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SuzukiSavage.com
/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> pistons again! /cgi-bin/YaBB.pl?num=1172345089 Message started by tbalam on 02/24/07 at 11:24:49 |
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Title: pistons again! Post by tbalam on 02/24/07 at 11:24:49 anyone notice that you can buy factory oversized pistons for the savage. at least the microfiche from ron ayers and bike bandit show it and you can order it for around 80? I think it might be fun to have an oversized, HC piston in the savage. can you use a 97mm, hc, piston from a harley or other maker? |
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Title: Re: pistons again! Post by Greg_650 on 02/24/07 at 16:13:02 Yep. I believe that Wiseco has one that can be used to bump her up to 700 easily. I think that Lancer has an overbore in his too. |
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Title: Re: pistons again! Post by tbalam on 02/24/07 at 17:38:10 Lancer, Can you comment on your experience here. What size piston did you go with, and where did you get it? Did you do anything to up the compression ratio? |
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Title: Re: pistons again! Post by Reelthing on 02/24/07 at 19:22:47 Do a search on Wiseco and set the days back to 800 or so - we've been kicking this around for a long time - last year all was that was needed for them to make us a 9.5:1 overbore custom was an order for 24@$122 each - wonder if we have enough interest yet? |
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Title: Re: pistons again! Post by LANCER on 02/24/07 at 20:01:13 tbalam wrote:
I had engine damage and had to bore it. At the time I just wanted to go to the next size up so that there would be room for another bore later if something happened again. So I went from the stock 94 to a 95, which makes for 667cc +/- I believe. I sent the cylinder and new piston to Bore Tech (www.bore-tech.com) for the bore/hone work and also had the silicone carbide treatment done at the same time. Very reasonable work, even today the price for the bore/hone is just $60 and the silicone carbide is just $115 ... and worth every penny ! "BORE TECH has developed the only permanent surface enhancement process for motorcycles and small engine cylinders for longevity and power robbing friction reduction. There is no spray coating or plating for cast iron liners that compares to the performance of CARBIDE BORE PROCESS cylinders. Immediate break-in Improved ring seal Superior oil retention Less friction provides lower temperatures Leaner fuel mixtures possible Excellent wear characteristics Anti-siezure properties The CARBIDE BORE PROCESS combines the best features of ceramics and cast iron cylinder bores. This evolutionary process of impregnating diamond-hard silicon carbide particles into the cylinder wall is truly a technical advance directed at the problem of bore surface wear. The advantages of the process are compelling" This technique is not a coating that builds up or is a layer on top of the base metal, thus cannot be used to restore worn bores back to size. Imbedding the carbide particles into a straight, round bore locks the ceramics into the pores of the base metal in a manner that prohibits the particles from dislodging. A "Plateau" finish bearing curve provides good oil retention sites with optimum surface for ring sealing During the development, carried out by BORE TECH on the CARBIDE BORE PROCESS, all types of engines have been tested in various forms of competition. The extreme conditions of racing provided us with quick and accurate data feedback. Motorcycle roadracers, motocross, and drag racers to snowmobile, watercraft, karts, and mini-sprints have gained phenomenal engine life as a result of this technology BORE TECH uses mechanical infusion technology to force fine particles of silicon carbide under pressure into the cyclinder wall. The carbide being twelve times harder than steel, gives an unusually wear-resistant surface... one that is also oil wettable. The result is a cylinder that won't wear out (at least, not at anything approaching the normal rate) but actually breaks in like plain iron. |
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Title: Re: pistons again! Post by tbalam on 02/24/07 at 20:23:45 Did you do anything to increase the compression ratio? Also FYI, wisco has the ls650 under the offroad bikes. i dont think these pistons are HC ratio though. http://www.pistons-online.com/motorcycle1.asp?br=Suzuki&st=43&end=43 And ross pistons will make 4 pistons for $100 each. |
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Title: Re: pistons again! Post by azjay on 02/25/07 at 05:22:51 just the act of putting a larger piston in the hole, and not changing the combustion chamber size, raises the compression ratio. would need numbers to calculate how much. |
