Learn me: BMW 2.5L engines

I have been toying with the idea of swapping a 24 engine into my e30 since the m20 is getting tired and they're getting hard to find at this point. If I go above 2.7 liters of displacement, I'll get stuck with a restrictor for stage rally, so I'm going to stick with a 2.5 liter engine. But as I was looking through the wikipedia pages for BMW engines, I noticed that they decided that the M52 should get a fairly significant power decrease compared to the m50 or m54. Anybody have any idea why this is?

On another note, I'd really like the m54 since it's an aluminum block and has dual vanos so it makes peak torque sooner, but if I recall, a lot of them had overheating issues. Can someone point out things to look for when I'm perusing junkyards for these motors to try to avoid one that's been overheated?

All can say is the M50 in my 1992 525i was one of the best engines that I have ever owned.  Dinan chipped with hotter coils with a close ratio 5MT and 390:1 LSD behind it probably helped a bit.  Probably a rare combo my mine came that way from the factory.  Absolutely loved it, very tractable and pulled hard all the way to redline.

No fancy pants Vanos stuff either.

I can't speak to the exact reasons for the difference in power between the variants, but if you're inclined toward the M54 I can offer a few tidbits that may be useful.

The cooling issues aren't really any different than other BMW engines of the same era; the issue is that when overheated the M54 tends to warp its cylinder head and forcefully yank one or more head bolts out of the block. The iron block variants don't do this. What I'd look for are any signs of blown up cooling system parts, especially the expansion tank. If you have a chance to pull the valve cover, you can check torque on the head bolts for a more definitive examination.

The other problem M54s have relates to the low-tension rings BMW used, which fail and allow significant oil consumption, and the related problem of the CCV failing. If you're tearing down the motor you can replace them with earlier spec rings and resolve the ring problem. The CCV can be rebuilt with new parts easily. If, however, you stick with the stock rings, even a brand new CCV may not solve the oil consumption issue, as the low vacuum of the CCV is overpowered by the high vacuum in the cylinders under deceleration, pulling oil past the rings. The quick-and-dirty fix is to add a vacuum line between the unused nipple on the CCV and the back of the intake manifold. This adds a lot of vacuum to the crankcase, equalizing pressure with the cylinders, and thus stopping the oil being drawn in. A quick search for the "02Pilot Mod" will turn up lots of info; I can point you to the development thread if you want it.

For the M54, expect to reseal everything, replace the VANOS seals, the CCV, and the cooling system at a minimum.

In reply to 02Pilot :

That's great information, I appreciate it! I'll definitely do some reading on those.

Has anyone here had experience with both the M50B25 and the M54B25? I'd be curious to hear how different the power delivery feels with the dual vanos. Obviously it'll all be anecdotal, but interesting nonetheless. 

artur1808 said:

I have been toying with the idea of swapping a 24 engine into my e30 since the m20 is getting tired and they're getting hard to find at this point. If I go above 2.7 liters of displacement, I'll get stuck with a restrictor for stage rally, so I'm going to stick with a 2.5 liter engine. But as I was looking through the wikipedia pages for BMW engines, I noticed that they decided that the M52 should get a fairly significant power decrease compared to the m50 or m54. Anybody have any idea why this is?

The M52B25 was intended to be the base engine while the M52B28 was the big dog. The M52 also received a more torque-oriented manifold (with the M50 one being a direct bolt on). It looks like a case of detuning for a market niche.

In reply to akylekoz :

This has been my experience with the M50 in my 1992 525i touring as well. At 214,XXX miles and the engine is still silky smooth in its power delivery. 

The non-Vanos engines have a bit of a reputation for lasting longer. I've heard that Vanos adds area under the curve, but it is still pretty negligible in the case of the M50's.

As 02Pilot already mentioned, the M54 is nice for the lighter weight, but you do run a higher risk of warping heads. If I were in the OP's shoes I would be looking for an early non-vanos M50. Less to go wrong and you don't give up much in terms of performance.

The M50 had a much freer flowing intake manifold and was more "peaky" in nature. The M52/M54 has a different manifold designed to fatten the curve at the expense of peak power; the M50 manifold is a popular swap and really wakes those motors up. 

The internet lore has also always said that BMW choked out the small-displacement M52 and M54 with the introduction of the larger displacement variants to create a, uh, "more marketable" difference between the options.

Really the question is if you are willing to deal with VANOS in exchange for a fatter curve because with the M50 manifold and tuning the newer motors WILL make more power than the M50. I believe the M52TU and M54 are DBW throttle as well so may want to avoid for that reason.

