Endurance Trialling a Citroen AX, & Bike Engine Swapping it
Discussion
As Background:
Sometimes I stagger even myself with what I get my into after a few fizzy beverages... but this New Year's was slightly different. I managed to talk myself and then very quickly s mate into going endurance trialling, more specifically The Motor Cycling Club's 100th running of the Land's End Trial. For those unfamiliar with the event Jonny Smith off of the Late Brake Show, Smith & Sniff and all that has just done a 3-parter on it. Coincedently we were the car behind him in the running order so kept running into camera crew and ended up featuring in the 3rd installment a surpring amount.
It was our first dabble into any form of motorsport and what a baptism of fire. Neither of us think much of 6+hr drives, and both of us can hustle our old land rovers over pretty technical terrain, and thought these would translate well. But nothing really prepared us for 400miles (including the drive to the start line) of near continuous driving over ~26hrs. We were up for 38hrs in all, there's no long motorway stints to get into a grove, just endless little lanes and junctions only broken up by special sections, which were easily some of the hardest off-road driving I've ever done.
I'm sure 1/2 the lanes used in the event are a stroll normally; but by the time the course had been subject to 29" of rain and snow in the week, and 240x bikes, trikes and cars skidding up them. What are usually near-forgotten, westcountry byways of gravel covered tractor tracks. Were now a ruiness combination of slick bed rock, thick clay, foot-deep slury, jaggered banks, massive sump-skimming ruts, gnarly tree root steps and fords that'd have the x5 driving yummy mummies of Surrey u-turning in a heart beat. Oh also, you're only allowed 2wd, road tyres, 4 forwarding facing lights on the front of the car, a paper route book and one attempt at each section. So no LED Lightbar-clad Discovery 2s on 35" mud-terrains with 3 diff locks, Warn winches and ipad-sized satnavs on the entry sheet.
The rule book is far from what my navigator and I would call definitive though, there's a mind bending amount of exceptions, exemptions, amendments and appendices, which leads to 7 bike, 9 car and 2 mixed classes.
Our weapon of choice, dubbed the Battle AX, is a 28yr old, 0.95l, 3 door Citroen AX, purchased hastily off FB Markteplace in the dark the Monday before entries had to be finalised. We'd considered hundreds of cars in the 5 week search for a car, reached out to dozens, either to find it had sold, the ad was a scam, or that they lived in the lake disctrict (apparently that's where every cheap k11 is??). But looking round it after the 100mile drive home, in the cold light of day, the AX fit our clueless criteria very well:
1. Cheap - we'd resided ouselves to the car would likely have to be scrapped after.
2. Reliable - well it lasted the 'test-drive' home.
3. Wasn't rotten - ours only had small hole in the rear arch. 40 minutes of burning in some scrap plate, a lick of hammerite and a dab of underseal later and it was more obvious than before in a non-matching shade of green and (I think) waterproof.
4. Small over hangs & good ground clearance - if you look at the side profile of an AX they're comically good at both of these from the factory
5. Good power:weight - the AX has sweet FA of both, but especially little power in sub 1 litre form, although luckily ours is a later one with bosch efi and weighs a feather-like 630kg...
In the end it was the lack of power that let us down more than anything else, which leads me to the second part of the title:
Does anyone have any experience swapping the whole engine of the BMW K1200RS 'Flying-Brick' era bike into a PSA car (such as our AX) or even just swapping the head?
Why?
1.Compared to most of the other entrants seemingly carrying several hundred kilos of balast for traction, we found lightweight and momentum our friend. For cars that are already heavy, going even heavier over the driven wheels helps gain traction. But as we're currently less than 800kg soaking wet at the startline we simply didn't get bogged down where others did, so going for a powerful but light bike engine helps maintain this.
2. Trialling's an odd one; it's like a mixture of hill climbing, rallying and rock crawling. The end result being that you do everything in 1st gear to give yourself the most torque and no chance of stalling trying to grab 2nd, the sections we did were short enough that being sat on the limiter only doing 10 mph wasn't really an issue. So a freer, higher revving engine is a big bonus.
