Why did MW dish pistons make soo much more power?
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Forum Name: Farm Equipment
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Topic: Why did MW dish pistons make soo much more power?
Posted By: Unstylish
Subject: Why did MW dish pistons make soo much more power?
Date Posted: 28 Nov 2010 at 9:33pm
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Seems like the turbo dish pistions make the '45 and 17 motors LUG SOOOO much better. Other than displacement, why is that?
------------- The problem with reading MLPANKEYS posts, is that they dont make boots that tall. |
Replies:
Posted By: wi50
Date Posted: 28 Nov 2010 at 10:35pm
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the compression ratio isn't that high but the M&W is roughly 7.5 to 1
You get an extra 14 cid displacement, or about 6-7% increase
the wrist pins are offset a fair bit, less side load or loss of power due to friction. Somewhere I've seen some numbers on measured side thrust of both centered and offset pins from the M&W pistons. I don't imagine it would make a lot of difference on it's own.
The top of the piston is shaped to help mix the fuel, burn better and contain a bit more of it in the piston, wasteing less energy. It's better than a straight dish or a flat top, the downside is the low ring placement and a small amount of wasted fuel trapped above the top ring
It's a combination of little things added togather that make the difference.
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Posted By: Steve M C/IL
Date Posted: 29 Nov 2010 at 12:13am
| It would seem that the heart shaped bowl which is also angled would create good swirl on compression which in theory at least makes for better/more complete combustion. |
Posted By: john(MI)
Date Posted: 29 Nov 2010 at 6:36am
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They make it a hemi !! ------------- D14, D17, 5020, 612H, CASE 446 |
Posted By: mlpankey
Date Posted: 29 Nov 2010 at 9:59am
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quench or squish band only starts to show benefits of adding swirl at .030 of the piston striking the head. wrist pin offset can if offset was done for this reason move the piston away from tdc sooner thus creating a depression on the under side of the intake valve sooner . 6.5 hp was all the increase mailto:m@w - m@w advertised wich is not much of a power increase in my opinion. ------------- people if they don't already know it you can't tell them. quote yogi berra |
Posted By: TedBuiskerN.IL.
Date Posted: 29 Nov 2010 at 8:33pm
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6.5 HP may not sound like much, but on a 43 PTO HP tractor that is over 15%. You are going to notice that in the field. ------------- Most problems can be solved with the proper application of high explosives. |
Posted By: mlpankey
Date Posted: 29 Nov 2010 at 8:49pm
------------- people if they don't already know it you can't tell them. quote yogi berra |
TedBuiskerN.IL. wrote:Posted By: Butch(OH)
Date Posted: 29 Nov 2010 at 9:16pm
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Back when we were installing such things in farming tractors another supplier whos brand escapes me was trying to sell dad on a set of flat tops with a couple bumps on them to raise compression. may have been Sealed Power? Supposably the compression ratio the same as M&W but dad was sold on M&W and wouldnt buy. The guy finaly said buyem and if you dont like Ill take em back and buy the gaskets to switch. We put them in over the winter and plowed with the tractor all spring. When done we took it to the dealer for a dyno test and HP results were for all practical purposes the same as M&Ws installed in other tractors. Off sets, volumes, swirlies and other rocket sciences? who knows we were interested in turning a few extra furrows each day not running at Indianapolis.
To answer your question a fellow who had been inside lots of tractor engines told me that M&W "secrete" to HP was about 10% bore increase, 89% compression increase, .5% dome shape and .5% pin offset with an added dose of marketimg hype for good measure. He had no way to know this other than seat of the pants knowledge and in my years since I have come to the conclusion that he wasnt far off. To answer your question the differance opther than displacment? Compression ratio pure and simple,, the other factors are negligable.
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Posted By: Olsem
Date Posted: 29 Nov 2010 at 11:59pm
| How are you getting more displacement just by switching pistons? The bore and the stroke should be the same... |
Posted By: Brian Jasper co. Ia
Date Posted: 30 Nov 2010 at 6:01am
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1/8" overbore... ------------- "Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford |
Posted By: TedBuiskerN.IL.
Date Posted: 30 Nov 2010 at 6:52am
------------- Most problems can be solved with the proper application of high explosives. |
Posted By: firebrick43
Date Posted: 30 Nov 2010 at 9:39am
| Just how much compression will these engines take and still be able to run on 87 octane fuel and not have detonation problems? I know alot of car engines are in the high 8/low 9's range but realize they are not constant load engines and there are many varibles in head/valves/piston design that can effect that. |
Posted By: wi50
Date Posted: 30 Nov 2010 at 10:16am
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how much comp for these engines and 87 oct gas?
