Which engine would you choose for a swap?

[Das Delfin]

The M54 is great on paper and would be my choice for a daily driver, but I've read a ton of stories about head bolts pulling out their threads when you go to change the head gasket. That's a deal breaker for me. Can anyone with first hand experience comment on the prevalence of this?

[wazzu70]

The M44 has the different cam follower/rocker setup. The M44 was even more of an economy engine design. Just FYI.

[Andrew325is]

FWIW I swapped an M42 into my 325i :) This was a long time ago though when there were not a lot of good options available. I drove a friends 85 318i and liked the feeling on turn in with less weight over the front axle and my M20 was tired so I decided to put in an M42 because I didn’t want the weight of an iron block 24v.

My swap was not stock though so it was more fun than usual. Standalone engine management, bigger cams, ltw flywheel, ZF320, 3.73 rear gears. Its pretty fun and throttle response is good with the cams and better engine tuning. The 3.73 gears with the ZF is like 4.44 gears with the G240 so it is geared to go! Overall pretty fun car and the original intent was to turbo it.

I don’t dislike the swap but if I were to do something today it would be an N52 hands down. Lightweight, 6cyl sound, torque, power.

Not that anyone cares but I figured I would weigh in since I went from M20 to M42 thats tweaked a bit but wish I had an N52...

That's awesome! N52 sounds nice, but it's too custom for me and things like cruise control and A/C won't work without some electronics dedication, plus there is no dipstick... I decided on M44. Installs with original E30 parts and everything will work. Perfectly adequate power for a daily driver with good MPG. And it's reliable and parts are cheap. A little more complicated design than an M20, but nowhere near as complicated as an N52.

[wazzu70]

N52 isn’t on the list because it requires too much custom work. These 3 engines are easy to put in an E30 using off-the-shelf parts. In regards to DBW on the M54, there’s no reason to delete it. The electronic pedal is easy to install and I believe it gives a nicer experience than the cable throttle.

Also, let’s assume the E30 you’re putting this into doesn’t have an engine. There’s this weird purist thing going on where people think M42s only belong in a 318is, and it seems people either love them or hate them and those who hate them seem to be very vocal about it. It’s very odd. Kinda thinking I should stick an M42 into my 325is just so people can hate on it. :)

FWIW I swapped an M42 into my 325i :) This was a long time ago though when there were not a lot of good options available. I drove a friends 85 318i and liked the feeling on turn in with less weight over the front axle and my M20 was tired so I decided to put in an M42 because I didn’t want the weight of an iron block 24v.

My swap was not stock though so it was more fun than usual. Standalone engine management, bigger cams, ltw flywheel, ZF320, 3.73 rear gears. Its pretty fun and throttle response is good with the cams and better engine tuning. The 3.73 gears with the ZF is like 4.44 gears with the G240 so it is geared to go! Overall pretty fun car and the original intent was to turbo it.

I don’t dislike the swap but if I were to do something today it would be an N52 hands down. Lightweight, 6cyl sound, torque, power.

Not that anyone cares but I figured I would weigh in since I went from M20 to M42 thats tweaked a bit but wish I had an N52...

[lukeADE335i]

The AWD must be pretty bad for ecconomy. I manage 9L/100km highway with the M30B35! City mileage is a bit sobering though - between 14L/100km and 17L/100km depending on how enthusiastic I am feeling ;)

[Kershaw]

That definitely is. The best I've gotten in my manual ix with highway cruising is 22mpg. I had an automatic ix years ago that I used to get 26mpg pretty regularly. I got 29.5-30mpg in my 325es before that. Standard mileage for a 325i/is that I've seen is around 24-25mpg.

[digger]

The best I've gotten in my E30 with the M20 is 9.8L/100km / 24 MPG.

Hope that's not highway cruising

[Andrew325is]

The best I've gotten in my E30 with the M20 is 9.8L/100km / 24 MPG.

[varg]

And they can't do that anymore because it would fail modern emissions testing.

[djjerme]

State of tune has a lot to do with it. If you don't use mild camshafts and tune to get every last horsepower and ft-lb of torque you definitely do some harm to fuel economy, you can only go so far leaning out cruise areas and transients for economy with an engine that was specced out for peak power. Powerful NA 4 cylinder cars like the S2000 get fuel economy in the mid 20s, and those were tuned with being daily driven reliably and cheaply and passing emissions in mind. Sounds like the MM is tuned to make some unimpressive horsepower to avoid sacrificing economy and emissions passing motor status.

