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mlpankey 
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 Topic: power crater vs flat top looking at squish
Posted: 26 Nov 2012 at 8:44pm |
lets say for simplistics we are doing a 201 ci 4 inch bore 4 inch stroke 7.5 rod with a static cr of 11.1 . Our dish piston will have a piston to head clearance aka squish of .035 since its a dish and the outer edge is our squish area we will give it a value of 20 percent . Now then this scenerio has a squish velocity of 5.09m/s and womping .36mj of kenetic energy.
flat top has the same bore stroke rod length and comp of 11.1 it has a total counting the head gasket thickness of .392 squish distance but it has a squish area of 80 percnet being a flat top . It has a squish velocity of 0 goose egg but comes in on kenetic energy at 7.8mj . for the guys who want to follow along the rpms were at 2000 and the exhaust valve abdc was figured at 83 degrees. most values like exhaust was just hypothetical some was realistic like compression ratio of a flattop .392 in the hole with gasket on a 201
Edited by mlpankey - 26 Nov 2012 at 8:53pm
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Dipstick In
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Posted: 26 Nov 2012 at 10:58pm |
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Hope you know what you said, because to me it was a bunch of garbeldeegook meaningless crap!
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You don't really have to be smart if you know who is!
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Mrgoodwrench
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Posted: 26 Nov 2012 at 11:16pm |
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gotta say i got nothing outa that either
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There are 3 ways to do job GOOD, FAST, CHEAP. YOU MAY CHOOSE 2. If its FAST & CHEAP it won't be GOOD, if it's GOOD & CHEAP it won't be FAST, and if its GOOD & FAST it won't be CHEAP!!!!
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mgburchard
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Posted: 27 Nov 2012 at 6:59am |
anyone can see the flattop has more squish area
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Butch(OH)
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Posted: 27 Nov 2012 at 10:17am |
Since Mr Spock was not available to help me understand I passed the info on to the next best expert I know of,,.
[TUBE]2pWSwfVDiq8[/TUBE]
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Dipstick In
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Posted: 27 Nov 2012 at 7:43pm |
Shoot, all I need is an S Q H D, a SQhd, or doctorate of squishology, and I could/would understand!
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steve(ill)
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Posted: 27 Nov 2012 at 9:54pm |
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NAW, you still wouldnt understand Dipstick... spanky talks funny like that all the time. Just the way it is. Sometimes he even puts a period here and there.
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Like them all, but love the "B"s.
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Rod B
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Posted: 28 Nov 2012 at 1:31am |
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It's basic human psychology. Whenever pankey realizes he's wrong he starts another topic on the same subject.
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mlpankey
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Posted: 28 Nov 2012 at 6:18am |
Back in 1990 when we did the piston like i posted on the other post not started by me . We didint have the information highway enet. we learned by experience reasoning and every now and again bits and pieces from factory sponsored riders and their mechanics. What we learned is my to share and you and others should be thankful I share it . We learned there is a maximim squish speed you do not want to exceed . When exceeding the msv number the friction from the velocity errodes the thermal barrier of the piston. When playing with squish one should know his maximum squish velocity so he doesnt run into this damage.
Wi posted that on his superstocker they were signs of the piston touching the head through piston rock. It is of my opinion this is done when the engines at temp and at low rpms and low boost where the thermal growth or rod stretch is prevalient . Under full rpm and boost if it is a high as he stated it is my opinion the rods would be in the compressed state .Meaning his squish distance would be wider and squish velocity would be lower . If squish velocity was in the upper msv then on a turbo he would be experiencing some power loss.
it is hard subject if you think my explanations is hard to understand you should read the engineering paper on it from the university of michigan.
Edited by mlpankey - 28 Nov 2012 at 6:28am
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mgburchard
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Posted: 28 Nov 2012 at 8:12am |
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you can do it butch
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Breeze
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Posted: 28 Nov 2012 at 8:39am |
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do it to Butch?
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Butch(OH)
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Posted: 28 Nov 2012 at 9:20am |
Never fear men! I have put Spock on it!
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Gary
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Posted: 28 Nov 2012 at 10:27am |
Pankey Could you post a Link to this "Engineering paper from the University of Michigan" I would very much like to read it and learn more about 'Maximum Squish Velocity' and also 'Erosion of the thermal barrier of the piston'. This is terminology I have never heard before. Gary
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mgburchard
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Posted: 28 Nov 2012 at 12:12pm |
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i am sure its not new to you, you may not have heard the terms before but its common sence Gary you have seen it just didnt know what you where looking at
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lussetto
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Posted: 28 Nov 2012 at 1:02pm |
Theory means nothing to me without seeing or putting it in practice. I would rather get my information from the "been there, done that" guys.
Greg
ps. We have pulled as a family and me personally for many years.
