Quench grooves

[Nashco]

OK, INERTIA.

Oh, an INERTIAL dyno.

-meant
-can't
-inertia
-mercury
-throttle
-improvement
-noticeable
-toward
-carburetor
-inboard
-though
-measured
-later
etc...

It's hard to consider somebody competent enough to do advanced design and testing work and to get valid A-B comparisons if they don't even bother paying attention to spelling and grammar. Perhaps English isn't your first language, in which case you're doing pretty darn good and I take it all back. Tinkering in your shop is all well and good, but I'm still not giving this any credit on a modern engine until there is some clear A-B proof on a dyno.

Bryce

[Mach10]

Where I was going with that is to say that the squish velocity is less under say 15" of vacuum as compared to an engine at full throttle and maximum VE. The quench groove is then what a reflective cone is to a flash light, It focuses the velocity directly tward the plug.

I don't buy it. Why would a grooved chamber be better at moving (disturbing) air at lower pressures than higher?

So what your saying is that it does that anyway and I'm saying it does it much better and even while under a high vacuum condition to the point that it runs noticably better now, even with a big cam, and I have a strong steady idle even at only 500rpms.

I'm not suggesting the effect isn't real--I'm saying that the explanation is completely lacking.

And if you can't explain WHY it works, you can't realistically adapt it to other applications with any certainty that it will work.

In any case, a rough idle with a large cam isn't from inefficient combustion chamber shape, it's from the cylinder being unable to efficiently draw a large enough charge and/or expell enough exhaust gas due to valve overlap.

I'm sorry, but I just don't buy it. :salute:

[bigblockfiero]

OK, INERTIA.

Oh, an INERTIAL dyno.

-meant
-can't
-inertia
-mercury
-throttle
-improvement
-noticeable
-toward
-carburetor
-inboard
-though
-measured
-later
etc...

It's hard to consider somebody competent enough to do advanced design and testing work and to get valid A-B comparisons if they don't even bother paying attention to spelling and grammar. Perhaps English isn't your first language, in which case you're doing pretty darn good and I take it all back. Tinkering in your shop is all well and good, but I'm still not giving this any credit on a modern engine until there is some clear A-B proof on a dyno.

Bryce

Marginalized by speling and gramer? Catch words like tinkuring?

I have a-b back to back dyno comparisons.

Can you describe or come up with something mechanical and more concrete to base your opinion on?

[bigblockfiero]

Where I was going with that is to say that the squish velocity is less under say 15" of vacuum as compared to an engine at full throttle and maximum VE. The quench groove is then what a reflective cone is to a flash light, It focuses the velocity directly tward the plug.

I don't buy it. Why would a grooved chamber be better at moving (disturbing) air at lower pressures than higher?

These are two seperate points that I was making but I put them in the same paragraph to speed things along and because I thought you were not having trouble following this. Just a barrage of different information.

Point # 1.
Where I was going with that is to say that the squish velocity is less under say 15" of vacuum as compared to an engine at full throttle and maximum VE.

point # 2.
The quench groove is then what a reflective cone is to a flash light, It focuses the velocity directly tward the plug.

In point # 2 my improper use of the word THEN I now realize, kind of grouped these two together. We do this all the time in my native isle of man, Its kind of fucked up but we know what each other mean and where a little bit telepathic.

[Mach10]

These are two seperate points that I was making but I put them in the same paragraph to speed things along and because I thought you were not having trouble following this. Just a barrage of different information.

I'm pretty sure I follow what you're saying--but if there's misinformation due to wording or whatever, I won't hold it against you.

I'm no engineer, so if any of my assumptions are false, then please, feel free to educate me.

Point # 1.
Where I was going with that is to say that the squish velocity is less under say 15" of vacuum as compared to an engine at full throttle and maximum VE.

Why would that be? Lower density air has less mass, and takes proportionally less energy to accelerate; at the temperatures and pressures we're talking, the air/fuel mixture isn't what you'd call a viscous fluid. It's going to travel in relatively straight lines in direct response to the motion of the piston. It's going to move towards the lower pressure spots, with the quench area representing a high-pressure point, and the combustion chamber being the lower pressure point.

