tuning an m20b25 to the max?

[deian]

ok, so after seeing some bmw video's on the net, i might just stick to a 2.5i m20 engine and tune it to the max.

http://videos.streetfire.net/Player.aspx?kw=13

So are there any knowledgable guys here who can explain to me the engine modifications and bhp one can make to the 325is without resorting to forced induction? as u all know, i've been toying on the idea of firstly an s38 engine, too rare too much money, an m30 still an option, but i like the idea of a well rebuilt/modified 2.5i M20 engine. please discuss with me please. just how solid is the m20 engine over the m30 for mad modifications?

thanks
deian

[Andy325i]

With a 2.7 crank these can make upto 250bhp, but look at what it will cost you to get it there. Total respect for those that have done it, but look at what it will cost you. For the same money you could well have an M power engine that will give a lot more power.

M20B25's seam to crack heads more than the B20 as well :(:(


Andy

[M5pilot]

Without doing anything to the bottom end your really restricted to around 205 bhp max.

As an example a memeber called Dale had his standard 325i engine modified with the following:

Schrick 284/272 cam
Alpina 6 branch Manifold
Scorpion Exhaust
Dbilas Throttle Bodies
Standalone management.

He made 196 bhp

You could go a bit further by porting the head to quite an extent. BTB manifold could be used. Instead of spending huge amounts on throttle bodies do a MAF conversion. Use a big bore throttle body.

Bexleys did a 325i with cam 6 branch and MAF and got 195 bhp. No head work.

You could better boith if you raised the compression ratio by skiming the head.

All really depends on what state your bottom end is in.

With a 2.7 conversion you could easily knock on 230 BHP if your prepared to build it using very high compression pistons and all of the above mods.

The C2 which I have access to puts out a huge amount of torque everywhere and makes 215 bhp - very very fast car.

[jonb]

why plough loads of money into a m20 to make it as quick as a bmw/golf diesel.

try the m30 engine. this is a boat anchor, but makes lots of power out of the box. sals mate has spent thousands on his engine to make it put out the same power as an m30.

the m30 is easyly upgraded to 250bhp.

[E30Adam]

I think before people start coming up with ideas we need to know what your budget is.

If you've only got a couple of grand then you aren't going to end up with huge amounts of horsepower.

You're going on about tuning an M20B25 to the max but that could cost you tens of thousands of pounds. If you really spent enough on it you could probably hit near 300bhp without FI but it would probably cost you fifty grand in high perfornamce specialist parts and tuning.

It all depends on how deep your wallet is but there's no easier and cheaper way of getting BHP than doing an engine conversion.

[nikos]

mine is 2.7 with cam, gas flowed head, and haltech management and last week it gave 186 with 31 kgr but costed a lot and and it was better to go for another engine either the e36 m3 or the e30 m3

[E327UKL]

the car that bexleys got 196 bhp out of was mine. it had a full race head, shrick cam, 6 branch, bbtb and a unichip. it was remapped at 196.5bhp and 177.0ib/ft. that lot a bought new and cost about Ԛ£2500.

why waste that money when for the same money you can turbo or fit a evo in there?

[M5pilot]

2.5k is alot of money for 25bhp. Thats 1k per BHP!!

Some people pay 5k for 210 bhp!

Best thing in my opinion is to fit the S50/S52 from the E36 M3 3.0/3.2. Proper M power engines which will give huge performance. 3.2 a buit fragile but still will monster everything on the road in an e30 shell.

If youve got more time then fit the S38 engine from an M5.

Other than that there is Turbo - some people prefer NA power though. huge torque with a reliable 250+ BHP.

[Danstable]

"2.5k is alot of money for 25bhp. Thats 1k per BHP!!"........erm no

Shift the decimal point one place to the left and you'll be closer to the truth

[deian]

well dotted

[Kos]

on a 325i, m20 using tripple down draught webbers, stainless powerflow manifold (hartge copy), head skim port n' polish and finaly a 284 cam 225bhp and 211torque. that was yeras ago,
270-300bhp is possible with bigger valves, alloy flywheel, over bore or stroker kit to 2.7 and 3.0 and use forged high comp pistons arp bolts maybe H section rods and a 2.4d steel crank if you want to be real flash. top it of with the monster 302 cam, car would have been totally useless up to 4000rpm but it would go to 8500rpm maybe 9000rpm !! ignition system would need uprating, i'd would have used MSD 6AL ignition module(which you can incorporate full throtle gear change launch control and set your own rev limit) and one of their power coils.
you are looking at Ԛ£5000-Ԛ£6000 but its the ultimate m20, be different and DONT do an engine swop!!

[Toby_Unna]

be different and DONT do an engine swop!!

for use on the road? yeah

it's pretty obvious you can get silly power out of any engine if you replace enough of it and build it to race spec.

and an alloy flywheel won't make much difference to your power figure

[Ant]

I'd still go turbo

the engines will certainly take the extra stresses and you can do it without any internal mods

yes of course I'm biased but you could buy a late exchange engine from BMW in a crate, spanner up a turbo system and stick it all in, even with some aftermarket ECU fitment you'd still have change from 3K

So thats all new engine, making 250 ish BHP(5.5psi) reliably all day long and with immense torque right through the rev range.

I know the original post on this subjetc did state "wiothout going FI" but why resist the urge to purge ??


be different, fit a turbo

[E30BeemerLad]

must be such a cool experience having M20 noise with a turbo helping it along the road. Boost driving is an addictive thing, find yourself quite often going along the road and seing something up ahead knowing you need to slow for it and then you feel a bit of boost and think to yourself, i'll just let this spool up a bit more...

Don't forget to uprate your brakes

[Kos]

be different and DONT do an engine swop!!

for use on the road? yeah

it's pretty obvious you can get silly power out of any engine if you replace enough of it and build it to race spec.

and an alloy flywheel won't make much difference to your power figure

it would be fun on the road sound the nuts!!
fly wheel helps it rev like round the clock, pointless doing all the mods and not change the fly wheel, it all goes hand in hand. he did ask what is the max possible, and thats about it with out a turbo. be a complete loon and do both, have a c/r of 8.5:1 with 10psi, you'd be looking at 375bhp, silly torque . oh and 10 grand outa pocket!!!!

[E30BeemerLad]

Kos, looking at your 13.9 second 1/4 mile time in your sig with that engine and mods doesn't make me feel too bad with my 15.9 times without having a sport box or LSD and Nankangs at the time

[Kos]

Kos, looking at your 13.9 second 1/4 mile time in your sig with that engine and mods doesn't make me feel too bad with my 15.9 times without having a sport box or LSD and Nankangs at the time

i'm guessing you got a 2.5? thats pretty good, unfortunately i got a 5 sp overdrive box and a 3.25 lsd in the m3, its geared for about 185mph, but that will change over winter. my old 2.5isport (phase 1) with a manifold and cam did a 15.4 and with 50hp shot oh nitrous did a 14.9.