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Lizard
Joined: 03 Nov 2002 Posts: 9364 Location: Abbotsford BC. Canada
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Posted: Thu Jan 11, 2007 10:22 am Post subject: |
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Khal wrote: | This went the way of my OOTB faux pas, didn't it?
I think the lesson is not to criticise someone elses work and just keep your mouth shut. |
yes in this case it was wayne whom should have stopped flinging the insults around. _________________ 3 928s, |
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sequential
Joined: 18 Nov 2005 Posts: 500 Location: BANNED
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Posted: Thu Jan 11, 2007 10:28 am Post subject: |
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deleted _________________ 928 gts prototype
baby blue engine block
steam in 1,2,3,4 sometimes
cold star issues while on stands
112 whp with new 4 valve head and MIS 2 |
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Lizard
Joined: 03 Nov 2002 Posts: 9364 Location: Abbotsford BC. Canada
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Posted: Thu Jan 11, 2007 11:34 am Post subject: |
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Quote: | This is funny, ignorance has many friends.
a'rnt you in the wrong section , this is technical stuff and as ususal , you have nothing to add.
should'nt you be in the section discussing how to make muffins before my man come home .....
Rasta this is
T-H-E P-E-R-F-O-R-M-A-N-C-E S-E-C-T-I-O-N ,
y-O-U A-r-e i-n t-h-e w-r-o-n-g s-e-c-t-i-o-n.......
but i'm sorry i cannot explain any slower or lower
Morghen , you have nothing to offer nothing , just a numb nut at best , please do not get offended by this as it is just my observation and god honest opinion,
Gday |
these are all insults that you have made in this topic alone. It was only after you started to berate people did they start to snap back at you.
your additions (if you can call them that) to this topic were cryptic and not in any sort of language most could understood.
When asked a STRAIGHT question which was what do you mean by gasket matching the combustion chamber, you NEVER ONCE aswered the question. Even after I had edited a picture to display what I though you had meant by this, you completely avoided it. You could have even said yes that is what I mean. Raceboys responce which you seem to hold high was that it would be more detonation prone. However you always were stating that it would be more pre-ign prone.
One of the board members provided a definition as to pre-ign, you didnt bother to even recognise that he had posted.
However from everything that I have ever read/can find, every tech article, research paper etc. agrees with the definition that arx supplied which is that the air fuel mixture gets ignited by a HOT SPOT in the cylinder. Such is a high spot in the combustion chamber. What Nick did to his head may not be optimum but I cannot see that it would cause the combustion tempatures to rise so significatly so as to cause a large hot spot for pre ign.
Your definition that pre-ign is the point at which detonation occours, which I cannot agree with.
And when asked about it you said you ment pre ign, and not detonation, yet again raceboys post clearly states that he would see detonation being a problem not pre ign.
So on that make up your mind.
Please stop insulting/berating other members and calling them "slower and lower" than yourself.
If you are trying to just be funny about it you have failed MISERABLY.
I found your repsonces where you said nick blah blah blah extremely insulting and that which I would expect to hear in the argument of 5-10 year olds.
If you care to comment about what someone has done,and he then asks a question answer him and explain in laymans terms what you mean. If you cannot handle that PLEASE DONT RESPOND.
responding to a post about what someone has done, and when they ask a legit question about your comment, and you then battering and belittling them because they cannot understand what you have said is very poor manerisms.
Also you need to understand that pretty much all the board members I keep in touch with were rather happy when you left after the last round of manure slinging you did. And I know that you had pissed off alot of people while you were here last.
If you are trying to be funny though you may be funny in person and your jokes may be able to be understood/accepted, we dont know you personnally and your "jokes" appear to be personal attacks on others. _________________ 3 928s, |
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CBass
Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada
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Posted: Thu Jan 11, 2007 11:57 am Post subject: |
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Haha oh wow... I can`t be sure of whether or not Sequential is a troll or whether he suffers from some pretty severe personality disorders. He certainly does get people whipped up into a frenzy, although it seems he works himself up into a frenzy in the process.
In before flaming about frozen brained northerners. _________________ '81 931 in various states of assembly |
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sequential
Joined: 18 Nov 2005 Posts: 500 Location: BANNED
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Posted: Thu Jan 11, 2007 12:25 pm Post subject: |
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deleted _________________ 928 gts prototype
baby blue engine block
steam in 1,2,3,4 sometimes
cold star issues while on stands
112 whp with new 4 valve head and MIS 2 |
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flosho
Joined: 01 Jul 2004 Posts: 3155 Location: Eau Claire, Wisconsin
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Posted: Thu Jan 11, 2007 12:50 pm Post subject: |
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I almost feel obligated to post the special olympics macro.
We ah... should just delete a few of these pissy posts and drop the whole thing and keep it civil.
Knocking (also called pinking or pinging)— colloquially detonation—in internal combustion engines occurs when fuel/air mixture in the cylinder has been ignited by the spark plug and the smooth burning is interrupted by the unburned mixture in the combustion chamber exploding before the flame front can reach it. The engineered combusting process ceases, because of the explosion, before the optimum moment for the four-stroke cycle. The resulting shockwave reverberates in the combustion chamber, creating a characteristic metallic "pinging" sound, and pressures increase catastrophically.
