Engine Performance - Page 5 - Fiberglass RV



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Old 04-11-2019, 09:38 AM   #57
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An engine guru at a machine shop I used long ago told me that ring friction was such a power loss that some racing folks would remove a ring to increase available hp. I don’t remember for sure but think it was one compression ring. He also pointed out that valve train losses were about one third of hp. Turns out that while it is easy to turn a valve train at slow speed because the valve spring forces balance out, at typical engine rpms they don’t balance out.
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Old 04-11-2019, 03:53 PM   #58
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my kid's diesel army truck has no glow plugs, instead it had an ether based cold start system. he's never charged the ether system, instead just cranks it til it coughs over.

its a 14L old cummins 6 cyl, non-turbo.
I remember an old coot telling me one time that the diesel engine should only be able to "smell" the ether. No liquid, ever. Any more than just a whiff, was dangerous. He was right. I've seen a lot of people use ether and not many of them ever use it correctly. And I've seen the carnage as a result. Gas engines, on the other hand, can run on it without damage.

I had a Perkins in my boat. It's pre-heat system was to push a button next to the ignition key, that opened a valve that allowed fuel to trickle into the intake manifold. At the same time, an electric heating element heated up that would ignite the trickle of fuel and start a fire in the intake manifold. Then you'd crank the engine, which would draw the fire into the cylinder and fire the engine. Another way to do this is to simply point a burning propane torch into the air intake at the manifold. Or even more crude, light a small piece of diesel soaked paper and drop in into the intake while cranking.

The whole "diesel starting" problem is another interesting aspect of combustion chamber design. Pre-combustion chamber engines are inherently hard to start because there is so much cold surface area compared to the overall volume in the chamber, that the cold walls absorb too much heat before injection occurs. The key reason for this is that the smaller the overall volume of a container, the greater the surface area of that container, per volume. More cold surface per heated volume. It's why direct injection diesels start easier, even with lower compression ratios, than pre-combustion engines, with their small combustion chambers. Direct injection engines have a greater radius to the cold surface than the pre-combustion design and less surface area per volume to cool the compression heat.

It seems to be part of the reason why ducks can leap from high nests in trees and fall to the ground unharmed. They are so small that they have a much larger surface are per volume than larger animals. More surface area means more drag per volume, so their terminal velocity is quite low. Of course, they are covered in down to add more drag. A bit off topic, but the volume vs surface area is an interesting relationship with all of it's side affects.

A square house with four equal length walls, has less overall wall area than a rectangular house with the same interior floor area. So, a square house should be easier to heat than a rectangular one.

Even though, at idle, a diesel has much more air than needed for combustion, it is never too lean to fire. Conventional gas engines can get so lean they will not run, even though they have barely more air than required to burn the fuel. In the diesel, the injection is the ignition timing. The chamber is already filled with superheated air. At the actual injector nozzle orifices, pure fuel begins to enter the chamber. There is no air in it and it is too rich to burn. Across the chamber, away from the injection point, there is pure air and it is too lean to burn. But somewhere in the middle, as the fuel atomizes and mixes with the charge air, and heats up to the ignition temperature, it ignites where the ratio is right and burns all available fuel that is within the required air/fuel ratio and not below the ignition temperature at the cylinder wall surface.

The oil left behind on the cylinder wall by the rings is too thin to be affected by the heat of combustion. The top two rings in gas engines are compression rings and are designed to seal on their way "up" and hold compression on their way "down". The oil ring has the remove enough oil that the two upper rings can't scrape oil in front of them on their way up, that would then burn, even though they are designed to not leak in that direction. It's hard to see how the system can work as well as it does. Then consider two stroke engines that are lubricated by a 50-1 fuel/oil mist. It doesn't take much oil to form a wedge that can hold parts apart to prevent wear.
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Old 04-11-2019, 04:00 PM   #59
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An engine guru at a machine shop I used long ago told me that ring friction was such a power loss that some racing folks would remove a ring to increase available hp. I donít remember for sure but think it was one compression ring. He also pointed out that valve train losses were about one third of hp. Turns out that while it is easy to turn a valve train at slow speed because the valve spring forces balance out, at typical engine rpms they donít balance out.
Interesting. Thanks. That is part of the reason we have to find a better engine design than the piston/poppet valve engine.

Achates is addressing the valve train problem with opposed pistons. And I want to personally boycott any overhead cam V6s. I had no choice with my Rubicon though. Get the V6 or don't get the Jeep. Hmmm. I thought about it for a while.
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Old 04-11-2019, 10:38 PM   #60
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Just wondering if itís OHC V-6ís or is it Jeep? My 2000 Grand Cherokee (V-8) was never a prize with multiple annoying to aggravating failures before the transmission failed at 120k. OTOH, both the 3.8L and 3.3L Hyundai engines with variable timing OHCís have never had any engine related issues. The 120k still has original plugs. Nice thing about Hyundai is the 60k bumper-to-bumper warranty; I had a steering wheel replaced under warranty at over 40k because there was a 1/8 inch chip in the steering wheel plastic, and an entire seat belt replaced because the little plastic button broke off. Call me a Hyundai fanboy, I guess.
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Old 04-11-2019, 11:27 PM   #61
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OTOH, both the 3.8L and 3.3L Hyundai engines with variable timing OHCís have never had any engine related issues. Call me a Hyundai fanboy, I guess.

On the other hand, my buddy was without his 2009 Santa Fe for more than six months while Hyundai searched North America for parts for his engine. The dealer finally equipped a loaner with a trailer hitch and brake controller so he could go camping. Needless to say, he sold that Hyundai and bought a Highlander.


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Old 04-14-2019, 10:55 PM   #62
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The Koreans seem to be quite weak on aftersales support. Korean major appliances like Samsung, LG, you flat can not get parts for, so when that controller board hiccups, boom, the $2000 fancy washing machine is DOA.
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Old 04-15-2019, 06:35 AM   #63
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On the other hand, my buddy was without his 2009 Santa Fe for more than six months while Hyundai searched North America for parts for his engine. The dealer finally equipped a loaner with a trailer hitch and brake controller so he could go camping. Needless to say, he sold that Hyundai and bought a Highlander.


Enlarge the picture. It says "Service Vehicle" on the side.
A fine example of going from bad to worse .
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