jgorm
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I'm pretty new to nitro, and it has frustrated me to say the least. I'm giving it one serious attempt before I go brushless. I've very experienced with tuning real cars, and I could have tuned 5 blown mustangs for $500 each in the time I've spend messing with this 'toy'. I didn't know much about how the little 2 strokes worked, but some local guys helped me out and schooled me a bit. (mostly 2revo1maxx and olds97_lss). Thanks guys! I wanted to summarize my view of how these engines operate so I know better how to make them run great.
1. Air enters the air filter and goes into the carb. The LSN (point) actually sticks into the HSN (tube) to slow the fuel flow for low rpm / load conditions. As the throttle opens it allows more air, and when its WOT, the LSN no longer protrudes into the HSN. This is not the best picture, but the LSN is on the right side, HSN on the top left.
2. The air fuel mixture exits the carb into the crankcase. The piston creates vacuum in the crankcase as it goes up towards TDC. The crank has a rotary valve that blocks the mixture from getting pushed back into the carb as the piston comes down on the power stroke. You can see the rotary valve about half way closed in the port under the carb.
3. The mixture travels through the center of the crank into the crankcase. You can see the port in the picture above if you look close down the crankshaft center on the right side.
4. The mixture gets pressurized on the power stroke and gets forced through these ports on the piston sleeve as the piston reaches BDC.
5. The pressurized intake charge fills the combustion chamber and helps (?) push the exhaust out the exhaust ports on the opposite side. I'm not sure if the port at the top of this picture is intake or exhaust, but I suspect its intake. The exhaust ports are on the right side.
6. The piston rises towards TDC and compresses the mixture to critical temperature and pressure before it detonates. (does it detonate, or does it ignite off the glow plug?)
7. The piston comes down on the power stroke and the combustion gasses / still burning fuel, etc gets pushed out the exhaust as the new mixture enters the combustion chamber. You can see the internal sleeve ports looking through the exhaust port with the piston at BDC.
I had a new thought I had after learning a bit more on nitro operation.
When these engines get flooded, I'm assuming that the entire crankcase gets flooded too. I used to see no need in pulling the glow plug and spinning it over with the fuel pinched off, but now that seems like a great idea! This is also the reason that you need to 'clear it out' with heavy throttle, to minimize the mixture that is in the crankcase.
These pictures are before I cleaned everything up and I'm resealing everything mentioned in some thread. I'm getting a new exhaust seal thing too.
Please critique, fill in the details, tell me everything is wrong, etc. I'm trying to learn as much as I can.
I built this 'dyno' when I first got the truck so I could adjust the mixture while at wot. I have plans to add some more load to it via some sort of braking device. You guys might get a kick out of it.
[ame="http://www.youtube.com/watch?v=ubHiSyCsW-c"]500 Internal Server Error[/ame]
1. Air enters the air filter and goes into the carb. The LSN (point) actually sticks into the HSN (tube) to slow the fuel flow for low rpm / load conditions. As the throttle opens it allows more air, and when its WOT, the LSN no longer protrudes into the HSN. This is not the best picture, but the LSN is on the right side, HSN on the top left.
2. The air fuel mixture exits the carb into the crankcase. The piston creates vacuum in the crankcase as it goes up towards TDC. The crank has a rotary valve that blocks the mixture from getting pushed back into the carb as the piston comes down on the power stroke. You can see the rotary valve about half way closed in the port under the carb.
3. The mixture travels through the center of the crank into the crankcase. You can see the port in the picture above if you look close down the crankshaft center on the right side.
4. The mixture gets pressurized on the power stroke and gets forced through these ports on the piston sleeve as the piston reaches BDC.
5. The pressurized intake charge fills the combustion chamber and helps (?) push the exhaust out the exhaust ports on the opposite side. I'm not sure if the port at the top of this picture is intake or exhaust, but I suspect its intake. The exhaust ports are on the right side.
6. The piston rises towards TDC and compresses the mixture to critical temperature and pressure before it detonates. (does it detonate, or does it ignite off the glow plug?)
The stoich point of nitromethane is SUPER rich, 1.7:1:whhooo: The stoich point of methanol is 6.4:1 so the stoich point of 20% nitro is about 5.5:1. But none of this really matters because we can't easily measure the mass of air on these little engines.wiki said:4CH3NO2 + 3O2 → 4CO2 + 6H2O + 2N2
The amount of air required to burn 1 lb (0.45 kg) of gasoline is 14.7 pounds (6.7 kg), but only 1.7 lb (0.77 kg) of air is required for 1 lb of nitromethane. Since an engine's cylinder can only contain a limited amount of air on each stroke, 8.7 times more nitromethane than gasoline can be burned in one stroke.
7. The piston comes down on the power stroke and the combustion gasses / still burning fuel, etc gets pushed out the exhaust as the new mixture enters the combustion chamber. You can see the internal sleeve ports looking through the exhaust port with the piston at BDC.
I had a new thought I had after learning a bit more on nitro operation.
When these engines get flooded, I'm assuming that the entire crankcase gets flooded too. I used to see no need in pulling the glow plug and spinning it over with the fuel pinched off, but now that seems like a great idea! This is also the reason that you need to 'clear it out' with heavy throttle, to minimize the mixture that is in the crankcase.
These pictures are before I cleaned everything up and I'm resealing everything mentioned in some thread. I'm getting a new exhaust seal thing too.
Please critique, fill in the details, tell me everything is wrong, etc. I'm trying to learn as much as I can.
I built this 'dyno' when I first got the truck so I could adjust the mixture while at wot. I have plans to add some more load to it via some sort of braking device. You guys might get a kick out of it.
[ame="http://www.youtube.com/watch?v=ubHiSyCsW-c"]500 Internal Server Error[/ame]
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