Normal combustion
Under ideal conditions the common piston internal combustion engine burns its fuel air mix in the cylinder in an orderly and controlled fashion. The combustion is started by the spark plug some 15–40 crankshaft degrees prior to TDC (top dead center) the point of maximum compression. This ignition advance allows time for the combustion process to develop peak pressure at the ideal time for maximum recovery of work from the expanding gases. This point is typically 14–18 crankshaft degrees ATDC (after top dead center).
The spark plug produces an electrical spark that jumps a small gap from its center electrode to its ground electrode. This spark, if the fuel air mix is within the flammable range for the fuel, initiates combustion. The initial phase forms a small kernel of flame approximately the size of the spark plug gap. For the first few milliseconds of the combustion process, this flame kernel is struggling to survive, producing only slightly more heat than is necessary to continue the combustion process. As it grows in size its heat output increases allowing it to grow even faster.
After this early slow burn phase passes, the flame kernel grows much faster expanding rapidly across the combustion chamber. This growth is due to the travel of the flame front through the combustible fuel air mix itself and due to turbulence rapidly stretching the burning zone into a complex of fingers of burning fuel air that have a much greater surface area than a simple spherical ball of flame would have. This greatly accelerates the combustion process.
In normal combustion, this flame front moves throughout the fuel air mix at a rate characteristic for the fuel-air mixture. Pressure rises smoothly to a peak, burning nearly all the available fuel then falls as the piston decends. In normal combustion this produces a rapid increase in cylinder pressure as the piston passes TDC and begins to move down the cylinder. As mentioned above in a properly tuned engine the maximum cylinder pressure is achieved a few crankshaft degrees after the piston passes TDC, so that the increasing pressure can give the piston a hard push when its speed and mechanical advantage on the crank shaft gives the best recovery of force from the expanding gases.
[edit] Detonation
The fuel/air mixture is normally ignited slightly before the point of maximum compression to allow a small time for the flame-front of the burning fuel to expand throughout the mixture so that maximum pressure occurs at the optimum point. The flame-front moves at roughly 33.5 m/second (110 feet/second) during normal combustion. It is only when the remaining unburned mixture is heated and pressurized by the advancing flame front for a certain length of time that the detonation occurs. It is caused by an instantaneous ignition of the remaining fuel/air mixture in the form of an explosion. The cylinder pressure rises dramatically beyond its design limits and if allowed to persist detonation will damage or destroy engine parts.
Detonation can be prevented by:
* The use of a fuel with higher octane rating
* The addition of octane-increasing "lead", methylcyclopentadienyl manganese tricarbonyl (MMT), isooctane, or other antiknock agents.
* Increasing the amount of fuel injected/inducted (resulting in lower Air to Fuel Ratio)
* Reduction of cylinder pressure by increasing the engine revolutions (lower gear), decreasing the manifold pressure (throttle opening) or reducing the load on the engine, or any combination.
* Reduction of charge (in-cylinder) temperatures (such as through cooling, water injection or compression ratio reduction).
* Retardation of spark plug ignition.
* Improved combustion chamber design that concentrates mixture near the spark plug and generates high turbulence to promote fast even burning.
* Use of a spark plug of colder heat range in cases where the spark plug insulator has become a source of pre-ignition leading to detonation.
Correct ignition timing is essential for optimum engine performance and fuel efficiency. Modern automotive and small-boat engines have sensors that can detect knock and retard (delay) the ignition (spark plug firing) to prevent it, allowing engines to safely use petrol of below-design octane rating, with the consequence of reduced power and efficiency.
A knock sensor consists of a small piezoelectric microphone, on the engine block, connected to the engine's ECU. Spectral analysis is used to detect the trademark frequency produced by detonation at various RPM. When detonation is detected the ignition timing is retarded, reducing the knocking and protecting the engine. See also Automatic Performance Control (APC).
[edit] Pre-ignition
Pre-ignition is a different phenomenon from detonation, explained above, and occurs when the air/fuel mixture in the cylinder (or even just entering the cylinder) ignites before the spark plug fires. Pre-ignition is caused by an ignition source other than the spark. Heat or hot spots can buildup in engine intake or cylinder components due to improper design, for example, spark plugs with heat range too hot for the conditions, or due to carbon deposits in the combustion chamber. Spark plugs with a high heat range will run hot enough to burn off deposits that lead to plug fouling in a worn engine, but the electrode of the plug itself can occasionally heat soak, and begin glowing hot enough to become an uncontrolled ignition source on its own. Bits of carbon that build up in a combustion chamber can also heat soak to the point where they also are glowing hot and ignite the air-fuel mixture before the proper time.
Pre-ignition and "dieseling" or "run on" are the same phenomenon, except in the latter case the engine continues to run after the ignition is shut off with a hot spot as an ignition source. Pre-ignition might cause rough running due to the advanced and erratic effective igniton timing and may cause noise if it leads to detonation. It may also cause "rumble" which is fast and premature but not detonating combustion.
