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Re: Why wouldn't you want quench in a supercharged motor? [Re: HotRodDave] #2716337
11/16/19 11:21 AM
11/16/19 11:21 AM
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Originally Posted by HotRodDave
Originally Posted by dthemi
The reason I don't look for quench in supercharged engines is because every stupidly high powered one I've seen has none. Enough evidence for me. lol


I bet if they could they would, no reason the laws of physics would be suspended just because it is a higher pressure than 14.7 PSI. I would be willing to be the reason has more to do with other things that make more power than good quench would that prevent quench from being an easily acomplished goal. Things like big valves and compression ratio are just bigger factors than quench, for example... if good quench adds 20 HP but but a bigger valve might be worth 50HP and make it impossible or very hard to get quench witch one are you going to choose?



Did you read what poly wrote right above your post?

Quench is a band aid for issues with the combustion chamber. It isn't voodoo or magic. It CAN help suppress detonation in a crap combo.

And yes, I've tested this enough that it became redundant and a waste of money.

I've run .150 to .030 quench and if everything else was correct, there was zero HP. Timing stayed the same...as in if an engine needed 42 degrees total timing it didn't matter where the quench was it still took the same timing.


Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: Why wouldn't you want quench in a supercharged motor? [Re: dizuster] #2716338
11/16/19 11:24 AM
11/16/19 11:24 AM
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Originally Posted by dizuster
Lets back up a second... and answer what the purpose of quench actually is...

Think of the fuel mixture as a series of fireworks, all connected by lines fuses. You light the fuse at one end and it slowly moves towards the first firework. Once it reaches the firework, it rapidly goes off. The fuse continues slowly to the next firework, and it goes off... on and on. When the burn is moving through the fuse, it moves slowly, but once it gets to the firework you have an enormous release in energy. Then it goes back to moving slow on the fuse again. This is an analogy of what's going on with fuel mixture. As you have lean spots from the mixture not being evenly distributed, the burn slows down as it moves across the chamber through the lean areas with no fuel (like the fuse). Once it gets to the pocket of fuel molecules again, it rapidly releases energy (like a firework).

Now this isn't exactly how it works, because we are talking about VERY high speed, and chemical reactions to create the heat release in chamber. But gives you an idea.

So you can see how pushing all of the fuel molecules together (essentially shortening the fuse length between each firework), would have a benefit to burn it all as quickly as possible. This is essentially what quench is doing.

As the piston gets to TDC, in the area of quench you get a localized "squeeze". The air/fuel mixture is then essentially "squirted" (for lack of a better term), towards the spark plug side of the chamber where the burn has started. This helps not only create turbulence and mix the fuel up for better even distribution, but also gets the molecules closer together to speed up the burn as described above. Faster burn means lower timing numbers. Remember any pressure created in chamber at TDC doesn't actaully rotate the crank, When the crank is at zero degree's, and the rod is straight in the cylinder... all it does is try to push the crank out the bottom of the block!!!

So why is quench less meaningful in a boosted engine then? If you think about it... the turbo/blower has already "packed" the molecules closer together to start with. This means there is less space for these "lean" pockets to hide like there would be on an N/A motor. The "fuse" length is essentially shorter between fuel molecules on the boosted motor, because the molecules of fuel are pushed closer together.

This is the primary reason why boosted motors run less timing. The burn speed in chamber is much faster, because everything is packed closer together. As boost goes up, timing comes out... its just a function of packing the fuel tighter together in chamber from shoving more air and fuel into the chamber.


So it's not that boosted motors don't "need" quench, it's just that effectively the boost pressure is already doing the same thing as the quench would.

Now I'm sure on some very high HP stuff with mega boost, we could debate if quench is detrimental to those motors... but for most of us living in normal HP land... it really doesn't matter.

Put the flat top in it that gets the compression right, and let it rip.

For reference... my boosted motor has the piston .050" in the hole with a .040" gasket... so doesn't have really any quench. It's been ran at 23psi non-intercooled on E85 with ~22 deg of timing. I am very confident it's not detonating, because if it were... the cast 360 crank would have been in many pieces years ago.


