How To Convert A BMW M3 CSL From SMG to Manual

Car Tips, How-To | September 13th, 2019 by 4
BMW E46 M3 CSL 21 750x500

Not the easiest job in the world, but converting a BMW M3 CSL from SMG to manual is quite a project. 

It was never available in the US but, for the rest of the world, the E46 BMW M3 CSL is said by to be the best M-car ever made. One point of contention was that it was only ever available with the divisive SMG transmission. M3 Specialist Darragh Doyle andI had different ideas…

When I bought this car five years ago I was fulfilling a dream. I had bought a car that I’d wanted to own ever since a certain Mr. Clarkson had introduced it as possibly the most extreme road-car BMW had produced to date. He chose the Isle of Man, a place that is arguably known only for its extreme motorbike racing event that takes place every year, as the venue. When the review hit our scenes, I was barely seventeen years old and only just old enough to drive in the UK.

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Fast forward to eleven years later and I’d saved up enough cash to buy the cheapest M3 CSL in the country – a 114,000 mile car that was in surprisingly good condition. At the time, prices were still pretty reasonable and so I took literally all of my money out of the bank and spent it on my dream car.

When I bought the car I already had some reservations about the SMGII from friends who’d experienced it for short periods of time and disliked it. At this point I should make it clear that this post isn’t a dig at SMG – in fact, I’ve driven the car for five years in that configuration and a lot of the time it’s been really quite enjoyable.

I get it. It’s quick and it was the best option available at the time. It doesn’t ruin the car but personally? I was never happy with a computer doing all my hard work for me!

I’m the type of person who likes that special, extreme “race-car on the road” feeling and the CSL gave me that. What it didn’t give me was complete control over the driving experience.

As I said, the SMG system is quick and, when you’re at full acceleration and grab the paddle, the way it just throws the next gear in – mechanical sympathy be damned – can be absolutely hilarious. To get it to even contemplate setting number six you have to turn DSC off, otherwise you’d be triggering traction control with every shift. At this point it feels like the car is firing the gears at you with a canon from somewhere behind the rear bumper.

In my opinion however, it’s not consistent. When the SMG makes a bad gear change, you end up annoyed that you could have done it better yourself and it can do this a lot at anything less than full speed. I enjoy driving my car on the road and rarely use the car on track.

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I guess the main question people will be asking is, why did you do this? Why not just modify a Manual M3 instead of hacking your classic car apart?

Well firstly, I like the way the CSL is put together. It’s nearly perfect. I don’t like huge amounts of power on the road – I like lightness and I love the way the CSL looks – the pinnacle of the E46 family. All it needed was a clutch pedal and a real gear stick.

If I search through my forum posts you can already see that I’d toyed with the idea since I bought the car back in 2014 but was never brave enough –there would be a multiple people with the same answers… “You’ll devalue the car! SMG is fine! SMG is better, you just can’t drive it properly!” This always scared me enough to put me off.

Fast forward again to five and a half years later. I looked through my phone recently and realized I’d not taken a picture of my so-called “pride and joy” for about ten months. I was falling out of love.

After putting myself back on the market for something new and exciting, it wasn’t long before I came to the decision that the next best option was a GT3RS but I didn’t have the extra £50,000 sitting in the bank that was required to get to that point. As fate would have it, I decided instead to do a few things to get the CSL back up to scratch.

That’s when a friend from work introduced me to Darragh Doyle at Everything ///M3’s in Banbury, UK. After the first raft of work, we soon realized we had a lot in common and quickly became friends. Over a beer some weeks later, we started to cook up a plan.

I began researching and already knew that people had been converting standard M3s from SMG to Manual. The engineering is undeniably clever – the base gearbox is the same. The difference is that the SMG has an ECU and hydraulic pump to move the gear selector, whereas the manual has a clutch and gear lever. Some guys on the US M3Forum had already done the hard work of researching the parts required, it was just a matter of sourcing a bellhousing to add the springs required to centre a gear lever (they can also be machined to convert them, but finding a genuine manual one takes away some uncertainty).

So I got to work. I bought all the parts I needed and checked off my list until I was ready to bite the bullet. I would be converting a genuine M3 CSL – my genuine M3 CSL – to have the gearbox I always thought it should have had. Since very few had ever been done (at time of writing, there may only be four in the world), Darragh and I decided that it would be good to document the process.

The first step is to make some space under the car. We removed the undertrays, exhaust, propshaft and heatshield from the transmission tunnel.

We then removed the original transmission and put it onto the bench next to the donor. Removing both bellhousings gave us the opportunity to inspect the gears and have a look at what else was different. We also decided to tap the gear position sensor to go full OEM with the job. This part is optional if you don’t mind being able to start the car in gear… just be careful!

The next job was to remove all of the SMG paraphernalia. This included the actuator, pump and reservoir which all came away as one system once the gearbox was out of the way.

The bellhousing was swapped onto my original SMG box – a couple of other bits were changed just because it was easy to do so whilst it was on the bench and it was ready to go back in the car.

Now for the scary part. The body-in-white is essentially the same from an SMG to Manual – the only difference is a blanking plate that the SMG controller bolts to where the linkage would normally pass through the body. The underseal was removed, the welds were ground off and the plate was free to be removed. The area was then treated and painted.

With the gearbox refitted it was time to tackle the other body difference – the linkage bracket. This can be bought from BMW, presumably for crash repair reasons, although goodness knows how much else you’d have to damage the car to need one…

In order to locate it correctly, the new linkage was fitted to the box and the bracket was then spot welded exactly as it is during production (using a human arm rather than a robot one). Again, the area was treated and painted to return it to factory standard.

It’s possible to buy a full manual wiring harness but we wanted to have the ability to put the car back to its original condition if required and so we kept the SMG harness and ECU in the car. This may change in the future if I ever decide to make the modification more permanent. In this case however, all that was required were a couple of wiring adaptations and for some extras to be added when we routed in the clutch line.

Next, the pedals went in. Amazingly, the SMG pedal box simply has an empty axle on the side where the clutch pedal would sit. All brackets are present for springs and switches. We found a lot of this as we went around the car – it’s all there ready to go. As luck would have it, we found a donor pedal box pretty easily, meaning we just needed to buy a clutch master and slave cylinder.

Finally, after the clutch was bled, it was time to code the car. This is where the CSL was a little tricky. The DME was just different enough that it threw up some errors and, in the end, a remote desktop session from Martyn @ ECUworx saved the day.

The car was then put back together and a BMW ‘ZHP’ shift knob and Alcantara performance gaiter finished everything off, making the car look exactly as if BMW themselves had done the job.

And now, time for a drive. It’s a strange feeling… Almost the same but somehow different. Having a clutch and a gearstick suddenly means I’m using the whole left-hand side of my body again instead of just my finger tips to click a paddle. It’s changed the car completely – for the better. When I really want to, I feel like I can actually change gears just as quickly as the SMG box, but this time, I know exactly how long each will take. I don’t have to select the “ferocity” of the gearbox for different situations. I just have to change the way I drive.

I’m not saying this is how all CSLs should have been but, just like Porsche with the 991 GT3, it really should have been an option.

From the perspective of someone who works in the car industry, I can understand why. In BMW’s mind, this was the fastest M3 they’d ever made and the SMGII system was their fastest transmission – those fractions of seconds add up around the Nürburgring and maybe SMGII was the only way the car could go “under 8 minutes”.

For me however, this isn’t just a track car. It doesn’t just exist for its Nürburgring time. I consider the M3 CSL to be a truly great road car – and mine just got a whole lot better.

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