This heat buildup can only be prevented by eliminating the overheating (through redesign or cleaning) or the compression effects (by reducing the load on the engine or temperature of intake air). As such, if pre-ignition is allowed to continue for any length of time, power output and fuel economy is reduced and engine damage may result.
Pre-ignition may lead to detonation and detonation may lead to pre-ignition or either may exist separately.
[edit] References
* Charles Fayette Taylor, Internal Combustion Engine in Theory and Practice: Vol. 2, Revised Edition, MIT Press, 1985, Chapter 2 on "Detonation and Preignition", pp 34-85. ISBN 0-262-20052-X
1. http://naca.central.cranfield.ac.uk/reports/1942/naca-report-727.pdf
2. http://naca.central.cranfield.ac.uk/reports/1940/naca-tn-774.pdf
3. http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930091978_1993091978.pdf
4. http://www.avweb.com/news/pelican/182132-1.html
_________________ [This Space For Rent] |
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Rasta Monsta
Joined: 12 Jul 2006 Posts: 11723 Location: PacNW
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Posted: Thu Jan 11, 2007 2:01 pm Post subject: |
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_________________ Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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flosho
Joined: 01 Jul 2004 Posts: 3155 Location: Eau Claire, Wisconsin
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Posted: Thu Jan 11, 2007 2:09 pm Post subject: |
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Looks like seqsy was banned..
Kinda sucks cuz he did seem knowledgable. _________________ [This Space For Rent] |
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Rasta Monsta
Joined: 12 Jul 2006 Posts: 11723 Location: PacNW
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Posted: Thu Jan 11, 2007 2:13 pm Post subject: |
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Well, there are plenty of people here who know plenty, man, yourself included. We'll survive - what's too bad is his mean streak.
CBass wrote: | In before flaming about frozen brained northerners. |
What, he lives in BC? Hot damn, I might get to meet him after all! _________________ Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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Lizard
Joined: 03 Nov 2002 Posts: 9364 Location: Abbotsford BC. Canada
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Posted: Thu Jan 11, 2007 2:19 pm Post subject: |
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flosho wrote: | Looks like seqsy was banned..
Kinda sucks cuz he did seem knowledgable. |
what is the point of having someone knowledgable on the board if they are unwilling to actually post helpful information. _________________ 3 928s, |
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Min
Joined: 04 Nov 2002 Posts: 2368 Location: Vernon, British Columbia, Canada
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Posted: Thu Jan 11, 2007 4:21 pm Post subject: |
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Lizard wrote: | what is the point of having someone knowledgable on the board if they are unwilling to actually post helpful information. |
I agree completely with this, if a knowledgable person is on this board, its not becuase they need help from us. And if they are like sequential, we are better off if they arn't here.
Min _________________ Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting. |
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Chrenan
Joined: 15 Jan 2003 Posts: 3903 Location: Canada
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Posted: Fri Jan 12, 2007 1:34 am Post subject: |
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Skimming through his past posts yesterday led me to beleive he actually wasn't too knowledgeable at all. I couldn't easily find a post where he answered a question clearly, maybe aided by a picture, and solved the problem of another board member. That is what I consider knowledgeable. We have lots of knowledgeable members, -Nick, Flosho, Lizard, Peter, Peter in Aus, Joe, Smoothie, Gohim, Khal, and on, and on, and on. I think the performance upgrades section in great, we have simsport, leadfoot, raceboy, Min, CBass, and tons of other guys who have done really creative things with the 924, and who are willing to help and guide. I don't mind crusty members, if they are knowledgeable, but for someone to just be crusty, insulting and post hairbrained scemes really doesn't add anything to the board. Seems like every year in the middle of winter (for North America) things get crazy around here. Must be cabin fever kicking in. _________________ 1987 951 - M193 Version for Japan |
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-nick
Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA
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Posted: Fri Jan 12, 2007 2:00 am Post subject: |
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Wow, that was quite a mess.
For the record - to the best of my knowledge, my head carving shouldn't cause any problems. If it does, I'll be sure and let you folks know so you don't make the same mistake. What's the saying "my only purpose may be to serve as a warning to others"
I'll hopefully be ready to pop the car on a dyno in a month or so. _________________ 1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet |
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Lizard
Joined: 03 Nov 2002 Posts: 9364 Location: Abbotsford BC. Canada
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Posted: Fri Jan 12, 2007 3:01 am Post subject: |
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-nick wrote: |
I'll hopefully be ready to pop the car on a dyno in a month or so. |
knock on wood _________________ 3 928s, |
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CBass
Joined: 03 Nov 2002 Posts: 2807 Location: Vancouver, Canada
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Posted: Sat Jan 13, 2007 5:10 am Post subject: |
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Back on topic again, I found the VW pistons to be unsuitable for my goals with a 931 head d-pro style motor and adding up all the costs I found that slinging in a 3.0 968 engine would be more cost effective and would actually take less time.
Looks like I may be going this approach with my brother's new project however, M31 build with VW 87mm flat tops. Hunting for around 300bhp and excellent driveability.
And no, Cbass isn't dead, just lurking _________________ '81 931 in various states of assembly |
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