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Title: Re: pistons again! Post by Greg_650 on 02/25/07 at 07:21:03 azjay wrote:
Ah, it's not just a larger piston. It's a larger piston in a larger hole which also changes the combustion chamber size (displacement). Did I read that wrong? The stroke is 94 MM. |
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Title: Re: pistons again! Post by Trippah on 02/25/07 at 16:18:06 Greg- are you talking about displacement while azjay was talking compression ratio's? |
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Title: Re: pistons again! Post by Greg_650 on 02/25/07 at 16:43:05 Trippah wrote:
Yep. But my point is the reverse. Larger displacement doesn't mean higher compression. But then if you'll notice, I also questioned my interpretation... |
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Title: Re: pistons again! Post by Rockin_John on 02/26/07 at 15:17:10 Greg_650 wrote:
It is an interesting point. Just exactly how would increasing bore affect the compression ratio? More fuel/air squished into a smaller(?) or larger(?) chamber? Personally, it's my opinion that there would be much more power unleashed by a little higher compression ratio than a tiny bit of cylinder displacement... But if both could be had for the same money... why not? |
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Title: Re: pistons again! Post by barry68v10 on 02/26/07 at 15:39:04 All things being equal, a larger bore and piston(s) in the same motor will increase compression ratio. But that assumes all things are truely equal. If you had a piston with the same deck height, valve reliefs, and ring positions a larger piston and bore would increase the compression ratio, but......what are we talking here 0.020-0.060 inches?!? That's not a good way to increase compression ratio. You'd be better off hooking up a hair dryer with the heating element removed to the intake side and "supercharging" the intake air. BTW, used that technique on a moped to double the HP. Burned the motor up pretty quickly tho :-[ But that was in my younger days ;D |
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Title: Re: pistons again! Post by Greg_650 on 02/26/07 at 15:45:18 barry68v10 wrote:
Sure it will, but not as significantly as changing the squish area in the combustion chamber or changing the stroke. Simply a larger piston like this one won't do so much that you'll be needing more octane. Yet, I think that Wiseco will make you a crowned piston with valve clearance. You moped intake heater is interesting. Turbo 2 stroke :) http://i21.photobucket.com/albums/b277/gmdinusa/Piston_1693.jpg |
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Title: Re: pistons again! Post by barry68v10 on 02/26/07 at 15:50:32 You could also use a mechanical smog pump for the same purpose ;D (driven mechanically instead of electrically, of course ;D) |
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Title: Re: pistons again! Post by Greg_650 on 02/26/07 at 20:54:27 barry68v10 wrote:
There's another member in here with a Motobecane. Wonder if that would work for him ;D |
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Title: Re: pistons again! Post by YonuhAdisi on 02/27/07 at 16:19:52 Once I get up the money I plan on completely rebuilding my engine and I would love to put in a dome piston. BTW does anyone make a roller cam and lifter kit for the Savage? I think that would be pretty sweet. |
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Title: Re: pistons again! Post by LesGolden on 03/22/07 at 22:15:24 Ross pistons 4 for 100 a piece! Or close to that anyway.. hmm wonder how much more to have valve reliefs cut in try for maybe 9.5:1-10:1.. Anyone interested in a group buy? maybe go for 96-97mm bore? Easier to get 4 people than the twentysome for Wiseco, course i don't know anything about the quality of Ross pistons.. |
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Title: Re: pistons again! Post by Kropatchek on 03/23/07 at 03:09:48 Compression RATIO can only increase if you decrease the combustion chamber volume. Assuming all other parts remain the same. http://en.wikipedia.org/wiki/Compression_ratio A compressor ( or hairdryer) will increase the filling of the cylinder with more air/fuel mixture. |
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Title: Re: pistons again! Post by LesGolden on 03/23/07 at 05:41:03 Kropatchek wrote:
Was this reply for me? If so, i agree! 4 of us should get some domed pistons with, if necessary for the savage, valve reliefs so as not to destroy our valves with the taller pistons. oh and more specifically increasing compression ratio involves changing the cylinder volumes at bdc and tdc. a larger piston will increase compression because the volume at bdc has increased more than the volume at tdc. just my two cents. i just really want to up my power and was hoping to get a few people to bite on some bigger pistons. |
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Title: Re: pistons again! Post by wvhunter62 on 03/23/07 at 05:57:33 I've used Ross products before in automotive rebuilds, quality as good or better than OEM. I'm in for a 96mm Wiesco or Ross. |
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Title: Re: pistons again! Post by vroom1776 on 03/23/07 at 09:20:53 Here are the results of some calculations for flat head pistons with no valve cutouts I did a while ago... VH = volume of the head, i.e. size of the combustion chamber Bore(mm),Extra_Piston_Height(mm),Displacement(cc),VH(cc),CR 94 0 652.3 87.0 8.5 (stock) 94 1 652.3 80.0 9.2 94 2 652.3 73.1 9.9 94 3 652.3 66.2 10.9 95 0 666.3 87.0 8.7 (lancer?) 95 1 666.3 79.9 9.3 95 2 666.3 72.8 10.2 95 3 666.3 65.7 11.1 96 0 680.4 87.0 8.8 96 1 680.4 79.7 9.5 96 2 680.4 72.5 10.4 96 3 680.4 65.3 11.4 97 0 694.6 87.0 9.0 (woodworker ?) 97 1 694.6 79.6 9.7 97 2 694.6 72.2 10.6 97 3 694.6 64.8 11.7 I posted similar calcs previosly, but there was a minor msitake in the comp ratio for a 94 mm piston and 1 mm taller. uh let me check these again... I think these #s are okay, VH is calulated by: VH = VHstock-ExtraPistonHeight*(PI*(bore/2)^2) CR is calculated by: CR = (Displacement+VH)/VH For the extra height pistons, this is saying that when the engine is as TDC, the piston will go above the cylinder and into the combustion chamber. If we go w/ over bore pistons, we also need to know if they will fit inside the combustion chamber, as well as if they will smack the valvies. (unless I don't get it) |
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Title: Re: pistons again! Post by LesGolden on 03/23/07 at 12:08:15 Thank you vroom! That's some good info to have! I would've done something similar except that my math skills suck. |
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Title: Re: pistons again! Post by LesGolden on 03/23/07 at 12:22:11 Okay, to get a little more serious about a group order, looking at these figures, and considering the previous post about a 9.5 piston from wiseco, i'm guessing we could do 96mm with 2mm additional height and minor valve clearances that should get us around 10:1-10.4:1, i'm not sure how much compression we would lose with the valve cutouts.. i'm guessing those figures are with flat top pistons? might be able to do a 2mm higher dome top and forgo any valve destroying problems.. the earlier decision for the 9.5's from wiseco was based on valve clearance right? i think we could get away with closer to 10:1 with the right pistons and that with a 2mm overbore should give some pretty serious gains.. We'll probably need the higher duration cam to go with it. Most likely need to run premium too.. SE GA has 93 everywhere and with a 2.5 gallon tank i'd be fine with that.. i don't think 10:1 would need any higher octane, and if we're not changing deck height timing should be okay.. shouldn't it? hmm.. anyone else have any thoughts on this? And anyone else ready to make a group order? just need 4 of us, i'm in, cash in hand. think i'll do the cam same time.. (gonna need a carb too huh? ... maybe lancer wants to put together a package deal?) |
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Title: Re: pistons again! Post by vroom1776 on 03/23/07 at 12:28:05 yes, those are for flat head pistons. Small cut outs for the valvies would increase the VH by maybe 5 cc at most, is my guess... lowering the comperssion ratio by some small amount (maybe 0.2 ?). the one thing I'm not sure about, and maybe this is just do to my lack of experience, but would the combustion chamber need to be bored out to accomodate a taller &/or oversize psiton in addition to the cylinder ? That would affect the above calculations A LOT! |
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Title: Re: pistons again! Post by vroom1776 on 03/23/07 at 13:13:40 here are the numbers for spherical dome pistons w/ no valve cutouts: Bore(mm),Extra_Piston_Height(mm),Displacement(cc),VH(cc),CR 94 0 652.3 87.0 8.5 94 1 652.3 83.5 8.8 94 2 652.3 80.0 9.2 94 3 652.3 76.6 9.5 95 0 666.3 87.0 8.7 95 1 666.3 83.4 9.0 95 2 666.3 79.9 9.3 95 3 666.3 76.3 9.7 96 0 680.4 87.0 8.8 96 1 680.4 83.4 9.2 96 2 680.4 79.7 9.5 96 3 680.4 76.1 9.9 97 0 694.6 87.0 9.0 97 1 694.6 83.3 9.3 97 2 694.6 79.6 9.7 97 3 694.6 75.9 10.2 this is on the assumption that the head doesn't have to be messed with. The formula I used for the dome is: ExtraVolume = 1/6*pi*Extra_Piston_Height*(3*(bore/2)^2 + Extra_Piston_Height^2). Got the formula from my math text... Then I used the same equation for VH & CR as above. Here is a link to the spherical cap volume. (http://mathworld.wolfram.com/SphericalCap.html) Equation 2 |
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Title: Re: pistons again! Post by vroom1776 on 03/23/07 at 13:30:27 I stole these pics from greg. Hope you dont mind Greg! combustion chamber: http://i21.photobucket.com/albums/b277/gmdinusa/HeadChamber_2528.jpg piston in cyl: http://i21.photobucket.com/albums/b277/gmdinusa/Piston_1693.jpg greg, can you put any type of scale on the combustion chamber pic? It's prolly got to be on one of the flat surfaces, maybe from bolt to bolt? |
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Title: Re: pistons again! Post by vroom1776 on 03/23/07 at 13:40:05 okay, so does the piston come all the way up to be flush with the top of the cylinder? If so, it looks like the combustion chamber/head would have to be bored to accomodate an oversized, taller piston... or am I missing something here? It's not like the gaskets would be tall/thick enough to take care of that... |
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Title: Re: pistons again! Post by vroom1776 on 03/23/07 at 16:06:55 So, based on the two above pics and the fact that that the piston is 94 mm wide, the narrowest point on the flat surface of the combustion chamber (i.e. between the words "Intake" & "Exhaust") is ABOUT 59.1 mm. I say "about" because of the various aspect ratios of the photos and the fact that I used straight lines to determine this (the photos are a little crooked). SO, unless I am missing something, we would need to bore the head/cumbustion chamber at least a little to fit a taller piston in there. OR AM I CRAZY? |
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Title: Re: pistons again! Post by vroom1776 on 03/23/07 at 16:13:24 What I want to know is, what's our deck height? http://www.rbracing-rsr.com/turbo/squishband.jpg link (http://www.rbracing-rsr.com/squishcalc1.html) Anyone know how thick the gaskets are? |
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Title: Re: pistons again! Post by LesGolden on 03/23/07 at 18:39:53 Reading back and checking around it seems wiseco know what they're talking about, crowned pistons with valve cutouts seem to be the route to go. It does seem like anything further would take modifying the combustion chamber. There may be enough squish area (thanks for the link vroom) for a slightly taller piston, but that was probably considered when deciding on the 9.5.. Still though, maybe we should take advantage of the much smaller buy in from Ross and get some 96mm's made? |
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Title: Re: pistons again! Post by vroom1776 on 03/23/07 at 23:49:29 This old post by woodworker (http://suzukisavage.com/cgi-bin/YaBB.pl?board=RubberSideDown;action=display;num=1082342982;start=15#15) |
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Title: Re: pistons again! Post by Mr 650 on 03/24/07 at 02:29:11 $100/ slug for a plain ol' Ross Flat top piston ???::) Or $1272.24 for a set of eight Wiseco? :o You can but a whole set of Chevy pistons for $100. Should be more like $20-$50 if a Chevy will cross ref. Anyone to know the rod length, the pin height or piston weight of our 650? I did some surfing awhile back and I think a 307 Chevy flat top piston diameter is within .001 or .002. of the LS650. I expect a piston could be cross referenced. I don't think a piston supplier would have to do to much work to make a LS650 slug, from a good forged or Hypereutectic Chevy (or Ford) Flat top piston to raise the compression one point to 9.5:1, they are available in many overbore sizes. I am hoping someone might have access to both pistons and could tell us the pin locations. It would be sweet if one of those could be found to fit or one that could easily be modified to fit the 650. Of course really good race pistons like this Manley would be more but not $100 each! http://www.seanhylandmotorsport.com/online/images/FTF3.552.jpg Noticed the Ford 5.0 litre DOHC Cobra crate motors also use our 3.70" bore; http://www.seanhylandmotorsport.com/images/cobra-shortblock.jpg I forget the recipe that Burt Monroe used to make his, 2 parts Chevy & one part Ford? ;D tbalam wrote:
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Title: Re: pistons again! Post by LANCER on 03/24/07 at 08:29:04 Deck clearance ~ 0.157" (4mm) Compressed gasket ~ 0.030" (0.78mm) |
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Title: Re: pistons again! Post by verslagen1 on 03/24/07 at 09:44:27 do the valves open below the head? how about with the new hi-perf cam? |
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Title: Re: pistons again! Post by LANCER on 03/24/07 at 13:48:09 The valves open 0.153" down below the head surface toward the piston. The deck clearance is 0.157", so the clearance between the piston and the edge of the valve when it is open is the thickness of the head gasket when it is compressed. With those numbers, the only way to get the compression up is to machine valve grooves into the piston which would then enable machining of the cylinder to raise the compression. If an older DR650 piston has the valve grooves in it already then that might do it. |
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Title: Re: pistons again! Post by LANCER on 03/24/07 at 14:10:17 LANCER wrote:
