Lightweight e30, have platform/engine ideas, leaning 318is/N52… talk me out of it

[hoveringuy]

The E30 rear suspension, by the way, must be tried to be... appreciated???
A bunch of years ago, having spent decades in E30s and older, I got a beater E36.
The increase in rear grip is... incredible.
For outright handling performance with no other considerations, the E30 chassis is a turd.
There are dozens of better places to start.
Just like the 911, ('wow this is fast. imagine what a fantastic car it would be if the engine was in the right place')
the E30 is flawed by design.
Yes, you can still make it fast.
Yes, it takes more work for less effort than 4 corners of a-arms would give you.
(Miata, wot?)

.

As an instructor I've gotten to ride in quite a few E36's and the way they plant the rear still amazes me, like the harder you push them the harder they stick...

but I think a lot of it is also that they can run wider tires and larger plus a more modern selection of rubber.

Their aero is markedly better.

The funny thing is, I still keep up with them on my little 225's with trailing arms; it's just not as easy. I need to use 100% of my traction budget on cornering.

[varg]

the M42 is disappointing. It doesn't make all that much torque, it doesn't rev to 8500 so it doesn't really make F20C horsepower,
and it has an almost- square bore to stroke ratio, so it doesn't even feel all that peppy. Couple that with a massive dual-
mass flywheel, an E30 that, by 1990, wasn't really very light, and it's just... not all that. Especially by modern standards.
The M42 was a test for 4- valve cylinders and new block features like the 'eco' oil filter,
but it also has that goofy Alfa idler (yes, late E36 parts get rid of that) a timing chain guide
that costs more than 2 or 3 'ran when pulled' engines, an oil pump on the crankshaft (which they never did again)
and relatively low production numbers. It's not a huge surprise that 2024 BMW doesn't give a hoot about them.

Shame about that crank-driven oil pump that they never did again, it's the one thing the M42 has over every other BMW engine of the era. A pump like that would have made the modified M/S5X engines so much better. Imagine an M5X that doesn't need a hole drilled in the block for an oil pump chain tensioner, an upgraded shaft, and a safety wired/tack welded nut to rev safely, and can instead rev to 7500rpm out of the box if you upgrade the cams to make it worth doing. That would be so nice. Instead we got oil pump shafts that snap and nuts that back off, and two different pumps, one of which has no upgraded parts available for some reason.

The other stuff is what I always come back to when the E30 318is comes up. I read articles and forum posts about my 318is, people say "it loves to rev" or "revvy 4 cylinder" and I think: have you ever actually driven one? Have you ever driven anything else with a 4 cylinder engine? It doesn't love to rev, it's out of steam soon after 6,000rpm. It doesn't love to rev, the throttle response is unremarkable with its massive flywheel. Swapping my 318is and driving back to back within a week of each other, my M20 clutch and flywheel equipped turbo M42 was no more of a rev happy little engine than my turbo M20. A K20 swap is what 318is sounds like when described by an autoblogger, "poor man's M3", except it's better than an S14 because it's lighter and makes more power at a fraction of the cost.

At the end of the day, the logically 'right' answers don't really apply, and we do what makes us happy.
And that, for each of us, is the right answer. But my right answer might not be the right answer for you.

t
has e30s. has M54B30s. Needs to do it.

E30s got popular because they were cheap and an excellent platform for modding. Easy to work on, strong drivetrains with easily available parts, handsome interior, easy on the eyes, pretty light. Once they started being $10,000 cars again they lost some luster imo. They need mods; stock steering sucks, the chassis is so flexible that it makes the doors harder to close when you jack it up, it has poor traction under power if you make power, and the shifter is the worst of any sporty car I've ever driven, even rebuilt with a DSSR. I love my E30 but the car has some drawbacks, which is why I said earlier in the thread to let an E30 be an E30 and appreciate what it is.

Now get on that M54 swap since you have them.