3.We want to stay in class 1 as we've already got the car and it's already proven pretty good; which basically means <1300cc, fwd, and it'll have to remain 4 cylinder as that's what we started with.
But why this engine speicially? Well I'd heard a while back the original BMW K75 bike just had a reorintated PSA TU engine with a cylinder 'chopped-off', which does appear to be true (mostly according to wiki). After the K75 in the 'Flying-Brick' family came the K100, K1, K1000, K1100 and finally the king of the castle being K1200RS. I can't find any paper trail at this point linking the final 4 cylinder version of the 3 cylinder version of a 4 cylinder PSA engine anywhere, but it would make sense when BMW evolved the 3-pot 750cc engine into the 4-pot 1000cc that the 'extra' cylinder would be exactly the same as our existing block in the Citroen.
The most common swap for AX seems to be Saxo VTS 1.6 16v, getting us a respectible 120hp but we would change class because of the cc and saxo engines are now worth real money... Where in comparison the engineers at BMW completely went to town on the original TU... starting as a 954cc, SOHC, 8v, carb'ed, cambelted 4-cylinder making 35hp at 6,500rpm (49hp, in ours with the single point efi), to a 1,171cc, DOHC, 16v with timing chains making 128hp at 8,750rpm and with a similar the torque increase too.
Very long story short; we've got the trialling bug now, the Edinburgh Trial is in September, and we need a lot more POWER for when we get there... any advice on that would be much appreciate!
Sometimes I stagger even myself with what I get my into after a few fizzy beverages... but this New Year's was slightly different. I managed to talk myself and then very quickly s mate into going endurance trialling, more specifically The Motor Cycling Club's 100th running of the Land's End Trial. For those unfamiliar with the event Jonny Smith off of the Late Brake Show, Smith & Sniff and all that has just done a 3-parter on it. Coincedently we were the car behind him in the running order so kept running into camera crew and ended up featuring in the 3rd installment a surpring amount.
It was our first dabble into any form of motorsport and what a baptism of fire. Neither of us think much of 6+hr drives, and both of us can hustle our old land rovers over pretty technical terrain, and thought these would translate well. But nothing really prepared us for 400miles (including the drive to the start line) of near continuous driving over ~26hrs. We were up for 38hrs in all, there's no long motorway stints to get into a grove, just endless little lanes and junctions only broken up by special sections, which were easily some of the hardest off-road driving I've ever done.
I'm sure 1/2 the lanes used in the event are a stroll normally; but by the time the course had been subject to 29" of rain and snow in the week, and 240x bikes, trikes and cars skidding up them. What are usually near-forgotten, westcountry byways of gravel covered tractor tracks. Were now a ruiness combination of slick bed rock, thick clay, foot-deep slury, jaggered banks, massive sump-skimming ruts, gnarly tree root steps and fords that'd have the x5 driving yummy mummies of Surrey u-turning in a heart beat. Oh also, you're only allowed 2wd, road tyres, 4 forwarding facing lights on the front of the car, a paper route book and one attempt at each section. So no LED Lightbar-clad Discovery 2s on 35" mud-terrains with 3 diff locks, Warn winches and ipad-sized satnavs on the entry sheet.
The rule book is far from what my navigator and I would call definitive though, there's a mind bending amount of exceptions, exemptions, amendments and appendices, which leads to 7 bike, 9 car and 2 mixed classes.
Our weapon of choice, dubbed the Battle AX, is a 28yr old, 0.95l, 3 door Citroen AX, purchased hastily off FB Markteplace in the dark the Monday before entries had to be finalised. We'd considered hundreds of cars in the 5 week search for a car, reached out to dozens, either to find it had sold, the ad was a scam, or that they lived in the lake disctrict (apparently that's where every cheap k11 is??). But looking round it after the 100mile drive home, in the cold light of day, the AX fit our clueless criteria very well:
1. Cheap - we'd resided ouselves to the car would likely have to be scrapped after.
2. Reliable - well it lasted the 'test-drive' home.
3. Wasn't rotten - ours only had small hole in the rear arch. 40 minutes of burning in some scrap plate, a lick of hammerite and a dab of underseal later and it was more obvious than before in a non-matching shade of green and (I think) waterproof.
