Vince
Cool air is more dense than warm air so you're cramming more O2 molecules in the cylinder. The downside is the cooler air also affects the aerodynamics so it depends upon how you handle that extra air going into the cylinders. In cool air you should get more punch but might lose top speed because you're pushing through thicker air.
When I worked on the farm as a kid it was noticeable how much better the tractor pulled as the air cooled down in the evening. Diesels handle mixture control a little differently than petrols, though. I'm sure that Teazer can enlighten us on jetting for cool / hot air conditions.
I was also surprised at how early you are doing these high speed runs on a fresh engine. It obviously hasn't gone bang so you're probably OK. :-)
G
Japan Meets Britain
No it hasn't gone bang, and no smoke or leaks or strange sounds or anything along those lines, so I do think we are okay. I haven't only been doing high speed runs though -- I have been varying the riding, and we have been combining 'normal' riding with the high speed runs, so lots of variety. And it's not like I've been holding it at 9000 rpms for 30 seconds or anything like that. I think we already have done about 300 miles, and the high speeds are really only for short periods of time.
I have heard different methods for breaking in an engine -- keep it below a certain rpm for the first 500 miles, don't go over 50 mph, etc. I've also heard that if you baby the engine too much, then it will not have built up a 'tolerance' (for lack of a better term) for higher speeds and more 'stress'. I think the sealing of the piston rings and cylinder wall glazing is also affected by the method of the break-in, though this is venturing a bit out of my sphere of knowledge (and I'm sure you guys know way more about that than I do). I like the idea of varying it so that it never really stays at one single rpm for an extended period of time, and then changing the oil after the first few hundred miles. I've broken in at least 3 engines this way and never really had any issues. I think the worst thing you could probably do when breaking in the engine is to run it at too low an rpm (i.e. 'lugging'), but that's just my perspective. As well, a few of you suggested dyno-testing on my bike -- if I had done that, I think they'd have likely been running it at full throttle as well? Just to confirm all this, I emailed John (my mechanic) to verify the wisdom of how we are going about things, and this is his response: "FOR BREAKING IN THE NEW TOP END, IF YOU ASK FIVE DIFFERENT MECHANICS YOU WILL GET FIVE DIFFERENT ANSWERS. MOST FOLKS HAVE NO IDEA WHAT REALLY IS HAPPENING INSIDE OF A NEW ENGINE. FOR THE MOST PART IF THE PARTS ARE OF GOOD QUALITY , ALL OF THE MACHINING WAS DONE PROPERLY AND THE PERSON BUILDING IT KNOWS WHAT THEY ARE DOING, THE BREAK IN TIME IS VERY SMALL. CONSIDER THIS: THE MECHANIC BUILDS A TOP TO BOTTOM FRESH ENGINE. IT IS THEN RACED AT THE 24 HOURS OF LEMANS . IF IT IS DONE CORRECTLY IT WILL BE GOOD FOR MORE THAN JUST THAT RACE. ALSO WITH THE NEWER MATERIALS AND TECHNIQUES BEING USED TODAY, THE ENGINE IS ALMOST READY TO GO, DO WHATEVER IS ASKED OF IT AFTER A VERY SHORT TIME, AND WITH NO HARM TO THE ENGINE. AS FOR YOUR ENGINE, WE DID THE TOP END AND A NEW TRANSMISSION, BUT NOT THE BOTTOM END AS IT ONLY HAS ABOUT 12000 MILES ON IT. SO DON'T WORRY. I WOULD NOT LET YOU HURT THE NEW REBUILD BECAUSE I DO NOT WANT TO HAVE TO REBUILD IT ALL OVER AGAIN SO SOON." Sounds good to me! Vince
Sounds like you have it under control with John in attendance. Now, a Mechanic that shouts in blue - not sure whether that's novel or not!! :-)) Also - I'm surprised that asking five folks would only turn up 5 opinions. If they were real engineers you'd have 10 or 15! G '60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160 '66 Matchless 350 '67 CL77 '67 S90 '77 CB400F
Full agreement with Graham; it's (relatively) common knowledge that a denser cylinder charge combusts faster and more efficiently due to the 'greater' oxygen content. It's why turbocharged engines (especially diesels) are more efficient when an intercooler -- an air-to-air heat exchanger, basically a high-throughput alloy cooling radiator matrix -- is incorporated between the turbo and the intake manifold. If you've ever driven/ridden in foggy/misty conditions, you'll notice a marked increase in throttle responsiveness. Example: I used to 'tune' SAAB turbos in the '80s; my favourite creation was 1980, eight-valve model to which I fitted an intercooler and water injection -- basically a small-orifice jet in the intake tract which dropped small 'blobs' of water, from a reservoir, via a small electric screenwash pump and a microswitch on the 80%-plus throttle quadrant. The result was the ability to adjust the wastegate to enable 17psi of boost (6.5psi higher than standard) without sustaining damage to the motor's internals. The motor, as standard, incorporated a vacuum-driven enrichment device which came into play at full throttle; this is a crucial requirement on turbo or supercharged vehicles. That car needed 205/50-15" tyres, instead of the OE 195/60-15", in order to cope with the additional power, and Tarox front discs to rein it in again! Damn, it was quick! 0-60mph took 6.6 seconds, a vast improvement on the 9.5 of the standard ton-and-a-quarter-weighing car; 145mph -- up from 120mph -- with 182bhp (at the front wheels, on a dyno), up from 145 crankshaft-bhp! All from a denser charge allowing the use of more boost. That was in '86. The car still lives and breathes on the English south coast......
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||