I'd have to guess that if one built it at 8.7 to 1 you will be alright. For one with slightly better breathing ability, maybe drop a bit to 8.5. I'm sure someone will have a specific magic number but if I want to use it for farm work, any time and not worry about killing parts I'd target the above numbers. It's really nice when they will lug verry slow or be able to open the trottle at high load and low speed and not detonate.
One could build a "quench" engine and get by with more, but like you say, head, piston design will vary things a bit.
Compression ratio is no more than an indication on how poor an engine breaths, you can have 15 to 1 but if the induction system chokes it, or is not capeale of filling large cylinders, you may as well have smaller cylinders, at a lower comp ratio, it'll likely make more power depending on other factors.
I'll have to run some numbers for sure but I think one could use the M&W pistons from a WD with the taller comp hite, do some machine work to them and build a nice "quench" engine with the 4.5" crank and stock rods, build for about 9 to 1 comp and have a good running little tractor that would make around 70hp
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Posted By: mlpankey
Date Posted: 30 Nov 2010 at 10:28am
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with the amount of ethanol percentages increasing in todays fuel i would be willing to say 9.5 cr is obtainable. remember when increasing compression ratios over factory ratios the factory timing recomendations and sparkplug heat ranges go out to the trash bin with the old stock pistons. keep it choked with small carb on it and bumb the cr up even more. jmho ------------- people if they don't already know it you can't tell them. quote yogi berra |
Posted By: wi50
Date Posted: 30 Nov 2010 at 10:37am
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the common pump or farm delivery gas is 87 oct, no eth here,
in town is's 87 no ethanol, or 89 oct with 10% ethanol, and most places have 91-92 with no ethanol for the 3 choices.
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Posted By: firebrick43
Date Posted: 30 Nov 2010 at 10:47am
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Ok, Lets just use say 8.3 or so to 1 for a good safe field work number. Can we agree on that? Allows for slight fuel variations and such. Why doesn't any one provide that? Seems the aftermarket crowd touts their over bores so much but they are low compression ration of somewhere around 6.5 to 1. The agco 170/175 pistons are the highest available but nothing is available to the B/C/CA out there. Seems like some one would spec it in their kits. Does aftermarket providers such as Tony and OK tractor have any pull on what their suppliers provide? or is there just no market in it? |
Posted By: Dans 7080
Date Posted: 30 Nov 2010 at 10:52am
| All gas today has 2%to 5% ethanol in it, They dont have to advertize amounts that small. |
Posted By: Kevin in WA
Date Posted: 30 Nov 2010 at 10:57am
| One thing to keep in mind when you start comparing Hp of a WD45 or D17 to a 175 is that some of the increase was because they rated the 175 at 1800 rpm instead of 1400 for the WD45 and 1650 for the D17. They did'nt go from 43 hp to 62 just with compression increase. |
Posted By: mlpankey
Date Posted: 30 Nov 2010 at 11:08am
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i ran a wd with 11.1 static with 240 cranking psi on 93 octane with cold plugs and lower total timing . Add 110 octane bump timming up 10 additional degrees. not a field tractor . A fellow told me that e 85 was withstanding 12 to 13.1 ratios in car engines. you guys have bp stations in your area they always have gas with a percentage of ethanol . I would tend to think that there is not much market . I can provide you with a forged aluminum piston of any cr ratio up to 4 11/16 bore size. somewhere in the price range of 700. for four. most want a complete rebuild for that price. You have to realize a guy willing to do field work with a 1950 2500 dollar tractor isnt a big spender. If he was he would be doing his field work with at least a 1980s era tractor. Butch my quote at the bottom of my posts says it all . It did before my time and does still today. kevin they did it with compression and cam change that allowed it to breath at a higher rpm . Its hard to make cam changes to help one breath without needing the compression ratio upped. Ever seen a automobile cam that says needs headers and a compression ratio of ----- for best performance with cam profile. some things just work hand in hand for a better complement. ------------- people if they don't already know it you can't tell them. quote yogi berra |
Posted By: firebrick43
Date Posted: 30 Nov 2010 at 11:24am
I agree with that statement. I am not saying that 700 for a custom set of pistons is not worth it on a performance standpoint. And yes, I am a tight wad, not a big spender. But I still don't understand why the aftermarket kits are so low of compression. I mean they will spend the money to alter the bore of their kits, but 6.5 to 1 ratio, come on? Low octane gas hasn't been around for what, 40 years now? A 7.5 or 8 to 1 ratio piston wouldn't cost anymore if they made them in similar numbers, and why shouldn't that ratio be standard now for replacement parts? A piece of paper with the kit stating you should use x part number plug, x degrees timing setting, and x number of turns on the main needle as a starting place. I guess the main issue is not even the "extra" horse power provided but the wasted energy/fuel economy that excessively low compression(which originally matched the available gas at the time) ratios bring. |
Posted By: mlpankey
Date Posted: 30 Nov 2010 at 11:28am
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the extra cost in material of making a longer piston ------------- people if they don't already know it you can't tell them. quote yogi berra |
