I 3D Printed a Transparent Combustion Engine in Resin

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[tsbrownie]

1) ignition timing, each fuel has a different burn rate and that means power will be applied early, late, or on time. 2) spark plug gap varies with fuel and compression. 3) different fuels require different carb jets.

[Crowbars]

One idea to possibly make the engine run better, and be a bit more _scientific_ is to give the engine a load. I think the best idea is to use some kind of generator hooked up to a multimeter, so you can directly compare the different fuels.

[fireballmx]

Biggest issue you have is the lack of fine tuning on the fuel injection side - all those fuels have different stoichiometric ratios for combustion as you mentioned in the video so you need to adjust the carb/jet to inject more of the methanol/nitrometh fuels (and possibly adjust the gas injection too - you could just be dealing with misfires)

[dapz]

idk if you have done this in the past, but could you make a piston engine powered by the pressure generated from sublimation of dry ice? You might be able to 3d print almost all of the components

[loadstone]

Hey integza, I’m a car and motorist enthusiast myself, so perhaps I can explain some of your inquiries.

The reason rpm decreases as more highly combustible fuels are used is because the fuel expands with more energy. This means that the force applied to the piston is greater thus a greater torque is produced. The rpm decreases to compensate for the increased torque because the force is applied over a shorter length of time meaning that the impulse of the piston will decrease (dp=Fdt). Even though the respective force has increased, it is applied over a much shorter time. This means that the object will accelerate slower yet apply more turning force (torque) to the axel.

Furthermore, the reason you weren’t getting the 4 cycles may be due to (as you’ve alluded to) the spark plug timings. In a car, a vital component for efficiency is the timing belt which dictates the spark plug’s the moment of ignition. If the spark plug is ignited before the fuel is compressed enough then it will fail it’s cycle. This is common in smaller engines (especially I4’s) because the piston has to travel further in order to compress the fuel enough and have a successful ignition. Also check for seals. Metal is good for engines because of its high melting point but also because it can create a good seal with itself. Plastic, being a polymer, is not too good at making seals (especially with metal) so this can lead to leaks and a decrease of pressure in the combustion chamber. This may also be the reason for the drastic decrease in rpm for higher energy fuels.

[UncleJimmema]

As others have mentioned the fuel/air ratio and ignition timing are probably a factor. The lack of a head gasket might be playing a role too, at 10:05 you can see exhaust gases poofing out of the seam which would suggest its not getting as good compression as it could.

[jimmyb]

My guess as to why it's firing inconsistently, is that the air fuel mix is VERY rich. As is often the case with engines as small as that.
If there isn't a mixture screw on the carburettor, there's not much you can do about that, aside from removing the "jet" (which will be a small tube in the centre of the carby in this case) and replace it with a new tube with a smaller hole in the end in order to lean out the A/F ratio.

You can either do a lot of maths to work out how much to reduce the jet size, or you can just do it by trial and error. I'd wager that if you reduce the jet orifice by 10%, it will fire much more reliably. It will also run hotter, and may not have enough lubrication.

You could try restricting the flow of fuel with a valve, that might allow you to tune it.

[Ghostmany]

Yo, when you switch fuels like that, you have to retune the engine timing and carb flow rates (i.e. rejet) for that fuel type. Also, engines running race fuels tend to run at higher than normal cylinder pressures than their stock counterparts. That little green o-ring on that piston probably not gonna cut it. Maybe vent the crankcase to monitor blow-by with a pressure guage. Just a few tips from a fellow engine enthusiast. Happy Brapping!

[tomasjosefvela]

Distributes on cars have always had a mechanism to advance the timing when at higher RPM's . As the engine revs up the pistons move faster and the spark needs to happen earlier to catch the fuel and compression at that perfect spot that allows the fuel to ignite before the exhaust valve opens. Great video as always, thanks for sharing!

[BPBomber]

An integza upload. Hell yes, exactly what I needed right now. Thanks for the smiles buddy.

[TheTartopum]

First thing would be mixture, as all of these fuels have different air/fuel ratio. Bad mixture would cause the engine to run poorly, if it even runs.
Second thing, it would provide better data to use some form of engine load to better test the performance of each fuel.

[justfivz]

Tomatoes are disgusting!

Nice video.

My idea is a 3D printed inverted Wankel engine, maybe a transparent one made with resin.

[BuZZarDFPV]

I think it has to do with timing, by changing the octane of the fuels as you are, you change the ignition point in the cycle, you'd have to tune the timing to match the ignition time, useful for increasing compression to avoid detonation (Lower octanes self detonate under higher compression).

[dincao]

When the power stroke occurs creates massive pressure. The opening of the release valve might not be enough to release all that compressed pressure, so the fuel entry valve when opened, because there is still compressed material in there, instead of fuel entering it will be repelled.

[PatchesTheProtogen]

Hi Joel,
The reason why this engine is not doing a power stroke every 4 strokes could be that it might have speed governing, specifically hit and miss where it doesn’t combust the fuel when it is running above the set speed. Just something to consider :)

Kind regards
Hunter

[jacks__]

your engines/rocket content just keeps getting better, love the videos

[Beltonius]

Valve and ignition timing (IE when the valves open/close and when in the stroke the spark happens) may all need to change with the different fuels. In addition, the carburetor is built assuming the required air/fuel ratio for the original fuel. Those ratios, as you pointed out, are different for any other fuel.

[KanedaNLD]

You need to adjust the timing of the motor. So it sparks a little early. The way your spark will be in time with higher RPM.

Same as with the top fuel drag racers. They run terrible at low RPM, but a high RPM they run super smooth.

[marsgizmo]

Love the see-through mini engine! Awesome project Joel! 👏

[josephjefferson]

I love your content I show it to my 4 son's, and I have to say thank you because your videos has made their love of science equal to or surpass my love of science.