ERROR ... ERROR ... that should have been 8mm or 0.315 for the deck clearance. So there is room for shaving the cylinder. |
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Title: Re: pistons again! Post by LesGolden on 03/24/07 at 15:02:40 it's amazing how much information you guys have! So with 8mm clearance we should have room for the 2mm taller pistons? and no valve cutouts! I think we have two takers on 96mm higher compression pistons, can we get two more? |
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Title: Re: pistons again! Post by verslagen1 on 03/24/07 at 16:04:48 Lancer, I take it the .153" is with your high lift cams? And how much are we talking here for a piston? |
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Title: Re: pistons again! Post by barry68v10 on 03/24/07 at 18:37:02 Guys, one thing to keep in mind here is this: With all else equal (yes, I know that's a big a$$umption), higher compression will simply move the same torque curve higher on the RPM scale, yielding higher peak HP... BUT.... you WILL sacrifice some low-end torque as a result. If I could figure out how to get my DYNO2000 results posted here, I'd show you all how this works :-/ |
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Title: Re: pistons again! Post by Mr 650 on 03/25/07 at 23:39:18 Interesting, I would like to see a simulation too. Thinking it would increase area under the entire curve, like more compression increases efficiency up & down the scale, resulting in a more pronounced, higher curve everywhere. barry68v10 wrote:
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Title: Re: pistons again! Post by LANCER on 03/26/07 at 04:20:58 Quote:
I do not have the hard data to back it up at this time but I think it would raise the entire curve. When an explosive is compressed more the resulting energy release from the explosion will be greater regardless of the rpm. |
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Title: Re: pistons again! Post by barry68v10 on 03/26/07 at 14:44:04 Quote:
As it turns out, increased compression also increases the speed of the burn. This is bad at lower RPMs since more of the fuel is burned during pistion compression which has the OPPOSITE effect than desired. At low RPM's, slower burn is better. As RPMs increase, less fuel has time to burn on compression stroke and more power is produced with remaining fuel after TDC. Again, keep in mind this a$$umes all things are equal. You can retard timing at low RPMs to counteract, but remember: the higher the compression ratio, the more energy the pistion bleeds on the compression stroke. |
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Title: Re: pistons again! Post by barry68v10 on 03/26/07 at 14:50:11 Remember: gasoline engines ignite the mixture before top-dead-center. If we were talking a diesel which ignited at TDC, then higher compression (to a point) would result in higher power. This is one reason why diesels have so much more torque...they can ignite at TDC, and therefore have the ability to use 35:1 compression. |
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Title: Re: pistons again! Post by wvhunter62 on 03/26/07 at 15:58:00 I will out of the loop for a couple of days, I drive a truck for a living. So if we decide to do a group buy I am in, but it will be Thursday before I have a chance to check back. I am also going to get one of them thar improved bumpsticks...... :PI need more torque, more torque gooood :P |
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Title: Re: pistons again! Post by LesGolden on 03/26/07 at 18:42:34 I will get with Ross pistons and give them all our information. It looks like for a couple bucks extra (10-20) we can get them lightened and coated, i'm not sure i need the coating, but lighter would be nice, maybe give a few more rpm. Also not sure if rings are included in the price, i'll see what their's cost included. work is keeping me busy right now but i will update as soon as i have the information. Unless someone else beats me to it. Then i will just buy the piston. |
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Title: Re: pistons again! Post by callado on 03/26/07 at 21:25:52 I'm interested in a buy and get them lightened and coated |
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Title: Re: pistons again! Post by justin_o_guy on 03/26/07 at 21:54:47 It would be interesting to know how the "Lightened" piston compares to the stocker. Would be nice if it was lighter. I would be interested in this. I wanna know the $$. Stickin that piston on the shelf till I get enough miles on the cam & chain to need to do it again, then do that & go to rhe chain.THEN I will have to find Hutch & run him down, since I weigh 15 pounds less & will have a cam & piston on him. Anyone know a cheap way to make the ignition cut out at redline? |
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Title: Re: pistons again! Post by Reelthing on 03/26/07 at 22:06:43 there are tachs that will do it - define cheap? |
