Posted by T.O.O. on June 21, 1998 at 12:05:53:
In Reply to: What is "quench"? What is a "quench area" Why is it good? n/m posted by body on June 21, 1998 at 10:09:42:
Quench, or squish area is typically the flat area on the top of the
piston that's almost level with the top of the block deck. It must have
a corresponding flat area on the deck surface of the head to qualify as
If you look at a combustion chamber, you will usually see these flat areas, and they will have the volume of the actual combustion chamber between them. When the piston is compressing the mixture, as the piston nears the head, the flat areas on the head and piston come together and force the mixture from those areas to "squish" into the chamber, where the spark plug and burning mixture reside, so you achieve a more complete burn.
The quench area also runs cooler than the rest of the chamber / piston. These lower temperatures are where the "quench" comes from.
When properly designed, the quench areas can have a tremendous effect on the quality of combustion, and allow higher compression ratios, and due to this they are considered "artificial octane" by scientific types.
Bottom line is "properly designed, quench is good".
ps. As it is like (more octane), and promotes a better burn, why do the turbo people do away with it?? Go figure.
Posted by alloy_625 on June 21, 1998 at 20:32:27:
T.O.O., thanks much for the piston ring pack info. It does bring up another question though which is perhaps very basic.
Given that we wish to mirror the quench pads as closely as possible (although valve reliefs seem to be a problem), conventional wisdom seems to state that detonation will be a real problem. Many books have a graph of compression ratio and/or boost vs. octane. Are these typically obtained through qualitative experiments, or is there a formula predicting this behavior. If the former, is the difference in practical results due to the greater efficiency with which "you" can disperse the fuel in the mixture for a complete and homogenous burn? If the latter, what assumptions are being made about the mixture; it seems hard to believe that a model exists that universally describes the non-uniform mixture present in the "average" combustion chamber and when a hot spot will cause detonation.
Regardless, it seems that unless one has access to your "soft head" technology, low compression ratio is a must for high boost applications which means we the backyard enthusiast must stick to conventional 8.5:1 or so ratios. If that is indeed the case, will preserving the mirrored quench pads on the piston and going deeper with the dish in the "center" still give us the "free" octane we need?
Thanks for your time
Posted by T.O.O. on June 21, 1998 at 22:03:43:
In Reply to: T.O.O. Detonate my Quech Please posted by body on June 21, 1998 at 20:32:27:
The tables that are available are valid because the tests were deemed
valid. We've constructed VCR engines for the Livermore Labs, Sandia, and
the Ethyl Corp. and they all work the same way. While the engine is under
test load, the cylinder with the head attached is mechanically moved closer
and closer to the piston, and when the volume is small enough you'll get
detonation. Now, it's reasonably common knowledge that for "some reason"
some engines can run more compression than others, with the same octane
All we've done is research all the various attempts from all over the world, and we've used things that looked promising from this and that, and combined with a great deal of stubborn dedication we succeeded in integrating many of these ideas into a mix that works remarkably well. I didn't start all this to prove thermal laws wrong, I simply saw some things that didn't work for certain applications, and looked close enough to see that certain things did work, and if I could make some of this work on racing engines, perhaps we could eliminate some detonation and for road racing, Indy, aircraft (the Voyager), and NASCAR, a small mileage improvement could be the difference between a pit stop and winning, or landing the airplane in the ocean. Had anyone told me that we'd be doing what we're currently doing 20 years ago, I'd have said the same thing that people have been saying about me for a very long time , "bullshit, he's crazy", I also have a lot of customers that are crazy now too.
On the subject of crazy, at the end of the VCR program with Livermore, I sent them another single cylinder VCR engine with something other than a generic chamber and piston configuration. I called them a couple of weeks later to see if they'd tested it. The answer was yes, and they'd lowered the cylinder enough for piston / chamber contact (maximum quench!) and could not induce detonation regardless of octane (within reason). They were now in the process of digitizing the shapes so they could allow their Cray computer tell them why.
So the best I can say is that someday, the stuff we're doing will be main stream, and everything will be done this way because it's safe, until then, experimentation can be very expensive, and the IRS doesn't allow you to deduct costs of "development", that's all your's out of profit.
The NASCAR community was rocked with the rest of the automotive world back in '85, when word was out regarding our 16 - 17 -1 CR's. It scarred them to death, but now NASCAR has a 12-1 cap on CR because people were all running 17 -19 - 1 CR's and they had too much power. It all just takes time.
I was pulverized by everyone regarding swirl inlet ports and combustion, but 15 years later and it's hard to find an OE or aftermarket head that doesn't use "swirl technology" and this is from people who said I was crazy a few years back. I think Smokey is about the only one who just sat down and watched, and he enjoyed it because it was nice to see someone else being dumped on for a change.