I'm pretty sure that chart is either wrong or missing an engine or two. The m52 in the 328s was making the same or very similar power to the m50 in the 325.

There was also an m52 in the 323 that made less power than the m50 (but it was really replacing the 318's m42/44, which it was more powerful than).

I think the goodcheap recipe is m52 from a 328 for the aluminum, plus m50 intake for slightly better. Some folks used to swap all the obd1 stuff from the m50 as well, but I'm not sure the value of that, unless you have a "chipped" m50 ecu.

Oh wait, maybe the more powerful m52 is a 2.8l motor....

Robbie said:

[...]

Oh wait, maybe the more powerful m52 is a 2.8l motor....

Yeah, unfortunately I need to stay under 2.5 liters, so the chart(s) have been cropped to just show the 2.5L variants.

M52 is a 2.8l typically. But I think the one posted is from the 323i. It’s a 2.5l with a crappier exhaust from what I have gathered.

M54 is a 3.0l from what I know. 

The M50 is a great motor, good linear power band and in my experience, very reliable. The vanos work isn’t too bad. I did it with basic tools and a high schoolers confidence. 

M50, M52, and M54 all come in 2.5 liter variants, which is the basis of this comparison. M52 also had a 2.8L, and M54 also had a 3.0L.

I'm starting to think I should lean towards the M50 for the sake of simplicity if nothing else. I wonder what the weight difference is between an M20 and M50....

This is relevant to me since I just got an e46, 1999 323i with the M52B25TU. It's mated to an automatic right now so it's a little boring, but not too slouchy in a ~3300lb car. I plan to drift with it eventually, so it may get boost or an M54B30 in the future. 

M50 would make more sense for simplicity, non-Vanos, etc.

M52/M54 would probably be more available. (Readily available in e46s and e39s I believe.) M50s are mostly going to be out of e36s, which are starting to get more rare and pricey as they are somewhat desirable right now. 

In reply to AWSX1686 :

I've heard nothing but good things about the M54B30. Part of the reason I'm considering an M54B25 is the potential of any "easy" upgrade to an M54B30 once I get enough events under my belt that my novice restriction is lifted.

Full disclosure, I bought the car like this.  But I am really enjoying the combination in my E30.

I was able to track down the builder, the motor is from a low mileage '91.  The provider of the chip to run it is:  http://www3.sympatico.ca/mdsylva/products.htm

I have a 180 hp chip that will run on west coast 91 rated premium and the 190 hp chip that required fuel I can not reliably find locally.  The 180 chip is really sweet, power delivery is very liner up to red line.  

The oil pan to allow the motor to fit has two versions, E34, one with the windage tray on the oil pan, one that you bolt to the engine.

Sorry, "big" pictures.

The e30 5 speed works with the M50 motor.  You do want to drill the holes, at the correct angel, in the bell housing, at the bottom, to get to the last two mounting bolts on the motor.  You will find this "surprise"  if you have bolted the engine and trans together before you install the combo in the car.  The front end sheet metal on the E30 does not "unbolt". Your choices are to lift the combination of engine/trans over the radiator support or do it like the factory and put the body over the drive train.  Your choice.  

And I would add the sump guard.

From www.red46.com     They have a version that is made to cover the M50 motor in an E30 chassis.

David   

M52 non-TU gets you single vanos w/ a simpler control method (basic on/off solenoid vs. PWM controlled on the m52TU and later motors). The extra area under the curve w/ the vanos is a good thing for rally. It's basically the same as the m50tu outside manifold, so you could go that route as well. OH! And both are NOT dbw to simplify the swap

artur1808 said:

In reply to AWSX1686 :

I've heard nothing but good things about the M54B30. Part of the reason I'm considering an M54B25 is the potential of any "easy" upgrade to an M54B30 once I get enough events under my belt that my novice restriction is lifted.

Can you not just start with the more desireable engine and restrictor, then pull the restrictor when your novice tag is lifted?

 

It's funny to see how many people are talking about using a nearly 30 year old motor for "simplicity," the single VANOS unit is not difficult. 10 years ago when I finished my OBD-I S52 swap into an E30, guys were already working M54 and S54 swaps into E30s.  

spandak said:

M52 is a 2.8l typically. But I think the one posted is from the 323i. It’s a 2.5l with a crappier exhaust from what I have gathered.

M54 is a 3.0l from what I know. 

The M50 is a great motor, good linear power band and in my experience, very reliable. The vanos work isn’t too bad. I did it with basic tools and a high schoolers confidence. 

