pearl111
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DavidBoren do you have any other hobbies besides lawnmower carburetors?
Carburetor thread... jets & stuff...
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DavidBoren
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Other hobbies? Paintball... I love tinkering with paintball markers. I have more paintball markers than I can count, and most are "in progress". Real guns, as well, particularly long range precision rifles... and reloading... it's as much an art as it is a science. And, Dungeons & Dragons... well, Pathfinder 1st edition... I enjoy building characters, even if said characters never actually get playtime... I probably have close to 200 different characters in the notes on my phone.
I like anything I can tinker with. My friends consider me the mad scientist. I like messing with cars and everything else mechanical. I find satisfaction in pulling something apart to gain a better understanding of the processes that make the mechanism work. And I also find satisfaction in diving down rabbit holes of research... just consuming all the knowledge I can find on a subject... learning new $#!+ is awesome, and people just post stuff, for free! People with decades on experience will casually drop little pieces of wisdom on message boards, and I gobble that $#!+ up.
I like anything I can tinker with. My friends consider me the mad scientist. I like messing with cars and everything else mechanical. I find satisfaction in pulling something apart to gain a better understanding of the processes that make the mechanism work. And I also find satisfaction in diving down rabbit holes of research... just consuming all the knowledge I can find on a subject... learning new $#!+ is awesome, and people just post stuff, for free! People with decades on experience will casually drop little pieces of wisdom on message boards, and I gobble that $#!+ up.
Denny
Canned Monster
You would also need a way to put the engine under a variable load to pull the engine rpms down. In a controlled way and time. I can’t see what a log of rpm would do. Since the early days of cars some sort of crude dyno has existed for engine tuning. I would imagine small engine manufacturers employed the same technology. Carburetor theory is a deep rabbit hole. After 140 years of internal combustion engines and we still have not got it exactly figured out. We just have it mostly figured out. Even with electronic fuel injection the best we can do is still a compromise.
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karl
Well-known member
It's the same concept as putting the motor on a go kart , and measuring
the time it takes for the kart to hit X rpm= speed, with a fixed gear clutch. Kinda like tuning at the drag strip?
Not a true dyno, but better than running a push mower with no load in the air. Or snow?
the time it takes for the kart to hit X rpm= speed, with a fixed gear clutch. Kinda like tuning at the drag strip?
Not a true dyno, but better than running a push mower with no load in the air. Or snow?
Denny
Canned Monster
You are very correct! Think of a dyno as a stationary drag strip.
DavidBoren
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Correct.
I am going to turn up the RPM's on my 160cc until it meets the air/fuel demand of the 190cc running at the speed Honda rates the output of these motors... in my particular case, I have to take my 160cc from ~3100rpms to ~4100rpms to meet the demand of the of the 190cc at 3500rpms. Honda rates these engines at 3500rpms, but they come preset at ~3100rpms.
I am doing this purely to gain a better understanding of tuning carburetors... there is literally no other benefit I seek to achieve. I was curious if one could use extra fuel to cool an air-cooled engine, and found out that there is a term for doing exacty that... it's called rich of peak.
Down the rabbit hole I went... head first. I looked up the part number of my lawn mower's carburetor and found out it has an emulsion tube. Upon realizing that literally nobody tinkers with push mowers, I started looking at pit bikes and go karts to see what people were doing with modified lawn mower engines.
Found this forum, and it had more recent posts than whatever other forums I was looking at, so I joined to pick your brains, study your habits...
I am going to turn up the RPM's on my 160cc until it meets the air/fuel demand of the 190cc running at the speed Honda rates the output of these motors... in my particular case, I have to take my 160cc from ~3100rpms to ~4100rpms to meet the demand of the of the 190cc at 3500rpms. Honda rates these engines at 3500rpms, but they come preset at ~3100rpms.
I am doing this purely to gain a better understanding of tuning carburetors... there is literally no other benefit I seek to achieve. I was curious if one could use extra fuel to cool an air-cooled engine, and found out that there is a term for doing exacty that... it's called rich of peak.
