You speak the truth, you've done empirical testing which is of great value unlike a lot of the book reader repeaters with no actual real experience on the topic. I greatly respect your knowledge and experiences. To add from my experiences: My experience is with calibrating car engines, learned by doing on two boosted cars of mine, hundreds of flashes and hundreds of hours tinkering, with successes like making 500 bhp with a 2.4L ecobox engine. That landed me a job doing engine development in the dynos professionally where my engine projects all used cylinder pressure transducers and hope someday these become affordable (like they come standard on factory cars). In addition we used a powerful tuning aid that is the wide band O2 lambda sensors to measure lambda and AFR. I also used this tuning privately and in addition engine tuning companies require access to wide range O2 readings. I thought I was clever bringing O2's into 2 strokes, however I have recently found a flaw with my approach in using 4 stroke automotive AFT targets for 2 stroke small engines. I may be able to accurately measure AFR, however I don't actually know what AFR is good for each load with a 2 stroke or with my 2 stroke engine model. In addition, there could be an offset in my AFR measurements based on the location of the O2 sensor (in fat part of pipe). I run a Paramotor that spins a propeller, the propeller spinning on the ground making static thrust is a very good analog of in-flight loads. Recently I found a hole boring through my piston from detonation, right above the spark plug. I've been running 93 octane + boostane making it 100 octane fuel. On my Dyno stand with the O2 sensor, I targeted about 14.7:1 at idle and cruise rpms, and 12:1 at WOT. I correlated these numbers with the EGT readings. There is good correlation when you are near stoichiometric AFR, however EGT can read high if you are too rich. New piston on order and going to get back on the Dyno stand to develop / validate more rich tunes at higher loads.
What EGT did it give at 12/1? I thought idle was supposed to have the richest mixture. Have you tried richer? Probably best to set mixture for strongest idle and then just measure its AFR.
@@MichaelForrestChnl Sorry looks like youtube may have lost my first reply. With the Polini Thor 202 specifically and the factory EGT location, I see about 620C at WOT. 700C at mid-range cruise (~6,000 rpms, in flight). This correlates with what other pilots with many hours on the engine suggest, hearsay the factory also confirms 700C at cruise rpms. Nice thing about a factory EGT location with a special metric thread so we all use the factory EGT sensor (type, depth same). As mentioned I'm coming at it with 4T tuning in mind and I am suspicious, risking engine health to see for myself what running at stoich will do. "There is one way to find out" method of development I guess. Here is a video when I installed the O2 and I'm playing around with it, you see when I choke it AFR drops (what I was looking for) and engine speed increases as you've alluded to. ua-cam.com/video/242JgRsWnpA/v-deo.html This is now in my mind to recalibrate the idle AFR richer, as I do run idle RPM over 2000 to prevent stalling. So maybe the leaner idle is part of my challenge.
This comment was from the previous version of this video. @markburden6265 : "Great video Michael....thumbs up dude ....top end jetting feel is so important..I run castor and jet with feel uphill ....everything is a compromise...I jet for engine life as well as performance." My reply : "yes, jetting is a combination of getting good peak power without ruining reliability. I forgot to include that if you happen to jet it so lean to get peak power that it causes the oil to start burning on the piston, and you don't want to change to a more heat resistant engine oil, then it's probably because the squish velocity is too low."
Also it is possible that the type of engine oil used can close the gap between those two peaks, possibly an all synthetic oil, or an all group two oil, or like the Kawasaki oil which is a combination of the group two and synthetic. dragonfly75.com/moto/oilpower4.html
a dyno won't show the true peak horsepower unless the jetting is changed to match the load of the dyno, or the load of the dyno is changed to match the jetting of the bike. I think dynos are a useful tool but i wouldn't use one to select the main jet.
on my Facebook forum "Two Stroke Tuning/Modifying" Nick Rhine had this to say; "spot on knowledge. How I have jetted my race bike engines I have developed for 50 plus years. Over 200 Championships and three 2 Stroke world titles. The World titles were won at Glen Helen by the way." He told me that he jets for the sweet spot on a medium sized uphill. ua-cam.com/video/FeD4OCFxI_0/v-deo.html
You speak the truth, you've done empirical testing which is of great value unlike a lot of the book reader repeaters with no actual real experience on the topic. I greatly respect your knowledge and experiences. To add from my experiences:
My experience is with calibrating car engines, learned by doing on two boosted cars of mine, hundreds of flashes and hundreds of hours tinkering, with successes like making 500 bhp with a 2.4L ecobox engine. That landed me a job doing engine development in the dynos professionally where my engine projects all used cylinder pressure transducers and hope someday these become affordable (like they come standard on factory cars). In addition we used a powerful tuning aid that is the wide band O2 lambda sensors to measure lambda and AFR. I also used this tuning privately and in addition engine tuning companies require access to wide range O2 readings.
