I did this last year as an exercise to find out why a vacuum guage was relevant. I used
PV=nRT where:
P=the guage pressure inside the manifold
V=volume of cylinder
n= number of mols gas
R= gas constant
T=temperature of the gas.
What I did was take case one where the engine isn’t running but the valve is open. A vacuum guage would say 0 vacuum. This is the case where the cylinder is as full as it can get naturally.
The next case (case two) is where we pick a pressure on the vacuum guage. Same volume, same gas constant and same temperature. When you compare the two equations the only difference is the number of mols (n).
Remembering that the first case is at atmospheric pressure and the second case is less than atmospheric pressure (vacuum), it is easy to see the first case is the maximum number of mols, and the second is less mols then the first.
Mols are the chemistry description for the number of molecules of a type. Example…2 mols of hydrogen combined with 1 mol of oxygen gives 1 mol of water plus heat. So in your question, the first case is the max power because the max number of mols are in the cylinder. The second case is the derated amount and is directly related to the vacuum measurement.
The exact amount of heat is found by looking at the chemical equation for the reactions. The heat given is measured in BTUs per mol (or kilocalories per mol).
The final link is knowing how many mols are in the cylinder. That is found by plugging in the actual numbers into PV=nRT and solving for n.
My adventure into this was seeing if a vacuum guage could tell me the dynamic compression ratio. It does, because there is a relationship between how much gas (mols) is in the cylinder and the pressure in the cylinder (vacuum).
Yeah no kidding. Very noticeable when you have a governed top RPM of 3600.
All the old timers on that forum coveted the old flatheads because of not only the older look but also the higher torque. Very jealous of the older guys on there up in Michigan and Wisconsin with their piles of 1950s Briggs, Wisconsin, Tecumseh, etc engines and old Vanadium steel bicycle frames ready to fit one of those 3hp or 5hp engines.
Hot rodder guys use the indomitable Honda Clone, and then throw upwards of 2 grand on new rods, flywheel, crank, cam, Conrod, piston, side cover, bearings, Mikuni carbs.
Just to spin it to 6 or 9 grand at maybe 20hp on a reinforced bicycle frame for racing. Very short lifespan for a 196cc engine at those powers.
If I make a comparison with a diesel engine and a gasoline engine, we can easily see that the gasoline engine has about 30% more torque than a diesel engine, why, because it uses fuel with a higher hydrogen content and thus the expansion of gases during combustion is greater. The wood gas engine, however, experiences an expansion of the combustion of this energy source, where we cannot always say what its composition is. Theoretically, the drop in torque with a gasoline engine would be almost 50%, with a diesel engine, looking at the previous power, about 20%, but if 10-20% of diesel fuel remains, there will be no loss of power. The question of how pressure - vacuum affects the torque and power of the engine, I can say that if we talk about a pressure loss of 30-40 inches, that would be 0.1 bar, according to my calculations, this would mean somewhere around 15% less power, please note that engine in a negative pressure lower than -0.7 bar, can no longer work. Another thought, if wood gas was produced in a gasifier heated from the outside, without adding air, it would be possible to produce gas with a much higher energy density, probably 2x higher or more than the classical process allows us.
An interesting experiment would be to have a vacuum guage connected to the intake manifold, climbing a long hill on woodgas vs gasoline and adjusting the throttle to have the motor pull equal amounts of vacuum. That would kinda give us a feeling for the true power loss - woodgas vs gasoline.
(Don’t try this at home without using a shut-off valve, or you risk destroying an expensive guage with a closed throttle )
JO, in my Subaru I have a built-in Lpg gas mixer, which creates damping, somewhere around 0.1 bar at 3000 rpm of the engine and there is no noticeable change in power. Subaru im cr 1:13 and thus the damped engine develops even better torque than without damping with the original cr 1:10. According to its composition, wood gas would allow under ideal conditions in an engine with cr 1:14 30% less power compared to the same engine with cr 1:10, my opinion and analysis.
Click on the picture for sound. Even the routing of the pipes feeding the air has a significant effect on power. The rest of the engineering conversation is beyond my ken, but if anyone wanted to build a gasified engine to put on a dyno I’d be glad to contribute to the expense of the testing. I was a little surprised about Tone’s statement about gasoline providing more torque than diesel. I assumed that diesel provided more torque because it could be ignited at a much higher CR.
