Launch: KTM TPI fuel-injected two-stroke enduros in Lesotho
KTM have transcended engineering and entered the realm of witchcraft. You cannot install fuel-injection on a two-stroke – it’s a known fact – And yet they have. To show off, they hosted a launch in Lesotho.
Story: Donovan Fourie
The Motul Roof of Africa is one of the toughest enduro races in the world. People train throughout the year – strict diets, intense gym sessions every day and hard riding every weekend – in order to finish the comparatively easy Bronze Route. The true gladiators tackle the Silver Route, while the Gold Route is completely impossible. I’ve checked – there’s no possible way of getting a bike through all that. The riders that do finish it are using sorcery.
So what the hell am I doing here?
For starters, these TPIs are hugely intriguing – fuel-injection on a two-stroke? Is that even possible? Four-strokes, with their lovely extra set of non-igniting strokes, have time to cool and compose themselves, the fuel/air measurements taken in the exhaust are quite accurate and therefore everything is somewhat predictable.
Two-strokes, on the other hand, are relentless. They go bang every time the piston reaches the top of the cylinder, they require strange ports in the cylinder to both push air into the cylinder and to extract the exhaust gasses, and trying to accurately read the fuel measurements in something like real time has alluded engineers for decades. Until now, the only carburation that works on two-strokes is, well, carburettors. The reason for this is that the motor dictates exactly what sort of mixture and volumes is required per stroke.
The problem here is that two-strokes have a sort of motor autism. That, mixed with ADD and hyperactivity, means they don’t communicate with the engineers who then get it wrong. This was apparent with the Bimota Due, a 500cc two-stroke V-twin with fuel-injection that was released in 1997. By 2001, all the units that had covered any sort of distance ran terribly and seized. Bimota cured the problem by recalling every bike sold and replacing the FI with carbs.
That’s Bimota, surely KTM – the biggest selling name in European motorcycles – with their technological might and resources, can do better? Well, it took them some time. The first working concept of these TPI motors was unveiled in 2004, and the production model was imminent at any moment after that, but it took KTM 13 years from that first model to develop something that they had enough confidence in to release to the public.
And here they are. At last.
Being dropped in the deep end
When the invite from KTM’s amiable marketing manager, Riaan Neveling, to go to Lesotho right after one of the hardest enduros in the world arrived, it was most certainly suicide for a non-enduro ride like me to attend. But to ride the world’s first fuel-injected two-stroke, something that has been spoken of since the 90s? My death would be a glorious one. Plus Riaan’s friendly tone is a difficult one to say no to.
KTM had set up a pit at Bushman’s Pass, the start and finish location for the Roof of Africa. Already things were not looking promising.
To assist, KTM’s international enduro father/son duo, Andrea and Manuel Lettenbichler, were on hand to guide us through the day. Both are enduro legends, which means that the fact that they are also the two nicest guys you will ever hope to meet makes it even more special.
The route for the day was the Time Trial that the Roof riders rode on the first day. It’s 40 km long, a laughable distance by anyone used to everyday travels, but this is 40km through routes that shouldn’t really exist and have a tendency to go over unsurpassable mountains rather than around them, like civilised folk.
Roof winner Wade Young finished it in an hour and a half, which sounds quite easy, but let’s not forget that he is superhuman. The average for everyday enduro racers is somewhere closer to four hours.
And I’m not anywhere close to an everyday enduro rider.
Diving in with arm bands
We set off, plummeted down a mild cliff, and immediately found a tar road that the route crossed. The Lettis explained that there were some hard sections coming up, and that the route re-crosses this tar road a few kilometres down the hill. Would I know prefer cruising down the tar road an meeting up with them again there?
With the comfort of familiar tar below me, and significantly less terror, I could concentrate on how this new motor actually feels. The TPI models are available in 250 and 300 configurations, and we were graced with the more powerful latter.
Mostly, the motor is the same as the previous successful 300 carbed model, but with obvious modifications. Instead of a carb running into the crank case intake, it has a 39mm Dell’Orto throttle body that controls the air volumes. What is interesting is that the throttle body also hosts an auto-lube injector that sends a fine film of oil into the crankcase with the air. What is also interesting is that, with no fuel accompanying the air and oil, they are able to run with significantly less oil than the previous models. Where your average two-stroke enduro bike ran pre-mix of approximately 40 parts fuel to one part oil, this new automatic system can run the oil mix as low as 100 to 1. Also, obviously there is no premix, and the oil is kept in a separate oil tank with a refill cap just behind the handlebars. This means that riders need not carry extra oil, and can simply refill at a garage like the four-stroke riders.
Then the fuel is injected directly into the transfer ports at the back of the cylinder with one injector per port, hence the Transfer Port Injection (TPI) naming. The upside of this whole system is that the bikes burn cleaner and uses an insignificant amount of oil. Really, there is none of that trademark blue smoke wafting out of the rear of them. The upside of this is that they can meet the stringent emission tests laid out by the ever more enforcing Euro overlords.
