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SuzukiSavage.com
/cgi-bin/YaBB.pl General Category >> The Cafe >> Interesting Discussion /cgi-bin/YaBB.pl?num=1451621021 Message started by cheapnewb24 on 12/31/15 at 20:03:41 |
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Title: Interesting Discussion Post by cheapnewb24 on 12/31/15 at 20:03:41 I pinned this tab several days ago. Thought it was interesting. http://www.southbayriders.com/forums/threads/22539/ |
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Title: Re: Interesting Discussion Post by Flint on 12/31/15 at 20:15:27 If you want to spend money on your scoot get the crank machined out of titanium and titanium con rods made as well. Triumph did that to get the Bonnie to do 120 on the salt flats. Any time you lighten up the reciprocating mass you make more HP. Titanium does not stretch like aluminium con rods do. It is VERY notch sensitive and likes a generous radius on the crank fillets. If you want to store energy use a heavy fly wheel like a lot of the early trials bikes did. |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 12/31/15 at 21:21:03 A heavy flywheel may be what makes our thumper so tame and controllable. Ya think? Am I wrong? Maybe stroke length also has something to do with it? |
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Title: Re: Interesting Discussion Post by Art Webb on 01/01/16 at 07:20:29 heavy flywheel, mild tune, and a rotating counterbalancer |
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Title: Re: Interesting Discussion Post by Steve H on 01/01/16 at 10:15:25 Longer stroke gives you more torque at the expense of top end rpms. |
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Title: Re: Interesting Discussion Post by Kris01 on 01/01/16 at 12:41:08 213A63606166646B520 wrote:
I've commented about this before. It seems to me that our 6500 RPM redline is a little high for a stroke of 3.78". http://www.csgnetwork.com/pistonspeedcalc.html 6500 rpm = 4094.488 ft/min (or 68.24 ft/sec). For an engine that's high tech for 1970, that seems exceptionally fast. I have no data to back this up though. |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/01/16 at 12:54:48 I guess that's the disadvantage of a big single: Either the bore gets huge or you have a long stroke. If you have a long stroke, you can't go fast. However, if you go slow, you need a humongous flywheel or else you'll have jolting in the low end because the power strokes are so far apart. Can't go fast--can't go slow. :P What do you do? Singles, strangely enough, seem to be known for low end torque. But then, I read someone say that they can't lug down as far as a twin, or V-twin, or something. Am I missing something here? Is it a matter of engine tuning? Ignition/cam timing, cam profile, fuel mixture? By the way, can anyone tell me why many engines don't have retarded timing at low rpms? Ever lugged one down to stall only to hear it knock/ping before it died. I remember my Savage sometimes did that. I haven't noticed it since the spacer mod, though. Shouldn't timing retard so far that it will continue to run even at extremely low rpms without knocking? |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/01/16 at 12:58:05 2A1308125150610 wrote:
I've commented about this before. It seems to me that our 6500 RPM redline is a little high for a stroke of 3.78". http://www.csgnetwork.com/pistonspeedcalc.html 6500 rpm = 4094.488 ft/min (or 68.24 ft/sec). For an engine that's high tech for 1970, that seems exceptionally fast. I have no data to back this up though.[/quote] I don't really know about ideal piston velocities, but isn't it true that a longer con rod will help reduce undesirable piston forces? How long is the con rod? |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/01/16 at 13:04:13 http://www.corvetteforum.com/forums/engine-mods/1324568-safe-maximum-piston-speed.html These Corvette guys are discussing this sort of thing. From a quick glance or two, you have a point: It is a bit fast for being an old design, but it's not unheard of. |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/01/16 at 13:11:05 Well...Reading further... Assuming that you did the calculations correctly, that does seem very high for a cheap old engine. Maybe that's part of why motorcycle engines don't normally last 200k. Anyone here get 100k without at least one overhaul? Maybe there is some secret ingredient Suzuki threw in there to help it take those velocities. :-? |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/01/16 at 15:45:54 Actually, it's closer to 3.70 inches, not 3.78. According to Wikipedia, the bore/stroke is 94 mm x 94mm. Using the calculator, it's around 4009 FPM, substantially less. It's still high, but closer to reasonable. Are you sure the engine was designed so long ago? The first Savage came out in the mid 80's. |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/01/16 at 16:01:12 Are the forces within the engine proportional to the square of the velocity or something?Or is the relationship linear, like momentum? I read somewhere that the friction is proportional to the square like that. :-? I know that kinetic energy is proportional to the square of the velocity. It could be that they are inversely proportional. :-? I'm not a physics buff. The point I am proposing is that a small change in piston velocity could have a huge effect. Maybe that is why redlines are so important. Once you get so fast, the smallest speed increase could change the stresses immensely. Am I getting mixed up here? :-? I would think the most important thing is stress rather than friction. Does stress increase exponentially like friction, or does it increase linearly? |