4. Small over hangs & good ground clearance - if you look at the side profile of an AX they're comically good at both of these from the factory
5. Good power:weight - the AX has sweet FA of both, but especially little power in sub 1 litre form, although luckily ours is a later one with bosch efi and weighs a feather-like 630kg...
In the end it was the lack of power that let us down more than anything else, which leads me to the second part of the title:
Does anyone have any experience swapping the whole engine of the BMW K1200RS 'Flying-Brick' era bike into a PSA car (such as our AX) or even just swapping the head?
Why?
1.Compared to most of the other entrants seemingly carrying several hundred kilos of balast for traction, we found lightweight and momentum our friend. For cars that are already heavy, going even heavier over the driven wheels helps gain traction. But as we're currently less than 800kg soaking wet at the startline we simply didn't get bogged down where others did, so going for a powerful but light bike engine helps maintain this.
2. Trialling's an odd one; it's like a mixture of hill climbing, rallying and rock crawling. The end result being that you do everything in 1st gear to give yourself the most torque and no chance of stalling trying to grab 2nd, the sections we did were short enough that being sat on the limiter only doing 10 mph wasn't really an issue. So a freer, higher revving engine is a big bonus.
3.We want to stay in class 1 as we've already got the car and it's already proven pretty good; which basically means <1300cc, fwd, and it'll have to remain 4 cylinder as that's what we started with.
But why this engine speicially? Well I'd heard a while back the original BMW K75 bike just had a reorintated PSA TU engine with a cylinder 'chopped-off', which does appear to be true (mostly according to wiki). After the K75 in the 'Flying-Brick' family came the K100, K1, K1000, K1100 and finally the king of the castle being K1200RS. I can't find any paper trail at this point linking the final 4 cylinder version of the 3 cylinder version of a 4 cylinder PSA engine anywhere, but it would make sense when BMW evolved the 3-pot 750cc engine into the 4-pot 1000cc that the 'extra' cylinder would be exactly the same as our existing block in the Citroen.
The most common swap for AX seems to be Saxo VTS 1.6 16v, getting us a respectible 120hp but we would change class because of the cc and saxo engines are now worth real money... Where in comparison the engineers at BMW completely went to town on the original TU... starting as a 954cc, SOHC, 8v, carb'ed, cambelted 4-cylinder making 35hp at 6,500rpm (49hp, in ours with the single point efi), to a 1,171cc, DOHC, 16v with timing chains making 128hp at 8,750rpm and with a similar the torque increase too.
Very long story short; we've got the trialling bug now, the Edinburgh Trial is in September, and we need a lot more POWER for when we get there... any advice on that would be much appreciate!
Edited by REUBS1215 on Tuesday 7th May 23:39
nakedninja said:
I know it's not exactly the same, but have a look at what the folks at Sparrow automotive are doing. They put air-cooled BMW bike engines into 2CVs and use some GSA/Visa parts, if memory serves. Might be worth looking into.
Yh a mate of my dad's who got me interested in signing up bought a Citroen Ami 8 running BMW 1100R engine, 95hp and goes like muck off a shovel, and still on the 2cv suspension. He did better in the trial than Jonny and I hahaBut those engines are longitudinal boxer engine, same as stock just twice the cc and and 5 times the power...
Jhonno said:
daver1184 said:
Would an AX GT 1.4 lump not make more sense?
There's an AX 1.1 on ebay that's had the 1.4 conversion. It reads that it's had some mild tuning work done and makes well over 100hp.
Food for thought?
Not when he wants to stay in the sub 1300 class.. There's an AX 1.1 on ebay that's had the 1.4 conversion. It reads that it's had some mild tuning work done and makes well over 100hp.
Food for thought?
But as Jhonno confirmed, we're trying to stay sub 1300cc still so we can the lowest psi allowed on stage. Which is 13 psi... (picture below by https://www.instagram.com/photographybygarry?utm_s...