You would think that these changes would have a significant impact on the running of the motorcycle, but on that tar road there really was none. That in itself is already a victory for KTM. The throttle response was snappy, there was no lagging, no flat spots and the bike revved cleanly and sharply, just like a carb. This may lead one to ask the question, what was the point of all this additional electrickery then?
It became apparent when I rejoined the real-men group at the bottom of the tar and began my enduro induction. The first few kilometres meandered along a river in a valley between the towering mountains. The temperature was mild, the scenery from all sides was a masterful portrait and everything here was hunky-dory. There were some rocky river crossings, some little climbs and the odd corner, but really this whole enduro thing didn’t seem too hard.
We then stepped out of the river gorge, and from there the landscape became ominously vertical.
And the sharks begin to circle
Right, I told myself in the world’s most optimistic pep talk. I’m an experienced rider. I’ve been riding since slightly after I could walk. I’ve done (some) off-road. Just build up some speed and keep going. This can be done.
The optimism lasted another 74 metres where the bike stopped dead and I was left hanging on for dear life.
“Just give it some gas, yes. I will help you,” said the ever cheerful Manuel Lettenbichler a few metres above the impassable cliff.
I tried. The back wheel spun. I failed.
Eventually, he walked down, gave me a warm smile and then blasted up the hill in that annoying style of people who make difficult things look easy.
On ground considered by experts to be not completely vertical, he handed the bike back to me with another genuinely warm smile and we set off again. 53 metres later, I was vertical and stuck again. He climbed down, he rode the bike up and once again handed it back to me. Repeat this again another 47 metres later. Then again 29 metres after that.
Finally, we crested the top of this now increasingly impassable hill, much to my relief, until I surveyed the land and discovered yet more up-ness. A lot more up-ness. Actually, the crest of this hill was just a ridge about a third of the way up a full-on mountain.
Approximately 45 minutes later, we crested the real summit – actually, I was once again walking, and one of the Lettis was again waiting for me with my bike that he had effortlessly ridden up. From this vantage point, the world stretched out before us. We were somewhere close to 3000m above sea-level, and here is the interesting part – the bikes had not been tuned at all since they left the factory.
Normally, in the pits of The Roof of Africa, we would see a flurry of mechanics holding up various jets and needles, consulting charts and doing plug chops with the hope of finding the right fuelling setup. Of course, the moment they climbed hills like these, much of that careful tuning would go out of the window as the air thinned, and they stand a real chance seizing in some of the lower valleys.
The TPIs, on the other hand, run six different sensors – a roll over sensor, a crankcase pressure sensor, an engine speed sensor, a throttle position sensor, a coolant temperature sensor and an intake air temperature sensor. With these sending data to the ECU, the bikes will not only not seize, but they accurately work out the correct fuelling for any temperature and any altitude. So despite us towering above all other mere mortals on top of this mountain kingdom, the bikes were still crisp, smooth and perfect.
With the major climb out of the way, we did a few kilometres of more gentle riding, meaning a Letti had to come and fetch me only every 500 metres. While not holding on for dear life, an element of the TPI that wasn’t as apparent on the tar road made itself known – most of the riding we were doing at this point, while not completely impossible, was still nonetheless very difficult. And yet I was managing most of it.
Apart from not having to mess around with jets, fuel injection also has the benefit of being cleverer than humans. In the road world, this has eventually resulted in advanced traction control, wheelie control and rider modes. These TPI models are not there yet, but they do know more about what you want when you open the throttle than a neanderthal carburettor. The motors felt crisp and perky, but also somehow more gentle, less physical. All riders on the day found that they were fighting the bike less with less wheelspin and less sudden spurts of power that might not have been asked for. And with that the bikes inherently became a good deal easier to ride.
The entire route was 40km. At close to 30, we came across an open dirt road near our path, and I gracefully bowed out and took it back to the pits, allowing the other riders to carry on without having to wait every few kilometres for “that one guy”.
The TPI models are remarkable. This is no suck up to KTM; they have done a genuinely good job here. I made it close to 30km, and I’m fairly certain I wouldn’t have managed half of that without a TPI. This is the beginning of a new engineering revolution, and hopefully it will have more far-flung implications that just enduro. With this new technology, they can create two-stroke motors that comply with the tree hugger wishes, and can therefore be made eligible for public road use.
Image that – a 300cc two-stroke motor much like the one in this enduro model but in the chassis of, say, a Duke 390. Even better, perhaps they can revive the 550 two-stroke Goliath from their past and put that in something like a 790 chassis.
The future is looking very bright indeed.
More info: www.ktm.co.za
Gallery – click to enlarge: