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SuzukiSavage.com
/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Cylinder PSI /cgi-bin/YaBB.pl?num=1524475038 Message started by eau de sauvage on 04/23/18 at 02:17:18 |
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Title: Cylinder PSI Post by eau de sauvage on 04/23/18 at 02:17:18 Mine was 125 with 20k kms and well looked after so I'm now wondering how many bikes are actually above the min spec. |
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Title: Re: Cylinder PSI Post by justin_o_guy2 on 04/23/18 at 07:44:00 I'm never gonna know. I can't get caught up with stuff that needs done. |
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Title: Re: Cylinder PSI Post by DragBikeMike on 05/06/18 at 13:59:21 2016 LS650, 1150 miles, 155 psi |
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Title: Re: Cylinder PSI Post by Armen on 05/06/18 at 19:09:02 Might want to ask more specifics, such as stock or hi compression piston? Carb off? Stock carb? With a CV carb, even with the throttle open all the way, the slide sits down. Prob get a lower reading than with a slide carb. Warm or cold? |
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Title: Re: Cylinder PSI Post by batman on 05/06/18 at 21:42:00 What Me Worry ? start your bike ,does it pour out smoke or fuffs when you shift? if the answer is no, you have compression. Clymer gives the range of acceptable pressure as 140to 200 psi (a 29% swing) ,and there are to many things that can change your results ,battery charge /condition, valve settings ,air cleaner ,exhaust , intake ,oil weight/temperature, cam wear , camchain age,to name a few . I don't sweat if I have compression and I don't waste time checking it . If your bike runs normally but you do a test and the pressure doesn't measure up to what the book said ,are you really going to waste the time and money to rebuild the top end? I rather be riding! |
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Title: Re: Cylinder PSI Post by eau de sauvage on 05/07/18 at 00:32:36 @Batman, still you'd think that a bike that's just done 1000 odd miles would be at least in the high end of the spec range rather than the bottom end. @Armen, good point about the slides, however the specs would certainly be for a stock slide. |
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Title: Re: Cylinder PSI Post by DragBikeMike on 05/07/18 at 01:00:36 Good point about the CV carb and slide not opening during cranking. If the spec is genuine Suzuki, then it should take that into account. If the spec is something Clymer just pulled out of their XXX, then the spec is worthless. I generally don't worry too much about the spec because my scooters don't remain stock much more than a 1000 miles or so. I use the compression test to keep track of my personal setup, and to also evaluate changes to that setup. For instance, if I change my cam I am usually concerned about the effect on cranking pressure. If the intake valve closes later then cranking pressure may go down. How much? Will it hurt my low end power? If the intake closes earlier the cranking pressure may go up. How much? Will I have a problem with starting or detonation. Its a good tool that will help you understand your particular engine setup and also diagnose problems. I posted my cranking pressure on this survey because I took the reading on a basically stock engine with very low mileage. I figured it might help some members evaluate their own engine condition compared to essentially a brand new engine. The comments about listing all the details about a particular engine are excellent. I should have elaborated on my post and went on to state that it was a stock engine. My apologies to all. Never look a gift horse in the mouth. If used properly, compression readings can be very beneficial. The key is to know all the specifics on the engine under test (stock, modified, what mods, mileage, etc.). And of course, if you are taking the readings on your own engine, and keeping track of them, and recording all the mods and conditions at the time of the readings, you can learn a whole bunch of good stuff. |
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Title: Re: Cylinder PSI Post by batman on 05/07/18 at 16:28:22 DBM with a DR cam I would expect to see a compression test with lower pressure, with valve overlap the exhaust valve is also open. I don't think you'll notice any less low end torque/hp , if your using the DR cam with a stock piston, the cam dino's for the DR still show the torque peak at around 3400-3500 just like the stock cam . I think you would have to go to a larger piston (with 10.5 ; 1 compression) before you see a higher peak torque , somewhere between 3500 and 4000 rpm, and some low end losses. |
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Title: Re: Cylinder PSI Post by Armen on 05/08/18 at 02:54:11 FWIW, I always do a leak down test along with a compression test. Had a few times where tired rings allowed oil to sneak by, carbon up the top end, and make for a 'high compression' motor. Leak down test then shows that the rings are pooped. |
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Title: Re: Cylinder PSI Post by eau de sauvage on 05/08/18 at 05:12:40 @Armen, If a motorcycle is barely using any oil, say 300ml over 6000kms, would that indicate that rings are OK? Or can they still be a bit worn. |
