Doubleclutch, I don’t know what you have been reading and what experience that you have with ruined engines but I am skeptical of your statement. I have personal experience with a Harley engine that I frequently shifted into higher gears and lugged the engine with no regard for it and at 30,000 miles it burns no oil and runs like new. My car engines, although not treated similarly, have been good for me too, GM and VW products, if you will.
Engine oil, oil and air filters, internal engine manufacturing tolerances and surface finishes are very good now and if you can ruin an engine if you do oil and filter changes according to the recommendations from the manufacturer (owner’s manual), I’d like to know how that is done. Please specify the brand of engines that you have ruined and what you will do to prevent that in the future.
I tend to agree with Wha Who, I have a 2001 Kawasaki ZRX1200 four cylinder motorcycle. Not only do I short shift it when I’m not in a hurry but I exchanged the stock 17 tooth transmission chain sprocket for an 18 tooth sprocket as well as exhanging the stock 42 tooth rear wheel chain sprocket for a 41 tooth sprocket. This gearing has the engine spinning only 92% as fast while cruising the highway and lets me get 50+ mpg.
If this is hard on the engine, my bike has a funny way of showing it.
In fact, as an engine’s stroke has such a profound effect on this, the really extreme piston speeds aren’t in F1, but in NASCAR: At superspeedways, their 358-cu.-in. V-8s are said to be approaching 10,000 rpm. At these revs, a typical 3.5-in. stroke translates into a piston speed of 5833 ft./min., more than twice the Pomeroy dictum.
Well, after all is said and done, more is Said than Done. I cannot tell from all the posts how fast is too fast. I am convinced that a piston traveling at 5833 ft/min is much harder on an engine than one traveling at, say, 2500 ft/min. My Dodge V8 runs about 2000 RPM at 70 mph. Now it might perform better if that was 2500 RPMs, but no more.
I am convinced that a piston traveling at 5833 ft/min is much harder on an engine than one traveling at, say, 2500 ft/min
Well of course it is! I don’t think anyone can successfully dispute that the forces on the reciprocating assembly do not increase with RPM. The point is that an engine is designed and built for a purpose. Those that are designed to operate at higher RPMs require a different design and use more expensive, robust and/or exotic materials in order to withstand the rigors of their intended application.
Right. Not sure of the Nascar rules but, in general a Nascar motor that last 500+1 miles is all they need. F1 teams are now limited to 8 engines a season.
even if an engine was built to stand higher RPMs or higher compression, I think it will last longer if you drive it a little easier. My son-in-law just had to replace a valve spring in his Dodge Hemi. Of course I can’t say it was due to high RPMs.
I don’t have my book on me, but this is what I can remember. The combustion is not an explosion, it’s a controlled burn of fuel and air. The flame front speed of this reaction is slower than the speed of sound. For an engine to work, the flame front needs to be slower than sound, because a flame spread by a shockwave (speed of sound in that enviroment) results in pinging. Now the flame front speed is a result of octane, pressures, AFR, compression ratio, etc and I think it’s only in the 30-50 ft/s range, it just doesn’t have to travel very far and the piston stays at TDC for a while to give the burn time to, well, burn.
And yes, an explosion is a combustion speed exceeding the speed of sound. everything else is a burn. Dictionary.com often oversimplifies things to the point of confusion.
That’s the problem with generalizations, they don’t necessarily apply. Often, an engine that is designed to run at higher rpms is best run there because that is how it is designed to run. For example, if you run the engine consistently at a lower rpm, you don’t achieve the intake and exhaust velocities necessary to keep from coking up the engine. It runs most efficient and clean at the designed rpm range. It is designed to live for the anticipated lifespan of the application.
Here’s another way to look at it- why would you attempt to preserve the engine beyond the normal working life of the rest of the car? It’s like living so that you end up a good looking corpse!
"Here’s another way to look at it- why would you attempt to preserve the engine beyond the normal working life of the rest of the car? It’s like living so that you end up a good looking corpse!"
Now that’s a stupid remark!! In other words you want to make sure the engine is shot by the time the rest of the car is!! AND just what is a “designed RPM range”? Does the manual tell you to keep the RPMs up around 4,000?
Why can’t you ever play nice with people who disagree with you?
What, may I ask, are you going to do with your engine after the rest of the car has rusted away and is unsafe? The car will be so depreciated the engine will be virtually worthless.
As to your questions about “designed RPM range,” I suggest you take a look at Car and Driver’s review of the Honda S2000. They mention how the engine is designed to run at high RPMs and how well it is designed for that task. Basically, if a car is designed to run at higher RPMs, it will achieve the most horsepower and torque at the high end of the RPM range, unlike engines with a lot of low end torque, like most V-twins.
Well, the obvious downside to high rpm are the parts of the engine moving in a predominately “non-circular” motion: the con rods, valves/valve springs, pushrods (if applicable)…as well as the parts they immediately interact with, such as the crankshaft journals and camshafts.
For the cylinders and rings, it would seem a mixed bag…upping the RPMs (and dropping manifold pressure, as would result in a constant power output) would result in more total revolutions, but the lower chamber pressures would result in the rings pressing towards the cylinder walls less forcefully, as well as higher hydrodynamic (tribodynamic?) protection from the oil.
Considering that RPMs have risen steadily, while “blown rods” seem to have become something of the past (last one I recall hearing about was my dad’s aged Malibu) suggests either better metallurgy or better quality control (included flaws can drastically reduce fatigue life, as demonstrated by UAL 232 in Sioux City…the one that lost all 3 hydraulic systems after a turbine “grenade” failure.)
Now that’s a stupid remark!! In other words you want to make sure the engine is shot by the time the rest of the car is!!
Well, I think Ron-man summed up the point pretty well so there’s no need to address it further.
This is a prime example of someone who has a little knowledge but thinks they know everything. A dangerous combination. If you ask in a nice way and carefully consider before spouting off, people might just explain it to you. But if you’re ignorant AND obnoxious, it’s not worth the effort…
suggests either better metallurgy or better quality control
I’d say it’s both and I’d include design as well.
Not only have the alloys improved but the process controls are much improved. Machining tolerances are astoundingly tight for even high running production volumes, especially compared to years past. I wouldn’t doubt that the high end parts are also shot peened or otherwise stress relieved as part of the normal production process. That kind of treatment used to be reserved for the exotic aftermarket parts or applications.
No, of course you don’t have to run at peak HP. We are just talking about where the power arc reaches its peak, not how the driver operates the car. Those are two totally different things.
By the way, what, may I ask, are you going to do with your engine after the rest of the car has rusted away and is unsafe?
Have you notices that V-twin engines, which only have two cylinders, have a lot of low end torque? That means they don’t have to operate at high RPMs in spite of the low cylinder count.
“This is a prime example of someone who has a little knowledge but thinks they know everything. A dangerous combination” .I think most of these posts are from those who have little knowledge.
“Well, the obvious downside to high rpm are the parts of the engine moving in a predominately “non-circular” motion: the con rods, valves/valve springs, pushrods (if applicable)…as well as the parts they immediately interact with, such as the crankshaft journals and camshafts.” Now this is true
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For the cylinders and rings, it would seem a mixed bag…upping the RPMs (and dropping manifold pressure, as would result in a constant power output) would result in more total revolutions, but the lower chamber pressures would result in the rings pressing towards the cylinder walls less forcefully, as well as higher hydrodynamic (tribodynamic?)" Now I doubt that this is true.
