Only us that drove Fords. 
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Haha, from what I remember very few people could afford a car newer than 5 yo back then. Volvo’s were considered just about broken in at 100k miles and had an unnecessarily powerful engine at 82 hp. Many people settled for a cheaper VW, Fiat, Opel or a Saab V4.
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I was trying to remember what I was thinking about when I worked out the gas equation. I was seeking a way to understand how to control detonation in high compression engines.
That fascinating part that caught my attention was how compression ratio is calculated. We always say it’s the difference in volume between when the piston is down and when it’s up. That’s the static number. Buuuuuut, with engines with throttle plates the actual compression ratio is different. The dynamic compression ratio is a function of how much charge is in the engine.
It doesn’t seem right. That’s because we associate the physical change in volume as a linear relationship with compression pressure. So if you start out with a cylinder and piston at btdc at 14.7 lb per square inch, and then compress that seven times (7to1 compression ratio) you get 102 lbs per square inch (psi). But if you are running a throttle plate and high vacuum then your end pressure is less than 102 psi.
It boils down to watching the vacuum gauge while the engine is running, and keeping a high enough vacuum to stop detonation. Keeping your foot out of the pedal.
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That is something i thougt about, just as over-boosted engines often need lowered compression ratio, a woodgas engine with it’s lower cylinder filling due to vacuum/restriction, needs the direct opposite, higher compression ratio. Just the word i looked for: dynamic compression ratio. 
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I’ve read this post ten times because I know there’s something I’m missing but compression and compression ratio are measured in a totally sealed chamber. The only variable is how much gaseous mix can be crammed into that chamber before it’s compressed. Furthermore if you watch this video, at about 4:45 he says that a greater volume of cylinder is a factor in increased CR. Maybe longer stroke, I don’t know but the volume of the chamber in the head increases the same amount as the bore so there is no difference between a small bore and a large one as far as CC’s of compressed area go. I tend to get lost in some of the technical aspects of these things.
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Yes BruceJ, exactly.
All factors in a working internal combustion engine become “dynamic”.
Yes I did say ALL.
One of the engine building guys here on the DOW mentioned power crankcase vacuming for better racing power. He also inferred to piston rings flutter.
Combustion pressure pushing down than pressure pushes the upper rings down in thier grooves going behind those rings. And behind the ring pushing it outward to seal better.
Crank shaft pushing up the same piston drags that same ring down on it’s groove. Back side of ring pressure is reduced for less ring drag. Ring flutter.
Then the function of the ring to distribute, and remove the excessive, the spray&splashed up lubrication and cooling oil.
This ring fluttering is also dynamically changed by piston up and down speed changes. RPM changes!
So free to move piston rings, versus carboned up sticking; or stuck piston rings will affect the dynamic compression ratio. Blow by making no combustion power. Excessive oil in the combustion changing the burning too.
This one factor is ignored mostly by hot-rodders. A big factor by endurance racers. Working engine designers and builders.
A heck of a lot of engineering into those long lived “economy” engines of AMC, IHC, Ford and others.
Not just stuffing a tiny carburetor onto a largish displacement engine.
The best mileages one’s stayed with manually needed adjusting valves the longest. Hydraulics self-adjusters needed larger power sucking oil pumps. I-6’s with four main bearings had better economy then seven main bearing engines. I-4’s with three main bearings capable of higher milages than later five main bearings units. Less internal drags, needing less pressure delivered oiling.
The AMC economy engines I mostly used 19-24 y.o. you had to very light feather foot to keep from pinging too much. Road trips especially in the summer and if up and across the mountain passes, I’d cheat and just put in mid-grade or even premium grade gasoline to keep the detonation down.
And an added vacuum gauge was my friend. Keep above 7-8" of vacuum to keep out of the power enrichment adding valve in the carburetors.
Read of that trick in the old magazines from the early 60’s. When they did unmodified factory economy cars racing for mileages.
Regards
Steve Unruh
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I have messed around with rail anvils from time to time:
I am pretty sure I reference a “Wyegers” blacksmithing book where he explains how to heat treat a rail anvil.
Pete Stanaitis
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Tom, you are right. I’m not explaining myself very well but you have given me the perfect opportunity, thank you.
When you were in school they taught you to disable the ignition ,remove the spark plug, screw in your compression gauge, block the throttle all the way open and crank the engine four or five revolutions or until the needle quits bouncing on the compression tester. What’s going on is the engine is rolling over at about 200 RPM and it is slow enough and there is no restriction in the intake so all the possible air can fall into the cylinder. It is the most ideal condition you’re going to get for testing compression, which is an indirect measurement of volumetric efficiency.