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Title: Re: Interesting Discussion Post by Kris01 on 01/01/16 at 17:03:03 7D767B7F6E707B697C2C2A1E0 wrote:
I think you're right. I was thinking 96 mm for some reason. |
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Title: Re: Interesting Discussion Post by Kris01 on 01/01/16 at 17:05:58 29222F2B3A242F3D28787E4A0 wrote:
I just meant this engine would be state of the art in 1970. It was actually designed/built years later. |
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Title: Re: Interesting Discussion Post by Kris01 on 01/02/16 at 11:22:57 According to this: http://www.mustangsandmore.com/ubb/SteveWmaxpistonspeed.html ...with a 94 mm (3.701") stroke and 3500 fpm mean piston speed, we probably shouldn't be spinning any faster than about 5674 rpms (or around 85 mph in 5th gear). How did Suzuki get their 6500 rpm redline? Just advertising mumbo-jumbo? I'm not seeing anything about this engine that would allow it to survive very long at 6500. |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/02/16 at 19:59:52 So, what's the best rpm, you think, for engine longevity? Depends on throttle? Just go by feel? Seems like at low speeds/low gearing, the engine can lug down lower than during highway riding. It seems as though there is an upper limit to gearing, whereas the amount of load/work demanded at high speeds places limit on how tall the gearing can be without causing perpetual lugging. Ya gotta wind the throttle so much that you'll beat the bearings out of the poor thing if ya gear it too tall. :P I gather that the Honda Rebel folk talk about that problem especially. I gather you have to keep those things wound up. I wonder if you can gear one tall enough to lug going downhill 80 mph. :o Seems as though below 3000 in the higher gears generally = lugging. Even then, if you give it much throttle, you should be around 3400 at least (around peak torque). However, you would think that it should run lower than that, given it's stroke length. There's no winning! Drag it down and lug, or rev it up and blow! We have such a wide torque curve, but should we use it? Is it better to feel it shake or wring its guts out? :P I've read on this forum to let it rev a little, and that seems alright for the higher speeds/loads, but that stroke length leaves some questions. :-/ I guess I'm overthinking this a little. After all, I can instinctively tell approximately where the bike should be running by feel (vibration/sound/throttle response). I wonder if I don't keep it revved a little higher than necessary. Sometimes it has a hidden store of low-end torque I don't always utilize. But then, as some of the Harley people might agree, just because you have the torque, doesn't mean it's healthy for the engine. I'd just like to get a better idea of precisely where I should sit. I've read that the science of bearings is pretty complicated. They have a sweet spot where friction is lowest. Above that, and the friction increases quickly (I assume fluid friction). Below that, the oil film breaks down, and metal-to-metal contact begins, also increasing friction. Of course, load complicates everything. I think this is partly why you need a higher engine speed to support higher loads: to support the oil film. I think I am referring to hydrodynamic bearings. I'll post a link. I haven't read it very much, so I might have missed some things. http://www.epi-eng.com/piston_engine_technology/engine_bearings.htm I wonder if I should stay around 3500-4000 at all times at highway speeds, or should it be okay to gear up to 5th gear at 45mph or something? I've noticed that I can sometimes do that if I'm taking my time. Should the engine smooth out completely, or should there be some putt-putt left? should I be able to feel the pulses? I tend to lean toward the smooth side in the long run. Low rpm+low load=smooth. High load+high rpm=smooth. I noticed that the ol' Subaru supposedly doesn't reach peak torque until in the 4K's for some reason, but I usually highway cruise in the 2-3K range. V8's seem especially known for cruising low on their torque curves for economy's sake. It seems as though the max efficiency/peak torque thing is not necessarily a hard rule. However, cars usually don't have the wind resistance of motorcycles. Trucks, on the other hand-- especially the older, boxier (and perhaps better looking ::) ) trucks-- I wonder. :-? Seems as though 1st gear seems happy around 15 mph; 2nd is best around 15-25 (around 20); I like to try 3rd on the city streets to cruise easy. 25 in second starts getting a little busy. However, 2nd is really too far from 3rd, and so 3rd almost lugs at 25. It's probably best 30-45.I like to go to 4th at 45, I think. 4th is happiest 45-55. It probably pulls 40 okay. :-/. 5th is best around 55-60 mph for pulling. If you're taking it easy, It seems comfortable at 50. You might go to 45 if you're light on the throttle. Be aware that my gearing is a little shorter than many of you because I have a worn 140/80 rear. Speeds are indicated, not actual. Of course, it's just a guess anyway. No need to be so OCD about it. ::) If I go strictly by the chart of actual speedsat, say 3400 rpm, I get the following numbers (from Gearing Commander). 1st: 19.3 2nd: 28.5 3rd: 39.4 4rth: 47.1 5th: 50.9 It seems that, on the average, I probably drive at (higher gears) or a bit below (lower gears) torque peak EXCEPT in 5th gear, and this is partly (only partly) because it is the last available gear. The other reason is that the four lane seems more demanding for some reason :-? It seems that right around highway speed, demanded throttle opening seems to get high. :-? Is it just me, or does anything above 50 mph take alot of throttle? :-? Would different gearing have any effect on engine longevity? Any thoughts? |
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Title: Re: Interesting Discussion Post by Kris01 on 01/02/16 at 20:45:26 With a 140/90 rear tire, I'm pulling a hair over 4000 rpms at 65 mph. That seems to be a good cut-off point for me. Above that rpm the engine seems to be really busy. I try not to rev much beyond that...roughly speaking. |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/02/16 at 20:47:41 Look at my previous post, I've been working on it. |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/02/16 at 20:50:18 Strangely enough, 75 is rather smooth and comfortable on the superslab. I might have read someone else attest to this. :-/ However, it starts HATING you at 80! Of course, who needs to do 80? ;) |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/02/16 at 20:52:43 (That's not saying I didn't at least wonder about heating issues, or worry about the fact that I needed an oil change) :o That was before the spacer mod, too :o. |
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Title: Re: Interesting Discussion Post by Kris01 on 01/02/16 at 21:01:45 That's really all subjective. 65 is fine for me. I don't want to push her too hard. Oil consumption goes way up at those speeds BTW. ;) |
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Title: Re: Interesting Discussion Post by Dave on 01/03/16 at 04:48:48 The flywheel is a rotating mass that helps to maintain inertia, and smooth out the engine pulses. The crankshaft doesn't run at a constant speed as the engine is running....and the tachometer shows an average rpm and not the constant variations. When the engine hits the power stroke the crankshaft gains speed, and then at the bottom of the stroke the engine begins the exhaust stroke and the crankshaft begins to slow a bit, then during the intake stroke it slows a bit more.....and during the compression stroke it slows the most. The speed variations are the largest at lower rpms, and as the engine speed increases the variations are smaller. In the early days of the internal combustion engines the speeds were very slow and often were only a few hundred rpm, and they would put really heavy flywheels on engines that were used to make electricity - so you wouldn't see the lights go "bright, dim, dimmer, dimmest - bright, dim, dimmer, dimmest" as the engine went through the power strokes. The Savage is a pretty big single, and it has a lot of rotating mass in the crankshaft, flywheel, rotor, and counter balance shaft. All of those rotating pieces have to accelerate or decelerate in order to change the speed of the motorcycle when you use the throttle or brakes. Making the flywheel lighter will result in a bit faster acceleration - but it also allows for quicker changes in the engine rpm in a potentially negative way. The clutch, transmission, belt and rear hub will see larger pulses coming from the crankshaft drive gears, and they may not be able to dampen those larger pulses properly. On multi-cylinder engines the variation is crankshaft speeds is made smoother as there are multiple cylinders firing on each revolution. Lightened flywheels are used by drag racers, motocross bikes, road racers.....folks that need to be able to accelerate quickly and the engine are generally tuned for high HP and run high rpm. Heavy flywheels are used on low speed engines, trials motorcycles, tractors, touring bikes and cruisers that operate at low rpm and need smooth engine operation. Light flywheels do not make or HP or allow and engine to spin at higher rpm - heavy flywheels to do not make torque (they do however make the engine a bit harder to stall at low rpm as the engine has more inertia). So.....for the Savage engine their is very little to be gained on a stock engine by making the flywheel lighter. I would guess that a small amount of weight might be removed with problem - but the gain in acceleration might be offset by a loss of smoothness in operation. One of the first things that Yamaha, Suzuki, Honda, KTM and other bike builders do when they take a sport bike engine and adapt it to use in a Sport Touring bike - is to increase the rotating mass and use different camshafts and smaller valves to make the engine smoother. Youzguyz has over 140,000 miles on his stock Savage motor, and the engine have never had the cylinder head removed or done any work to the piston, cylinder or crank. He has done the normal cam chain, and other maintenance as parts have worn - but he has proven that the stock engine is durable during normal touring around Texas. The modified engines with Wiseco pistons, bigger cams, ported heads, different carbs, etc. on this forum are all made to increase HP and torque within the 1,000 - 6,500 rpm speed of the Savage engine - as the big single stops making HP as the rpm goes over 6,500 rpm. It is important to realize the big single will never make a lot of HP, as the formula for HP is torque x rpm.....and the rpm on the Savage engine is limited. So far I really don't know how long a modified engine will go before it wears out....mine has gone about 7,000 miles since the addition of the Wiseco and cam. |
