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airmanjay 01-04-2010 10:33 AM

S50 M50 swap anyone?
My question is if anyone that has done this swap let me know about how they did it, using Zionsville? Difficulty doing the swap, worth it or not, does it change the weight ratio that much in driving, and the biggest thing reliability. Your imput would be greatly appreciated, since it is an option that I am looking into and would like all in information before i do it. thank you.

dannyb 01-04-2010 11:17 AM

Im doing a m50 swap this winter, ill let know what i think about it after.

richie_s999 01-04-2010 11:19 AM

talk to SamE30, he did the swap last year. Beleive he has a tonne of pics!

T.Dot_E30 01-04-2010 12:12 PM

Spend a few days reading before asking questions start here:
and then here:

Here is a short bit of summary info:

Basic FAQ:

How difficult is the swap?

On a scale of 1-10, 1 being an oil change and 10 being rebuilding a transmission, I’d give this somewhere around a 7 or 8, depending on how you go about it.

How much will it cost?

This can and will vary greatly from person to person. It’s possible to do this swap for $500 or less, or you can spend upwards of $10,000. I’d say count on $2k for a basic m50 swap and $5k for a well done s52 swap. These are very rough estimates. It can be done much cheaper or at a much higher cost. It depends if you buy new or used parts, do the labor yourself, etc…

What are the major basic required parts?

Engine: m50, m52, s50, s52, complete with wire harness, ECU, accessories.
E34 525i oil pan, oil pump, dipstick
E36 engine mount arms
E28 motor mounts
E34 throttle cable
E21 brake booster

These are only the basics, and some may be substituted for other parts. People find cheaper/better parts to use all the time, but the above listed are the common parts that the majority of people use.

What needs customized?

If you use an e30 325 transmission (Getrag 260), you’ll need to modify the transmission cross member and the shift linkage. Some welding experience is required for this, or you can purchase these parts from members of the forum who currently (as of 8/2009) produce them.

The e21 brake booster needs to have the shaft modified. It basically needs shortened, thinned down, and threaded. There are other ways to get the job done though.

Radiator hoses aren’t always a direct fit.

The wiring harness on the engine will need spliced into the body harness at the connector near the firewall.

How involved is the wiring?

There are about 15 wires that need connected. The best way to do this is look at the schematics and create a pin out chart. This process takes time and research, but isn’t physically hard to do. You don’t want to mess it up though, as you can heavily damage the wiring and components, or even start a fire. There are several companies that sell harness adaptors if you don’t want to mess with the wiring.

Most people get a spare body side plug from an e36/e34, as well as a spare engine side plug from an e30, and then splice these two parts together. This way, you aren’t hacking your cars harness or your engine harness.


How to read the wire diagrams:

Go here:

Find the manual for your car or engine, whatever side you are doing pinouts for.

Open the manual, and skip to the section that starts talking about power distribution and various under hood parts.

This is what it will look like:

You want to look for any instance of either c101 or x20, such as what is circled. C101 is the e30 engine connector, x20 is the e36/e34 connector. So if you are looking at an e30 manual, just look for c101. When you look at the e36/e34 manual, look for x20.

The c101 connector is the big round connector on your firewall. It has 20 or so pins on it (it’s a square connector with less pins if you have an 84-85 model). Each pin will be drawn out in this manual. Here, in the example, we are looking at pin 10 (see the 10 next to where it says c101).

The curved lines show which way the signal is coming through the connector. In this example, you see it’s coming FROM the oil level sensor, TO the engine oil fault indicator (the oil level light in your car).

The VI/GN and BU/WT are the colors of the wires. The wire between the sensor and the connector is blue with a white stripe, the wire between the connector and the warning light is Violet with a green stripe.

The .5 next to the color is the wire size. Apparently this is in millimeters squared. .5 will be a little wire, .75 medium, 1 is big. (I think).

You now know what color the wire is on the engine side, what color t is on the body side, what pin it is in the connector, and what its function is.

The schematics are generally laid out as power (+12 volts) from the top of the pages, to ground at the bottom of the pages. Further details of what various symbols mean can be found in the beginning pages of the manuals.

e30_kid89 01-04-2010 05:07 PM

Wow....I can't believe people still ask what do i need? Has anybody done it?? It's kinda irritating...


Dissembler 01-04-2010 05:44 PM

If you can't research properly and need to ask "what do I need?", then you can't do it.

There are plenty of reputable shops who sponsor this site that would be more than happy to help you out.

Conversly, buy an e36 or e46. Bam, swap done.

And, as pointed out before, r3vlimited is THE place to go if you are infact serious about this.

Red_Rocket 01-04-2010 11:34 PM

Hey, im in the same boat. I was wondering if anybody has tried to swap an M20 in a 325is. Id really like to get some know how to do this. Is there a big HP gain?

Dissembler 01-05-2010 01:05 AM


Originally Posted by Red_Rocket (Post 1379027)
Hey, im in the same boat. I was wondering if anybody has tried to swap an M20 in a 325is. Id really like to get some know how to do this. Is there a big HP gain?

lol, seriously?

An e30 with the "325" designation already has an m20 in it...:rolleyes:

craz azn 01-05-2010 01:22 AM


Originally Posted by Dissembler (Post 1379045)
lol, seriously?

An e30 with the "325" designation already has an m20 in it...:rolleyes:

You fail at sarcasm.

e30_kid89 01-05-2010 01:30 AM


Originally Posted by craz azn (Post 1379052)
You fail at sarcasm.


ok bye

Dissembler 01-05-2010 01:46 AM


Originally Posted by craz azn (Post 1379052)
You fail at sarcasm.

I was being sarcastic? Wasn't trying to be.

El Gato Liso 01-05-2010 01:49 AM

^^^ fail to cover up the fail fail

richie_s999 01-05-2010 01:51 AM


Originally Posted by Dissembler (Post 1379063)
I was being sarcastic? Wasn't trying to be.

NO thats the scary read Devons post and think sarcasm....

richie_s999 01-05-2010 01:54 AM

:cool:forget the M50, go M42!!!!!!!!!!!!!!!!!!!!:cool:

Dissembler 01-05-2010 02:02 AM

oh lol, i do fail :(

I thought that car in his pic look familiar, but theres so many red e30s on here its hard to tell.

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