MPG

[Toms306]

Bit late for me now, but yeah I woulda done lol!

[Ben hdi306]

Yes I would make a thread how to do this please.

[sweeney1987]

Ah, now i get it Sweeney, thanks, and i suppose anyone attributing the total mpg difference between two completely different cars to be down to just injector type is remarkably intelligent?

Im not saying its just injectors, it was an example, i said comparing two different design engines with different injection systems wondering why theres an mpg difference is stupid
there are many design factors which are all small differences but help mpg wise.
Injectors with varying spray patterns is one for example. Others would be flow of head(almost sure PD engines are crossflow design whereas hdis are not, meaning less efficient flow in combustion chamber) better breathing means more mpg
Turbo difference, again PDs using more efficient VNT turbos meaning better volumetric efficiency in cylinder
oh and gearbox ratios as already mentioned
all small changes which mean better economy and power

and im not saying im remarkably intelligent, just toms a bit silly for wondering why different engine designs have different charachteristics

They're hardly completely different, they weigh the same for a start. And Infact everythings heavier in the golf drive line (dmf, massive thick shafts, big heavy wheels)....and let's face it both cars are boxy and not particularly aerodynamic.

Anyway, fair enough if it is mainly down to the injectors, obviously the inside of those isn't visible lol.


Aircool, I've noticed this too, the HDi actually prefers revs! . The other diesels I've owned would sit just above idle (not labouring) and get good mpg. BUT. I think the difference is the crap HDi turbo isn't blowing extra air in at idle, so you have to drive a bit faster to get the benefit of the non vnt. That's my excuse when I'm caught speeding anyway haha.

not mainly down to injectors, just one example - see above...

Would anyone be interested in how to fit a 406 trip computer to their 306?



Please excuse the shoddy cutting on the panel.

Yes, sounds awesome, how you do it?

[Toms306]

PDs aren't crossflow btw. You're not always right.

[sweeney1987]

are they not? was near sure they were for some reason??
either way dffernent port designs still have an effect

[Toms306]

Tbf, the newer ones might be, but the older ones aren't.

[DeeTurbo]

Bit late for me now, but yeah I woulda done lol!

Yes I would make a thread how to do this please.

Yes, sounds awesome, how you do it?

I shall write a guide in the next couple of days then.

It's the TC off a mk 1 406 and it's basically four wires from the instrument panel, one from the ECU and the ones from the clock, but the only down side is you lose the clock and that's starting to annoy me. I've got a little lcd one off ebay but it keeps going fast.

The TC can take signals from a 406 head unit as well, so you can have the radio station and other bits of info on it. I was thinking it might be possible to input a time signal to it but I don't think I've got the knowledge to do that.

[Just Sean]

Since I've got my hybrid on, I've driven back from krisbs and to Gloucester and my fuel gauge hasn't moved! Either broken or highly economical!

Am going to fill it up today and see if it moves again. Could be doing so e epic empeegeez

[Poodle]

Don't rely on the fuel gauge, it's crap lol.

Just teasing, Sweeney, although you bring up an interesting point. Is there a cross-flow head that will fit the HDi...?

[Just Sean]

The needle was pretty good. but its only moved form the top of the 1/4 line to the very bottom of the1/4 line in 100 miles!

Its been De EGR'd and full service which might help it

[Toms306]

That sounds like mine tbh Sean, it drops quickly after the first ~150 or so miles though.

Will be interesting to see what your actual mpg is when you fill up though.

[Poodle]

Actually, you've just given it an unusually long run haven't you? They do like long journeys, and i should think you spent a fair while cruising on the m4, which would have helped.

[Just Sean]

So I've just worked out I did 87 mpg!

That included being thrashed!

286 miles and 14liters...


Shame is wont b like that when she is mapped!

[Toms306]

That's not possible.....

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It's wrong as well lol, 92mpg according to your figures.

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It's wrong as well lol, 92mpg according to your figures.

[Just Sean]

Tom. Get a hybrid turbo!! You'll never moan about mpg again!!

[Poodle]

I'd be very, very surprised if that turns out to be accurate, was that brim to brim?

[Toms306]

Tom. Get a hybrid turbo!! You'll never moan about mpg again!!

What is yours made from though, cos its not even vnt is it?

Oh and, ill just buy another car with a vnt lol, save me moaning about mpg haha.

I don't believe you got 92mpg though, pump clicked off far too early I reckon.

[Just Sean]

I worked it out wrong! /face palm!!! It was about 60 ish.

I'll out the figures up so you can work it out tom!

[Toms306]

Ah, that sounds better lol, was expecting 60-70mpg lol. Good for a HDi though!

[Just Sean]

278 miles & 24.3L

[Toms306]

Are you sure thats right this time?

It only works out as 52mpg.

24.3/4.54 = 5.35

278/5.35 = 51.96mpg

[Poodle]

What he said. ^^^

[Just Sean]

I got 40mpg with the new turbo, the leak and about 6 30 - 70 runs.

Cant wait to get paid so i can slap a tank in it!

[DeeTurbo]

Bit late for me now, but yeah I woulda done lol!

Yes I would make a thread how to do this please.

Yes, sounds awesome, how you do it?

Just to let people know I've written a guide on how to fit a trip computer to a 306 with a HDI in the guides section HERE