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What exactly is QUENCH and why is it important?
#924058
02/08/11 09:55 PM
02/08/11 09:55 PM
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Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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I have read and talked to guys about the advantages of quench in wedge engines, but its still a little confusing to me.
I am looking at the realization that I'll have to pull the 493 from my Charger, and while the motor is out, I might consider some changes.
As is, the pistons sit .017 in the hole at TDC. I have used the Fel Pro .039 head gasket and have Edelbrock 88cc heads. From what I have read, I would need to be at ZERO deck to get any QUENCH effect, but I am already at 10.8 to one now. another .017 would certainly push me into the 11s and I cant see that helping detonation any. I want the engine to be MORE streetable with the ability to run midgrade if I am on the road and cant get anything better. I heard that once you get more than .040 clearance from the piston to the head at TDC, the effects of quench goes away. I guess I COULD order a set of $750 custom dished pistons, but unless the fine members here want to start an engine rebuild charity fund, I think I'll pass on that.
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Re: What exactly is QUENCH and why is it important?
[Re: Kern Dog]
#924059
02/08/11 10:29 PM
02/08/11 10:29 PM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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YOu don't need a zero deck for a quench engine.
Imagine if you will, a closed chamber head and a flat top piston. If the clearance between them is small enough at TDC you will have quench. Very generally speaking .035-.055" is where you want to be. The tighter you go the greater the possibility you will smack parts together, the looser you go the less quench effect. It take good machining to set this up.
No, why quench? The theory is that a tight quench squishes the air fuel mixture as the piston rises mixing it more thoroughly and lessening the possibility of a lean area in the mix detonating. Another theory is that the closeness of the parts help draw excessive heat out.
Another variant is a double quench setup, with what amounts to a trough shaped piston and combustion chamber, this forces the air/fuel mix into a more compact shape that optimizes combustion speed and rate, lessening the chance of detonation. A perfect sphere is the most compact shape for a given volume, so the closer you can get the air/fuel mix to a sphere the better.
Not sure if any of those theories really explains how it works, but it has been well documented that it can help. Mind you all of the above is a gross generalization.
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
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Re: What exactly is QUENCH and why is it important?
[Re: Kern Dog]
#924066
02/09/11 02:54 AM
02/09/11 02:54 AM
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Joined: Oct 2007
Posts: 3,884
Oregon
hooziewhatsit
master
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master
Joined: Oct 2007
Posts: 3,884
Oregon
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I have a picture in this thread of the quench area. https://board.moparts.org/ubbthreads/show...vc=#Post5175716There's a video on youtube of a hollowed out melon, filled with with gas and lit. Sitting there the flame is gently flickering around. Until the stupid kid hits it with a golf club  Have you run a leakdown test yet?
If you ever find yourself in a fair fight, your tactics suck.
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Re: What exactly is QUENCH and why is it important?
[Re: Kern Dog]
#924067
02/09/11 10:03 AM
02/09/11 10:03 AM
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Joined: Jan 2006
Posts: 8,162
USA
360view
Moparts resident spammer
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Moparts resident spammer
Joined: Jan 2006
Posts: 8,162
USA
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There is a very interesting graph in Taylor & Taylor's big two volume 'bible' of the engine, titled 'Fundamentals of the IC Engine'
that shows General Motors research that Quench works,
especially if half the piston top is a flat,
and if a 4 inch diameter piston comes within 0.026 inches of the flat on the cylinder head.
Quench does two things:
First, as the piston approaches top dead center,
'tsunamis' of air and fuel mixture get shot out toward the center of the cylinder. This speeds up the burn, like when you blow onto a flame.
Second, as the piston begins pulling away from top dead center,
the Quench areas form metal 'caves' where the burning air and fuel get cooled and snuffed out because the nearby metal walls provide 'air conditioning' due to the coolant behind them.
Why would you want to 'snuff out' (quench) the last part of the burning?
The reason is that pure gasoline vapor will not 'detonate'
but if you put the gasoline into a 'chemical factory' and use high temperatures and high pressures to chemically transform the original gasoline into something more like dynamite,
then you can get 'detonation'
which is a fancy word for
'burning faster than the speed of sound'.
This detonation can damage pistons, head gaskets, rings, the edges of valves, etc
In engine geek speek,
these chemicals that can detonate are called
'end gases'
and the key thing to remember is that they are no longer just gasoline, they have been changed by the heat and pressure.
Quench cools the 'end gases' just enough to prevent damaging detonation.
However,
Quench also increases unburned hydrocarbons,
or HC Pollution in engine geek speek,
so modern engines use as little as they can get away with.
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Re: What exactly is QUENCH and why is it important?
[Re: hooziewhatsit]
#924068
02/09/11 10:30 AM
02/09/11 10:30 AM
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Joined: Jan 2003
Posts: 75,005
U.S.S.A.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,005
U.S.S.A.