The VE of the engine, throttle position... None of these things matter because they only dictate the mass of the aircharge that's in the cylinder when the intake valve closes and the piston is moving upwards.

point # 2.
The quench groove is then what a reflective cone is to a flash light, It focuses the velocity directly tward the plug.

In point # 2 my improper use of the word THEN I now realize, kind of grouped these two together. We do this all the time in my native isle of man, Its kind of fucked up but we know what each other mean and where a little bit telepathic.

I spent 2 years in a british middle-school. I'm comfortable with both north american and english grammar styles. Don't worry about it.

I disagree with the analogy, and with the explanation; if anything, the word you're looking for is "venturi" because you're talking about accelerating a fluid. But the groove won't work as a venturi; you aren't placing a restriction that would cause the air moving through it to speed up relative to the motion of the rest of the air.

At the very, VERY best, you could make the argument that it changes the direction of the flow.

Personally, I suspect that an earlier poster is right; that you could get the same (if not better) effect by dimpling the quench area like a golfball to improve laminar flow out of the quench area.

[bigblockfiero]

Mach 10 wrote
"I disagree with the analogy, and with the explanation; if anything, the word you're looking for is "venturi" because you're talking about accelerating a fluid. But the groove won't work as a venturi; you aren't placing a restriction that would cause the air moving through it to speed up relative to the motion of the rest of the air."

Actually I would compare this to a venturi. The grooving method that I favor is just one groove aimed at the plug.

Try and visualize a 1" long groove but that the first 3/4" (farthest from the plug) is surrounded by a slight spoon shaped dish that captures extra volume and then dirrects it thru the final 1/4" of groove that is not surrounded by a dish. That 1/4" Could be compared to a venturi.

Does this make sense now? Every time I try and retell this story I discover how unclear my description really is and this venturi comparison will help me in the future. :thumbleft:

[bigblockfiero]

The squish velocity comparison at different vacuum levels could instead be compared at different air density altitudes.

So would it be your belief that the squish velocity would be greater at sea level then it would at a high altitude?

Dynamic and cranking compression is higher at sea level.

[p8ntman442]

I dont buy it.

Every point in the chamber is at the exact same pressure, during the compression stroke and before the combustion process. Therefore, a high volume of air at one end of a groove has no force to speed it up through the groove and to the plug.

Please explain where I am wrong with your setup? I'm not a disbeliever of the grooves, But I dont buy that reasoning.

[bigblockfiero]

Can I assume that we all agree that there is a such thing as squish and also squish velocity expelled from a quench area? This stuff is very old and pioneered by sir harry R ricardo. This is detailed with explination and pictures in his book the high speed internal combustion engine.

Or are you saying that you believe that the velocity is the same (or even less) coming from a groove as it is from any part of the quench area?

I believe that this is kind of true but not if you steal volume from other parts of the squish area with a slightly dished out 3/4" diameter tear drop shaped area, it funnels mixture into the groove and this groove then becomes an orfice when the piston is at TDC and so this becomes a high volume/velocity groove. Also the dish extends to the cylinder wall and top ring clearance volume that then becomes a groove feeder port wile the piston rocks over TDC and in doing so causes further quench volume displacement. The mixture cant overcome its INERTIA quick enough to flow out and around the top ring clearance volume so it serves better as a groove volume feeder port.

[p8ntman442]

Can I assume that we all agree that there is a such thing as squish and also squish velocity expelled from a quench area?

I think that is where I lost you. Please explain, and is this a fact, or theory?

[Mach10]

I believe in squish velocity. The pressure will be different in various parts of the combustion chamber because the volume changes for things like plugs, valves etc.

What I don't believe is that air will willingly make a break from the path of least resistance, pick up velocity and change directions without something pushing against it, FORCING it through the venturi. There is nothing holding a mass of air in the quench area, so you can't make the claim that the groove forms an aperture; if anything, you'd be lowering the velocity, because you are opening the area up.

