#31
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I must have run in 100 racing engines and came to the conclusion that it was easiest on the dyno if the fan could push enough air to keep the normal water temperature. Done with some respect to the ring to bore relationship would result in the same power and engine longevity. In the old days of air cooling, miserable pistons, 1/2 arsed machining, and hard to mix or crap oil, people would over heat their engines by running them at standstill forever or ragging them before the final piston clearances had been scraped off the interface making them viable as a performance engine.
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'07 EC300 GG '14 TXT250 GG '? 496 CPI Cheetah RZ/RGV hybrid '22 765 Street Triple RS '21 XTrainer '69 Stinger T125 Suzuki '23 TRS 250RR (it's a Trials thing) |
#32
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#33
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seriously,what's hard to understand about it? Quote:
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I don't know. I never did any heat cycling. I get a brand new bike and ride it. Done. Which leads back to the question, is anyone doing heat cycles before the bike is just ridden normally? And if the answer is yes, how and why? I only can say JTD9's from P&W just run on the test stand before delivery. There is no braking in period once the engine is installed. No clue if that is also valid for newer super fan engines aswell, but I'd assume it. |
#34
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I have always heard that the engines are tested in the factory (probably to pretty high revs) anyway so any heat cycling once it is delivered to the customer is probably already too late isn’t it?
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2003 txt250 Pro 2013 Ossa 280i |
#35
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I think the answer is yes, and probably for everyone. No one builds a fresh engine and smashes it hard on it's initial start up. There will always be a series of heat cycles prior to really putting a heavy load on it.. I don't particularly call it heat cycling in regards to tempering or changing the structure of metals. It's more so to ensure the engine is sound.. That there are no unexpected issues (oil leaks, fuel leaks, coolant leaks, air leaks, unexpected noises or behaviour). From there on in, the heat cycles occur every time it is used. PS. Even buying a new bike from a dealer the engine will have been started/tested in the factory, again at pre delivery, and most of us will give the bike a start or light ride somewhere before really put it to work. Thus, I'm not really concerned with 'heat cycles'. I care about a sound engine with correct tolerances. I care that the fuelling is correct, and the cooling too. Then I focus on bedding the rings. |
#36
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I see it like you, I probably do what everyone does when starting a new engine for the first time. I don't heat cycle it nor do I brake it in. For me the most important is to let it completely warm up under low loads. And I use 40:1 premix the first full tank. But other than that I don't do anything special. The Sapnish guy said, and here is probably the answer for you swazi_matt, that when they have a brand new engine they treat it very special. I assume its either brand new or overhauled (new piston, rings etc.) and hasn't been started, tested or used before. I never heard that before on simple engines but I know a lot about how multi cylinder race engines are treated. I know that the legendary Judd V8 is broken in in a very special way as I had the chance to talk the tech chief. Any time before its started oil and water are warmed up or it goes west, but that's another story... |
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All to do with tolerances, operating temps, and thermal expansion. Generally speaking bigger parts require bigger tolerances to allow for greater variations. In a race engine with tighter tolerances you need to remove some of the variables.. thus specific start up/warm up procedures. From my research, it seems to be the same with most of the 2T reading about heat cycles. Usually bigger bores (think jet skis/snow sleds, etc), moving from a cast piston to a forged. Forged by nature expands more and needs more tolerance. Add to that the bathtub curve and infant mortality, and odds are that when you make significant mechanical changes, that if it's going to fail it's going to do so sooner rather than later. If you're going to have a big piston nip up due to thermal expansion you're best chance of avoiding is a slow warm up, and in the event that it does nip it's best on a low load slow idle than wide open down the track. Factories probably tend to stick to a certain procedure for consistency and fault finding. The less variables you are dealing with the better. |
#38
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Here is a little video of the car https://www.youtube.com/watch?v=84rE2LcwHIw Unfortunately Georg, the driver died in a horrible accident at a hillclimb race in 2011. It was a great honor for me to know him. |
#39
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Here's some food for thought.
Why do we believe that the piston and liner would "wear" to itself in the first hour of operation, but not in the following 100 hours? |
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2003 txt250 Pro 2013 Ossa 280i |
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