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Title: Re: pistons again! Post by justin_o_guy on 03/26/07 at 23:01:39 If I could I would post my picture now. but, since I can't,, 50$$ would make me giggle. I don't care what it looks like. I wouldnt even mind if I had to mount it down by the engine & couldnt even see it. I just want to protect the engine from Desploding atweeen my legs.. |
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Title: Re: pistons again! Post by Reelthing on 03/26/07 at 23:14:28 take more than $50 to hang a revlimit tach on one these Ithink - you ready for that gasket and brace? |
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Title: Re: pistons again! Post by LANCER on 03/27/07 at 04:01:10 I would like to get in on the pistons but it just occured to me that mine is one size larger...dang! Do the pistons ordered have to be all the same size, or can we get assorted sizes? Oh well. |
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Title: Re: pistons again! Post by LesGolden on 03/27/07 at 09:34:14 It actually looks like ross doesn't have rings in 96mm, so 97 might be where we need to be. I'd be ok with that, just might have to resleave later on down the road, no biggie. just on lunch break now, i've gotta get all the necessary information and then i'll try to call ross this evening. |
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Title: Re: pistons again! Post by vroom1776 on 03/27/07 at 09:38:41 resleaving.... Lancer may know the answer to this... how much thickness can be added to the cylinder wall with the ceramic coating process (by Boretech)? and Lancer said: LANCER wrote:
but I imagine that having this dond would GREATLY reduce the need to ever resleave, except maybe WAY in the future... yamaha has been doing this (well, ceramic coating their cylinders) for years (at least since 1999), and I've never heard of a stock engine having to be resleaved... other probleme, sure... |
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Title: Re: pistons again! Post by smokin_blue on 03/27/07 at 10:22:09 Depending on your final configuration I definately might be interested in getting in on the buy. Thanks! (Now I just have to get these wood projects done so I can make metal chips again!) ;) |
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Title: Re: pistons again! Post by Mr 650 on 04/06/07 at 17:26:52 I was wondering, the Savage is counterbalanced. If the piston is lightened, so should the counter-balancer, unless this is only about "more steam", in that case remove the balancer and gain even more HP. W/ the stock counter-balancer I expect it will want to buzz more, not much fun on long rides...just a hunch. Didn't Lancer remove his counter- balancer? LesGolden wrote:
barry68v10 wrote:
Man, every NHRA Prostock racer out there is running sky high compression, pushing 16:1, on VP-C25. Quote:
Sure they have variable timing but that is a given. Compression is good, octane and cooling are the limiters as to how much compression you can run, but more is always better for HP. Suzy has the patent on the TSCC head and it works better the more you squeeze it, ask someone like Byron Hines. ;D Also 8:1 practically sucks. If decking the jug will move the cam a little I don't think it will hurt perf much. Back in the day when EPA 1st started killing compression, smart guys were tweaking the valve overlap to effectively bump up compression too, but w/ our air-cooled 650, I would expect problems to arrive as you approach 10:1, on a streeter. Remember (cylinder) volume is cubed the as dimensions go up. Think the 650's OHC will suffer w/ the extra heat as opposed to a pushrod OHV (HD) design. Come to thinkof it, how many bikes today have similar swept volume that are OHC AND air cooled as opposed to water cooled? Now I gotta go look... Recall how the original GSX-R was oil (not water) cooled 8) http://www.suzukicycles.org/photos/GSX-R/GSX-R750/1985_GSX-R750_whbl_wb_450.jpg |
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Title: Re: pistons again! Post by barry68v10 on 04/07/07 at 05:07:43 Quote:
Now we're not even talking apples-to-oranges, let alone apples-to-apples. First, most if not all engines running excess of 12.5:1 are not running gasoline. They almost always run alcohol. Second, they have cams with such CRAZY valve overlap that on the compression stroke air is being pushed out the intake AND exhaust valves at rpm's below 4000, effectively reducing the actual compression ratio significantly. Added to that, they run MUCH richer mixtures than any of us prolly want to run, especially if your paying $7+ per gallon on racing fuel. Low compression is not necessarily a bad thing, especially when you consider the extremely inferior pump gas we are forced to live with...but that's just my 2 cents worth ;D |