As far as I see it, the very best you could hope for is a bit of tumbling right at the groove--which doesn't explain the gains.

So would it be your belief that the squish velocity would be greater at sea level then it would at a high altitude?

Ambient pressure is irrelevant; as far as I understand it, at all the pressures an engine works at, air behaves fairly consistantly.

At lower pressures, it has less density, and therefore requires less energy to move (which is what I think you're getting at). HOWEVER, along with this reduction in inertia (right word to use in fluidics?) comes an EQUAL loss in mass and energy from the air being forced up by the piston.

So no, my belief is that the velocity in the cylinders (with all other variables except pressure being equl) is more-or-less the same regardless of pressure. The piston's velocity at 3500rpm is the same regardless of throttle position.

[The Dark Side of Will]

Maybe this will help visualize it...

Imagine a hypothetical cylinder with a flat top piston and a wedge combustion chamber with a lot of quench area. Say the stroke is 3", chamber is .5" deep and quench clearance is .040.

With the piston at the bottom of the stroke, the distance from the piston to the quench pad is 3.040. The distance from the piston to the deepest point of the chamber is 3.540. As the piston comes up to TDC, the volume under the quench pad gets compressed from 3.040 to .040 (76:1), while the volume under the deepest point of the chamber gets compressed from 3.540 to .540 (6.5:1). With the different compression ratios and radically different pressures, air will definitely be expelled from the quench space into the chamber.

What BBF is talking about is taking advantage of that differential pressure to make sure that well mixed mixture is flowed directly to the spark plug at low manifold pressures. With low manifold pressures, EGR, reversion, the flow segregation BBF mentioned, etc, there could be lots of reasons that the mixture is a bit rarefied around the plug.

The effect isn't discernible at high manifold pressures because there's ALREADY lots of good mixture around the plug under those conditions.

[Mach10]

I get that part...

What he won't answer is how the air being expelled from under this quench pad is being convinced to take the path of greater resistance and pick up enough speed relative to the rest of the air under the quench pad to force the rest of it to change direction and flow directly at the plug.

[whipped]

I was doing some reading on ultra tight squish and FWIW some race team was running into issues with detonation running something like 0.030" quench/squish. I guess the problem was some of the air/fuel mix was getting trapped in that boundary layer between the piston and the head. The solution was to taper the piston face 3 degrees.

Now, my question is what does this groove give you that can't be achieved with a tight squish?

Someone with access to CFD should just run some sims.

[p8ntman442]

Now, my question is what does this groove give you that can't be achieved with a tight squish?

possibly economy, as in tight squich cost big bucks to do correctly, and grooves are free. Possibly the gains (from tight squish) being seen could be achieved in other manners eg groovs.

The squish velocity kind of makes sense, but I understand what mach is saying too.

I think what BBF needs to tell Mach is that the groves provide a greater area for a higher pressure zone to transfer to a lower pressure zone from the squish to the plug. the mixture under the grove and inside will be at the same pressure/velocity but more volume will move through the grove and you can direct that volume.


Am I getting it now? three Pressure zones? squish zone highest, grove zone middle, plug zone lowsest. In rings working out from the center.

[bigblockfiero]

p8ntman442 Quote--- "I think what BBF needs to tell Mach is that the groves provide a greater area for a higher pressure zone to transfer to a lower pressure zone from the squish to the plug. the mixture under the grove and inside will be at the same pressure/velocity but more volume will move through the grove and you can direct that volume."

:thumbleft: I agree with this explination and its very well put..

[Nashco]

OK, INERTIA.

Oh, an INERTIAL dyno.

-meant
-can't
-inertia
-mercury
-throttle
-improvement
-noticeable
-toward
-carburetor
-inboard
-though
-measured
-later
etc...

It's hard to consider somebody competent enough to do advanced design and testing work and to get valid A-B comparisons if they don't even bother paying attention to spelling and grammar. Perhaps English isn't your first language, in which case you're doing pretty darn good and I take it all back. Tinkering in your shop is all well and good, but I'm still not giving this any credit on a modern engine until there is some clear A-B proof on a dyno.

