good 1500rpm headstart.

Not without massaging the clutch... But not impossible.

Well I typically get 55 to 65 avg. mpg in my fabia. The other week I had a 71.2mpg on a 169 mile trip from Oxfordshire to Oldham. Anyway, for those in a Fabia 1.9TDi - if you hear the engine starting to struggle and you're below 1500rpm change down, that knocking noise ain't doing much good. If you're driving on the motorway - keep it at 65MPH and do not try to go past 70MPH. So keep it just under the 2250rpm (which is about 70MPH). Trust me, you will save a shed-load of fuel by doing this. You may feel a bit of a tool not joining all the nutcases in the outside lane, either wanting to slam into the back of someone, or looking to get knocked through the central res. but you have to be disciplined in order to get good fuel economy. You really do have to chill out - and not be in such a rush to get home. Just think about getting where you want to safely and that's pretty much it.

Although, the following will reduce fuel economy:-

Open windows/sunroofs,

Air Con switched on,

Heated Seats on,

Fans on,

Radios and Super Sound Systems - especially with that volume up loud- no.. no.. off it must go.

Large tyres,

Incorrectly inflated tyres,

Lots of people in the car,

Lots of rubbish in the boot - i.e. excessive extra weight.

roof racks,

towing a trailer,

bad driving style - keep to the inside lane on that motorway folks!

electric heated wing mirrors switched on,

heated rear windows switched on,

possibly lights, but then - I wouldn't advise driving at night without them! I've seen some people do it and it's not clever.

Blend of fuel - bio-diesel returns lower MPG than you're bog-standard diesel.

Windscreen front wash will be heated up below 5degC but then that will only affect certain models of skoda and not always be an issue.

there are probably a few more which I'm forgetting, but that's about the crux. of it.

Regards,

Hi

Colder Day means you have heating on, alot of heat comes through from the engine, there is some drain from the engine, Heat and electrical.

The radiator gt a generous supply of cool air therefore cooling the engine far more then you think

As these cool your engine a cold engine is inefficent, especially diesels no matter if colder air gets into the chamber for 'More Bang' if the egine is not running as hotas it should you aint gonna get the economy.

I know that sounds a little crazy, but I have seen it to be true. But I leave it to the boffins here. This is simply a opinion thing as I am far from being a mechanic

Timelord

PS Forget the MPG you have a VRS, use it like it ismeant to be lmao

Wow it's a rave from the grave OP 2004

1.4 Tdi. Takes <9 miles to get to proper temperature. Cold weather makes huge difference, but 10C isn't really cold. Get close to 80mpg @ 60mph on quiet flat motorway. The sweet spot (FFBs G spot!) is around 2K with a slight increase if using 2 stroke. Letting the revs drop below that leads to greater fuel consumption. The engine will pull from 1.5K but seems inefficient. The oft quoted 'change diesels before 2K for economy' is just plain wrong. By going up to 2.5 the drop on change puts the engine in a more efficient band for accelerating. My experience, others have different cars. Now 115K miles and much smoother than when new.