If this is true, why does the combustion chamber with the WORST quench only need 30-32 degrees total timing? Again, quench is a fix, not a need if everything else is correct.




Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
Re: Why wouldn't you want quench in a supercharged motor? [Re: madscientist] #2716398
11/16/19 02:05 PM
11/16/19 02:05 PM
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Originally Posted by madscientist
Originally Posted by HotRodDave
Originally Posted by dthemi
The reason I don't look for quench in supercharged engines is because every stupidly high powered one I've seen has none. Enough evidence for me. lol


I bet if they could they would, no reason the laws of physics would be suspended just because it is a higher pressure than 14.7 PSI. I would be willing to be the reason has more to do with other things that make more power than good quench would that prevent quench from being an easily acomplished goal. Things like big valves and compression ratio are just bigger factors than quench, for example... if good quench adds 20 HP but but a bigger valve might be worth 50HP and make it impossible or very hard to get quench witch one are you going to choose?



Did you read what poly wrote right above your post?

Quench is a band aid for issues with the combustion chamber. It isn't voodoo or magic. It CAN help suppress detonation in a crap combo.

And yes, I've tested this enough that it became redundant and a waste of money.

I've run .150 to .030 quench and if everything else was correct, there was zero HP. Timing stayed the same...as in if an engine needed 42 degrees total timing it didn't matter where the quench was it still took the same timing.



To use the term “band aid” in this, and so many other discussions usually shows a poor understanding of the ultimate goal.
Why would you not want to take advantage of every power stabilizing procedure you can when you are literally making the parts for a performance engine? As an example, why would anybody port a head? Is it just a band aid for getting the right head to begin with.
Why get or use a flow bench? Just buy heads that are made as you need them. Why add stroke to an engine? Band aid for buying a bigger engine to begin with... and on and on.

I have seen the effects of quench. My friend makes performance cylinder heads for aircraft engines. He has made more power on less fuel with more durability because of it. Testing/ proving is complex and expensive.He has logs of data on in- cylinder pressures for head to head comparisons.


"use it 'till it breaks, replace as needed"
Re: Why wouldn't you want quench in a supercharged motor? [Re: jbc426] #2716427
11/16/19 03:21 PM
11/16/19 03:21 PM
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New York
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The original purpose of quench, as described in the patent application, is knock suppression. It does this by creating a layer of charge (generally opposite the plug location) thin enough that shock wave-induced ignition (not the expanding kernel from the spark plug) cannot occur: the mixture burns slower than it loses heat to the *matching head and dome surfaces.

It does other things too; squish occurs whenever 2 surfaces (they need not be parallel, flat, or horizontal) approach each other and the charge between them is ejected into the larger chamber volume, regardless of the final separation distance.

BTW: the genesis of using a heat sink* to prevent combustion is even older: the 19th century Sir Humphrey Davies mine safety lamp, in which a wire mesh cage surrounds the illumination flame. Any flammable vapor in the atmosphere catches fire inside the screen, but is extinguished by heat loss to the mesh and cannot blow up the miners.


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Re: Why wouldn't you want quench in a supercharged motor? [Re: Cab_Burge] #2716493
11/16/19 06:13 PM
11/16/19 06:13 PM
Joined: Oct 2004
Posts: 3,033
back in Georgia
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Originally Posted by Cab_Burge
I've been told that the blown alcohol Hemi motors need around 11.5 to 1 or higher mechanical compression to make good power with 30+ Lbs. of boost shruggy work
I'm thinking of finding out on a wedge all aluminum street motor with a Pro Charger with EFI devil luck


Wedge, or hemi blown alky works with 11 to 12:1 static. they'll work with lower static, but most are around 11 or higher. My roots blown hemi is 12:1 static. Piston is .045 down, with a .052 gasket. I run my nitrous motors the same in place of softening the chamber, .09 to .120 away from the head with nothing sharp in the chamber, or on the piston. Once you soften the chamber it's a long road back to a good NA head so a big space between the head and the piston has about the same result.

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