Posted By: firebrick43
Date Posted: 30 Nov 2010 at 11:45am
LOL, In a cast piston, if designed right, we are talking pennies, maybe not even that. For example, I know that some harley sportster pistons, such as the Wiseco 1200 pistons weight the same as stock 883 pistons and don't' loose any strength and are much better balanced than HD stock 1200 pistons because of their lower weight. The biggest expense would be the molds but even then, if the they dropped the low compression pistons and offered the ~8 to 1 pistons as standard fare the cost would be minuscule. Even your 12 to 1 high performance jobbies would be cheap if a manufacture could sell enough of them, but because of the low volume, guns and butter take over. |
Posted By: Butch(OH)
Date Posted: 30 Nov 2010 at 11:51am
As somebody else said you threw the tune up book away. Again going back to sooped up farming tractors the timing was done seat of the pants. You ran the timing up until you had detonation and backed it off until it quit and tightened the clamp, then if it kicked back on the starter when warm you either back it down a bit more or didnt try to start it hot or maybe added the M&W reduction starter. We even changed the advance stops to kill initial timing. If you could get the ole man to spend 26 cents per gallon for mid grade, verses 24 cents for "farm gas" you were in like flint and ran the timing up and amazingly the muffler didnt glow nearly as red at night like it used to and you could pull the hills a little easier. In a lot of ways it was like pulling or racing, I messed with the timing and valve settings, the carbs all so we could go an inch deeper or maybe a gear higher. I was lucky and had good mentors and ts how I became a motor head, LOL.
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Posted By: Brian Jasper co. Ia
Date Posted: 30 Nov 2010 at 12:04pm
------------- "Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford |
Posted By: firebrick43
Date Posted: 30 Nov 2010 at 12:33pm
| I thought the main reason to offset piston pins is to reduce piston slap and therefore reduce noise. A lot of race motors with centered pins have lots of noise when cold due to piston slap. |
Posted By: mlpankey
Date Posted: 30 Nov 2010 at 12:36pm
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the piston being slid and showing on the allis manual as to which way the piston should be slid for each bore was for one or two things .1 the rods were directional 2 it helped lock the wrist pin .thats all again different from the Offset wrist pin is the pin hole in the piston was bored off center on the piston . It reduced piston slap and could affect dwell time by changing the rods trianglur path by moving the apex .the trig. thingy again .
http://www.jepistons.com/TechCorner/Pin-Offset.aspx - http://www.jepistons.com/TechCorner/Pin-Offset.aspx
------------- people if they don't already know it you can't tell them. quote yogi berra |
Posted By: Gerald J.
Date Posted: 30 Nov 2010 at 1:23pm
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The offset piston pin causes the piston side load to swap on the compression stroke when the pressure is light compared to after ignition and on the power stroke. So its much quieter. This can also be accomplished by offsetting the crankshaft. That lets the connecting rod angle be greater with respect to the cylinder bore on the compression stroke than on the power stroke. My dad told me about family relations coming to SE Missouri from Oklahoma for a funeral when he was young driving a '24 Chevy with cast iron pistons. He said you could hear the piston slap further than the exhaust. As they approached the piston slap was the first thing he heard. In 1951 he built a garden tractor cutting down model A Ford axles and drive train using a belt clutch and belt speed reduction and a new Wisconsin Model AEN engine. Its run nicely ever since. I have it yet. A couple years later a neighbor bought a heavy duty tiller with that same engine model. It always had piston slap. The dealer took it apart and turned the piston around, thinking the offset was backwards but it had no effect on the piston slap. That was a 7 hp rated engine with a Fairbanks-Morse gear driven magneto with an impulse start like the mags on bigger tractors that made it a really good starter, usually one time through ignition, exhaust and intake and then next time over compression and ignition it was running. Maybe someday I'll look up the shop manual on that engine to see if the piston was drilled offset. Maybe they should have replaced the piston which they may have done since that neighbor was particular about how well his equipment worked keeping his car under a cloth in the garage to keep dust off even with the garage door closed. Gerald J. |
Posted By: mlpankey
Date Posted: 30 Nov 2010 at 1:53pm
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forged pistons require a larger skirt to cylinder wall clearance due to their thermal growth properties . I have personally never seen a quiet forged piston wither the wrist pin had offset or the piston were attached to (on center) rods or rods with offset. Some piston manufacturers say that the ceramic coatings are allowing tighter piston skirt to cylinder wall clearance removing alot of the piston noise. . Old timers say you know a performance build when you hear it . loose and sounds rattles like a bucket of bolts.
i ran a piston in a computer with no piston pin offset piston speed at 10 degrees crank angle was 5.664 ftps with 1 mm positive offset piston speed at 10 degrees crank angle was 5.6636. i ran out of time had to leave . the engine in the above is a small engine 90 mm stroke 25 mm rod journal 100 mm rod center to center. ------------- people if they don't already know it you can't tell them. quote yogi berra |
Posted By: Gerald J.