Tom, look at the data 2.0 diesel develops 140 Nm of torque, this much is already achieved by the 1.4 petrol engine. If we simplify it, I can say that the 1.0 l diesel engine reaches 70Nm, and the 1.0 petrol engine reaches 100 Nm, the difference is 30%.
You have increased my knowledge Tone because I had to look up Nm. For others who don’t know, one Nm is equivalent to 0.738 lb/ft.
However data aside, I still don’t understand why machines that rely on torque to do work such as tractors and Semi trucks, use diesel if gasoline is more efficient.
as I already stated, the difference is in the composition of the fuel, gasoline contains more hydrogen and needs less oxygen (H2O) for combustion than diesel fuel, which contains more carbon and burns in (CO2). Wood gas gasified from wood, which has 4 kWh/kg, cannot contain more energy per kilogram and cannot produce as much expansion during combustion, unfortunately. However, we can do a lot on efficiency, high compression of the engine restores power and reduces consumption, I think this is the right way, because increasing the pre-ignition does not bring adequate results, I should mention that I even had to reduce the ignition time on my tractor, because they were detonation too severe.
Now results from that test would have performed well against Wayne’s question if ONLY there was a vacuum gauge installed!!! Showing how much restriction the air filter was giving the engine! But that also begs another question even in our much smaller displacement Dakotas and such even at the lower power ratings we run, would it be a benefit to have a direct flow into the throttle body/ carb? Reducing just one spot of air turbulence could we see a net gain back at the engine? Wayne’s v10 is as close as I can think of to a straight in flow of a v engine, vs the old ammo box mixer from the original build that for sure caused air turbulence as the gas mixture was being introduced into the engine. Does this mean in some ways that the most direct undisturbed flow from gasifier to engine is something to seek out that little inch of power it could gain? My Toyota has a total of 7 90° bends in each gas pipe from hay filter to the carb. Each one is a potential loss of power maybe due to adding air turbulence/dwell time/ high vacuum needed to pull the gas up to the engine??? Would having a direct flow to the engine with as little bends as possible show a difference on a vacuum gauge as gas is delivered to the mill?? Would that in turn change how the refinery itself performs, in some ways a easier breath through the char bed? Now I’m excited to put my mixer box on, and do a direct felt comparison from the factory air box with a kn filter and see if I can tell a performance change if the new mixer box is more restrictive which I assume it is. This being a baseline of killing power on on gasoline would definitely kill MORE power on woodgas
Just as you describe it is something Mikkonen have talked about, drive on gasoline, trying to keep the vacuum at same level when on woodgas, should give an idea about how much open throttle on gasoline, equal fully open throttle on woodgas anyway.
He has also used sloped hills, measuring degrees of inclination, accelerating up these hills say 10 times on wood/10 on gasoline, taking time, there are some kind of formula giving approximate hp results.
With the help of a GPS, a timing clock, and maybe one of them acceleration measuring devices could give some interesting results? Anyway the fuel is free.
Sorry guys …saw I’ve been tagged a few times and quickly skimmed over the last couple days post in this thread . There is some great critical thinking exercises conversations and ideals here. Unfortunately I’ll be very limited for time until after the 8th of July …my parents are visiting for a couple weeks and it’s been 5 years since I seen them. So my family has been spending alot of quality time with them. The good news is I have introduced my father to gassification and he’s seen the projects I’m working on. He’s facinated by it and we have been drawing out a few different designs of variable on demand burn chambers and doing calculations on pumping loss and gass flows needed with the limited data I have already. Also he will be working remotely with me on this project. He is an engineer and machinist as well and where I developed alot of my thought process. So in a week or so I’ll be more involved in these discussions and also start posting video an pics of experiments and data collection. 1st is get the 89 1 ton up and going and driving with the Keith system gathering a bit more data for a week and alot of these questions can be addressed with hard data , testing and results. A big priority will be building a system for max power and see how close to gasoline power we can get and actually expect to surpass it by a little. However that gasifiers most likely will only work for max effort and not work at normal driving situations. So to be able to get to max power there will be an external source of vacuum applied to get gassifier ripping and quick change over to the truck on the Dyno via knife valves in the induction system… It seems backwards and a waste of time for most but Keith and a handful of y’all have already demonstrated well that the systems work fantastic at lower how or kwh …so we will go to other spectrum and figure out how much gas and data needed for high ho and work backwards and we all meet in the middle. It’s an exciting project and with my retired dad involved he will have alot of time to fabricate and then fly out in his plane and pick me up for dyno and test sessions …
My apologies for being a ghost the last week or so . Family is first and spending all the time I can with them
Hi All,
Some of y’all know a lot more about engines than me, and that’s cool. I know my way around all kinds of mechanical stuff without necessarily ALL the details of any of it. I have a wide angle lens. I’m a big picture kind of guy.