[TobyB]

The thing missing from this discussion-

the M42 is disappointing. It doesn't make all that much torque, it doesn't rev to 8500 so it doesn't really make F20C horsepower,
and it has an almost- square bore to stroke ratio, so it doesn't even feel all that peppy. Couple that with a massive dual-
mass flywheel, an E30 that, by 1990, wasn't really very light, and it's just... not all that. Especially by modern standards.
The M42 was a test for 4- valve cylinders and new block features like the 'eco' oil filter,
but it also has that goofy Alfa idler (yes, late E36 parts get rid of that) a timing chain guide
that costs more than 2 or 3 'ran when pulled' engines, an oil pump on the crankshaft (which they never did again)
and relatively low production numbers. It's not a huge surprise that 2024 BMW doesn't give a hoot about them.

If they'd made the S42 available to mere mortals... well, that would be a whole different story....

The M20 torque is fun, kind of like a straight- 6 pickup.
The M54B30 torque is even more significant, and starts earlier and lasts longer. And really, the ONLY
weight advantage of an M42 over the aluminum M54 is that the weight sits 10 cm further back. But there's
100bhp less to push it.
The N52 is almost modern, without most of the problems that BMW designed in thereafter...

The E30 rear suspension, by the way, must be tried to be... appreciated???
A bunch of years ago, having spent decades in E30s and older, I got a beater E36.
The increase in rear grip is... incredible.
For outright handling performance with no other considerations, the E30 chassis is a turd.
There are dozens of better places to start.
Just like the 911, ('wow this is fast. imagine what a fantastic car it would be if the engine was in the right place')
the E30 is flawed by design.
Yes, you can still make it fast.
Yes, it takes more work for less effort than 4 corners of a-arms would give you.
(Miata, wot?)

At the end of the day, the logically 'right' answers don't really apply, and we do what makes us happy.
And that, for each of us, is the right answer. But my right answer might not be the right answer for you.

t
has e30s. has M54B30s. Needs to do it.

[AWDBOB]

I get 26-27 hiway and 20 city. and about 3 1/2 laps per gallon

I have an electric water pump and electric PS plus variable valve lift so not pulling a constant vacuum, plus they have wideband 02 so it keeps the lambda tight.

on the other hand, I have e30 aero...

That's what I get in my 2.7l stroked m20, ~175whp

Edit: no a/c. sanden 7hp compressor on it drops down to 23ish highway

[hoveringuy]

That's my dream build! What are you MPGs if you don't mind my asking?

I get 26-27 hiway and 20 city. and about 3 1/2 laps per gallon

I have an electric water pump and electric PS plus variable valve lift so not pulling a constant vacuum, plus they have wideband 02 so it keeps the lambda tight.

on the other hand, I have e30 aero...

[packratbimmer]

I'm a little nostalgic for the M20, I definitely enjoyed the mechanical character of that engine.

Wouldn't go back to it in a 100 years, I have +110whp with the N52, ZERO leaks, it's lighter and I have a 6-speed, plus my oil pan is higher and more protected. When the engine was running rough INPA told me exactly which coil pack was going bad AND it has really good fuel economy from VVL.

That's my dream build! What are you MPGs if you don't mind my asking?

[hoveringuy]

Great thread!!! Wouldn't it be great if all the new E30 folks could drive an E30 325i with a perfectly working M20. I think a lot of folks buy a project car and think "ah these M20 engines are horrible - what can I do to upgrade" when they are not taking into account that the engine is tired and out of tune. Obviously, many folks on REV want mucho power, but what I'm saying is that potentially 50% of folks would be psyched with a light 325i and 175 HP.

I'm a little nostalgic for the M20, I definitely enjoyed the mechanical character of that engine.

Wouldn't go back to it in a 100 years, I have +110whp with the N52, ZERO leaks, it's lighter and I have a 6-speed, plus my oil pan is higher and more protected. When the engine was running rough INPA told me exactly which coil pack was going bad AND it has really good fuel economy from VVL.