This, redoing the VANOS stuff (at least on the M50TUV) is actually surprisingly easy. I'm not sure why so many people are scared of it. 

artur1808 said:

 

I'm starting to think I should lean towards the M50 for the sake of simplicity if nothing else. I wonder what the weight difference is between an M20 and M50....

M50 is about 425 lbs (give or take 5lbs if its VANOS or non-VANOS). Replacing the stock cast-iron manifold with the ebay tubular header (which you have to do anyhow to easily fit an e30) saves you about 10 lbs offhand.

Incidentally, that 425lbs is pretty much the same as an M42 PLUS a G240 TRANSMISSION :)

M20 is right around 400 lbs.

I went from an M42 (which is only about 325 lbs.) to the M50. Honestly, it doesn't feel that much heavier in the car, especially once I upped my front spring rates a bit. Going from an M20, probably would hardly notice the difference. 

jr02518 said:

Full disclosure, I bought the car like this.  But I am really enjoying the combination in my E30.

I was able to track down the builder, the motor is from a low mileage '91.  The provider of the chip to run it is:  http://www3.sympatico.ca/mdsylva/products.htm

I have a 180 hp chip that will run on west coast 91 rated premium and the 190 hp chip that required fuel I can not reliably find locally.  The 180 chip is really sweet, power delivery is very liner up to red line.  

The oil pan to allow the motor to fit has two versions, E34, one with the windage tray on the oil pan, one that you bolt to the engine.

 

Sorry, "big" pictures.

The e30 5 speed works with the M50 motor.  You do want to drill the holes, at the correct angel, in the bell housing, at the bottom, to get to the last two mounting bolts on the motor.  You will find this "surprise"  if you have bolted the engine and trans together before you install the combo in the car.  The front end sheet metal on the E30 does not "unbolt". Your choices are to lift the combination of engine/trans over the radiator support or do it like the factory and put the body over the drive train.  Your choice.  

And I would add the sump guard.

 

 

From www.red46.com     They have a version that is made to cover the M50 motor in an E30 chassis.

David   

 

If you talk to ben at Red46, he has the measurements that I sent him for a much larger stage-rally-size skidplate for the M50 in the e30 using different rear mounts (not the steering rack bolts). It's the one that's on my car. 

In reply to z31maniac :

That is also an option. I feel a bit uneasy putting a 55mm restrictor on a (relatively) modern engine that has an 80mm throttle body from the factory. I know there's a guy currently competing with a restrictor on his S52, but I believe that came with a 60-something millimeter throttle body from the factory and (as I understand it) a less advanced intake manifold. 

In reply to irish44j :

Yeah, I doubt I'd notice the extra 30(ish) lbs. I'm already getting rid of as much weight from the nose of the car as possible, so the M54 seems pretty tempting, but an iron-block M50 should do the job without any significant weight penalty. Plus, I like the idea of not needing to deal with deleting EWS and fabricating an oil pickup tube. 

And I actually sent Ben an email on the topic this morning! Hopefully he still has the dimensions. 

lol, until you add all that weight back with lighting and stuff lol. 

what are you removing from the nose to reduce weight (other than, I assume, all the A/C stuff)?

In reply to irish44j :

Yeah, but I figure getting rid of stuff will offset some of the lighting and huge skid plate. 

Entire A/C system removed, no power steering, currently removing the ABS pump/distribution block thing. Then some smaller stuff, like my car never had a windshield washer bottle so I just bought a generic amazon one that I'll probably mount farther back than factory, I removed the factory hood hinge mechanism when I installed hood pins, etc. None of which are going to be a huge savings, but I figure that if nothing else it'll offset some of the weight that has to get added back in with rally reinforcements and lights. 

artur1808 said:

In reply to z31maniac :

That is also an option. I feel a bit uneasy putting a 55mm restrictor on a (relatively) modern engine that has an 80mm throttle body from the factory. I know there's a guy currently competing with a restrictor on his S52, but I believe that came with a 60-something millimeter throttle body from the factory and (as I understand it) a less advanced intake manifold. 

Where are you seeing the M54 has an 80mm throttle body from the factory? That's how the large the throttle body is on the new 5.0 GT Mustangs making 460hp. 

Everything I'm finding says a 67.5/68mm internal diameter. Stock S52 is 64mm. 

I'd swap the better engine and use the restrictor. You're not going to hurt the engine using a restrictor, and you prevent yourself from ending up buying two engines and performing the swap 2 times.