7L/100km is 33.6 US mpg, 8L/100km is 29.4mpg. I've never heard of anyone getting anywhere near that fuel economy with an E30 325i, you must drive like the pedal is made of balsa. Very impressive. You'd have to be out of your head to be dissatisfied with 29.4mpg in a 6cyl E30.

I manage 16-18mpg, that's 13.1-14.7L/100km.

Just don't look to what car makers were doing in the 70's early 80's to get some of those stupid high economy numbers. The old lean burn systems with crazy 20:1ish ratios. No wonder performance took such a nose dive. But hey, we got something like 30 mpg in our lazy Datsun.

[MrBurgundy]

I really think you'd love an m54 in the e30, since you're going to be running around town mostly..

All the fun is in the middle of the power band. The grunt of that engine is nuts.

[Shangsta]

M4x with ITBs sounds pretty sweet.

https://youtu.be/0nysqbIuXJY

https://youtu.be/cQyGOB_uwjk

Ill agree with this. I absolutely love the way my itb m44 in my TI sounds

[digger]

State of tune has a lot to do with it. If you don't use mild camshafts and tune to get every last horsepower and ft-lb of torque you definitely do some harm to fuel economy, you can only go so far leaning out cruise areas and transients for economy with an engine that was specced out for peak power. Powerful NA 4 cylinder cars like the S2000 get fuel economy in the mid 20s, and those were tuned with being daily driven reliably and cheaply and passing emissions in mind. Sounds like the MM is tuned to make some unimpressive horsepower to avoid sacrificing economy and emissions passing motor status.

7L/100km is 33.6 US mpg, 8L/100km is 29.4mpg. I've never heard of anyone getting anywhere near that fuel economy with an E30 325i, you must drive like the pedal is made of balsa. Very impressive. You'd have to be out of your head to be dissatisfied with 29.4mpg in a 6cyl E30.

I manage 16-18mpg, that's 13.1-14.7L/100km.

camshaft is most important, just look at what vanos numbers something like an s54/s50b32 cruises at 2500rpm vs WOT 2500rpm. the cam centreline is something like 120-130 cruise vs 70-80 WOT. next to no overlap vs shit load of it. on a fixed cam engine if you dont cop big a hit to fuel economy you are leaving alot on the table for WOT, all depends on priority though

[varg]

State of tune has a lot to do with it. If you don't use mild camshafts and tune to get every last horsepower and ft-lb of torque you definitely do some harm to fuel economy, you can only go so far leaning out cruise areas and transients for economy with an engine that was specced out for peak power. Powerful NA 4 cylinder cars like the S2000 get fuel economy in the mid 20s, and those were tuned with being daily driven reliably and cheaply and passing emissions in mind. Sounds like the MM is tuned to make some unimpressive horsepower to avoid sacrificing economy and emissions passing motor status.

7L/100km is 33.6 US mpg, 8L/100km is 29.4mpg. I've never heard of anyone getting anywhere near that fuel economy with an E30 325i, you must drive like the pedal is made of balsa. Very impressive. You'd have to be out of your head to be dissatisfied with 29.4mpg in a 6cyl E30.

I manage 16-18mpg, that's 13.1-14.7L/100km.

[digger]

Good info. How about some numbers? And how does that stock M20B25 you're comparing the MM build to compare to an M54B30? Crude 2 bank semi-sequential/part time batch fire fuel injection with limited trim capability vs arguably modern fully sequential fuel injection setup with VVT. E46s get better fuel economy than E30s, they're more aerodynamic but they're also heavier and have more rolling resistance, a few of the factors at play. However, I'm willing to bet an M54B30 swap with stock EMS beats a stock E30 325i in the fuel economy department hands down but someone out there probably can speak from experience on the numbers. If fuel economy is the deciding factor between a $10,000 M42 and an M54 swap which will cost what, half that? You're just not going to recoup that cost in a timely manner.

i was getting 6.5-7L/100km i think its 35 US mpg running motronic with MM cam that was a decade ago. it was 13years ago it was stock b25 but i recall i was luckly to get 7.5/8L/100 on a run. you would really hope a m54b30 would get better economy than any m20. i wasnt suggesting anyone do anything for fuel economy but building a stroker doesnt always cause the economoy to goto shit.