I thought I was clever bringing O2's into 2 strokes, however I have recently found a flaw with my approach in using 4 stroke automotive AFT targets for 2 stroke small engines. I may be able to accurately measure AFR, however I don't actually know what AFR is good for each load with a 2 stroke or with my 2 stroke engine model. In addition, there could be an offset in my AFR measurements based on the location of the O2 sensor (in fat part of pipe).
I run a Paramotor that spins a propeller, the propeller spinning on the ground making static thrust is a very good analog of in-flight loads.
Recently I found a hole boring through my piston from detonation, right above the spark plug. I've been running 93 octane + boostane making it 100 octane fuel.
On my Dyno stand with the O2 sensor, I targeted about 14.7:1 at idle and cruise rpms, and 12:1 at WOT. I correlated these numbers with the EGT readings. There is good correlation when you are near stoichiometric AFR, however EGT can read high if you are too rich.
New piston on order and going to get back on the Dyno stand to develop / validate more rich tunes at higher loads.
What EGT did it give at 12/1? I thought idle was supposed to have the richest mixture. Have you tried richer? Probably best to set mixture for strongest idle and then just measure its AFR.
@@MichaelForrestChnl Sorry looks like youtube may have lost my first reply. With the Polini Thor 202 specifically and the factory EGT location, I see about 620C at WOT. 700C at mid-range cruise (~6,000 rpms, in flight). This correlates with what other pilots with many hours on the engine suggest, hearsay the factory also confirms 700C at cruise rpms. Nice thing about a factory EGT location with a special metric thread so we all use the factory EGT sensor (type, depth same).
As mentioned I'm coming at it with 4T tuning in mind and I am suspicious, risking engine health to see for myself what running at stoich will do. "There is one way to find out" method of development I guess.
Here is a video when I installed the O2 and I'm playing around with it, you see when I choke it AFR drops (what I was looking for) and engine speed increases as you've alluded to. ua-cam.com/video/242JgRsWnpA/v-deo.html
This is now in my mind to recalibrate the idle AFR richer, as I do run idle RPM over 2000 to prevent stalling. So maybe the leaner idle is part of my challenge.
This comment was from the previous version of this video.
@markburden6265 : "Great video Michael....thumbs up dude ....top end jetting feel is so important..I run castor and jet with feel uphill ....everything is a compromise...I jet for engine life as well as performance."
My reply :
"yes, jetting is a combination of getting good peak power without ruining reliability. I forgot to include that if you happen to jet it so lean to get peak power that it causes the oil to start burning on the piston, and you don't want to change to a more heat resistant engine oil, then it's probably because the squish velocity is too low."
It’s cool to hear someone talk about how reading a spark plug isn’t the way to jet.
Yeah, I know. But I rub people the wrong way with this. They don't want me to rob them of their simplistic ideas.
Also it is possible that the type of engine oil used can close the gap between those two peaks, possibly an all synthetic oil, or an all group two oil, or like the Kawasaki oil which is a combination of the group two and synthetic. dragonfly75.com/moto/oilpower4.html
a dyno won't show the true peak horsepower unless the jetting is changed to match the load of the dyno, or the load of the dyno is changed to match the jetting of the bike. I think dynos are a useful tool but i wouldn't use one to select the main jet.
on my Facebook forum "Two Stroke Tuning/Modifying" Nick Rhine had this to say; "spot on knowledge. How I have jetted my race bike engines I have developed for 50 plus years. Over 200 Championships and three 2 Stroke world titles. The World titles were won at Glen Helen by the way." He told me that he jets for the sweet spot on a medium sized uphill. ua-cam.com/video/FeD4OCFxI_0/v-deo.html