KTM entered MotoGP four years ago and is already battling with rival manufacturers who have been racing in the premier class for decades. Only Yamaha has won more races since the start of 2020, with KTM’s five victories equalling Ducati’s win rate and bettering that of Aprilia, Honda and Suzuki.
At the heart of KTM’s RC16 is its engine, the same 1000cc 90-degree V4 configuration used in Ducati’s Desmosedici, Honda’s RC213V and Aprilia’s RS-GP. At least, that’s what we always thought. Except that our recent chat with KTM’s Head of Engine Development Road Racing Kurt Trieb revealed that the RC16 isn’t a 90-degree V4, after all.
There’s no doubt that Trieb – who also designed KTM’s Moto3 250cc single and its original 2005 MotoGP V4 (used briefly by Team Roberts) – has played a huge part in the RC16’s success, from his original concept to detail work on firing configurations, combustion and so on.
Nowadays electronics take up more time than any other aspect of machine performance in MotoGP garages, but Trieb quickly realised the importance of creating an engine that doesn’t require too much interference from the various electronic rider controls, which all slow the bike down, rather than speed it up.
You used to engineer Formula 1 car engines, which are all about maximum horsepower, whereas MotoGP bikes are mostly about part-throttle, does that make the job more interesting – chasing a friendly engine instead of big numbers?
My background is automotive and automotive motor sport – engine design in Formula 1 and touring cars. The biggest difference in motorcycles is that you have the clutch and gearbox to think about. In car racing you don’t worry about that stuff, so that’s a big difference in MotoGP.
And, yes, in MotoGP the engines are used from 8000rpm to 18,500rpm. That’s a big difference from an F1 engine, where in my time there, the engine was always working above 12,000rpm. That’s something you cannot do in motorcycles.
What’s your speciality – engine architecture, combustion design or what?
It’s everything. From the start of the RC16 project it was very important to have a reliable and simple base which works, so you can go testing and develop your own package.
A 2020 RC16 engine in KTM’s new Motohall exhibition centre in Mattighofen, Austria
What’s most important when you’re trying to make an engine work effectively on part throttle?
Internally, it’s basically the gas exchange [the cycle of supplying fresh air and removing exhaust gases] which you have to set up correctly. That’s port design, turbulence inside the cylinder and so on.
Everything has to work together. If you have a port that gives good flow figures that doesn’t necessarily mean you’ll have better combustion. Let’s say the combustion could be bad at low throttle or at low engine speed, even if the port flows well, so it’s all a bit of a compromise and a combination.
What’s the difference between an F1 cylinder and a MotoGP cylinder?
Formula 1 has much shorter-stroke engines, whereas in MotoGP we are limited by the 81mm bore restriction, so I think we are racing long-stroke engines!
Can short-stroke engines be too revvy, too peaky for bikes?
I must say I’ve always been a fan of short-stroke engines. I think you can make them work well, especially if you get the port design and valve lift correct, because this can compensate for some of the benefits you get from longer stroke engines.
In MotoGP the acceleration limit until you reach fifth and sixth gears is grip and wheelie, not horsepower. How does that affect your work, or do you leave that to your electronics and downforce people?
Let’s say that in the first four gears of a MotoGP bike normally you cut the power with the electronics. From 2019 to 2020 we made a good step with our engine, by adjusting the power delivery to what the rider can naturally use on track, so that the electronics have to do as little work as possible.
So you designed an engine that doesn’t need electronics so much?
We still need electronics, that is clear, but let’s say we’re now working more in that direction.
Since Michelin returned to MotoGP the back tyre has become a crucial part of stopping the bike, so negative torque is very important. So when you design an engine do you think about getting the bike into corners as well as out of them?
You need negative torque to stop the bike, that’s clear. What we’ve learned is that you need an engine that burns consistently at very low throttle openings. If you close the throttle completely the engine will shut off and there’s a fine line where you can still keep the engine burning and also deliver some negative torque for engine braking. For the rider it’s very important to have a consistent feeling in this area of corner entry – because if the engine shuts off and cuts in again it’s a disaster.
Brad Binder chasing the lead pack on his way to victory in the Austrian GP, chased by fellow RC16 riders Iker Lecuona and Miguel Oliveira
Some factories use an adjustable exhaust valve in the exhaust to modulate negative torque. What about you?
We have tested these but they never rated as a must-have. As I said, if you have an engine that doesn’t burn at very low throttle openings then you have a problem. If this is the case an exhaust valve allows you to create back torque with the throttle, so it’s a workaround.
So if you do your work right inside the engine you don’t need one?
How many different firing configurations have you used since the beginning of the RC16 project while trying to find the best irregular firing from the engine?
We are now on our third version of the firing order. First we had the screamer, then the big bang and now we have the long bang, or whatever you want to call it. In the end it’s an irregular firing order across the cylinder bank, so you don’t have constant pulses going to the rear tyre, you have inconsistent pulses.
What does this offer? People have talked about this for years…
I don’t think there’s any fixed explanation, so I can only tell you what I think. I think it’s related to the frequencies and the gas exchange, with the irregular firing configuration translating well to the rear tyre.