2.7 or 2.8?

[Rik178m]

Really hope this hasnt been asked to death.

Is it more worthwhile doing the 2.8 conversion then the 2.7? what are the differences in power/torque? do the engines feel much different?

[DieselMeister]

It has. I'm not sure we had a definitive answer though! Depends on what parts you already have if any, I guess. That and whether you're a freak for two and seven or two and eight The result will be down to prep and tune but I can't honestly see them being hugely different..... No expert though.

[daimlerman]

One issue is the availability of cranks.Eta engines stopped being made more than 20 years ago. OK,if you have a mate in Europe you may be able to source a 324d crank but that's making it hard work as well.If you are starting with a 320,and can solve the crank issue,a basic spec 2.7 like mine is a simple way to a lot more grunt than your 320 has at the moment,think 129bhp to around 180...if starting with a 325,far more work and cash is needed for a worthwhile gain,not a lot of point going from 171bhp to 'only' 180(but a huge increase in low down torque) so a 2.8 makes more sense here.But remember,when tuning the M20,200bhp is available for around £2000,every 10bhp from here on will cost another £1000.... E34 525i's with M50 (192bhp out of the box) are available with low miles for £350ish....

[Rik178m]

I wonder if someone would do a stciky on the 2.8 build?

I'm starting with a m20b25 so i'd go for a 2.8. Whats the bhp likely to be? I'd only do it if I could get a few bargains.

I agree the m50 is a much cheaper and probs more reliable way of getting more power.

[stonesie]

Power... Its a stab in the dark but i would say 190-200, but power = bragging rights down the pub... Torque is what shoves you down the road (or makes your rear tyres squeal and self destruct) and you will get plenty of that too.

Sooo many things you could do depending on budget to get that up a bit, 6 branch manifold, cat cam, big bore throttle body, maby eaven ditch the air flow meter with its restrictive spring loaded flap and go megasquirt (stand-alone engine management)

If you really want to go mad then you could build it with lower compression and feed it some boost

[Rik178m]

Im thinking low budget 2.8 really then research the compression n turbo idea. so is it as simple as an m52 single vanos 2.8 crank and m20b20 conrods? on a late m20b25. obviously need to sort the ecu

[stonesie]

Yes and yes, need a better look into what compression that will give. Give it new bearings and get the head re-conditioned for piece of mind too, I think ant at A-tech has chips on the shelf for these, if not he can make you one that will run things safely.

[Rik178m]

Yeh I've read Jazzmans thread and Ant sorted his chip out. Is it only the 2.8 crank I can use or will say the 2.3 be the same? I realise that could be a stupid question!

I'm lost on compressions tbh. I know turbos need low comp and thats about it!

[GrindCulture]

The crank it what makes the engine a 2.8 by giving it a longer stroke. So yes, you will need a crank from an M52B28.

[Rik178m]

I'm good at asking stupid questions

[GrindCulture]

I'm good at asking stupid questions

It's all good, asking stupid questions is better than not asking stupid questions. Gotta learn somehow

[Rik178m]

[BadDave]

need a better look into what compression that will give.

It works at approximately 9.4:1 CR oobviusly there's a little leeway in that depending on how much of a skim the head has.



If going for an FI setup, you could machine a bit off the piston crown to reduce the CR to nearer 8.0:1 or use a decomp plate.


HTH

[Rik178m]

Dave Which option are you going for? Is a decomp plate just a thicker Head Gasket?

Whats the full spec of the turbo etc?

[jaffro]

templ8e30 did a good 2.8 build not to long ago ill try find a link as im looking into a 2.8 build 2

[Rik178m]

Yeh please post it up mate

[GrindCulture]

Go 3.1.

[Rik178m]

Go 3.1.

Ohhhhhh explain this 1

[GrindCulture]

Hehe, using an M54B30 or S50 crank (can't remember which), quite a bit more expencive again from what I hear, but 250bhp is a very real posibility with some other trick bits. Thought I'd just throw it out there

[Rik178m]

You shouldn't of said that cos now Im thinking about ripping my 330Ci 2 peices haha. Is it just the crank then or what other parts are needed?

[BadDave]

IIRC the 3.1 needs custom pistons

A well built 2.8 that's properly mapped can push out 250bhp

[BadDave]

http://www.gevans.info/m20/m20.php

some info on there fella

[march109]

most 2.7's need the block machining and the right parts, a budget build won'tnet you much over 180bhp, but the torque is worth while.

2.8 just needs 130mm rods, crank and spacer for a budget build all available from the bmw parts bin. Will net more power and torque than a 325i head slapped on an eta block.

2.9 needs custom pistons and over bored block but other than that is much the same as 2.8.

3.0 needs an M54 or S50 crank, more £££ again and then much the same again as a 2.8 but whats the point in a budget build when you have allready spunked a wad on the crank.

3.1 needs custom pistons and rods as well as overbore and M54/S50 crank.

Other combinations available especially for deep pockets.

[march109]

http://www.gevans.info/m20/m20.php

some info on there fella

Ignore the cr calculator, it needs work.

[jaffro]

http://www.e30zone.net/modules.php?name ... highlight=
this is iains build a it was amazing when finished

[Gunni]

IIRC the 3.1 needs custom pistons

A well built 2.8 that's properly mapped can push out 250bhp

not with a stock head and cam that´s for damn sure.
I´d say a 2.8 conversion, stock head and cam should net 200hp.


My 2.8 turbo should net out 400hp at about 1bar, and easily 400lb´s

[Rik178m]

I don't know what all the different cranks cost. Whats the ballpark for used cranks?
2.8 is looking favourite. I'd like to know what sort of options there are for turboing. Could you use a turbo off a similar sized engine? I doubt its going to be that simple.

[StuBeeDoo]

I would say that if you're planning on converting an M20B25, then 2.8 is the way to go. It's got to be good for 210bhp.
2.7's are soooo last year now. The supply of eta bottom ends is drying up - when did you last see a 525e on eBay?
Like someone (Daimlerman??) said above, if you've already got a 325i, there isn't a lot to be gained from building an eta/731 2.7 if it's top-end you're after.

[BadDave]

http://www.gevans.info/m20/m20.php

some info on there fella

Ignore the cr calculator, it needs work.

Gareth
I got the CR from Alex a while back

It works out at 9.4 ish for an N/A application

[BadDave]

OK,if you have a mate in Europe you may be able to source a 324d crank but that's making it hard work as well.

IIRC Midnight has a TD crank for sale.

That would make for a "bullet proof" bottem end.



HTH

[Gunni]

Show me one ETA crank that has failed from to much power or rpm.
It´s a myth.

[Simon13]

budget and engine build don't go! the cost will soon go over budget!

There are lots of 2.7's about and a few 2.8's. 90% don't make any power. But to get a 2.7 to give a good kick up the arse means £££

[DieselMeister]

I figure if you're rebuilding a 2.5, go 2.8 + FI. Not cheap but a worthwhile gain without fannying about trying to get an ETA bottom end. Either that or an S50

[Rik178m]

When I say budget I mean I dont want to spend thousands. If I aim low it wont go waaaaay over target. Cheapest conversion really.

Keep asking this bit - Can you fit say a turbo from another car with approx the same cc? I dont want to go over the capabilites of the standard drivetrain or spend £3.5k on turbo stuff. I thinking ebay used bits?

[march109]

Any engine rebuild is 2k + easy for a FULL rebuild, obviously you could change not only seals and gaskets but rods,pistons ect ect add a skim a cam and your waaaaay over budget allready.

Budget doesn't mean cheap, just means cost are expected or planned for in advance, if I heve to purchase something I won't pay over the odds I'll budget for it.

2.8 is £2k easy with stock head and aftermarket cam. my 2.8 cost a fair bit more than that as it was but Idin't pay for it and it did break ground for more out there.