[packratbimmer]

Great thread!!! Wouldn't it be great if all the new E30 folks could drive an E30 325i with a perfectly working M20. I think a lot of folks buy a project car and think "ah these M20 engines are horrible - what can I do to upgrade" when they are not taking into account that the engine is tired and out of tune. Obviously, many folks on REV want mucho power, but what I'm saying is that potentially 50% of folks would be psyched with a light 325i and 175 HP.

[amcp]

Having experience with a 318is M42 slicktop, a bunch of m20s 325s, a S52 swapped cammed 325 and a S54 325, I'll agree the lighter nose on the M42 is a sweet feeling. But the punch of the S54 is addicting. A well setup s52/s50 is a nice middle ground.

[AWDBOB]

Like many, I have been reading the N52 subform for ages when I can't sleep. My perception is that the complications are such that the juice doesn't seem to be worth the squeeze, yet.

I adore the way an M20b25 feels/sounds in a well set up E30.

There are a few affordable M20 stroker motors that you can build if you want a little more, with the bonus of a very simple, fantastic and sounding driving experience.

M52b28 crank 130mm M20b27 rods, late model short skirt 325i pistons, shave deck ~0.5mm to make a 2.8. Sometimes hard to find a b28 crank with small counterweights and have to have them turned to clear piston skirts which can be a pain.

or as I do it since M20b27s are practically given away at this point:

M20b27 crank/rods, late model short skirt 325i pistons, deck shaved 2mm.

Makes a 9.4:1 compression 2.7L, I have been very happy with the few I've done.

I do think as I get older I chase the dragon a bit in finding the "best combo", but the best car seems to be the one that I drive the most. I really think a stock M20b25 car that's well set up, with a pnp standalone and good exhaust as a bonus will get you most of the way there.

I don't love the way 24v engines feel in an E30. All of the 24v swapped cars I've driven haven't influenced me enough to switch away from the M20 platform, but that is purely preference.

[2mAn]

Go drive some E30s, that would help the decision making... Where are you located?

[Jb325is]

This is a great post, good to see some healthy activity on here.

I agree with most of the sentiments above, I think you're getting some good input here. My personal car went from M20-->M90-->S54-->S50-->M54 and my opinion is that the M54 is a really nice happy medium of power / balance. The M90 was too heavy, the S54 was too much, S50/M54 was just about perfect but the M54 was lighter.

That said, I think the supporting modifications are more important. Any nicely spec'd e30 with high quality dampers, fresh bushings/arms, proper alignment, good tires will provide the experience you're after... My opinion would be to skip the M42.

[packratbimmer]

Maybe, if all of the accessories are on the other side. But that M42 weight was wet + all accessories (PS, Alt, AC) and that picture is a dry weight with no visible accessories. Still, it shows the potential of the K24 swap to be lighter than M42 if you keep the same transmission.

Agreed: When we are studying these weights online one must also remember that the K engines were bolted to a transaxle which is heavier than the 260 Getrag--for instance.

[varg]

wow .. weighs out identical to the m42

Maybe, if all of the accessories are on the other side. But that M42 weight was wet + all accessories (PS, Alt, AC) and that picture is a dry weight with no visible accessories. Still, it shows the potential of the K24 swap to be lighter than M42 if you keep the same transmission.

[FredK]

If I wanted to make a nice canyon carving E30, I would probably get an M20B25-powered car, grab a used M20 for $500 or less, and build a slightly modified engine for a modest price--maybe around $3500 - 4000 inclusive of machine work for something with new pistons and balancing work. The best modifications will be to replace the suspension bushings and get good dampers and not going crazy with engine mods. I don't want an E30 that goes too fast, as it's not that safe of a car should something go awry.

If "driving a slow car fast" means taking pleasure in a momentum car, having more than say, 200 wtq at your disposal reduces the satisfaction of keeping the car on edge when mistakes can be nearly erased with torque on tap. On the other hand, it is satisfying to have a lightweight car with good power-to-weight.

I think an N52 swap would be a great mix of affordability, power, and reliability. The downside, as you've identified, is that you would have to do some fabrication and wiring. But, there are folks on the N52 subforum who are very knowledgeable and helpful, so if you have that DIY spirit, I think you can get things done.