The history behind itIt has taken me 5 years on and off to develop the engine in amongst all of the other tasks. As it stands today it is reliable and quite modestly powerful but I can see that I am stretching the limits of these modest crankcases. Primarily due to the weak open deck arrangment and the high cylinder pressures I have introduced. I have closed the unsupported cylinder castings in a hexagonal arrangement to provide rigidity to the thrust faces. Manufacturers tend to favour open cylinder decks due to lower production costs as a closed deck will require single use cores rather than an open deck utilising replenishable tooling. It has been relentless development; I love getting to work on new experimental parts and hate simply rebuilding or repairing as at best I am just catching up to what it was than making it better.
Slow to learnI lacked the time and resource to do back to back testing to really validate individual gains in components. It’s difficult to describe in words but from spending so much time immersed in each and every component in the way I have, coupled with experience from previous tuning you can attribute a factor of contribution to the power gains and equate approximate results to these areas. When a component contributes a far greater gain than expected you can start to explore the how’s and why’s; which led me to investigating two interesting areas; the induction turbulence of my very exploratory porting and the unusual effects of reverberating waves in the exhaust.
Lots still to do...If I had written this a year ago I would have told you the turbulence in the ports were the most important contribution. Or maybe the year before that would have been mechanical losses and friction. It’s just a snapshot of one man trying to run a factories worth of development rather than a comprehensive engine tuning story. I have addressed each area as it was required and fed my hunger for variety. Such as a new oil pump design for converting to a oil/ water interchanger, designing a cam shaft profile around the maximum valve bucket size or the consideration for oil and air flow to minimise windage and friction losses. I seem to have a hopelessly short memory; what I don’t document is sometimes lost, even though I felt I had mastered it at the time; something to do with my concentration for academia and the reasons I naturally take to making rather than read; I can just go and fabricate something with very little planning or knowledge and be totally immersed in it but when I need to concentrate on designing a new camshaft, clutch or steering system, I end up singing, tapping or day dreaming within seconds and drift in and out of focus without reward. Noticeable back when I was an art student back in my teens too. Are we still talking engines?
TestingOver the years there has been lots of dyno time. Back in 2014 when I did my first stage of reboring out to 836cc I spoke to Tony Scott for his opinion and we decided that the nikasil composite liners are worth testing to the limit. Back when I was a toddler these were special aluminium alloy impregnated bores with nikasil throughout rather than the conventional surface coating however so I learned the saturation of nikasil content was not consistent through the material. I also degraded it’s heat conductivity, structural rigidity and surface finish away from an ideal as I bored it to leave only 1.5mm of wall thickness of the liner. Needless to say it lasted a mere 40 minutes on the dyno before it picked up and started to loose power. Enough time to see the benefits of my initial induction and exhaust work; a 43% increase in hp. It was such a great experience using Freddys dyno; not only did it take 6 hours after a full days work to set it up and bolt it to the dyno, come midnight we were sat outside the room, I was controlling the aircraft style joystick hooked upto the throttle cable while Freddy did the load resistance. I had set the ecu to auto compute the majority of the cells so it needed just milliseconds in each box to verify the revs, lambda and throttle position sensor before making the fuelling change so we had to scan lots of dials and watch for temperature fluctuations and power at the same time. Full on concentration, but so rewarding. Modern day systems for big companies do all this automatically now, pre programmed dyno sequences to tune and test. We finished up around 2am, I had nearly a 2 hour drive home then up at 6 for work. It didn’t phase me. The first engines reved all the way to 14,000 rpm, newer motors had more in the mid range and fizzed out by 12,000 rpm – it was intentional; my focus was corner exit speed. Something I witnessed first hand at the southern 100; off the start and finish line I was absolutely matched with all the superbikes for acceleration from a stand still, but down 3 gears and enter the first corner; back on the power and every bike made 10 metres on me within a second. The rate of acceleration and gas speed were way down. Reciprocating mass was good as was friction losses but the difference in speed was embarrassing and possibly dangerous. I have moved away from using dyno's as good knowledgable operators are hard to find now. There simply isn't the demand to keep them in that role. I had a engine ruined by an inexperienced operator accelerating hard against a braked dyno which overcame the weak oil pressure film in the bearing shells. I now favour a complex data logger (home made of course) which gives me a full suite of information necessary to make adjustments far more accurately than any ordinary dyno.
20172017 brought the big bang engine, out to 938cc; a longer 52mm stroke, lighter and stronger conrods, a new shorter primary exhaust configuration and most importantly a 180 degree firing order. At the time I used a rolling road to do fine tuning and testing; a good one, but still only a rolling road. They have limitations and are harder to quickly change loads to do the mid range work but far simpler to load the bike on at least! April 2017 saw the new engine make 152hp at 13,400 rpm; a 58% improvement on the original. The most successful engine made 163hp in early 2018.
The 180 degree firing order is a vast improvement; silky smooth. The theory is the distance, consistency and balance of loads emitted from a combustion explosion to inertia at the wheel. Take a big v twin like a ktm; each piston is a dinner plate, with every nuclear sized explosion there is a huge momentary surge in torque exerted through the crankshaft, huge strain on the primary drive gears which quickly dissipates through normal mechanical losses as it finds it’s way through the gearbox down the chain to the back wheel by which time the next explosion has just taken place in the other cylinder, brace brace brace, here it comes, hold on tyre, are you ready. That surge in power graphically would form large waves of peaks and troughs which exerts greater spikes in torque to the back tyre to compensate for the fact it only fires 2 big dinner plate pistons which will wear it out faster and give higher chance of high siding. Now compare that to a 180 v4; each spike of power will be lower as each cylinder produces less power and the spread between them is narrower meaning less loss of inertia and greater consistency in reciprocating torque; producing a smoother, calmer, safer ride with a tyre that lasts longer. I think slowly the likes of Ducati and Honda are really sold on this. I’m pretty sure all motogp bikes are v4 or v5 for that reason, eventually all the road sports bikes will be V4’s (hopefully) and the world will be a better place