More efficient alternative to a 2.1i engine?

[centro]

Due to the ridiculous and almost daily rise in petrol prices, I am weighing up the options and was wondering about swapping my 2.1. Injection DJ engine for for a petrol engine which is more efficient. What would be my options and what sort of mpg could I expect?

Just gas it. 30mpg equivalent and if you use it plenty the payback gets quicker.

Simples.

Ian

What do you mean by equivalent?

[toomanytoys]

= to 30mpg running cost if on petrol..

the important factor to think about if cost per mile..
eg, below 16 pence per mile (0.16 pounds per mile) on lpg at 22 mpg on a T25, you would need to be doing 38 on a petrol engine to get that cost per mile and 40 on a diesel... (fuel price is different area to area but these were local to me so adjust accordingly..)

MPG petrol diesel lpg
pound L 1.339 1.429 0.78
12 0.507 0.541 0.295
14 0.434 0.463 0.253
16 0.380 0.405 0.221
18 0.338 0.360 0.197
20 0.304 0.324 0.177
22 0.276 0.295 0.161
24 0.253 0.270 0.148
26 0.234 0.250 0.136
28 0.217 0.232 0.126
30 0.203 0.216 0.118
32 0.190 0.203 0.111
34 0.179 0.191 0.104
36 0.169 0.180 0.098
38 0.160 0.171 0.093
40 0.152 0.162 0.089
42 0.145 0.154 0.084

[ajsimmo]

"Semi-sequential" injection? What b0ll0x

Succinct and to the point, but ExtraEFI/MS also use the phrase in their blurb.
"This setup has either 3 or 4 fuel injector outputs that can run the fuel injectors in pairs in a Semi-Sequential fuel pattern on a 6 or 8cy engine."
I reckon, as it's about 6 or 8 pot engines here, it makes sense. But the other lot were on about 4 pots, so isn't that just half-group batch fire? So as you say....What b0ll0x.

Great thread, I'll be watching this one develop, and hope to join in/help with a project if I get time.

[Dubmaster77]

? This is something I have been looking into as I now have a recon lump, and a lumpy idle!! So sorry to drag this thread from the depths, But there is a lot of talk about sequential injection which is what I wanted to do.... However it seems to me we cant run sequential injection on our engines as there is no way of telling the cam shaft position. Has anyone come up with an answer to this? I imagine "semi sequential" refers to firing two injectors at a time? of to do more research......

[silverbullet]

I'd forgotten about this one

Yes, semi-sequential is another term for "batch fire" which is what the DigiJet/Digifant system does on a flat 4 anyway.

Getting true sequential (each injector firing independently) fitted to a wbx is a matter of fitting a 36 tooth trigger wheel to the front pulley, a bracket for the trigger, finding a means to get a cam/distributor sensor rigged up (this means going coil-on-plug to eliminate the disi and use the body as sensor housing) and making a new loom for the engine.

Easy

[kiwirob]

I've just come across this thread in the hope of getting updates from all of you who are looking at alternatives.I also thought about putting a modern tdi or subaru into my DJ. However, the LPG vs engine management upgrade seems very interesting and quite doable financially for someone like me without huge mechanical knowledge.
Can we have some updates please on what decisions were made and how they're working out?
Cheers All
Kiwirob

[ninja.turtle007]

I've just come across this thread in the hope of getting updates from all of you who are looking at alternatives.I also thought about putting a modern tdi or subaru into my DJ. However, the LPG vs engine management upgrade seems very interesting and quite doable financially for someone like me without huge mechanical knowledge.
Can we have some updates please on what decisions were made and how they're working out?
Cheers All
Kiwirob

Hi Rob,

I have an AFN TDi with larger nozzles in my westy Syncro putting out around 120bhp and a lot of torque. I drive it pretty hard. Here are my figures.






Ignore the high and low, that's due to the tank not filling properly.