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Quote:
Have you run a leakdown test yet?
Exactly , Checking compression doesn't tell you much because many people crank multiple times to get the highest reading.
The easiest way to get quench in the above engines short block is to switch to a .021 shim gasket and ditch the 88cc head for a closed chamber head. Yes it will raise your compression but the the net gain will work in your favor , but building it to run on mid grade is a far fetched goal without a piston change also ...
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Re: What exactly is QUENCH and why is it important?
[Re: Kern Dog]
#924069
02/09/11 09:02 PM
02/09/11 09:02 PM
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Joined: Jan 2007
Posts: 7,664
IN
ahy
master
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master
Joined: Jan 2007
Posts: 7,664
IN
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Quote:
Cute.
The engine actually ran great with the above combination until it started smoking and burning oil. I'm sure that the combo had nothing to do with it.
My motor has been an enigma. It has great oil pressure and consistant cranking compression numbers but smokes under throttle and on slowdown. The intake sits squarely to the heads and I have tried different valley pans, gaskets, PCV arrangements, valve stem seals, blah blah. I suppose that it is possible that I can have damaged rings but still show decent comp #s, but it seems to run counter to what I have experienced. A teardown may be the only way to know for sure.
It will be nice to have this problem fixed so I can feel comfortable driving the car again.
I had a problem similar to yours. My engine was dead rich at first fire but I kept it running for 20 min to get a good cam break in. After that I got the mixture dialed in and it ran fine but started using oil. On teardown, the rings were completly shot. The fuel wash had apparantly wiped out the lube oil film. The edges of the rings were sharp enough to shave with. Expensive lesson... even though the cam breakin was sucessful.
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Re: What exactly is QUENCH and why is it important?
[Re: hooziewhatsit]
#924070
02/09/11 09:45 PM
02/09/11 09:45 PM
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Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog
OP
Striving for excellence
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OP
Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Quote:
Have you run a leakdown test yet?
I have asked around but I dont know where to get one. Maybe I'll check with NAPA or Car Quest stores. I have never used one of these.
***MISTAKE*** I wrote that I have 88cc Eddy heads, They are actually the 84cc heads, and they ARE closed chamber.
Ahy mentioned that he broke in an engine with an over rich carb and he wasted the rings. He said that the edges were sharp. This is interesting. My conventional wisdom leads me to think that damaged rings would be rounded off. This is what I need... good advice from guys who have been there. In the event that I DO pull the motor to dissect, Besides the rings, is it common to have bad valve guides that suck oil but still allow high compression #s? Last year when replacing the valve stem seals I noticed some valve stem wear, so I pulled the heads to take to the machine shop. 7 Intake valves had stem wear and one exhaust valve as well. I mentioned this to some car guys that wondered how the stainless valves got worn without damaging the softer bronze valve guides that the Edelbrocks have. That issue has had me wonder as well.
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Re: What exactly is QUENCH and why is it important?
[Re: Kern Dog]
#924071
02/09/11 11:15 PM
02/09/11 11:15 PM
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Joined: Jul 2003
Posts: 6,167
Maryland
GO_Fish
master
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master
Joined: Jul 2003
Posts: 6,167
Maryland
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On the compression test, the "high water" (compression) mark is set with both intake and exhaust valves closed. The valve guides are not inside the combustion chamber, so they are out of the picture during this test (unless they are so far shot that the valve is wobbling and wedged slightly and not seating completely, unlikely, IMO)
Scott B.
"I'm a self-made man... I started with nothing, and I still have most of it!"
68 360 rusty B'cuda 'vert (GO Fish)13.59@ 98.72 mph
69 340 GTS stock 14.18@ 95.60 mph
01 5.9L Ram 1500 Quad Cab 4x4
01 3.5L 300M 16.23@ 86.97 mph
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Re: What exactly is QUENCH and why is it important?
[Re: Kern Dog]
#924073
02/10/11 06:48 PM
02/10/11 06:48 PM
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Joined: Dec 2006
Posts: 3,533
Indiana
Fury Fan
master
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master
Joined: Dec 2006
Posts: 3,533
Indiana
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Quote:
Besides the rings, is it common to have bad valve guides that suck oil but still allow high compression #s? Last year when replacing the valve stem seals I noticed some valve stem wear, so I pulled the heads to take to the machine shop. 7 Intake valves had stem wear and one exhaust valve as well.
You mentioned earlier that you had smoking on decel. Vacuum created during closed-throttle decel could pull oil in thru worn valve stems/guides.
I've often wondered about rich-mixture/new rings/cam break-in too. Here's an interesting article on pistonring break-in. Probably some folks will refute it, but I think most of us could agree there is some valid info in there, and good food for thought.
http://www.ntnoa.org/enginebreakin.htm
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Re: What exactly is QUENCH and why is it important?
