MPG

[sweeney1987]

Im always right...

regards to other question, most likely completely different engine design using unit injectors, HDI on 306s is the first version of commonrail, since then theres been different revisions and improvements, higher rail pressures, piezo-electric injectors and vnt turbos, all attribute to better atomisation of fuel in cylinder leading to better mpg

Well, I've just had to do some research to check and it appears youre right.

What a ridiculous system lol. Must've just been coincidence that mine read right at the time (idling in a car park at a dubmeet). I think knowing that isnt accurate is more worrying than knowing the exact temp!

Edit - But that brings up another question.........if its not the temp that ruins the hdi mpg, why is it so poor comparatively?

Im always right...

regards to other question, most likely completely different engine design using unit injectors, HDI on 306s is the first version of commonrail, since then theres been different revisions and improvements, higher rail pressures, piezo-electric injectors and vnt turbos, all attribute to better atomisation of fuel in cylinder leading to better mpg

Well, I wouldn't say always right.

The block/bottom ends are almost identical weirdly, the piston 'hole' is even the same shape and everything, so it can only be the top end that makes the difference, and even then the older PD is still only 8 valve, so that just leaves the injectors. But I can't really see how the unit injectors are much better for mpg, the only real difference is the top mechanical 'pump' type part, the nozzle end and solenoid opening operation is near enough the same isn't it?

Granted the VNT turbo will help mpg, as it's nearly always slightly on blow. And the 6 speed 'box helps on a run, but when you're averaging like 30mph (just going off the trip computer, I can't work out avg speed in my head lol) then even the 'box can't make much difference either.

I was really surprised when I stripped the Golf how there wasn't loads of extra sensors and clever things, infact, it only has the same sensors as a HDi (one extra but thats MAP for the VNT), I was expecting loads of amazing new tech, that just wasn't there lol. I'm just struggling to get my head around how you can have two engines that seem extremely similar, but one has twice the power, tonnes more torque and still gets over 60mpg with ease while the other left the factory with 90bhp and will struggle to even hit 50mpg unless you drive it carefully.


As for apples and oranges Chris, I'd say more like Granny Smiths and Pink ladys...they're not totally different. And PDs mainly cost more because they're in VAGs....1.4 petrol Golfs cost over twice as much as 306 1.4s, but they're no better.

I'll stop talking about VAGs now though.........but it's ridiculous I can have a better VAG discuassion and learn more about them over here than I can on the Dub forum.

Did you not read that line?
better atomisation of fuel in cylinder means using less fuel for same energy and less emissions which means more mpg.
and as dave said, the gearing is a considerable help too, the ratios on 306s is terrible in general and not as well calculated or engineered, hate to admit it but its true