[Aidan]

my average on gas works out at the moment (1600 miles in 6 weeks) at just over 16p p mile same cost as a diesel doing 35ish, that's now the gas price has come down a bit, mostly using Morrisons at 65p litre, when I was paying over 80p it was more like a diesel doing 28-30mpg

[christofy]

I get about 30mpg out of my subaru 2.2. Noticeably better than my 1.9dg and bags more power, not to mention how awesome it sounds

[ricicles]

High twenty's mpg on a 2.1 sounds rather good. Also if it can be done at a cost of £600 it is much cheaper option than LPG and does not have the problems of having an extra gas tank and it destroying the valve seats. The quotes for a tdi look to be around 4-5k and you get avg 30 mpg. Efi looks like the way to go to me.

[AdrianC]

High twenty's mpg on a 2.1 sounds rather good.

Compared to the mid-20s we get from our hightop DJ, it's not a huge difference. About 3.5p/mile. 17k miles break-even.

Efi looks like the way to go to me.

2.1s all have - or had - EFI anyway, of course.

[ricicles]

Adrian my 2.1 is running twin40dellorto's mid twenty mpg is a dream I have never used it with efi so am thinking this year it will put on a decent system to get the mpg up there. I have been looking at all the different posts about conversions and am amazed that the tdi conversion only delivers 30mpg avg. is this because it is the only one that has been measured accurately ? The other question here is gearing. Why is the wbx gearbox geared as low? Did vw find the optimum revs at 70 mph for fuel economy? Or was this van never designed to cruise at this speed? So if you could get revs to about 2800 or3000 rpm at say seventy with a decent efi (MS with a decent throttle body) could I get an old dj to return v high twenty mpg! ( when I say old dj I mean fully rebuilt and balanced) the dj is a high comp engine so should be capable of decent return on fuel and when you look at the cost of going diesel you can drop a few mpg on this conversion by saving on the 4-5k to change the engine and petrol is a bit cheaper to.

[ninja.turtle007]

Longer gears don't necessarily give you better mpg. After having longer gears fitted my Syncro Westy the mpg didn't improve, maybe because the original gears were pretty long anyway. From memory it dropped about 450rpm at 70mph. I now get 70mph at 3050rpm.

The mpg would probably be better if if my van weighed less and didn't have a 50mm lift.

[AdrianC]

my 2.1 is running twin40dellorto's mid twenty mpg is a dream

Presumably it's a 2.1 fitted into a van that started off as a 1.9?

Why is the wbx gearbox geared as low? Did vw find the optimum revs at 70 mph for fuel economy? Or was this van never designed to cruise at this speed?

Depends on which box you have, which - unless it's been changed - would depend on which engine your van left the factory with. As well as the DJ hightop westy, we're currently looking after a KY 1.7D homebrew hightop, and did ~400 miles in it over NY. The gearing is... different. VERY different. But, then, the 1.7D _needs_ to be much lower geared, because it's so gutless. It's singing away at 55/60mph, and anything above a 50 cruise feels a bit harsh. But as soon as you hit a hill, be ready to change down.

http://rjes.com/html/gearbox_types.html" onclick="window.open(this.href);return false; tells you which boxes give what gearing. Your VIN plate will tell you which box and engine your van started with.

So if you could get revs to about 2800 or3000 rpm at say seventy with a decent efi ...

Of course you can. 2950ish at 70 on the standard AAP paired with DJs...

could I get an old dj to return v high twenty mpg!

Mid-20s with a Westy interior and hightop, definitely, so very probably in a bare tintop... That's based on longer cruising runs, of course.

Changing the injection may improve it. It may not. It depends on if you map it for economy or power. Same as slapping a pair of big carbs on will gut your economy, whilst possibly (but no certainty) give you more power.

[billy739]

2950ish at 70 on the standard AAP paired with DJs

isant a standard AAP / tyre set up more around the 3400rpm @ 70mph ?

2950 is an AAP with a .70 5TH gear fitted on standard wheels? (.84 standard 5th) ?