The air-fuel ratio was not constant through the test either - leaning toward best power as RPM is increasing - so that would also explain the rapid rise in torque, along with the increasing MAP.
Bingo. Yahtzee.
And don't forget ignition timing.
The data I provided was never intended to be a comprehensive test designed to replicate Lycoming's certification process, only to provide some requested test stand data showing an IO-540-D (or C) can run on lower octane fuel without detonation. I achieved that.
I have only made the assumption that your dynamic CR is different than that of an engine with a stock cam (likely lower) and that will represent differences in detonation potential between your engine and a stock engine. Yes, this IS an assumption, but so is your assumption that your engine will behave the same as a stock configuration.
The only
significant differences with my engine are the intake, modern EFII (SDS) and porting of intake and exhaust runners on the heads - it breaths a lot better. I'd talk about the custom exhaust as well, but that's not included in Lycoming's certificate. So yes, that is a basic assumption I've made, that my IO-540-D series engine will behave similar to another one - especially when considering detonation...more on that in a minute.
This isn't my first engine. I've built, owned, and maintained numerous other personally owned internal combustion engines (although mostly Continental,
and a lot of Fords as I think about it). Even more so, I've made a career of turning solid, liquid and gaseous fuels into power for over four decades - from splitting atoms with neutrons to burning bunker 'C', including just about every form of kerosene and naphtha running reciprocating engines that have piston cylinders large enough for a human to stand in, and yes, even AVGAS...but also solar and wind farms, large scale battery storage, hydro power dams, pump water storage and even a good ol' wood burner (only made 31MW, each hand crafted).
While I sincerely appreciate your time to provide me explanations to persuade me that my engine is not comparable to the OP's example engine, I have a great deal of experience that says otherwise, and the greatest argument is at the mercy of experience.
Fine, let's return to topic.
I thought we were actually done with this, but here we are. Glad to see we're back to discussing detonation.
You've demonstrated probable freedom from detonation at a single benign operating point (2700, 30", 100 ROP, low temperatures). Although useful to know, it is important to recognize it's nothing like a standard detonation test, and I'm not speaking of the temperatures. I can easily accept the argument that a reasonable operator will never allow maximum CHT. I'm speaking of the standard test protocol, which is setting a stable manifold pressure and RPM, then sweeping the mixture from full rich to detonation onset, or lean roughness, which ever occurs first. If detonation, it is ranked in terms of severity. No one is much concerned with light detonation, but heavy is rapidly destructive.
Previously I asked you to consider what happens if you suffer a partial injector blockage. The answer is "The individual cylinder may tip into detonation due to going lean". That's why the protocol is based on mixture sweep.
Below, a 540-K, standard test. It shows light detonation beginning at about 135 pph, and ran away into destructive levels at about 128.
.
You mean like this stock TIO-540-J2BD? Detonation onset is around 364 HP, with BMEP there being 207 psi. MP is 42.5".
BMEP has very little to do with this. But hey, I'll restate and simplify. Ron's single operating condition assures others of nothing outside that condition. Without a mixture sweep, he has no idea how close to the limit it may be.
It's just an example, so pick anything which makes it go lean.
Dan, thanks for providing your examples. In them, you've provided a K series engine, which is an angle valve model, and a J series engine - turbocharged no less, as comparative examples of how detonation can occur in an IO-540-D series engine. While others may disagree with your use of another model of engine as an example - I agree with your examples, mostly because detonation doesn't care about what internal combustion engine the fuel is contained within - or even an engine at all. Detonation is simply an unplanned combustion that resulted from meeting the needed pressure
and heat conditions. And of course having fuel available.
In both examples you've shown that if you experience a failure in your injection system, it can result in an engine failure. And I wholeheartedly agree, this is why it is important for a builder to include full telemetry on their engine, and then use it. Especially if you're going to experiment with non-stock modifications. I believe that any pilot that is competent enough to manage their aircraft controls, should be competent enough to properly operate their engine. Not properly operating the engine is a problem, but then again so is turning your aircraft into a lawn dart if you forget to pull back on the control stick.
While you have referred to the Lycoming test standard and provided the importance of cylinder heat temperatures (CHT) and intake air temperature (IAT) to be tested at, you did not provide either CHT or IAT in your two examples where detonation occurred. Please update your charts to show these two trends so that we can see how temperature affected the events.
You've said that my data is problematic in that I did not include a full sweep of air to fuel mixture implying a failure can occur in the conditions I tested at, so please provide supporting documenation for your statement. Please include a test or study that shows an IO-540-D or C series engine, having 9:1 compression, CHT limited to 420ºF and standard ignition timing of 25º advance that
demonstrates detonation. It must be shown to occur while running the OP's fuel requirement of 93UL or Swift 94UL, a Motor Octane Number rating (MON). You can use manifold pressure up to 31"Hg and any intake air temperature you think is plausible with AFR sweeps from, say 12.5 to 17. Or if you don't have that, an IO-540 running on lower octane MOGAS, such as 91 Anti-Knock Index octane that has limited power, i.e. MP and ignition advance reduced below 26" and 25º, respectively, while fuel mixture is not maintained between 100º ROP to 20ºLOP will work as well.
If you don't have the studies, this is all provable with math; I'll accept your mathematical analysis of this, as long as you show all of your work.
And Dan, unlike your instructions to me, note I said "please".