This also rules out most of the 100hp TU engines available
MrBig said:
Looking forward to this. I'm pretty sure you got a mention on the S&S podcast too?
BMW bike engine is a great idea... ignore the negativity, the question is not why, but how!
Yh my nav and I are both Patroens, so I messaged in to ask if they even got to the end! We were following each other for the first 150 miles or so from Cirencester to Felons Oak (section 1). But after we failed to get up first time we were wondering if broke somthing cos no one came up after us for ages, we all know why now ... BMW bike engine is a great idea... ignore the negativity, the question is not why, but how!
Here's our crack at it
https://youtu.be/UxW1WKN0mfU?si=u-kxgbJB-hJ6ioXF
boyse7en said:
Can't help much on the engine swap info, but well done on completing the LA Trial.
I marshalled some of the Devon sections a few years ago, and it was bad enough just standing in a forest for hours waiting for everyone to go through. Wouldn't contemplate driving it.
Looks like the K1200 has been fitted in a selection of Imp-based cars - https://davrian.net/forum/viewtopic.php?t=341
Ah see I'd say the opposite! To keep our mud-clogged rad from cooking the engine we'd the heater on max all night pretty much until we could rinse it off, Marshalling looked bleak compared to us baked potatoes lolI marshalled some of the Devon sections a few years ago, and it was bad enough just standing in a forest for hours waiting for everyone to go through. Wouldn't contemplate driving it.
Looks like the K1200 has been fitted in a selection of Imp-based cars - https://davrian.net/forum/viewtopic.php?t=341
Edited by boyse7en on Wednesday 8th May 09:40
In the clip from the Late Brake Show of us going up Beggar's Roost we even got the sunroof open!
RE engine swap - YES! managed to stumble across a couple swapped into Imps but nothing else yet....
Our current thinking is we might have to do an interim 1.6 VTi swap out of a 00s C3/4 to get us to the Edinburgh Trial and have the BMW engine swap going on the back burner. It'll mean we'll be running a slightly different class but hey ho, it's all a learning curve
Edited by REUBS1215 on Wednesday 8th May 10:17
darkyoung1000 said:
NorfolkAXMan on Retro Rides has a good thread on there about his 1.6 swap - I think the driveshaft lengths are slightly different, as you’re switching from 3 stud to 4 stud hubs etc. Possibly wishbones too.
If you want to stay 3 stud, a 1.4 engine from a Saxo will drop in, and you can mate the bottom end to your existing head. Are you single point or multi-point fuel injection?
Good luck!
Yh I think I read it even before we set off. Just had no time because of work and life getting in the way, we did all our prep the weekend before, final touches the night before and the morning of... If you want to stay 3 stud, a 1.4 engine from a Saxo will drop in, and you can mate the bottom end to your existing head. Are you single point or multi-point fuel injection?
Good luck!
Currently ours is single-point efi, it really does just look like a carb with a couple of wires running to it haha
Bike swap would give us itbs and multi-point.
We'd be keen to keep it 3 stud, mostly cos I managed to get 12x3 stud AX wheels for £30 when we were looking for one extra as a 2nd spare...but also cos tyre changes are a complete doddle even with hand tools. But now we have them it's of zero consequence if we bend them! Pretty handy as impromptu jack stands or tool bench lol
Also name another car supermini that can carry 12 of it's own spare tyres, still have spare for 2 people and see out the rearview mirror! Haha
sjabrown said:
I watched the LBS with interest. Quite fancy giving trialling a go some time. Might have to head south to watch a couple first. Good effort in the AX.
Can't recommend it enough tbh! I think the LBS did a really good job of illustrating the point but the world's your oyster with it. You can pretty much run whatever vehicle you want as long as only one of the axles is driven, it isn't diesel and it's not a 4wd vehicle that you've just disabled the second driven axle.If want to spend ten's of thousands - there's nothing stopping you other than inevitably end up in Class 7 or 8 which makes for a really hard course, they have to do all the restarts in all the worst places and start behind everyone else in the main trial.
But we spent naff all tbh in all; from the car to entry fees, 6x new tyres to fuel, insurance to even the bacon sandwiches while on course we spent £1900... Only things not included there are the spotlights I stole off my Land Rover for the event and our toolboxes.