Down the rabbit hole I went... head first. I looked up the part number of my lawn mower's carburetor and found out it has an emulsion tube. Upon realizing that literally nobody tinkers with push mowers, I started looking at pit bikes and go karts to see what people were doing with modified lawn mower engines.
Found this forum, and it had more recent posts than whatever other forums I was looking at, so I joined to pick your brains, study your habits...
Denny
Canned Monster
You need to worry about critical blade tip speed. I have had a blade come apart. It is not pretty and will wreck your mower. 1941 Wards Wasp with a cast iron deck.
DavidBoren
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Interesting... this is the first account I have heard of related to such [critical blade failure related to frequency]. Assuming you were simply running high rpms and the blade failed without contact. This also assumes the mechanical connection was sound, and the blade wasn't loose or otherwise already compromised.
I know the ANSI recommended blade tip speed is ~19000fpm... with a ~21" blade, that's about ~3500rpms... and I am pretty willing to exceed that. Or was.
I thought about blade harmonics but couldn't find a standard that blades had to be made to. Just the ANSI maximum speed, which seems relatively arbitrary, since blade material and shape would affect the blade's frequency quite a bit. Their maximum used to 21000fpm... what changed? Did people get easier to injure by projectiles ejected from the chute? Or is it simply to pollute less by burning less fuel? I couldn't find anything in the ANSI standards that would lead to such a change... granted I didn't read the whole thing because I would rather eat glass than read government jargon.
It makes sense, though, and I would rather not take unnecessary risks just for the sake of tinkering with a carburetor. I have kids, and quite enjoy running around with them... I'm not looking to turn my lawn mower into a landmine that will potentially detonate and remove my feet with shrapnel, or worse, possibly injure my kids. They jump on the trampoline when I mow, sometimes... and me being curious about carburetors just isn't that important at the end of the day.
DavidBoren
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So I will turn it up to ~3500rpms... which is both where Honda rates its output, and where I reach the ANSI maximum recommended blade tip speed.
I will then tune it rich of peak at 3500rpms. That will require me to get a data logger with both EGT and CHT sensors, an O2 snsor, and a tachmometer. That should satisfy my inclination to tinker...
I will then tune it rich of peak at 3500rpms. That will require me to get a data logger with both EGT and CHT sensors, an O2 snsor, and a tachmometer. That should satisfy my inclination to tinker...
DavidBoren
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Sorry for the third post [in a row], but I felt this deserved its own post to possibly spawn further conversation...
Wouldn't the blade, itself, kind of work as a makeshift dynometer... being able to "read" changes by what rpm you can achieve? Doesn't the mass/inertia of the blade provide load on the engine, and thus allow you a metric to measure the engine's performance... if rpms versus jetting is your current study?
Wouldn't the blade, itself, kind of work as a makeshift dynometer... being able to "read" changes by what rpm you can achieve? Doesn't the mass/inertia of the blade provide load on the engine, and thus allow you a metric to measure the engine's performance... if rpms versus jetting is your current study?
Denny
Canned Monster
No the blade will not work as a dyno. Not enough load unless hitting very tall grass. Like I said it was a 1941 Montgomery Wards Wasp a neighbor gave me. It had been sitting since the mid 1950s when the coil took a dump. As a kid genius (kind of like Wylie Coyote) I replaced the bad coil. Got it running good and removed the governor. It would cut anything, great in tall grass. I used it for cutting other people’s grass. Weekly I would wash it down then run it to dry it out. For some reason I don’t remember (1977) I readjusted the throttle cable to open the butterfly all the way on the carb. Then I tested it. After about a minute of running flat out about 4” of one side of the blade snapped off, went through the 1/4” cast iron deck blowing a big hole in it, flew across the alley and buried itself in the neighbors cinder block garage. Luckily I was in the house getting a drink of water at the time. I saw the engine running away jumping and dancing around grabbed a big crow bar and smashed the end of the plug off. When dad got home I started the autopsy he looked at both ends of the blade then took it to work with him. Gave it to a machinist who checked it out said it looked like it stretched and snapped. The mower was destroyed, crank was bent on engine it was destroyed. I never toyed with the governors again on my mowers. Learned a hard lesson that day.