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Title: Re: Interesting Discussion Post by HovisPresley on 01/03/16 at 05:45:33 Great post, Dave. I was wondering if the Wiseco piston (being lighter than standard) in combination with the standard weight flywheel, etc, makes it a little more 'vibey', as it's slightly unbalanced. Or is this negligible, in practical terms? I have a Wiseco 95mm piston still sitting in it's box :-[ |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/03/16 at 06:34:28 Is the Wiseco piston heavier than the original? Also, I wonder if there isn't something to be gained by adding flywheel weight |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/03/16 at 20:32:55 Does anyone think that adding flywheel weight will help engine health or hurt it? At low rpm? High rpm? Varying conditions? |
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Title: Re: Interesting Discussion Post by Art Webb on 01/04/16 at 07:14:35 that would be dependant on many factors, which you need to be an engineer to really understand an engineer designed the flywheel for the S40, and I'm not one, so I'll stick with the stocker |
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Title: Re: Interesting Discussion Post by Dave on 01/04/16 at 08:03:05 [quote author=765148574D6E4C5B4D525B473E0 link=1451621021/15#22 date=1451828733]I was wondering if the Wiseco piston (being lighter than standard) in combination with the standard weight flywheel, etc, makes it a little more 'vibey', as it's slightly unbalanced. Or is this negligible, in practical terms? I have a Wiseco 95mm piston still sitting in it's box :-[/quote] I used a postage scale and weighed the stock piston and the 97mm Wiseco and Woessner pistons and pins (no rings or clips). The stock piston was 1LB - 0.8OZ, the 97mm Wiseco was 1LB-0.3OZ, and the 97mm Woessner was 1LB, 1.2OZ. Since the difference between the stock 94mm piston and the 97mm Wiseco is only 0.07%, I believe it is not really noticeable. (I don't know the weight of the 95mm or 96mm Wiseco). I currently have a 95mm Wiseco in my bike and I don't notice any difference in vibration when at a steady speed - but under full power the engine does make a more noticeable "pull" and the power pulses are more pronounced and vibrate the mirrors a bit more (until you roll off the throttle)....partial throttle seems to make very little difference in vibration - however the increased compression ratio makes the bike slow faster when you roll off the throttle. |
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Title: Re: Interesting Discussion Post by old_rider on 01/04/16 at 08:09:11 I've noticed my 2001 savage has no problem going 75.... but it starts pushing oil out of places and makes a mess. I have been driving it locally at 65 and under and no oil leaks.... so maybe compression does have its effect on higher revs vrs oil usage... |
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Title: Re: Interesting Discussion Post by HovisPresley on 01/04/16 at 08:26:27 Thanks for that info, Dave. 8-) I just weighed my Wiseco 95mm (with the pin, but without rings and circlips) and it is 15.27oz (433g) |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/04/16 at 08:58:31 5A616C7B6A667D7B6068657A090 wrote:
Hmmm.... an opportunity for increased flywheel weight? :-/ :-? Or not? |
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Title: Re: Interesting Discussion Post by Dave on 01/04/16 at 09:15:18 404B4642534D4654411117230 wrote:
Why would you want to increase the flywheel weight on the Savage? :o |
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Title: Re: Interesting Discussion Post by verslagen1 on 01/04/16 at 09:16:06 4E45484C5D43485A4F1F192D0 wrote:
Don't mistake flywheel with crankshaft. The crankshaft on most motors is balanced for the piston and whatnot. The flywheel just provides momentum for smoothness and compression stroke. There had been some talk of lightening the rotor awhile back if you know... search for it. |
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Title: Re: Interesting Discussion Post by cheapnewb24 on 01/04/16 at 09:55:37 The increased compression stroke resistance along with greater power stroke force, could bring up a situation where more flywheel weight might be advantageous, particularly for the low end. Perhaps it could help engine longevity under certain conditions? Hurt it? :-? Why don't diesels have aluminum racing flywheels? ::) |
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Title: Re: Interesting Discussion Post by Kris01 on 01/04/16 at 19:13:48 I don't think a lighter/heavier flywheel will do anything for longevity. Engine stress is engine stress. It's already there. Modifying the flywheel won't change that. |
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Title: Re: Interesting Discussion Post by Kris01 on 01/04/16 at 19:52:31 Read this: http://victorylibrary.com/tech/inertia-c.htm |
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