Date Posted: 30 Nov 2010 at 6:40pm
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The offset pin doesn't affect piston speed, just the time when it transfers the side load from one side to the other, preferable before ignition so there's only compression pressure on it, not combustion pressure. The offset crank shaft is another effect. An offset end on a connecting rod changes the dynamic balance and allows a longer skirt with offset pin or crankshaft position, but it doesn't change the stroke or piston speed any. Gerald J. |
Posted By: mlpankey
Date Posted: 30 Nov 2010 at 6:49pm
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quote Gerald just the time when it transfers the side load from one side to another . The crank is turning in degrees a measurement of time distance not traveled or traveled in the bore as the crank continues to tic off degrees affects speed at that given crank angle. . In the same way the drag strip measures speed known distance traveled in time . maximum torque applied to the crank is achieved when the piston and rod are at a right angle with the crank thus the short side of the triangle. The hypotenuse is the longest side that completes a right triangle . so if we move the pin off center radially the actual meaning of a offset wrist pin. depending on the direction can shorten or lengthen the hypotenuse . ------------- people if they don't already know it you can't tell them. quote yogi berra |
Posted By: mlpankey
Date Posted: 30 Nov 2010 at 8:28pm
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Andy its a good topic. One which brought out the thinking caps. whats your thoughts? ------------- people if they don't already know it you can't tell them. quote yogi berra |
Posted By: firebrick43
Date Posted: 30 Nov 2010 at 11:47pm
Where/what program are you running to do these calculations on and where could I possibly get it? I have been reading up on aluminum casting, something my father and I did many years ago and I have several projects that I could use some castings in, so I have been thinking of setting up another foundry. In one of the books I have been reading, by Steve Chastain, he has another book on casting and machining pistons so I may just have to get it and give it a read. It will be a while till I get around to actually doing it however as I just have to many other projects. |
Posted By: mlpankey
Date Posted: 01 Dec 2010 at 7:14am
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larry meuxs pipe max soft wear or Stan Weiss progams are good reasonable to purchase programs. wallace racing site has some free calculators a person can use but not one for wrist pin offset to my knowledge. ------------- people if they don't already know it you can't tell them. quote yogi berra |
Posted By: Gerald J.
Date Posted: 01 Dec 2010 at 9:22am
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Look into lost foam casting, its simpler than sand casting or lost wax and can make some fine results. Gerald J. |
Posted By: firebrick43
Date Posted: 01 Dec 2010 at 11:10am
| I have done lost foam and lost wax Gerald. It has its advantages, but I would have to make 6 or 8 foam/wax patterns, just to cast enough pistons(with a few extra for machining/scrap allowance. If I was casting just one, I did lost foam, otherwise we always made a pattern and core box if necessary. |
Posted By: Gerald J.
Date Posted: 01 Dec 2010 at 11:50am
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For production you could make one pattern, and make a rubber mold from that, then create foam patterns in that rubber mold as many as you liked so long as the foam didn't stick to the rubber. And if the surface of that rubber mold is smooth, the cast foam will have that smooth surface better than a carved block of foam. Gerald J. |
Posted By: firebrick43
Date Posted: 01 Dec 2010 at 12:06pm
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The foams we used were the dow blue board type foams. I recall that there are very few pourable foams that are suitable for lost foam casting. There is one(I have never used) but it was expensive) but using wax is a good solution for the method that you are talking about. But still, dipping multiple times in the plaster slurry, drying the slurry still need sand to back it up, cost of molding rubber and pourable foam/wax, it all adds up. Green sand and molasses baked cores are cheap, wood patterns and core boxes are cheap. Surface finish on cores is easy with a core wash. On the green sand, using a very fine facing sand gives decent finish but most of the outer surface is going to be machined completely anyhow and the interior surface as long is there is not serious defects, surface finish is of little consequence. Lost wax/foam has its advantages in parts that need excellent surface finish and no/very little machining. |
Posted By: mlpankey
Date Posted: 01 Dec 2010 at 1:40pm
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i sent it to you firebrick ------------- people if they don't already know it you can't tell them. quote yogi berra |