Not What I Expected

[El Dingo]

These pumping losses are caused by the throttle butterfly in the intake restricting the amount of air being drawn into the cylinders.

On a compression ignition engine, there is no throttle butterfly, and the consequent lower pumping losses is one of the things that contributes to the better efficiency of a diesel engine over a petrol engine. In other words a diesel runs permanently with a wide open throttle. This is also one of the reasons why turbochargers work so well with diesels.

 

...the latest FSI and FSI-T VAG petrol engines are also 'throttle-less'...

Edited May 21, 2007 by El Dingo

[seatkid]

...the latest FSI and FSI-T VAG petrol engines are also 'throttle-less'...

...wrong.....try again......

[El Dingo]

...the latest FSI and FSI-T VAG petrol engines are also 'throttle-less'...

...wrong.....try again......

 

Ha ha ha!

 

Quote: A high-pressure fuel line mounted on the side of the cylinder head, often dubbed common rail, injects fuel straight into the combustion chamber. The shape of the pistons and the clever working of a set of valves make the air tumble, thus creating more efficient combustion. Where FSI engines really impress is their behaviour under part throttle loads. Whereas before, part throttle meant just that, partially strangulating the output by closing a butterfly valve the FSI system can be run with the throttles in a more efficient open position by creating a rich fuel mix directly next to the spark plug and a leaner mix in other parts of the combustion chamber. Unquote.

 

Yes, I know it's not *exactly* throttleless, but it made you bite. :)

Edited May 21, 2007 by El Dingo

[Scorpiorefugee]

Seatkid, I'd love to hear what you have to say on this subject. I'm sure it would contain a lot more sense and fact than most of what has already been said. I reckon, if I really tried I could get up to the low fifties but spending 4 hours doing 10 miles in London does tend to screw up the averages somewhat. Nonetheless, you have my appreciation for showing the way.

 

Gio, I agree about oil pressure but it does still bother my concience. As for the rest, I'll stake my 2 million miles in the past 45 years on being able to substantiate my opinions. I have to have something to occupy my mind driving up to 700 miles a day. ;) :P :)

 

And, yes I do have 3 cars. Insurance for the old and decrepit is cheap and if you don't make a habit of breaking them they don't cost a lot to run. Also, you don't notice the depreciation until you sell them and I don't think I could face that. :D :lol:

 

Ron.

[mumof4]

OOOOOOooooo Scorp...your birthday is comeing up!..couple of weeks!! :)

[gio]

Seatkid, I'd love to hear what you have to say on this subject. I'm sure it would contain a lot more sense and fact than most of what has already been said. I reckon, if I really tried I could get up to the low fifties but spending 4 hours doing 10 miles in London does tend to screw up the averages somewhat. Nonetheless, you have my appreciation for showing the way.

 

Gio, I agree about oil pressure but it does still bother my concience. As for the rest, I'll stake my 2 million miles in the past 45 years on being able to substantiate my opinions. I have to have something to occupy my mind driving up to 700 miles a day. :16: :16: :10:

 

And, yes I do have 3 cars. Insurance for the old and decrepit is cheap and if you don't make a habit of breaking them they don't cost a lot to run. Also, you don't notice the depreciation until you sell them and I don't think I could face that. ;) :16:

 

Ron.

 

 

And i,ll stake my 3,000,000 miles in 25 years that some on here have problems with basic arithmatic.

[Scorpiorefugee]

I've been driving 40-60 k a year for most of my working life and it was a shock when I added it up. 750 k alone driving 4 Scorpios/Granadas into the ground.

 

Arithmetic can be quite enlightening when you get it right but you do have to get the decimal points in the right place and use the right units.

 

What really bothers me is how much I've contributed to the transport budget and how little I've got back.

 

At todays prices I reckon on about

[Scorpiorefugee]

Oops! Got a decimal point wrong. :(

 

Make that

[mike99]

My 115 auto used to average 35mpg.