As for watching a couple first; I'd watched the finish at Blue Hills for years as a lot of my family lives there, but I'd never seen the rest of the course and my navigator had never even heard of the sport until he paid his memberships subs and we flipped a coin to see who's driving. Just give it a go I say!
Thanks all for the recommendations - General consensus reads like we're along the right lines, at least in theory! Although I still haven't found any real information on their similarities... 
Our thinking of an interim engine swap may not be that silly either, as we could still have the AX comp ready while having the TU9 and the K1200RS engine next to each other on the bench
Might even end up running a hybrid, keep the original block, bore out by 0.5mm and fit the forged internals off the bike, along with the DOHC, 16v, ITBs, and Multi-point EFI. It would crucially leave us with all the existing ancillaries in place and fit straight up to engine mounts and gbox etc. The tubular manifold of the saxo engine would save us time and money too.
200hp/tonne (N/A & kerb weight) seems a reasonable ambition lol
As for wheels; we've a right mix - 2x 3-spoke GT alloys, at least 1 of the 4-spoke GT alloys, at least 2x forte 1.4i steelies and 12x normal steelies in all. Still need to go through them all tbh, 5 with the car and the 2 forte steelies are fine. rest I just picked up from one shed and took to another haha
Our thinking of an interim engine swap may not be that silly either, as we could still have the AX comp ready while having the TU9 and the K1200RS engine next to each other on the bench
Might even end up running a hybrid, keep the original block, bore out by 0.5mm and fit the forged internals off the bike, along with the DOHC, 16v, ITBs, and Multi-point EFI. It would crucially leave us with all the existing ancillaries in place and fit straight up to engine mounts and gbox etc. The tubular manifold of the saxo engine would save us time and money too.
200hp/tonne (N/A & kerb weight) seems a reasonable ambition lol
As for wheels; we've a right mix - 2x 3-spoke GT alloys, at least 1 of the 4-spoke GT alloys, at least 2x forte 1.4i steelies and 12x normal steelies in all. Still need to go through them all tbh, 5 with the car and the 2 forte steelies are fine. rest I just picked up from one shed and took to another haha
samoht said:
I'm personally sceptical that a BMW engine will have any useful similarities with the TU that would make it any easier to mount in an AX engine bay or to hook up to the Citroen gearbox than any other engine transplant, given that the way it's mounted in the bike and its gearbox are quite different.
I'm also sceptical that a disassembled BMW engine will yield a kit of bolt-on upgrade parts to power up your TU9, given the fundamental differences in bore and stroke, belt vs chain drive for the cams, etc.
I could be quite wrong, but based on a quick reading of online info I'm not sure there's reason to expect many easy wins.
FWIW I'm a fan of the CG13DE 1.3 Micra engine, 75hp, cheap, reliable and a nice even powerband. No idea how easy it is to get into an AX tho.
Yh I'll be honest there is a considerable amount of wishful thinking involved here... I'm also sceptical that a disassembled BMW engine will yield a kit of bolt-on upgrade parts to power up your TU9, given the fundamental differences in bore and stroke, belt vs chain drive for the cams, etc.
I could be quite wrong, but based on a quick reading of online info I'm not sure there's reason to expect many easy wins.
FWIW I'm a fan of the CG13DE 1.3 Micra engine, 75hp, cheap, reliable and a nice even powerband. No idea how easy it is to get into an AX tho.
I think of the BMW Flying brick is out we'll probably stick to one of the seemingly hundreds of varieties of TU and prince engines made by PSA / BMW.
The suggestion of a 1.1 with skimmed head and multipoint injection might be the most expendiant project!
Anything GTi or Rallye branded is silly money and rare now for little gain...
samoht said:
https://www.autotrader.co.uk/car-details/202403217... perhaps (claims 100hp)
Wow it really isn't a looker is it hahahIt's like someone designed a K11 by describing it over the phone
I'll have to doublecheck the rule book(s) to see if we're allowed to use other manufacturers / non-related engines... seem to recall some class don't allow it
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