Now what I’m talking about, is when you are running the engine and you have that throttle plate shut. A vacuum guage is measuring less than the surrounding air pressure. So high manifold vacuum is the condition you get with the throttle plate shut. High manifold vacuum also means you have a rarefied charge in the engine, OR not as much charge as you would with no vacuum. No vacuum exists when there is wide open throttle.
Why? Why do I care? Let’s say I do something really stupid like taking out the injectors in an 6.2l diesel and replacing them with sparkplugs. I would now have an engine with a 21:1 compression ratio. It could not burn pump gas…or could it? If I keep it in a high vacuum condition, I could bring the compression pressure down below the detonation pressure. So maybe it could start on gasoline and switch over to woodgas.
Basically if you raise the compression ratio High enough to accommodate wood gas, you can’t use gasoline anymore if you open the throttle. The vacuum gauge would tell you at what throttle settings things start going bad.
I don’t think I have to mention, but I will, that this has nothing to do with Venturi vacuum. That’s the measure of how much air is flowing past a certain point.
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Bruce, removing the injectors and installing spark plugs is by no means a stupid idea, but a good idea that I have been thinking about for a long time, what you mention, maintaining vacuum in the intake manifold and thus determining the compression ratio of the engine, is a spot on idea, I learned something similar on to its small diesel engine and the thing works well. An engine with a high cr limited to approx. 70% coverage of the combustible mixture enables a very very high efficiency and thus a negligible drop in power, probably something similar will be my next project, … as I said before, I am “doomed” to use diesel engines.
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Haa, now it is getting clear what you want and what you are talking about.
Detonation is unplanned explosion of fuel. One way but not the only way to ruin an engine. Normal engine WOT can be broken by thermal overload, not neccesary detonation. By your last post I understand wich way you want to go, interesting. Telling nothing new I hope.
And yes, I am thinking the same about my Lister. But there is stil a lot of oil to burn before I can make this step.
Edit, GEK APL had a project with changing injector for spark plug. They wanted to make it dual fuel by drilling a hole for the plug, but there was no room and decided to change the injector.
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Volvo Marine engines were and still are very good.
Some of them were quite high compression and performance too and that’s not an easy combination for long life.
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Aren’t Volvo marine engines partnered with General Motors? I know the intake plenums I can get for my 4.3L are labelled Mercruiser/Volvo for some reason.
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I’ve seen some volvo marine based on GM, smallblock 350 for example, some years ago i helped a friend with his boat, fixing carb, it was a volvo marine based on Ford 351 cleveland, seem’s they bought and converted many different engines? Even heard about some Mopar- volvo penta, and volvo penta- perkins.
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@Tone @Pelletpower
I hate to disappoint but I would never modify a 6.2l Detroit Diesel. I have too much biodiesel (methyl esters) to be burned, to do that. Also, they are much too complicated for all that.
What I am interested in doing is changing the compression ratio on a Farmall H engine. I have plenty of them, and they are extremely simple.
I have one problem to overcome though. With a 5 to 1 compression ratio, an H (150cid) can easily be hand started. A high compression version will not. I would like to add the decompressor like the Caterpillar has. The 632 cid Caterpillar has a lever that holds down the exhaust valves, while one gets the flywheel spinning a bit.
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Intnersting consept BruceJ.
The easy direct mechanical compression releasers like the Lister CS’s use a swing-in, swing-out tappet cam follower holds up system. That tapper having a machined flat with shoulder.
The modern four stroke small engine cranking rpm compression releasers use a camshaft mounted tappet lifter for just the exhaust tappet. Idle/running speed RPM then lowering this rotating lifter allowing the tappet to completely follow the camshaft lobe.
Both of these systems keep all of the exhaust valve train compressed, in-contact, and ready.
The modern GM, and Dodge systems work with complicated multipiece lifters; a lock-in/lock-out-pin electro-valved moved by engine oil. Complicated. Subject to wears and oil quality/quantity problems.
Honda and the Jacobs Brake systems work up at the valve stem ends. Complicated.
Try this: screw in a chainsaw in the head compression release valve.
I bet it will work. Ha! Take four? For your H. Quick finger resetting all four for each re-start try.
But hey! Easy-pleasie. See-Do, solution if it’d work.
Regards
Steve unruh
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I can’t comment on that today.