Bryce

Marginalized by speling and gramer? Catch words like tinkuring?

I have a-b back to back dyno comparisons.

Can you describe or come up with something mechanical and more concrete to base your opinion on?

Did you post your dyno comparisons and detail your testing info, test equipment, etc.? So far I haven't seen any direct A-B comparison shown from anybody, including Singh himself, that made any damn sense (including poor grammar and spelling, lack of scientific data, etc.). I'm not the one saying this magic dremelry drastically improves power/efficiency, just like I don't go around saying there is an Easter Bunny. I'm not the one bearing the burden of proof here. If somebody tells me Santa Claus exists and their proof is that they saw him and a bunch of guys they hang out with have seen him, that doesn't make Santa exist to me. They can tell me he exists all day, they can tell me that they had dinner with the guy, but until there's some scientific proof available to the rest of the world it doesn't mean anything to me. If I say Santa doesn't exist, and somebody asks me to explain why he doesn't exist despite lack of any good proof that he does, I'm not going to bother wasting my time.

I've already explained that I don't think a modern engine (with optimized flow/tumble/swirl) will see any benefit. There hasn't been any proof of otherwise, the burden of proof is on those that want the rest of the world to believe. If nobody wants to prove or disprove it, I'm not losing any sleep over the deal.

- spelling
- grammar
- tinkering

Bryce

[Mach10]

I think what BBF needs to tell Mach is that the groves provide a greater area for a higher pressure zone to transfer to a lower pressure zone from the squish to the plug. the mixture under the grove and inside will be at the same pressure/velocity but more volume will move through the grove and you can direct that volume.

And if you increase the area, and volume flow is the same, you reduce the flow velocity.

Adding the grooves will *decrease* the pressure gradient because you are adding to the volume in the quench area... Which implies less potential energy.

[bigblockfiero]

- spelling
- grammar
- tinkering

Bryce

In my native isle of man they know what I mean. My last name kneen is predominate there so I am an isle of manian, uga buga.

I have seen dyno changes with vs. without grooves. I ran these pulls at 1/16th to 1/4 throttle making hardly even 2hp and tapering off as the rpms increased because of the restricted throttle position. Groove advantages were seen but only within certain test range rpms and that varied with throttle position. These pulls where very long and I couldn't print them on one sheet. I may be able to print them on one sheet if I try tinkuring with some computer settings.

To offset the restricted throttle problem and to highlight the groove advantage comparison santa and I tried watching a vacuum gauge wile opening the throttle to keep the vacuum level constant but this single cylinder motor makes the gauge needle bounce quite a bit.

Next I made a pressure reservior bottle with an orifice in the supply line to keep the gauge from bouncing. The results where quite promising but the element of human error is ever present.

Now I'm tinkuring with my second design, diaphragm driven mechanical arm to open the throttle butterfly and keep the vacuum level constant. This will once and for all, remove that element of human error and give test results that are noteworthy and undeniable.

[bigblockfiero]

I think what BBF needs to tell Mach is that the groves provide a greater area for a higher pressure zone to transfer to a lower pressure zone from the squish to the plug. the mixture under the grove and inside will be at the same pressure/velocity but more volume will move through the grove and you can direct that volume.

And if you increase the area, and volume flow is the same, you reduce the flow velocity.

Adding the grooves will *decrease* the pressure gradient because you are adding to the volume in the quench area... Which implies less potential energy.

Which is why you can't make the grooves to big and they need to be fed by top ring clearance volume similar to a water pressure tank in a well system or a boost bottle on a two stroke.

Whipped wrote in his previous post about a race team that was unable to expel the quench clearance volume quick enough which is why two smaller quench areas nearer to the cylinder wall are better then one big one far from the wall and the squish to bore ratio is less in a higher rpm engine. The point being that volume is available in a wedge head having a bigger quench farther from the wall and especially if you enhance the groove shape to encourage that flow. At a higher rpm there is hardly time for a groove to flow against inertia.