[Re: Fury Fan]
#924074
02/10/11 07:05 PM
02/10/11 07:05 PM
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Joined: Feb 2003
Posts: 12,675
Columbia, CT
moper
I Live Here
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I Live Here
Joined: Feb 2003
Posts: 12,675
Columbia, CT
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With oil use issues you can have several things.. The piston to wall could have been too wide, the bore finish could have been too rough, the rings could have been damaged during assembly... Compression isn't a great test if it's oil use. Oil in the chambers helps compression be artificially high. The leakdown will tell more. Also, the 2nd ring is the oil scraper ring. Not the top (only) compression ring. I would be measuring the parts very carefully and look for anything that might indicate or enourage more piston to wall clearance.
Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
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Re: What exactly is QUENCH and why is it important?
[Re: Supercuda]
#924075
02/10/11 07:15 PM
02/10/11 07:15 PM
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Joined: Nov 2009
Posts: 2,275
Desert Tracker
HYPER8oSoNic
top fuel
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top fuel
Joined: Nov 2009
Posts: 2,275
Desert Tracker
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Quote:
YOu don't need a zero deck for a quench engine.
Imagine if you will, a closed chamber head and a flat top piston. If the clearance between them is small enough at TDC you will have quench. Very generally speaking .035-.055" is where you want to be. The tighter you go the greater the possibility you will smack parts together, the looser you go the less quench effect. It take good machining to set this up.
No, why quench? The theory is that a tight quench squishes the air fuel mixture as the piston rises mixing it more thoroughly and lessening the possibility of a lean area in the mix detonating. Another theory is that the closeness of the parts help draw excessive heat out.
Another variant is a double quench setup, with what amounts to a trough shaped piston and combustion chamber, this forces the air/fuel mix into a more compact shape that optimizes combustion speed and rate, lessening the chance of detonation. A perfect sphere is the most compact shape for a given volume, so the closer you can get the air/fuel mix to a sphere the better.
Not sure if any of those theories really explains how it works, but it has been well documented that it can help. Mind you all of the above is a gross generalization.
SuperCuda, super answer!! 
Strong theories!
"Stupidity is Ignorance on Steroids"
"Yeah, it's hopped to over 160" (quote by Kowalski in the movie Vanishing Point 1970 - Cupid Productions)
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Re: What exactly is QUENCH and why is it important?
[Re: 360view]
#924076
02/10/11 11:00 PM
02/10/11 11:00 PM
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Joined: Dec 2003
Posts: 22,696
Bitopia
jcc
If you can't dazzle em with diamonds..
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If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,696
Bitopia
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Quote:
First, as the piston approaches top dead center, tsunamis' of air and fuel mixture get shot out toward the center of the cylinder. This speeds up the burn, like when you blow onto a flame.
2 things, I would be very curious to know what the velocity is of the quenched mixture say in a typical wedge motor at say 7,000rpm, and does the quench effect/benefit apply across all rpm's, or is it rpm range specific? 
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
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Re: What exactly is QUENCH and why is it important?
[Re: jcc]
#924077
02/11/11 09:25 AM
02/11/11 09:25 AM
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Joined: Jan 2006
Posts: 8,162
USA
360view
Moparts resident spammer
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Moparts resident spammer
Joined: Jan 2006
Posts: 8,162
USA
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There have been studies of the velocities of quench ... and also of 'Swirl' and 'Tumble' air movements. Over at the Speedtalk.com forum Jesse Lackman, who is a member here http://www.revsearch.com/got into some interesting discussions that began with the idea of grooves cut into the flats of quench surfaces to create jet like mixture motion (Jesse actually did a dyno test on a 360 V8) and ended up with someone posting a paper where the total mixture motion from Quench, Swirl, and Tumble was combined and compared over RPM ranges. {can't find the title or author of the paper or book on this computer} At low RPM the paper predicted that increased mixture motion would improve Torque, but that you could have "Too Much of a Good Thing" and that too much mixture motion could hurt performance at the highest RPM. This confirmed what Jesse found with the grooves: they slightly helped ( 6 ft-lbs of Torque) at lower RPM but showed no benefit at higher RPM ... where increased mixture motion from higher Quench and Swirl were probably already in the adequate range of. {My foggy memory seems to be that 15 meters per second forms an upper limit to adequate combustion} Both Ford and Toyota have had recent production engines that had adjustable 'Tumble Valves' in the intake ports that could increase mixture motion at lower RPMS, but be turned for less motion as the RPM and throttle opening increased. There seems to be a trend that 'tumble' is preferred over swirl or quench, perhaps because too high a swirl can throw fuel droplets against the cylinder walls, and as stated in the post above, quench flat 'caves' can result in some fuel touching a cool metal wall not being burned, or being burned late. It takes some horsepower to create Quench, Swirl, or Tumble and these can also reduce total airflow into the cylinder, so at some point the benefits 'top out' compared to the costs.
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