Worth working the M20?

[TheRips]

Hello ladies and gents,

Just got my 325i a couple months ago and have just finished up all the maintenance work and swapped in the 5 speed.

Now I am on the pursuit of more power. Although over here in Australia, turbo-ing it while I'm still on probationary license gets me into all sorts of trouble that include me having no license.

So, my question is - for the cost of swapping in a 24V motor, could I make better power from doing some work to the M20, or would it be better to get the 24V in order to make better numbers down the track (considering I can't turbo for quite some time)?

Prices will be much larger over here in the land of expensive everything, but all is relative so what do you guys think?

Thanks a lot for the help!

[SkiFree]

I love the M20 and would recommend that route based on personal biases, however given your parameters it sounds like a 24v might be better suited for what your looking to do.

[jlevie]

Short of Forced Induction, additional power from an M20B25 will require major modifications to the engine, which are quite expensive. Here in the US you could spend more than $6k for not a lot of increased power. An engine swap to an S50/52 would cost less and provide more gain.

[digger]

no S50B30US or S52B32 in Oz unless they have been privatetly imported in which case they are like rocking horse shit. that leaves the S50 euro or better as being worthwhile which unless you are pretty handy would cost quite a bit for just the engine and these are not exactly low mileage these days.

How much will it cost you to do a 24V swap? that wil tell you how much work you can do to the M20

i like the M20 with a careful selectio of parts you can make a good improvement witout breaking the budget

[getouth]

Keep the M20, research all your parts and work it. 30 bhp can be had for as little as $ 2k. My $0.02.

[e30leigh]

we are getting big numbers from the strokers in m20s. strock to 2.8 with a m52b28 or 3.0 with m54b30 and it will fly. add to that a nice large shrick cam, a tune, injectors intake and exhuast and itll be really well. one of our customers at work has a 3.1 from using a s50 crank in his m20. hes got a big shrick cam, head work, possibly itb's? i can remember though. and the ussually supporting equipment and tunes and hes making about 250+hp at the wheels.

[TheRips]

Alright thanks for the info.

To give me an idea, what sorta money have you spent on your beast to reach those numbers if you dont mind me asking digger?

Can I expect fuel economy to drop a lot with a worked motor?

What new chip would be best to accomodate upgrades down the track? Was thinking the Miller intake and MAF combo would be a good place to start.

[TheRips]

Anyone?

Open to suggestions for the first mod to get the build underway!

[e30leigh]

almost every power increasing mods are gona reduce economy.

about the only power increasing modd that can surely add economy is an optimising tune. but these dont often see much added horse power. as the factory tunes are ussually rather good and theres not much to be done if all is in good order.

SOMETIMES things like CIA's and a better flowing exhuast can add fuel economy as it reduces the restrictions on the motor and lets it breath easier. therefore its not working as hard to create the power so fuel economy increases.

HOWEVER add a bigger cam, raise compression, low back pressure high flowing exhuast systems, and forced induction set ups will always reduce economy.

the basics of power = more air/fuel in and out faster the more power you will make.
of course thats broad. you need to get more in with the right misture and make sure its burnt fully for optimum results. but thats lengthy.

research a few basic things. start out slow. build up. you will learn heaps and will end up with something to be proud of.

[digger]

HOWEVER add a bigger cam, raise compression, low back pressure high flowing exhuast systems, and forced induction set ups will always reduce economy.

not true, far too generalised comments, i got a huge increase in MPG by stroking with higher CR and MM camshaft.

[digger]

Anyone?

Open to suggestions for the first mod to get the build underway!

starting with the miller PSIK is pretty good BFYB according to the dyno plots.

expect to pay 5-10k for a decent build 3L+

above a standard rebuild (gasket, seals etc) you need crank, pistons, cam, valve springs, rockers, porting, extractors/exhaust , injectors, bottom end machining, tune

i advise a budget 2.7L with eta crank, B25 piston, B25 head, eta rods. decked block, camgear

[e30leigh]

not true, far too generalised comments, i got a huge increase in MPG by stroking with higher CR and MM camshaft.

sorry. i stand corrected. my experiance was the opposite. i lost economy. but i picked up a large amount of power with big cams.

[The Humjet]

I love the m20 but mainly when boosted. However I do respect diggers car a lot.
These days you could pick up an m50b25tu or m50b25NV motor for almost the same price the old m20b25. And both offer more power out of the box. If you research and know what your buying and doing it all by yourself it shouldn't be an expensive swap.
I've done an m30b35 swap before on my friends car and I can tell you they really hammer I was very surprised when I first took it for a drive. This is thing upsetting Holden VZ SS Commodore drivers at the traffic lights. And this swap was done very cheaply with a junkyard motor and $60 m10 gearbox. But they are a pig on fuel you have to really try your best to even get just 350km on a tank. That's with a 3.15 ratio diff.
I think a 24v swap would make just as much power but the torque of the m30 is just so fun on the street. Especially with the 4.10 ratio diff it was first fitted with.
And an m50 should also be more fuel efficient considering my mums got an e46 330i with an m54 in it and that's not too bad.

[nando]

not true, far too generalised comments, i got a huge increase in MPG by stroking with higher CR and MM camshaft.

yeah, it doesn't take any more power than it did before to keep the car moving or accelerate normally. what you've really done is make the engine more efficient, it actually has to work less to keep the car at a constant speed. yes it will use more fuel at full load, because it's also making more power, but you don't always drive at WOT (I hope).

[u3b3rg33k]

That's got to be the single best benefit of a CR bump. Probably one of the most underrated upgrades you can do (not that it's quick & simple or anything).