Since I fitted one of theose cheap ebay tuning boxes (please no insults!) I have much better, indicates on dash 57mpg and actual is around 52mpg. so, providing the engine doesn't blow up it was 20 quid well spent. :lol:

[seatkid]

And i,ll stake my 3,000,000 miles in 25 years that some on here have problems with basic arithmatic.

I'll see your stake and raise you a basic problem in spelling.

 

It makes no difference to me if you believe me or not.

 

56 mpg over the last 500 miles. My Skoda Fabia 1.2 doesnt manage much more than 44mpg however

[Sher]

Maximum Thermal efficiency of the 115Tdi engine is reached at the position of maximum torque in the rev range.

 

This is when the cylinders receive the maximum density of air with the minimum of pumping losses (read gas flow frictional losses for this) and then the fuel, diesel in this case, is introduced at some time just before TDC, whch allowing for ignition delays inherent in the burning process allow for the maximum expansion of the now hot compressed gases before they are allowed out of the exhaust valve.

 

The presence of the exhaust gas turbine then allows some of the as yet unextracted energy to be used in compressing the inlet air for the next combustion stroke.

 

If the maximum torque is at 1900 rpm then I believe that (at 33mph per 1000rpm in 6th gear) this corresponds to 63mph.

 

I find that if cruising at about these speeds I manage over 45mpg. However I avoid this in the UK because of tailgating HGV's.

 

At 80 to 85mph because the Galaxy is a bit of a brick shape and the engine is no longer at maximum thermal efficiency I get 37mpg.

 

At around 95 to 100mph it drops to about 33mpg but I have only limited testing at that speed. (Guess where in Europe before anyone complains?)

 

I find that provided I manage reasonable mixed speed journeys over 10 miles with a maximum of around 60 mph whilst in Spain I get a very reasonable 46mpg.

 

I think the original figures quoted for the Automatic mentioned which started this topic are poor.

 

Modern automatics even of older design on petrol engines have slush pumps (torque converters) which lock at speeds over 1000-1500rpm.

This reduces pumping losses which is the main power/efficiency loss in older automatics.

 

I'm certain the auto Galaxies have these. 10% extra fuel consumption would give a Carbon Dioxide value 10% higher for the Auto Galaxy.

 

Is this the case?

 

(Galaxy Ghia 115tdi Manual 2002 loaded upto maximum GTW for about 4000miles/annum)

[gio]

And i,ll stake my 3,000,000 miles in 25 years that some on here have problems with basic arithmatic.

I'll see your stake and raise you a basic problem in spelling.

 

It makes no difference to me if you believe me or not.

 

56 mpg over the last 500 miles. My Skoda Fabia 1.2 doesnt manage much more than 44mpg however

 

 

your figures keep changing? 52mpg over 8000 miles, then a best of 63 over 800 miles! and now these!

 

Please enlighten me to how you achieved 63mpg over 800 miles?

or even how on earth you can claim 52mpg over 8000?.

 

You are right on one issue, no i don't believe your data........

[seatkid]

your figures keep changing? 52mpg over 8000 miles, then a best of 63 over 800 miles! and now these!

 

Please enlighten me to how you achieved 63mpg over 800 miles?

or even how on earth you can claim 52mpg over 8000?.

 

You are right on one issue, no i don't believe your data........

 

Latest figures below - I reset the trip computer about 3 weeks ago - this period has been about 50% around town, hence the low average mph.

 

Car has done 75000 miles so is fully run in - I didnt start getting these sort of figures until after it did 50000 miles.

 

Technique is all important - plan ahead - freewheel (not always the best technique) - avoid braking (lost energy) - accelerate confidently (not too slow) and don't hang on in intermediate gears. Stick to the speed limit and you're halfway there... B)

 

 

Oh.......and use decent fuel........e.g. Shell, I found mpg using our local Tesco's is s***e, though the local Sainsbury's was better.

Edited June 3, 2007 by seatkid