Worth working the M20?

[MaksV]

24V swap all the way.

[TheRips]

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.

As much as I would love to do the swap myself, don't have the know how, time to take in that much info. and then attempt it. From what I've gathered, the 24V responds better to N/A upgrades and has more after market support due to DOHC and VANOS. Is it by a huge margin or not really?

i got a huge increase in MPG by stroking with higher CR and MM camshaft.

Yeah I thought this happened, which is why I asked.

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

The budget stroker seems like a viable option considering I already have the B25 bits. Are the gains impressive with this method?

I'm guessing your engine was closer to the 10k mark haha?


Build might take some time considering I'm going to do a semester of university in the US next year, but would love to work out my plans!

[digger]

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

what is a big cam? The MM is "big cam" duration wise but wide LSA so same (or close to it) overlap area as stock therefore idles and drives like stock but has alot of topend. if you use a schrick then yes economy will suffer more than with MM. When you go from 8.8:1 CR to ~11:1 this is a big change in efficiency. it is also worth pointing out that the M20B25 is hardly what anyone would call efficient in the first place.

[TobyB]

The M52/M54 is a much more advanced engine... if you like the 'vintage' of the E30,
keep the M20,
but if you just want your right foot to put a big grin on your face,
get a 24v motor.

That's one of the nicest things about Jenn's E46- that motor is sooooo nice....

t

[digger]

As much as I would love to do the swap myself, don't have the know how, time to take in that much info. and then attempt it. From what I've gathered, the 24V responds better to N/A upgrades and has more after market support due to DOHC and VANOS. Is it by a huge margin or not really?



Yeah I thought this happened, which is why I asked.



The budget stroker seems like a viable option considering I already have the B25 bits. Are the gains impressive with this method?

I'm guessing your engine was closer to the 10k mark haha?


Build might take some time considering I'm going to do a semester of university in the US next year, but would love to work out my plans!

i wouldn't do a swap if you werent going to do a whole lot of the work yourself you'd have to pay a decent shop $100/hr in these parts for labour.

Also few people consider the cost in rebuilding a swap engine and just swap in a high mileage junk yard engine......

there is no question the 24V BMW engines are superior but i wouldn't be considering a M5X engine when SXX are not a whole lot more if going down the swap path

[TheRips]

Thanks for all the feed back guys, very helpful. I think sticking with the M20 will be a better option for now. Less issues with probation license.

My fuel economy is bad at the moment, even for an M20. 300-350 km's from a full tank. I' thinking the first thing I will do, preferably in the next couple of weeks is buy some new injectors. I was advised to buy some 4 pintle S50 injectors.

Do I need to change anything to make 17 lb/hr injectors function correctly in the M20 considering its a higher pressure? I was told they were just fine in the M20.

What are your opinions on the budget 2.7L build you advised earlier digger? Good BFYB considering eta parts are cheap?

Thanks again guys

[nando]

They will work if you have a functioning o2 sensor - be sure you've got one, and that it's fresh. If you dont have one, it runs open loop and will be way rich.

[digger]

Thanks for all the feed back guys, very helpful. I think sticking with the M20 will be a better option for now. Less issues with probation license.

My fuel economy is bad at the moment, even for an M20. 300-350 km's from a full tank. I' thinking the first thing I will do, preferably in the next couple of weeks is buy some new injectors. I was advised to buy some 4 pintle S50 injectors.

Do I need to change anything to make 17 lb/hr injectors function correctly in the M20 considering its a higher pressure? I was told they were just fine in the M20.

What are your opinions on the budget 2.7L build you advised earlier digger? Good BFYB considering eta parts are cheap?

Thanks again guys

the setup i mentioned is not the most budget you can do but if you want an actual well rounded performer you need a decent CR and proper squish that comes from the B25 piston and 885 is the cheapest. The 2.8L option also works well but finding a crank that fits without additional work may take time.

if you had an ETA you could do topend swap for an I which makes good gains over an eta but not a large increase in hp past 5000rpm compared to a healthy B25

[TheRips]

the setup i mentioned is not the most budget you can do but if you want an actual well rounded performer you need a decent CR and proper squish that comes from the B25 piston and 885 is the cheapest. The 2.8L option also works well but finding a crank that fits without additional work may take time.

Well rounded performance is what I want! Does this method increase CR by much? So considering I already have the B25 engine, all I would need is the cam gear, B27 crank, B27 rods and a machined block?

Any other info. you can give me about it? Will definitely look into it, thanks digger!

[u3b3rg33k]

I am under the impression that your average 2.8L mod lowers CR. I don't think there's any benefit to be had from lowering CR on an NA engine, unless you live in a part of the world where high octane fuel doesn't exist.

As for fuel injectors, I sent off a handful of OE injectors to be "rebuilt"/cleaned/benched, then picked the closest set and installed them. The end result is a happier engine that starts more easily after sitting for a while.

[digger]

I am under the impression that your average 2.8L mod lowers CR. I don't think there's any benefit to be had from lowering CR on an NA engine, unless you live in a part of the world where high octane fuel doesn't exist.

As for fuel injectors, I sent off a handful of OE injectors to be "rebuilt"/cleaned/benched, then picked the closest set and installed them. The end result is a happier engine that starts more easily after sitting for a while.

not correct the 2.8L is about ~9.7:1 and the 2.7L ~9.3:1 IIRC

the idea is to have the piston come to the same position at TDC so the chamber volume is the same and the squish is the same. If that is achieved the extra swept volume means the CR can't be lower it is higher

[u3b3rg33k]

I was pretty sure there was some version of that mod that ended up with either a lower TDC or different (shorter) pistons that hurt CR, but since i'm not planning on doing it any time soon, well, meh.

[digger]

I was pretty sure there was some version of that mod that ended up with either a lower TDC or different (shorter) pistons that hurt CR, but since i'm not planning on doing it any time soon, well, meh.

that is the I-topend swap onto a complete eta bottom end (crank, pistons and rods)which lowers CR

[TheRips]

So if there isn't any compression loss and it should be reasonably cheap (correct?), doing standard intake and exhaust work is still a good place to start? Does the block machining cost a decent amount?

[TobyB]

My fuel economy is bad at the moment, even for an M20. 300-350 km's from a full tank. I' thinking the first thing I will do, preferably in the next couple of weeks is buy some new injectors.

Before you start buying parts, try troubleshooting it first. You may find something
easy to fix that also goes a long way towards solving your need for performance.

Since you're planning on sticking with the M20, get it working right before you go any further.


t