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Title: Re: Cylinder PSI Post by batman on 05/08/18 at 08:15:44 EDS ,Chances are the oil that's missing went to your air box via the crank case breather tube , where it gathered or was ingested by the carb. losses of this nature are greater as speed increases (Highway speeds) but is quite normal for the Savage. and your doing a compression test on your bike with barely 1000 miles on it ,perhaps your not aware that your rings aren't considered to be fully seated until you pass 1500 miles. you need to ride more and sweat the small stuff less. |
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Title: Re: Cylinder PSI Post by DragBikeMike on 05/08/18 at 12:14:28 Quote:
I'm not sure what you are getting at Batman. Valve overlap occurs at the end of the exhaust stroke. It should have no effect on cranking pressure. Intake closing point determines how many degrees of crank rotation are left to compress the fresh charge of air. Close the intake at BDC and you have 180 degrees of crank rotation to compress the charge. Close the intake at 20 degrees ABDC and you have 160 degrees of rotation to compress the charge. Close the intake at 48 degrees ABDC (stock cam) and you have 132 degrees of crankshaft rotation to compress the charge. Close the intake valve at 42 degrees ABDC (DR cam) and you have 138 degrees of crankshaft rotation to compress the charge (6 degrees > than stock). How does the valve overlap event that occurs at the end of the exhaust stroke affect the compression stroke? Regarding low end torque, my stock engine dyno run showed 30.5 max HP, Suzuki says it makes 31 HP so I'm pretty comfy with the results of the dyno pull. I think it was accurate. The stock engine made 30 ft-lbs at 2000 rpm. The guy in Finland with the DR cam in a 692cc engine and 10.?:1 compression makes 25 ft-lbs at 2000 rpm. That's 5 ft-lbs less low end torque. I attribute that to the valve overlap. The intake & exhaust are swappin holes at low speed. Fresh charge is running out the exhaust. Also, he runs a straight pipe so there is most likely quite a bit of reversion during overlap (sonic wave running back up the pipe, through the open valves, and back out the carb). I put that DR cam in my engine over the weekend and have been fiddling around with it. Of course I checked compression before and after. It was interesting. To my surprise, it didn't change a bit (155 psi before, 155 psi after). Since I had the head cover off and the cam out, I checked the stock cam timing. It's a bit different than what I recorded when I checked it through the valve covers with everything together. That's understandable since you have to fight the valve springs and alternator, and access doesn't permit optimum placement of the measuring instruments. I will be posting an update to the valve timing data I previously posted. For this discussion, we only need to know the intake closing point, which is 48 degrees ABDC for the stock cam, and 42 degrees ABDC for the DR cam. The 6 degrees of additional rotation did not increase compression pressure. Keep in mind that as the piston moves further up away from BDC, the movement accelerates (the piston moves further for each degree of rotation). At some point, the intake valve closing is going to start having a significant effect on compression pressure. That point is obviously somewhere past 48 degrees ABDC. I can tell you this much for sure, the DR cam does not produce low end torque like the stock cam. The stock cam pulls harder at slow speed on surface streets. The DR cam comes into its own on the freeway. I'll post the results shortly. |
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Title: Re: Cylinder PSI Post by batman on 05/08/18 at 21:46:43 Mike , your right ,there is no neg. sonic wave in the exhaust at cranking speeds ,so it would have little or no effect on a compression test(my bad). but I agree that the DR cam is going to do it's best work at higher rpm due to the overlap which allows the neg .wave to pull the last remaining exhaust gases from the cylinder as well as helping to pull a fresh charge in, something the stock cam can't do because it has no overlap.reversion is only caused by the piston moving up for the compression stroke and the intake valve still open . |
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Title: Re: Cylinder PSI Post by justin_o_guy2 on 05/09/18 at 09:49:42 It seems everyone knows more about this than I do, but it seems to me that turning the crank 90* from BDC gets it to TDC, |
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Title: Re: Cylinder PSI Post by Dave on 05/09/18 at 12:07:05 332C2A2D30370636063E2C206B590 wrote:
I would be more apt to bet on 180 degrees of the crank (90 degrees on the cam). |
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Title: Re: Cylinder PSI Post by DragBikeMike on 05/09/18 at 12:29:44 On 5/8/18 Batman said "reversion is only caused by the piston moving up for the compression stroke and the intake valve still open . " Take a look at this short video from S&S cycles. It gives the lowdown on harmonic reversion related to drag pipes. https://www.hotbikeweb.com/ss-cycle-drag-pipes-carb-jetting-troubleshooting-video I may not have inserted the link correctly so you may have to copy and paste into your browser. Its an excellent video and gives a very clear and graphic explanation of why drag pipes don't work well in street applications. Also, regarding "the piston moving up for the compression stroke", the intake valve is closed on the compression stroke. I will concede that there will probably be some blowback through the intake at very low speed when the piston approaches top center on the exhaust stroke. |
