Indeed, all of the above posts are excellent.
Just as a bit of extra reference - a quick compendium on “ignition timing” in the context of super high revving engines like Formula One engines…
I had the good fortune in the early 90’s to speak to a Mr Peter Morgan (I’m really, really sure that was his name - apologies if I got it slightly wrong) and the gentleman was one half of the fabled Ilmor racing engine company emanating out of Britain - hence the “mor” in the “Ilmor” name.
At the time, Ilmor was owned by Chevrolet, and they (Ilmor) were making most of their money by selling Chevrolet badged engines to the Indy Car circuit. However, they were also making V10 hi-octane “gasoline” engines for Formula One - but I hasten to add that I use the term “gasoline” very loosely because the fuel used in Formula One is anything but normal pump gasoline.
Anyways, I asked some general questions at first, which then got more and more specific as Peter was gracious enough to keep answering them. My first question revolved around the design differences between the Indy Car engines and the Formula One engines - and his answer was most interesting. Bear in mind, I’m gonna try and repeat his answers as close to possible as verbatim as I can remember…
PM: “Disregarding the obvious, such as turbos and the lower compression ratios which turbos require, the single greatest design hurdle we’re consistently facing at the moment is how to guage the variable degrees of flame front propagation which the Formula One engines are experiencing compared to the ethanol engines in Indy…”
Me: “What the bloody hell is flame front propagation?”
PM: “Well, in the F1 engine, depending on the batch of fuel we get, it burns at different rates - it all has the same octane but the amount of Boron the ELF people are adding at the moment is variable from week to week based on what they’re discovering with the work they’re doing for the Renault people…”
(Note: at the time, the Renault F1 engine was the undisputed heavy weight hp per cc champeen of the world… for a normally aspirated engine)
Me: “The ELF people are stuffing you around are they?”
PM: “Oh for sure… they’ve got about 150 scientists working full time in France at the moment on absolutely nothing but Formula One racing fuel… almost every single aspect of that research is going into keeping the Renault engine at the top of the heap, but they sell to us as well as a 2nd teir engine supplier… the problem for us is that we can never tell when we’re gonna get a super batch of fuel… in any week the total horespower might jump as much as 50hp if it’s really wicked stuff…”
Me: “Far out… so what are they putting in it to make it so wicked?”
PM: “Well, it’s mostly pure Toluene but it has all sorts of wicked additives like Boron and stuff like that. The flame front propagation is a measure of how quickly the fuel burns from the centre of the spark to the cylinder wall. We’ve had to invent a crystal based solenoid which resonates with engine ping - and our on board CPU’s constantly push the ignition advance as close as possible to TDC before the solenoids detect the ping resonant sound waves. When the solenoid detects the signature sound wave, it notifies the CPU in the engine management system and the CPU moves the ignition further away from TDC…”
Me: “So how does this compare to the Indy based engines?”
PM: “Ahhh… you see, the ethanol provided in Indy is a control fuel - it’s the same fuel for everyone - and the nature of ethanol is that it’s very easy to distill to a very pure state - which means that the knowledge base for ignition timings and flame front propagation is a known constant. That’s why the ignition curves for our Indy engines are burnt into our CMOS chips and we never have to adjust them - ever. But in our F1 engines - man - the sky’s the limit. Every week there’s another tweek we have to do just to stay on the pace. It’s amazingly hard work.”
Me: “So what are the main differences in engine RPM?”
PM: “Our Indy engine tends to max out at around 12,500 rpm in terms of maximum horsepower. We can get more, but it’s a case of diminishing returns when we factor in the fuel consumption aspects… but in F1, this is our 2nd year of runnning pneumatic compressed valve actuation and we’re currently hovering around 16,800 in race trim, with the option for the driver to go to 17,500 for short bursts… but I think we’ll be seeing 18,000 rpm in all of the race engines within a few years without any doubts…”
Me: “Far out! The fuel burn in those cylinders must be like a constant oxy-acetylene torch!”
PM: “It seems that way, certainly. But we tune our exhaust systems to scavange the exhaust really well - our sensors show only about 5% unburnt fuel on valve overlap overruns… the main impediment is guaging the inlet manifold shock waves at those sort of rpm’s - it helps that the air intakes above the driver’s helmets kind of forces a ramjet effect, but still, we’re still doing research into our inlet trumpets to work out the best tuning lengths…”
Me: at this point I was in over my head and effusively thanked Peter Morgan for all his time and shook his hand profusely.
For your reference, not long after, the Ilmor company was bought by Mercedes-Benz and all the Indy cars which were running Chevy badges swapped to Mercedes badges. At around that time, also, McLaren cut a deal with Ilmor and soon thereafter went on to win a number of World Championships with Mika Hakkinen at the wheel.
