|11-26-2012 11:08 PM|
Quench is your friend. Zero deck the block. Run a piston that gets your target compression ratio for your chamber volume and fuel you will be using. Check piston to valve clearance. Have fun. Be happy.
|11-26-2012 05:58 PM|
|vinniekq2||also,computers dont have eyes or ears. theory is good and what a computer seems to have that some lose is,,,,memmory.|
|11-26-2012 04:57 PM|
What I find is a lot of guys that grew up on the computer donít appreciate that the machine is not innately smart. People who did things put that data in there. The cool thing is it can be manipulated quickly which lets you put different takes on the data thus taking different information away from what it may appear say.
But in the end, thereís no escaping that new obsoletes old.
|11-26-2012 04:36 PM|
I know by experience on three engines I assembled that a zero quench distance works to lower operating temperature of the engine.
A zero piston/deck quench distance with Fel Pro head gasket with .039" crushed thickness resulted in 20 degree reduction in operating temperature on three 455 Pontiac engines using 105 octane VP C-12 racing fuel. . My engine builder CNC machined the deck on all three engines about .030" to achieve a zero piston/deck height.
My associate's 428 Pontiac Bonneville ran 30 - 40 degrees hotter after he machined the piston tops 0.125" like a pieces of baloney in a futile attempt to run 93 octane pump gas. His piston/deck quench distance was about .155" plus .039" crushed head gaskets. He could not load the motor without severe pre-ignitioneven on 105 octane VP racing fuel. If he had dished the pistons 2.00" O.D. x .200" deep leaving 1.00" quench perimeter around the top of the piston, the engine would have run on kool-aid quality pump gas at 190 degrees on a 110 degree day. .
|11-26-2012 02:17 PM|
double E? really? maybe for ignition or sensors. Try mech e, materials e, aero e, chemical e, metallurgical e, etc. BTW, I went to an engineering school, and am very familiar with guys that do all o fthose things and what the differences of each field are. My schooling was in civil e- so you'd need me for the dragstrip, not so much on the car. (don't get me started on how little some mechanical engineers know when it comes to cars though- like anything else there are good and bad engineers in every field)
|11-26-2012 02:14 PM|
Squish and quench are two (2) different functions of the same part of the combustion chamber. This part exists in wedge, hemi, and pent chambers just in a different configuration. It also exists in the Ford flathead which would never have lasted into 1953 without it; it just looks different when you look inside of one. For a wedge the squish/quench step is on the side furthest from the spark plug. For the hemi and pent chamber it is a circular ring around the outside diameter. For the Ford flat head and the Briggs and Stratton it would be the extreme close closure of the piston to the cylinder head, because the valves are off in an anti-chamber beside the bore which makes a long and difficult chamber to design.
Both Ford and Chevrolet tried putting the squish/quench "wedge" into the piston in the MEL and the W motor while using a plainer surface to the head, neither worked as well as desired. While the Ford Cortina and other small bore Euro designs worked pretty well. Goes to show that bore diameter has a say in the outcome so hard fast rules will head you into problems.
Smokey skims a lot of subjects, while wanting to make money from his books, he really wasn't looking to add competition on the track, so there are a number of technical issues he leaves the reader with just enough information for them to be dangerous to themselves and everyone nearby.
Letís take Squish and Quench functionally apart, they are two different things happening at different times but produced by the same parts.
1) Squish---this happens as the piston is rising and ignition has not happened but will soon. Squish ejects the mixture from the distant side of the chamber regardless of shape (flathead included) toward the spark plug. It is intended to do two things to the mixture; first is to breakup remaining fuel globules into a fine mist and mix the air and mist into a homogeneous brew for a fast and complete as possible burn; the second event in Squish is to place as much molecular density as possible before the spark plug, this increases the likelihood of the spark actually starting a fire that also spreads quickly through the higher density of molecules than would be there in a more open chamber.
2) Quench---this happens at the end burn as the piston is passing over Top Dead Center and starting down the bore. Once ignition occurs the temperature inside the cylinder raises very high, thus in accordance with the Gas Laws so does the pressure. As the temperature and pressure increase, the yet to be combusted mixture ahead of the flame front is pushed into its self-ignition zone. The best example of this are the videos made of a home fire as it progresses in a closed room where combustible gases collect along the ceiling as the contents of the room burn. At some point the temperature and pressure along the ceiling come to the self ignition point of those gases and they just suddenly explode. A similar thing will happen to that mixture on the far side of the chamber as it gets hotter and more pressurized from expanding because of that heat. Suddenly it just explodes sending an even higher pressure wave to slam back into the flame front. So what to do involves Quench, which is nothing more than an area, the same area that did the Squish function nano-seconds earlier is now a place where there are two large surfaces that have a very small volume of mixture trapped between them. Lots of surface and little volume allows the surface to sink the heat out of the trapped mixture keeping it cool enough and lower the local pressure as a result to where the explosion of detonation is less likely to occur.
Since modern unleaded pump gasoline pump fuels cannot be doped with unlimited amounts of lead to push resistance to keeping the end burn from self-igniting, there has been a significant return to the Ricardo chamber to mechanically extend the octane of available fuel. Engines of the late 1950's through 1970 exhibit small and often sloppy degrees of squish quench as you the consumer could just buy more octane, if it pinged on 100, you bought 110. Today this option doesn't exist at least on the street, so we have to do a better job of design and manufacture which you see stating to happen in the mid 1980's as the manufacturers turn from add on gadgets to a systems integration approach to design to solve the problems of emissions, improved mileage, and increased power.
I'll offer a picture of a graph that is the output of the same engine in back to back dyno runs with the only change being an 18cc circular dish piston for an 18cc D dish piston. This because of the difference in dish shapes changes the amount of surface area in close proximity during squish and quench. The D dish has more activity than the circular dish. The big effect is to fatten the torque and power curves from midrange up to equality around the peak RPMs and the D dish carries its power fatter and longer into the rev range over the point of peak horsepower.
Bear with my I'm having quite a time getting old data into something that can be trasfered into here using this new Windows update.
|11-26-2012 07:42 AM|
|cobalt327||He was already a ~22 year veteran in '92- when the design began according to several sources. So he'd have been in his mid-40s. He was still at GM in 2011, w/more responsibilities. I bet if you asked him he's say he's picked up a few things since the beginning of the LS engine.|
|11-26-2012 07:32 AM|
|11-26-2012 06:47 AM|
What do you base that little blurb on???
Sam Winegarden was the head of the LS project- he's in his mid to late 50s. Tom Stevens wa said to be the "driving force" behind the entire project. He's like 63 now.
|11-25-2012 11:17 PM|
if g.m. did as you say, we'd not have the ls family.
we'd have the northstar p.o.s.
same with the engine program for nascar..
same at ford..
|11-25-2012 10:28 PM|
|11-25-2012 08:51 PM|
|11-25-2012 08:36 PM|
THE JERK WITH THE MOST MONEY will come out ahead.
|11-25-2012 08:27 PM|
|Custom10||comparing apples to oranges,,, its not about total performance or hp per liter, my point is that the one with more experience is gonna come out ahead everyday in his or her class, could be lawn mower racing.|
|11-25-2012 08:18 PM|
And that's exactly why in many cases the younger guys who grew up with DOHC, EFI, and turbos have the edge.
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