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Title: Re: Cylinder PSI Post by DragBikeMike on 05/09/18 at 12:37:21 Hey, Justin o guy 2, here is a simple explanation of crank rotation from BDC to TDC. There are 360 degrees in one revolution. For each revolution of the crankshaft, the piston moves from top to bottom and back to top. So the rotation in degrees from top to bottom is one-half of 360 degrees (180 degrees) and the rotation in degrees from bottom to top is also one-half of 360 degrees (180 degrees). Thanks for following this thread. I hope the info is useful. |
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Title: Re: Cylinder PSI Post by batman on 05/09/18 at 18:27:40 DBM there is some blow back (reversion ) in the intake anytime the motor is running the least amount at (ABOUT 3400RPM) where it develops peak torque ,consider that when the piston reaches BDC the cylinder is nearly full ,but the piston travels 48 degrees past BDC compressing the fuel/air mix before the intake valve closes forcing some of the fuel back through the intake at rpm less than 3400.Above 3400 the speed of the piston doesn't allow time for full loading of the fuel/air mix and some exhaust gases remain in the cylinder, and again there is some reversion , torque decreases yet with higher rpm hp increases. when you talk about reversion your talking about the intake . when you talk about the exhaust your talking about (sonic) wave tuning. Two different animals. |
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Title: Re: Cylinder PSI Post by Ruttly on 05/09/18 at 22:03:33 Same theory ,but reversed , both are triggered by the closing of a valve. One used for getting as much as possible of air/ fuel mixture in and the other for getting exhaust out , math is a little different , complicated stuff ! Math Math Math ! Performance of the exhaust relies on how cool it looks ! |
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Title: Re: Cylinder PSI Post by DragBikeMike on 05/10/18 at 00:29:44 On 5/9/18 batman wrote "DBM there is some blow back (reversion ) in the intake anytime the motor is running the least amount at (ABOUT 3400RPM) where it develops peak torque ,consider that when the piston reaches BDC the cylinder is nearly full ,but the piston travels 48 degrees past BDC compressing the fuel/air mix before the intake valve closes forcing some of the fuel back through the intake at rpm less than 3400.Above 3400 the speed of the piston doesn't allow time for full loading of the fuel/air mix and some exhaust gases remain in the cylinder, and again there is some reversion , torque decreases yet with higher rpm hp increases. when you talk about reversion your talking about the intake . when you talk about the exhaust your talking about (sonic) wave tuning. Two different animals. " Maybe we have a misunderstanding related to terminology. I have always associated reversion with sound waves traveling back up the exhaust, through the open valves (overlap), and back out the carburetor. The S&S folks refer to it as "harmonic reversion". Key word, "reversion". Maybe its a Harley thing. I'm an old Harley guy. So that's what reversion means to me. I'm pretty sure you would agree that S&S Cycle is an old and accomplished performance parts manufacturer. They got it goin on, lotsa records, great products, the whole enchilada. I think they know what reversion is. So I'm willing to entertain your definition of "reversion" (blowback starting at BDC when the intake valve is still open at the beginning of the compression stroke) as the source of loss of low end torque. Hmmmm! Let's see, LS cam makes more low end torque than DR cam. Hmmmm! LS cam holds the intake valve open 48 degrees past BDC, DR cam holds intake valve open 42 degrees past BDC????? Hmmmm! How does the DR cam allow more of that fresh charge to blow back out the intake than the LS cam, since the DR cam closes the intake 6 degrees sooner? |
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Title: Re: Cylinder PSI Post by batman on 05/10/18 at 14:05:50 DBM ,your forgetting the difference in valve lift between the two cams, when considering intake reversion. Exhaust wavy tuning. You have the misconception that when the exhaust wavy reaches the combustion camber that it travels across it and out the intake, this the exact opposite of what really happens. the returning wavy(if it arrives just before the exhaust valve closes - rpm dependent) has less pressure than the pressure that is placed on the gases in the cylinder by the piston rising, (think vacuum) . therefore the wavy aids in pulling the remaining gases from the cylinder as well as helping to pull in fuel because the intake is just opening (overlap),this boosts VE but is mostly dependent on header pipe length , longer headers favor lower rpm , and vice versa. the figures I've seen say that for 650 single the header length should fall between 30 and 34 inches, the stock header on the savage is 32 ,which makes sense seeing the bike is set up to make mid range power . |