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Title: Re: pistons again! Post by barry68v10 on 04/07/07 at 05:12:55 One final thought... Any engine SHOULD be designed specifically for the type of use and the fuel it will burn. Reliability should be a consideration. If you want to win races, reliability can take a back seat, but who wants to push their bike home, even occasionally? :-/ |
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Title: Re: pistons again! Post by justin_o_guy on 04/07/07 at 10:31:43 What happens if the thing fries halfway thru a turn & locks up? A fellow might not even be in good enough shape to walk, much less push. I don't see going over 9:1. I think the way to get performance out & keep reliability would be to give it a bit of a bore, not as far as it can go, just a bit, & a bit more compression, nothng big, say .5 to .75 to 1 increase, port both ends of the head, single wall header, work on the intake( aire box & filter) I prefer the Supertrapp for its tunability. I think this aproach will give a good bit more of a ride & still not stress the tranny & lower end too far. Now, understand, I havent even LOOKED inside the tranny. For all I know it is overbuilt & will take a good bit more horsepower thru it before it starts breaking. I don't know about the bottom end either. I have seen some with tons of miles on them & dont know if they were rebuilt, but from the looks I would say not likely. Maybe this thing will take the punishment of more power, but the power pulses coming from such a high compression as 10:1 I would think would destroy it. Now, consider the gas law rule PV=NRT where pressure x volume = moles x Gas law constant x TEMPERATURE. When the pressure is doubled so is temperature. So, if compression is raised from 8;1 to 10;1, the pressure is increased by 25%, so the temp will do the same. Not the temp from combustion, just the temp from compression. I dont know how that affects combustion temp, but I expect it to run the same direction. |
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Title: Re: pistons again! Post by barry68v10 on 04/07/07 at 11:31:23 I think this engine will relatively efficiently handle about 50 hp as far as cooling capacity goes. What does Lancer's setup run? There are a handful of 650 thumpers out there running roughly this power output. The DR650, BMW GS650, and Honda KLX650 to name a few...Also, I think someone around here is running higher compression, but I can't remember how high. That may also be Lancer... I think in the three examples above (all air cooled, except the DR650 which is air/oil cooled) the compression ratio is between 9.0 and 9.5:1. But keep in mind, all the other three examples have shorter strokes. I would have to agree with Justin, that 9.0:1 is the highest you can SAFELY go with this engine. Some on this site have gone thru the tranny and suggested it doesn't look beefy enough to handle much more power, but again I can't remember off-hand who's said that. |
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Title: Re: pistons again! Post by Mr 650 on 04/07/07 at 11:45:24 93 octane is common round here, so 9.5:1 would be OK, some places I have been to only have like 91 octane. Looking at current production lineups I find no bigger OHC cylinders that remain air cooled. Current EPA regs must factor into that. I think the old Gold stars were 10:1, but that was in the days of lead. http://www.batterystuff.com/fuel-treatments/ barry68v10 wrote:
Grab the clutch real fast! ;D justin_o_guy wrote:
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Title: Re: pistons again! Post by LesGolden on 04/07/07 at 18:46:34 What modifications can be made to safely run a higher compression? Higher flow oil pump and an oil cooler? route additional oil to the head? Routing air to the back of the cylinder? blueprinting the crankshaft? lightening all the internals? Getting a real amount of perfomance out (50 or so horse) is going to come at the expense of some reliability. Course if the tranny explodes and the piston hits the concrete it'd be an excuse to switch to a rotax motor.. barebones.net |
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Title: Re: pistons again! Post by klx650sm2002 on 04/08/07 at 01:17:40 My KLX (C1 model) runs 9.5:1 but the C3 runs 10.5:1, just for your info. Clive W :D |
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Title: Re: pistons again! Post by barry68v10 on 04/08/07 at 03:36:56 Quote:
Now, correct me if I'm wrong here Clive, but there are some MAJOR differences between the KLX engine and the LS650. First, I think the KLX has a 100mm bore, and either an 82mm or 83mm stroke. Secondly, the KLX is liquid cooled. Just some considerations to keep in mind. I'd hate to see someone go "gung-ho" on a can change and spend all that time and money to increase compression ratio, only to find out they don't like the driveability, or a much worse scenario... |
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Title: Re: pistons again! Post by barry68v10 on 04/08/07 at 03:59:18 Quote:
