Lightened flywheel / 5 speed conversion

I decided to swap from the 6 speed gearbox to a 5 speed and whilst doing so, also decided to replace the flywheel from the dual mass unit to a solid steel one. There is a weight saving to be had and I also felt my 6 speed was on the way out as there were a few funny noises. The 6 speed weighs 47kgs and the 5 speed 40kg's.
The new flywheel and clutch weighed 13.2kg's and the old setup was 16.2kgs so a total saving of 10kg's by fitting the lighter flywheel/clutch and the 5 speed box.
The M20 engine with its gearbox weigh 225kgs and the s50 and 6 speed weighed 270kgs so with these new additions it should now weigh 260kgs. (enough of these boring stats)

The clutch is from a e34 M5 and uses a sprung clutch disk to reduce gearbox chatter, I probably could have saved more weight if I'd gone for a different setup, but I want to use this on sunny weekends as well as track days so there was a compromise.


New solid flywheel.

New Sachs clutch (e34 m5)


Old clutch and flywheel removed and new flywheel fitted. (had to use BMW m20 flywheel bolts as the old ones were too long)


Clutch and pressure plate fitted.


5 speed gearbox fitted.

Fuel Pump

The E36 M3 Evo engine requires a fuel pump with a 5bar output and the standard e30 item is only 3 bar. Fortunately it's possible to fit the 5 bar unit in place of the standard pump.

Here is a photo of the E36 M3 pump (left) and the E30 item (right, this is actually an E30 M3 item).


And after a bit of measuring, cutting, soldering and general fiddling, you end up with one of these.

This first attempt failed fairly quickly, the rubber tube at the top joining the pump to the housing split under the 5 bar pressure, but luckily I was still at home testing. So it was quickly fixed with some fuel line I had.......

Here is a photo of what happens when you don't use the correct 'in-tank' fuel line!! (and means a ride home with the AA breakdown....)


The E30 M3 pump is slightly different to that in the standard E30 so I had to make up a new housing/pump assembly, and after learning the hard way how not to do it, I hope my newest creation will be fault free.

In order to stop the pump from slipping out of position and possibly disconnecting I kept the original solid metal return line which would give me something to strap the pump to. I had to modify the metal base plate as the pump wouldn't fit otherwise. I used a small piece of the original rubber to stop any vibrations from the pump making an annoying noise against the metal.


More vibration prevention. A length of in-tank hose cut lengthways and wrapped around the return pipe.


Job done.

Steering rack

The standard e30 steering rack is a bit on the slow side, 3.9 turns from lock to lock (if I remember correctly), when I fitted the 2.5L engine I also upgraded the rack to one from a e36, which I think was 3.4 turns, the difference was very noticeable, but I still wanted something quicker. I knew the 1.9L Z3 has a rack which is 2.8 turns but these are hard to find and usually very pricey too, so I settled for a E46 clubsport rack which is 3.0 turns but is also supposed to have a better 'heavier' feel than the standard E46 rack. These are much cheaper and very easy to find.
As with fitting the e36 rack there are some modification needed to make it all work. The rack needs spacers to stop it wobbling about in the mounting points of the subframe, these are simple round aluminium spacers, 14mm high, I just had a local machine shop make some up for me.

(Please note the rack should be mounted in the rear holes of the subframe)

Power steering lines - the mounting points aren't in the same place, you can modify (bend) the lines to make them work but I just didn't want to take the risk of it splitting where I'd bent it, especially if it happened on the track, so I decided to get a high pressure line made up for me by Pirtek as they have an outlet not far away. (photo below) I just took in the rack mounted to the subframe with the existing line, and they made that, worked fine and was rated to 3000psi!! But was just a bit ugly.



Ultimately though I wasn't happy with the chunky power steering line and when I saw custom sets being made by a guy on the e30zone I decided to get a set. (photo below is of the E46 rack with the custom power steering lines)

This then requires a 'p' clip to hold the line in place on the subframe, I used my 'rivnut' kit to insert a threaded sleeve into the whole after test fitting and marking the position.



I also upgraded the steering linkage setup. It comprised two E34 UJ's, one of which has been modified to have the top half of the e30 linkage (the part which connects to the steering shaft) and a knurled bar to fit the splines of the two halves together. I 'm hoping I will gain a few extra mm's clearance from the exhaust headers with this (to avoid them locking the steering under hard cornering!!), but I won't know until I fit everything in.





Power steering cooler - Some have said that with this E46 rack and extended periods of high intensity track use that you can boil the fluid and the steering locks!! So I decided to fit a power steering cooler. Some of the e36 racks used to come with a steering cooler mounted to the front of the rack, I happened to have one of these but as there is a possibility I might go off the track on the odd occasion I thought it probably wasn't wise to have it mounted so low without protection (and also right behind the sump I thought it wouldn't get much cooling air) and so I came up wth a plan to mount it behind the front kidney grilles.




After a few testing fitting I came up with this.


Had it sand blasted and powder coated.


As the cooler is mounted on the return line you can use jubile clips as its not under high pressure.


Done : )

Exhaust manifolds

One of the major problems with putting the S50 (e36 m3) engine into a RHD e30 is the exhaust manifolds. The steering linkage needs to go right through the middle of back set of three. Fortunately there is a company here in the UK who have taken the time to produce a set especially for this conversion, BTB. All you need to do is remortgage your house, sell a kidney, send them your old manifolds and they'll make you a set ; )

Here are some before and after shots



The lovely collector modification done by the guy who I bought the engine conversion from.

Nice new shiney system : )









Middle and back boxes.

Front subframe modification

The front subframe is known to occasionally crack at a few places so I decided to get those areas strengthened. AKG motorsports sell a bunch of parts designed for this along with other specific engine conversion parts for the S50. The areas that need strengthening are the engine mounting points and the anti-roll bar tabs.


I had the subframe sand blasted to removed the powder coating, then welded the plates on,



cleaned up the welds and had it powder coated satin black.


I will be using the AKG engine mounts as they compensate for the angle difference between the e36 and e30 mounting positions, and they are also a firmer compound so shouldn't allow the engine to move as much.


Here is the front subframe mounted up in the car. The front anti-roll bar has also been replaced with an Eibach adjustable one which has three positions to choose from on the drop link end.

Brief history

I've had my track car (Bmw E30) for several years now, it started life as a 318i, with the M40 engine, this then got replaced by the M20 2.5 engine as it was a cheap and easy way to get more power and fun, for the track days I was doing. The car took the back seat for a while as I bought an e30 m3 and stuck an s50 conversion in. The M3 has now been sold but I kept the engine conversion parts. There were several parts of the conversion I wasn't happy with and other parts which needed modifying as the M3 was LHD and my track e30 is RHD. This blog is to document the conversion process and any other modification I will be doing on the e30 along the way.
Here is a photo of the car as it was before. (My friend's car behind, both almost identical spec)