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Title: Re: Cylinder PSI Post by DragBikeMike on 05/11/18 at 01:01:11 Uh huh. Difference in lift? Like a whopping .020". Wavy??? It's dependent on pipe length and occurs at a very distinct and narrow rpm range (usually at very high rpm with drag pipes). Drag pipes work good on the drag strip (that's why they call em "drag pipes"), and they work crumby on the street (that's why they don't call em "street pipes"). So once again, if this so called reversion resulting from the intake valve closing point results in reduced low end torque, how does the DR cam allow more of that fresh charge to blow back out the intake than the LS cam, since the DR cam closes the intake 6 degrees sooner? Cmon Batz, throw me a bone. It closes the intake 6 degrees sooner. How does your concept work here. Never mind wavies, and HUGE variations in lift (WOW! One-half of one millimeter). Six degrees less for the piston to cram that fresh charge back out the carb. Six degrees less to compress the charge. Why is the low end torque less on that 692cc, 10.?:1, DR cammed, drag piped, Fin Savage? Why is that low end torque less than a stocker? Why does my stock displacement, stock compression, stock carbureted (except jets), stock exhaust (32" header and all) engine feel weaker down low with that DR cam? Oh! BTW, I don't have any misconceptions about "harmonic EXHAUST reversion" blowing back across the combustion chamber, out the intake valve, and backwards through the carb, and back & forth again & again at rpm below the sweet spot on those drags. It picks up fuel both ways. As it cycles back & forth at low speed, the charge gets so rich the thing will barely run. Your wavy thing don't work down there at 2200 rpm. |
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Title: Re: Cylinder PSI Post by DragBikeMike on 05/11/18 at 09:23:16 I've sunk to a new low. My apologies to all. |
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Title: Re: Cylinder PSI Post by Dave on 05/11/18 at 09:49:18 Well...maybe an actual PSI reading will clear things up. I am going to do some work on my bike this weekend, and it will give me a chance to get a compression reading on the 95mm Wiseco and Stage 1 cam. |
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Title: Re: Cylinder PSI Post by Ruttly on 05/11/18 at 15:10:41 Any baffles in drag pipe ? You have to have back pressure. Also DR cam was designed for a different head. |
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Title: Re: Cylinder PSI Post by batman on 05/11/18 at 22:07:48 DBM drag pipes don't work good anytime, If you watched the entire video they end up throwing the drag pipes in a dumpster. 2200 rpm was where the biggest slump occurred using drag pipes ,because the wavy didn't reverse until it reached the end of the pipe and therefore returned much to late and found the exhaust valve closed . Harley motors have much the same torque peak as our peak as our motors ,that is it occurs at about 3500 rpm not 2200rpm. the video I watched shows them installing a thumb screw near the outlet of drag pipe to breakup the wavy and prevent it from returning at all(. as it can also hamper performance if ill timed.) .this tended to relieve the slump at 2200 giving slightly better performance . the fact that you think that wavy tuning only occurs at higher rpm ,may be correct ,but it also occurs any time the motor is at the proper rpm( in all five gears.) as does tuning intake runner length. Does it stand to reason that if wavy tuning doesn't work at lower rpm that cylinder pressure would be higher and therefore intake reversion would also be higher? |
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Title: Re: Cylinder PSI Post by Dave on 05/13/18 at 13:38:57 OK......I need another pigeon hole added to the Poll. I have a 95mm Wiseco, and I got 195 psi. (Stage 1 cam). |
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Title: Re: Cylinder PSI Post by batman on 05/13/18 at 16:57:45 Dave , might be because you have a stage one cam (is there any overlap? -I think not being it based on a stock cam ) and your compression is not 8.5 :1 but 10.5 :1 . If DBM ,uses the DR cam in his bike with the stock piston and compares it with his stock test ,that should tell the story. I'd like to see the result even if I'm incorrect. |
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Title: Re: Cylinder PSI Post by batman on 05/14/18 at 08:27:15 DBM ,did a bit of research and you were correct their is reversion caused by the exhaust wavy moving through the head and out the intake at speeds below peak torque (my bad). but I still contend that static compression ,at cranking speed, will be lower than stock ,with the DR cam. |
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Title: Re: Cylinder PSI Post by DragBikeMike on 05/15/18 at 11:50:40 Thanks for the compression number Dave. It's really healthy (195). Do you have any issues with pinging or detonation? What sort of gas do you run? Do you have to use any sort of octane booster? I have one of those 97mm pistons but am not ready to install it yet. I have some more low hanging fruit to pick before I rip the jug off. So much to learn, so little time. Regarding my cranking pressure Batz, I was surprised. It didn't change, (155 before, 155 after). |
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Title: Re: Cylinder PSI Post by batman on 05/15/18 at 11:59:16 DBM ,I'm thinking that the early closing of the intake valve is offset by the higher lift of the valve,so no change. |
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Title: Re: Cylinder PSI Post by Dave on 05/15/18 at 14:12:03 7A7C730F0D0A0E3E0 wrote:
I run Premium pump gas.....I have never noticed any pinging or octane issues. The "premium" around here is mostly 91 octane E10 from a blender pump - so it is likely that I get a bit of 87 octane through the hose and nozzle before the 91 octane premium actually fills the hose and starts to flow into the tank. I try to keep a mental note of where the gas stations are that don't use blender pumps and have a dedicated nozzle for premium.....but those aren't always nearby. |
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