quench vs no quench?

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moturbopar

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Ok Im wondering if 2 hypothetical, almost identical engine are built, compression, cam, head flow, everything but piston and chamber design one quench head one open chamber, or piston down in the bore. say 10 to 1 engine running 100 octane or whatever. I guess the tuning could be different between engines, such as total timing, jetting maybe? Would they make the same hp and torque? What do you guys think?
Thanks
 
if you take detonation out of the question, as if the engine was fed whatever octane to keep it from detonating? would the quench head reqiure less timing, making less negative torque than the open chamber, which may require or like more timing to make peak power?
Thanks
 
quench is merely a way to avoid detonation. allows you to run slightly higher comp ratio.

like rumblefish or someone said, each point of compression gives you a 3% gain. so instead of 300hp you get 309hp. etc

there is no horsepower gain from the quench. most build it in so they dont have problems later
 
The two engines would not be built the same to reap any benefit from the quench effect. If you simply used a head gasket thickness to change the compression ratio, the quench distance would be negatively affected and the bonus goes with it. If an engine is designed, built, and tuned properly for quench, I'd expect it to be able to make a little more power for the same given amount of fuel over a non quench design, all else being similar. Quench makes the burn much more efficient. Capturing that efficiency and making use of it is up to the tuner.
 
if you take detonation out of the question, would the quench head reqiure less timing
Yes
, making less negative torque than the open chamber, which may require or like more timing to make peak power?
Not sure what you mean there.
Timing lead is needed because of the rpm window the engine operates in. An intake charge comprised of air and a given fuel burns at a constant rate assuming a homogeneous combining of the two component parts. That burn produces a pressure spike in the cylinder at a specific moment. By adjusting when that mix is ignited, we can tailer the pressure spike to happen at the period of highest leverage on the crank. As rpms rise, we need to ignite that mix earlier in order to keep that spike at the right place in terms of crank degrees because the crank is moving faster, where the burn is not. In larger open chamber, wide piston to head clearance engines, there is much a greater chance that the mixture will not be homogeneous throughout the space. Large combustion chambers promote waste areas such as around the perimiter of the chamber, down to the top of the top ring, recessed spark plug bosses, etc. The more of the intake charge is wasted, the less power per unit of fuel will be used and turned into power. Quench in and of itself is a cooling process - it's a part of the process that a well designed and exectuted, tight piston-to-head engine will give you. What really makes the power is tuble and swirl. Those, in addition to quenching, are produced by a close piston to head clearance (less than .040"). The mixture stays honogeneous and directly adjacent to the spark plug, so the ignition is instantaneous, the burn is complete, little of the intake charge is wasted, and it all can push the crank hardest at the right moment. All that translates in more power for the same given amount of fuel.
 
if you take detonation out of the question, would the quench head reqiure less timing
Yes
, making less negative torque than the open chamber, which may require or like more timing to make peak power?
Not sure what you mean there.
Timing lead is needed because of the rpm window the engine operates in. An intake charge comprised of air and a given fuel burns at a constant rate assuming a homogeneous combining of the two component parts. That burn produces a pressure spike in the cylinder at a specific moment. By adjusting when that mix is ignited, we can tailer the pressure spike to happen at the period of highest leverage on the crank. As rpms rise, we need to ignite that mix earlier in order to keep that spike at the right place in terms of crank degrees because the crank is moving faster, where the burn is not. In larger open chamber, wide piston to head clearance engines, there is much a greater chance that the mixture will not be homogeneous throughout the space. Large combustion chambers promote waste areas such as around the perimiter of the chamber, down to the top of the top ring, recessed spark plug bosses, etc. The more of the intake charge is wasted, the less power per unit of fuel will be used and turned into power. Quench in and of itself is a cooling process - it's a part of the process that a well designed and exectuted, tight piston-to-head engine will give you. What really makes the power is tuble and swirl. Those, in addition to quenching, are produced by a close piston to head clearance (less than .040"). The mixture stays honogeneous and directly adjacent to the spark plug, so the ignition is instantaneous, the burn is complete, little of the intake charge is wasted, and it all can push the crank hardest at the right moment. All that translates in more power for the same given amount of fuel.