But at one time Volvo as a single integrated entity made some engines that served double duty in cars and marine use.
One particular engine I recall was a 4 cylinder with 5 main bearings that was very strong and reliable ( and I think it was built the same for cars )
VOLVO PENTA used a lot of different engine including their own.
Some were from GM Ford and Chrysler ( remember outside America big displacement gasoline engines were discouraged. Some by high fuel costs some by direct displacement taxes to discourage automakers from building huge thirsty cars ).
Also some Volvo Penta units are or were made under licence to Nissan Marine and use Nissan engines.
I picked this off the wiki with regards to Iron…
it might explain some of the improved wear life of modern engine blocks to older blocks because of finer heat and alloy control.
I remember at Neelon Castings we paid close attention to temp and cooling times ( as well as alloy ) to make high performance brake drums and rotors for many different manufacturers.
A typical chemical composition to obtain a graphitic microstructure is 2.5 to 4.0% carbon and 1 to 3% silicon by weight. Graphite may occupy 6 to 10% of the volume of grey iron. Silicon is important for making grey iron as opposed to white cast iron, because silicon is a graphite stabilizing element in cast iron, which means it helps the alloy produce graphite instead of iron carbides; at 3% silicon almost no carbon is held in chemical form as iron carbide. Another factor affecting graphitization is the solidification rate; the slower the rate, the greater the time for the carbon to diffuse and accumulate into graphite. A moderate cooling rate forms a more pearlitic matrix, while a fast cooling rate forms a more ferritic matrix. To achieve a fully ferritic matrix the alloy must be annealed.[1][11] Rapid cooling partly or completely suppresses graphitization and leads to the formation of cementite, which is called white iron.[12]
The graphite takes on the shape of a three-dimensional flake. In two dimensions, as a polished surface, the graphite flakes appear as fine lines. The graphite has no appreciable strength, so they can be treated as voids. The tips of the flakes act as preexisting notches at which stresses concentrate and it therefore behaves in a brittle manner.[12][13] The presence of graphite flakes makes the grey iron easily machinable as they tend to crack easily across the graphite flakes. Grey iron also has very good damping capacity and hence it is often used as the base for machine tool mountings…
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Wood-gas wants displacement. it’s just tough to avoid. The flame speed of wood gas limits rpm and fast reving is a major, the major, way of increasing HP.
Wood-gas or chargas will be diluted by nitrogen and that’s tough to fix. Filtering out nitrogen is possible but impractical for the volume of air per second (though some carbon capture power plants are trying!). Even a partial reduction would help a lot, but again, I don’t know of any remotely practical method.
You can compress the fuel-air charge so there is more charge in a given volume of cylinder, say with a turbo. But you’ll be compressing a diluted fuel charge. Turbos are expensive and a maintenance item. And you’ll be compressing the fuel-air already mixed unless you use two. Kind of on the dangerous side?
You can increase the compression ratio. That helps with efficiency but won’t generate that much more power, especially since revs are limited.
You can ignite the fuel-air charge earlier in the cycle to help offset the slow flame speed and improve revs plus expansion-> mechanical efficiency but again, it’s not a game changer.
Char gas is richer than woodgas, esp with a water drip. That helps to. I guess in the end you have to add up a bunch of little things to get to your best outcome.
I’m more of a genset guy so derating works. For a vehicle it’s tricky. The engine is sized assuming it runs on pump gas. Best to start with the most displacement possible I guess, but that’s old news to you all!
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Hi Anthony, I have heard this ever sense I have been on the DOW site that wood gas limits your RMPS in a IC engine. If you are talking about how fast it will rev up in time on wood gas compared to gasoline. Yes then I will agree with you.
My 1992 5.2 L Dodge Dakota will Rev up to 5,000 plus. Between shifts of the grears and this is a automatic transmission being shifted manually. The engine is stock no modifications, other then the timing advancement . I think it depends on the gasifier ability to produce good quality rich gas. Important the timing needs to be advanced for this to be accompished.
The WK Gasifiers are The Real Game Changers compared to other gasifier designs. Wayne K. with his WK Gasifier set a world land speed record a few years back. So much for limited RPS for Horse Power and speed going down the road.
Bob
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I have no doubt I have hit 5000rpm on my top speed runs. Slower to gain those rippems, but it gets there
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Marcus and Robert, if your engines are doing those rpms then you are in that sweet spot for sure. Sounds like timing and good gas is enough in the right hands. Well done!
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