Anyhoo, back in the day, when I was still involved in foundry, someone told me that when an iron casting cools it outer .025" forms a lot of cementite (Fe3C) which is a type of ceramic and is very hard. See the lower right corner of the diagram. He told me this is very wear resistant and is why cast iron is used for cylinder liners. And when you rebore, beyond a point, the cementite is no longer there, so an increased wear rate occurs.
So, it would seem to me that sometimes a guy might somehow chemically harden the bores. A few possible methods occur to me: nitriding, electroplating with chrome or hard-dense, electrodeless nickle, TiN… Do they ever do something like this?
Rindert
Interesting topic… I know most blocks are grey iron and your dead on with the ceramic surface finish. During original machining it’s almost always over that 0.025 to standard bore but the deeper you go the softer the iron. Anyone who’s built old school v8s knows a horrible ridge would develope before 100k and engines were basically worn out needing rebuild by then… fast forward to today’s cast iron blocks and it’s very common to have near perfect bores with zero ridge at 400k plus. There is alot of contributing factors. Today’s grey iron closer resembles compact graphite iron. Although it’s technically not CGI it’s got higher graphite and sometimes more nickle depending on manufacturer. The biggest difference is the casting quality is far better and more precise with better control over pour and molds as well as finer raw stock as far as materials go…and modern engines generally have low tension rings and alot are gas ported for better ring seal at higher piston speeds. I pretty much stopped building gen 1 v8s because they just wear out to fast and modern engines are far superior in ho per cubic inch due to better castings which yeild more consistent cylinder head ports and refined ports in engineering of the power plant.
As far as hardening old blocks…yea there are methods to do so but not cost effective. Generally just build on newer platform
I built an auto repair garage at one time for some guys that raced sand drags. Father and son. I never got the chance to pick their brains much but they used big block pre-LS Chevy’s with liners and the water jackets filled with some sort of flowable ceramic. I have tried to research this to no avail. Rob is right that you seldom saw a old school engine hit 100K. Some of that was materials and some of it was sloppy assembly. It was common for Checker Cabs using a blue printed 327 GM engine to run 250 K though or so the legend goes. Back then very few people kept a car long enough to see a hundred K. If you had a five year old car you were a teenager or church people were bringing you care packages. My current truck has 297 K with a 5.3 LS. The engine is great. The floor boards are wood and the body is totally religious.
I just remembered that the top surface on railroad rails is flame hardened after welding. I’d be willing to bet OEMs are flame hardening their bores.
Rindert
That’s interesting…I’ll have to look up flame harden on tracks … I have a buddy who does railroad and went to a few repairs with him. In cracks he ground big vee into it and had a planishing hammer to impact harden the substrate then touched up with grinder and did some type of die test to make sure crack was gone… He then used a magnase steel welding rod if I remember correctly and carbon blocks to keep weld from sagging on sides…then planished the weld and ground smooth. Also watched him thermite weld 2 pieces of track together which was flat amazing to watch. He definatley never used a torch but this was relatively recently so I’m certain procedure has evolved. … I do know railroad make an incredibly badass anvil… I’ll have to look up flame hardening track …would be neat to learn that process on that type is alloy steel. Would make great knives I would think. Railroad track and locomotives in general have always been awe inspiring to me. Steam power especially
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Learned a lot .