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CTuckerNWIL
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Posted: 29 Nov 2012 at 4:05am |
Thanks Butch  Somehow I can't believe Pank has that degree yet. It is entertaining when old people start arguing with themselves though 
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Butch(OH)
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Posted: 29 Nov 2012 at 6:14am |
 CTuckerNWIL wrote:
Thanks Butch Somehow I can't believe Pank has that degree yet. It is entertaining when old people start arguing with themselves though |
Who ya'll callen old ya geezer?? 
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wi50
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Posted: 29 Nov 2012 at 10:07am |
It's more entertaining when they don't rember that last time they tried to argue the same point they had a completely different point of view. Last year my pistons in the WD45 too short and this year they are too tall.
I can't wait for pankey to tell everyone how the quench design of the alky superstock engine is a terable idea. I spend my time money based on the experiences of those in the winners circle, not based on free advice on the internet. What we find is that for one of these engines to run verry well, verry tight piston to head clearance is required, all the rest of them are just a bit lazy. Methanol and extreme boosted applications is a completely different set of rules to play by. If a guy wrote a check for a turn key engine to compete in the class one would be paying for the experiences and of those out there doing the work and competeing, not the opinions of "keyboard commandos".
Edited by wi50 - 29 Nov 2012 at 10:15am
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"see what happens when you have no practical experience doing something...... you end up playing with calculators and looking stupid on the internet"
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CTuckerNWIL
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Posted: 29 Nov 2012 at 11:34am |
Butch(OH) wrote:
Who ya'll callen old ya geezer??
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I was reffering to panky, at least he argues with himself like an old geezer. 
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mlpankey
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Posted: 29 Nov 2012 at 11:36am |
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you dont remember last years either it wasnt to short or to tall it was not enough cc dish to get the compression with the height . I forgot the crevice volume though and that makes all the difference in the world cause the trapped gases there never all get burned even after the second combustion cycle.
Edited by mlpankey - 29 Nov 2012 at 11:38am
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wi50
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Posted: 29 Nov 2012 at 1:35pm |
That was your second or third attempt at argument.......I realize I posted all this information in the past, and that pankey is no math guru. But the neat thing about mathmatics is that numbers don't lie. If one knows a specific number and how it's derived one can do a little reverse math and figure something in specific.
So if a WD has a 4" stroke, 7.5" rod and a deck height of 12.625", when M&W made the pistons for them they had a compression ratio of 8 to 1, and some sources say 7.75 to 1. None of this is up for debate but is actual information
A piston from M&W for the WD has a compression height of 2.94", that is measured piston pin center to top of piston. It has a bowl volume of 70cc in it to achieve the 8 to 1 compression ratio (now my surenge and plexi glass may not be the most accurate method but it's dang close). 7.5 rod + 2" (half stroke)+2.94 (piston comp hite) adds up to 12.44" which is .187" down in the bore. Head gaskets measure .055" give or take for a compressed gasket thickness (Fel Pro, Victor, OEM from teardown motors have all measured verry close .055"). Add whatever one feels for spark plug pocket volume, typically 1 or 2 CC and punch the numbers into a compression calculator. Depending on one's exact measurements and number manipulation we see a 7.8 to 8 to 1 compression ratio.
If I take that piston and put it on a crank witha 4 1/2" , or .5" more stroke, in the same block, same rod we see that it comes .250" up further and .250 down further than in it's original application with the 4" stroke. .250" up is a greater distance than the .187" that it would be down in the bore with a 4" stroke. Thus comeing up out of the block by .063.
So pankey, you have argued that the piston is to high, to low, not enough volume in the piston dish, and various other arguments. None of which hold any water. The fact is that numbers do not lie. A piston with a 70cc dish and a large vane in it can be easily trimmed out to enough volume to drop a 4.5" stroke engine to 11.25 compression and with the positive piston popout of the block, can be trimmed for a proper quench.
Nice try but numbers are numbers. The rules can't be changed allong the way. I'm certain that I spent less time machining on the pistons and putting the engine togather than pank has worrying about it.
Weather or not it's an ideal situation isn't up for debate. There's better designs if buying custom parts, but I'm surely not going to invest any serious $$$ in a custom set of pistons for an engine built out of what was laying around.
Edited by wi50 - 29 Nov 2012 at 1:52pm
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"see what happens when you have no practical experience doing something...... you end up playing with calculators and looking stupid on the internet"
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mlpankey
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Posted: 29 Nov 2012 at 3:31pm |
I will always believe this guy when it comes to squish . Especially on low rpm engines like mccullochs were.
Avraham Ziv - Engineering Div., McCulloch Corp .The study concluded that squish velocity has a major effect on optimum ignition timing and rate of combustion pressure rise, with a lesser effect on power, ignition voltage, and spark duration. I never posted it was to high or low I posted i didnt think it would make the compression because of the cc of the dish but as I said I forgot about crevice volume. Yes trying to provide squish on a dished piston in a faint attempt to burn trapped fuel in the crevice area was probably a good thing but it still doesnt get burned according to cal. tech.
Edited by mlpankey - 29 Nov 2012 at 3:36pm
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