So the more efficient chamber should take less timing, to make peak power or torque.
You want the greatest gas expansion when the piston is at the top of it's travel to use as much of the cranks travel for torque production, as combustion takes a little time it needs to be initiated just prior to the piston being at top dead center, hence the ignition advance.

Too much advance and the gas expansion will try to push the piston down while the crank is pushing it up (negative torque), too little advance or retarding the ignition will push the piston down as the crank is pulling it down which will reduce the force of the gas expansion.
to me it seems that making peak torque at a lower total timing would make more power. Im probably looking at this incorrectly though, just ideas running through my head.:tard:
 
The new hemis are an example. I was astounded to discover that max timing for them is in the low TWENTIES for some

And, remember, that HP and Torque are intimately related. Torque IS HP HP is merely a mathematical computation of torque. Look up 5252
 
Ok Im wondering if 2 hypothetical, almost identical engine are built, compression, cam, head flow, everything but piston and chamber design one quench head one open chamber, or piston down in the bore. say 10 to 1 engine running 100 octane or whatever. I guess the tuning could be different between engines, such as total timing, jetting maybe? Would they make the same hp and torque? What do you guys think?
Thanks

Wouldn't it be great if everyone who answered you knew what they were talking about?
 
Wouldn't it be great if everyone who answered you knew what they were talking about?

You must work for Microsoft. "Even though your answer was technically correct it really wasn't very helpful."
 
The Book to read about quench/squish is "The internal combustion engine" by Harry Ricardo

Hysteric
 
Another benefit of quench is requiring a slightly leaner mixture for max power (more efficient) and being able to run at light loads on much leaner (16:1 plus) mixtures. The fast burn reduces variations in combustion between each cylinder making it not have that "lean surge" and hesitation i'm sure everyone here knows of.
 
Tuble and swirl...please explain!


It's motion imparted on the intake charge both in the port areas and the chamber as the piston is in motion. It's not only produced by the tight piston to head clearance but also is affected by the lower intake tract. It's an extension of what a good port design does... Swirl is mostly produced by the port, valve job, and chamber shape. These cause the mixture to twist as it passes the valve, enhancing flow through the valve and helping ensure complete cylinder filling, plus helping to keep fuel in suspension during the intake and compression strokes. Tumble simplified is the motion imparted to the mixture as the piston moves up the bore during the compression stroke. It gets forced out of the areas between the piston and head and tumbles away from the flats and circumference to the center of the dish. The tighter the quench, the more that happens. the more that happens, the more efficient the burn can be.
BTW - the greatest leverage on the crank is not TDC. It's variable depending on the stroke and rod, but normally around 15° past TDC.
 
The new hemis are an example. I was astounded to discover that max timing for them is in the low TWENTIES for some

And, remember, that HP and Torque are intimately related. Torque IS HP HP is merely a mathematical computation of torque. Look up 5252

Dude, torque is NOT horsepower. When are we going to stop repeating junk like this?

Horsepower is king. Period. Unless you want to run 1 gear.

C'mon guys, stop the myths.
 
Dude, torque is NOT horsepower. When are we going to stop repeating junk like this?

Horsepower is king. Period. Unless you want to run 1 gear.

C'mon guys, stop the myths.

we are waiting for a lesson. lol
 
You must work for Microsoft. "Even though your answer was technically correct it really wasn't very helpful."

Sorta like a lot of yours, mine and everyone else's.
 
Without a good tire nobody's got anything.

Tires is King!!!!!!!!!!!! Lmao
 
tomsdart, thanks for the interesting link!
My "opinion" to the question is that a flat top piston with the proper combustion chamber and quench would produce more torque and horsepower. I "think" it would be easier torque/horsepower than a large chamber head with a dome piston. This is mt thought on the subject with no experience to back it up. The next engine that goes together will probably have flat top pistons with a small cc chamber head(Magnum-style).
 
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