I'd agree that an oil cooler would be a wise modification, not to mention cheap, and that's my own first step. You'll notice lots of examples of oil cooled motorcycles than can have significantly increase HP than their air-cooled only counterparts. Second, and I'll likely be jumped for this (duck), but as an engine starts to push the performance up, full synthetic oil becomes more and more critical. There's not a single jet, not a single NASCAR or Indy car that runs on anything other than full synthetic lubricants for internal engine parts, despite what you see on commercials. So the second low dollar, high payoff thing I'd do is run a quality full synthetic oil. Third, another low $ way to protect an engine is to limit RPMs. So I'd say an RPM limiter can pay big dividends. The more you limit RPMs, the longer the engine will last (to a point.) I'd stay in the 5500-6500 range as a max RPM. Now we're getting into more $$$. I really like Lancer's carbide coat cylinder wall process and I'd have that done no-matter-what if your changing pistons anyway. That will help alot. Up the scale would be a longer connecting rod and shorter throw crankshaft. Does anyone know the current connecting rod length? At any rate, for high performance engines the connecting rod should be at least 1.75 times as long as the stroke. In the case of the LS650 a 3.7" (94mm) stroke would necessitate at least a 6.475" (164.5mm) connecting rod. I'm willing to bet the current one is not that long. This would decrease peak piston speed and actually allow higher RPMs with the same peak piston speed (the only speed in an engine that really matters.) Higher RPMs would also demand more airflow. So cam change, port work, valve work etc. would need to be accomplished to take full advantage of the money you've now spent. I don't think it's been done, but I'm betting with the above changes you could have a 65 hp Savage. I don't know how long she'd last, but she'd be fun while she lasted ;D |
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Title: Re: pistons again! Post by justin_o_guy on 04/08/07 at 07:38:40 Does anyone know the current connecting rod length? At any rate, for high performance engines the connecting rod should be at least 1.75 times as long as the stroke. That there are ratios that work better than others in places is not a surprise. I would like to understand this , tho. Can anyone explain it? Also, how would that affect displacement? |
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Title: Re: pistons again! Post by LesGolden on 04/08/07 at 07:44:38 That was kinda my plan. Crankshaft work aint cheap though. Stroking or destroking is 200-300 bucks, full blueprinting is bout 300 bucks, a custom rod wouldn't be terrible, but prolly 50-100 bucks. Just blueprinting the crankshaft and shot peening the current rod should give a big increase in strength, 293 plus shipping charges. This does nothing for transmission strength though, what can be done with a constant mesh? I think 50hp is a nice number to aim for. If you get the weight of the bike to 300(not to hard) and keep your weight around 180(significantly harder) 50 horse will put the savage in the mid 12's (estimate) with the right gearing (3.5ish final drive). That could be acheived with the stock stroke. 695cc's with 10:1 (93 is generally recommended for this cr, of course running 300degrees would probably still detonate, so cooling is a must) with the mods for the necessary flow for this size and compression (porting the entire head, maybe bigger valves, carberator, free flowing air filter/exhaust, more aggressive camshaft...) 50 is not crazy, Lancer already has 42 right? So lookin for another 20% power over that.. Anyone know the conversion for flow capacity needed for desired power gain? Oh yea 8000rpm might be the upper limit for a single and beyond the savage, but 7k is not so out there, I think the weight of the bottem end is the current limiting factor for revs... |
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Title: Re: pistons again! Post by barry68v10 on 04/08/07 at 08:30:04 Quote:
I think two weak links we haven't discussed (much) are: 1) clutch 2) valve springs Yeah, I have the equation for calculating required intake and exhaust flows for a given displacement and rpm's around here somewhere. When I find them, I'll post... |
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Title: Re: pistons again! Post by barry68v10 on 04/08/07 at 09:00:55 Go here to play with this yourself, but I calculated a 171% increase in flow over stock to achieve 50 hp at 7500 rpm's. That seems pretty tough to do, although I haven't played around with this engine... NOT2FAST: Turbo Calculator (http://not2fast.com/turbo/glossary/turbo_calc.shtml?FeetASL=0&Tamb=21&Bore=94&Stroke=94&nCyl=1&RPM=6500&VE=60&Boost=0&Ec=75&Eic=70&PdropIC=0.5&TambIC=21&wiPercentMethanol=50&wiRate=100&wiTemp=21&SFC=0.49&AFR=14.1&maxInjectorDutyCycle=85) |
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