Fuel Question 2.0/2.5/2.7

[SilverShadow]

Lads,

This might sound like a stupid question but bare with meâ┚¬Ã‚¦Ãƒ¢Ã¢”š¬Ã‚¦.Question is from reading a lot of threads from the zone I understand that the 2litre M20 is very juicy on fuel compared to the 2.5 M20, But is it the same situation with a 2.7 M20?

Or does it all depend of how the 2.7 is built spec wise?

Any input would be much apriciated

[cubic]

I'm no expert but as far as i no! the 2litre is thirsty on account of the 731 head BM used which can flow enough air for 200bhp hence why you can get away with using this head for the 2.7 conversion.

as far as i know the best 2.7 build fuel consumption wise is when using 885 head and 325 pistons (head skimmed 1.5mm approx) and the thirstiest build using the 731 head and ( 9/1985> ) eta bottom end giving you a compression ratio of 10.1

[Gunni]

the 2.0 is weak
as the 320i is a heavy car, and the 2.0 isnԚ´t very efficient in power production,

[psychochild187]

far as i know the best 2.7 build fuel consumption wise is when using 885 head and 325 pistons (head skimmed 1.5mm approx) and the thirstiest build using the 731 head and ( 9/1985> ) eta bottom end giving you a compression ratio of 10.1

so with one is more powerfull.

[SilverShadow]

the 2.0 is weak
as the 320i is a heavy car, and the 2.0 isnԚ´t very efficient in power production,

Not sure about the 320i being a heavier car, as all 2 doors were the same weight regardless the engine size.

But the 2.0 is very unefficient compared to a 2.7!

[Templ8e30]

I'm no expert but as far as i no! the 2litre is thirsty on account of the 731 head BM used which can flow enough air for 200bhp hence why you can get away with using this head for the 2.7 conversion.

as far as i know the best 2.7 build fuel consumption wise is when using 885 head and 325 pistons (head skimmed 1.5mm approx) and the thirstiest build using the 731 head and ( 9/1985> ) eta bottom end giving you a compression ratio of 10.1

You don't skim the head, you need to skim the block for this method.

[qoute="gunni"]the 2.0 is weak
as the 320i is a heavy car, and the 2.0 isnԚ´t very efficient in power production[/quote]

Not really, the 2.0 makes 64.5bhp/litre wheras the 2.5 makes 68bhp/litre and the 2.0 isn't as heavy as a 2.5 either.

so with one is more powerfull.

The 885 head/325i pistons version is reputed to give more power but costs more than the 731 head/eta bottom end method because of the block machining costs.

Cheers,

Iain T

[liam012]

so hows the mpg working out on ur 2.7 Iain?

[cubic]

it comes down to the heads the 731 has 40mm inlet and 34mm exhaust valves and 885 has 42mm inlet and 36mm exhaust and different size and shape inlet and exhaust ports hence the 731 head is capable of around 200bhp and the 885 210bhp+ also the 325 piston has a specially shaped crown so when used with the 325 885 head means every thing works as it should bringing the compression ratio to 9.5:1 taking in to account that you are compressing 10% more air so will also run fine on supermarket fuels wheres as the 731 eta build would be super unleaded only.

there is many variations of the 2.7 build but in my humble opinion this is the best all round build short of coming across a set of alpina pistons

[cubic]

I'm no expert but as far as i no! the 2litre is thirsty on account of the 731 head BM used which can flow enough air for 200bhp hence why you can get away with using this head for the 2.7 conversion.

as far as i know the best 2.7 build fuel consumption wise is when using 885 head and 325 pistons (head skimmed 1.5mm approx) and the thirstiest build using the 731 head and ( 9/1985> ) eta bottom end giving you a compression ratio of 10.1

You don't skim the head, you need to skim the block for this method.

well spotted i miss typed that one brain rot ya see

[qoute="gunni"]the 2.0 is weak
as the 320i is a heavy car, and the 2.0 isnԚ´t very efficient in power production

Not really, the 2.0 makes 64.5bhp/litre wheras the 2.5 makes 68bhp/litre and the 2.0 isn't as heavy as a 2.5 either.

so with one is more powerfull.

The 885 head/325i pistons version is reputed to give more power but costs more than the 731 head/eta bottom end method because of the block machining costs.

Cheers,

Iain T[/quote]

[SilverShadow]

How can I find out what head I have on my 2.7? Is there some sort of number on the side???

[Theo]

Yes, on the inlet side of the head.