what do you guys think of this? Part II

General engine tech -- Drag Racing to Circle Track

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automotive breath
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what do you guys think of this? Part II

Post by automotive breath » Mon Jun 19, 2006 8:44 pm

Ed-vancedEngines wrote:I am not knocking your idea and concept of the Groove in the Quench Pad. I am rather intrigued with it. I am wondering if you have tried any variations of that groove. I look and I think and I wonder. I can easily think of several possible variations of your groove and am wondering if you have tried any of them or any other variation of the design you are showing the picture of.
Ed
It’s strange that you would ask about groove variations, I have three sets of heads in the shop for grooves; two sets will be getting a multi groove design.

The first set of heads I did was with a single groove, I stuck with that initial layout until I fully understood what was happening inside of the modified engines. Recently have I decided to veer from the initial layout.

I’m doing a set tonight; the picture is the three groove layout I will be using. The heads are Edelbrock Performer RPM,s with 64cc chambers. The engine is a street strip flat top 383. Most of the final details for the engine haven’t been decided. The goal is 10’s on pump gas in a stock body 72 Nova.

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Post by automotive breath » Tue Jun 20, 2006 4:29 pm

I was able to get all of the grooves cut in the RPM heads, will finish them up tonight.

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Here's a shot of a set I'm finishing up for a 383 street LT1.

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The camara died before I got a good picture of the Brodix heads I'm working, will try again later.

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Post by SWR » Tue Jun 20, 2006 4:39 pm

Are you using several grooves to make the swirl close to the exhaust valve the strongest? To "concentrate" the swirl around the exhaust like Mr Widmer is doing with the new line of pistons he has...?
-Bjørn

"Impossible? Nah...just needs more development time"

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Post by automotive breath » Tue Jun 20, 2006 4:56 pm

SWR wrote:Are you using several grooves to make the swirl close to the exhaust valve the strongest? To "concentrate" the swirl around the exhaust like Mr Widmer is doing with the new line of pistons he has...?
The flame kernel develops first in the hottest area of the combustion chamber. I believe the grooves will accelerate early flame kernel development creating flame flow instability, thus enhancing the transition to turbulence.

I have never tried this so this is just me thinking at this point.


Where can I find pictures of Widmers pistons?

Ed-vancedEngines

Post by Ed-vancedEngines » Tue Jun 20, 2006 5:19 pm

In my uneducated igorance, here is what I am seeing.

It is as if the grove depth is serving as a jet or spray nozzle when the piston is at full TDC. Maybe a little over simplifying it but kinda like a spray jet in a power washer that is squiching the yet unburned mixture with oxygen in a directed path instead of it just squishing to anywhere in the chamber.

I am wondering if you have tried any sort of a radius at the top of the groove? I is in my feebale opinion and very interesting idea of concentrating that last split second charge of fuel/air mixture to where the burn is slowing. Kind of like shooting gasoline with a bellows into a dying fire, so to speak.

I apologise that I not anyone else responded to your pics but I am seriously watching what you are doing and am saving the pics.

I will probably be trying this concept on an engine to be build for economy purposes in the next few months.

Yhx,
Ed

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Post by automotive breath » Tue Jun 20, 2006 5:38 pm

Ed-vancedEngines wrote:...I am wondering if you have tried any sort of a radius at the top of the groove?
I haven’t tried a radius, I was so impressed with the first set of heads that I did I just stuck with what works. Only recently have I been tempted to try something different. First I make sure I know where the water is then I cut the groove as deep I can at the entrance into the combustion chamber cavity to direct squish flow up to the roof of the chamber.

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Post by SWR » Tue Jun 20, 2006 5:38 pm

automotive breath wrote:Where can I find pictures of Widmers pistons?
I saw a few pics at his website...guess they're still there. :)
-Bjørn

"Impossible? Nah...just needs more development time"

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Post by SWR » Tue Jun 20, 2006 5:44 pm

Ed-vancedEngines wrote:I am wondering if you have tried any sort of a radius at the top of the groove?
Ed,do you mean a radius between the "groove wall" and the head gasket surface..? I've done that...didn't like the sharp corner that just cutting the groove (angle grinder...brutal :lol: ) produced.
-Bjørn

"Impossible? Nah...just needs more development time"

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Post by Ron E » Wed Jun 21, 2006 8:58 am

OK, the mixture is squished toward the open chamber in typical chambers. you said you make the grooves as deep as possible. I'd guess that means you get as much volume as possible in the grooves. Do you feel that the mixture in the grooves is forced into the open chamber later,(beginning near the end of the normal squish) actually extending the turbulence "phase" of the cycle?

Do you possibly have any chambers showing how the burn-patterns have changed? Also, with the famaliar wash around the bore in typical 23° heads, are you purposely extending the grooves into this area?, or is more a function of groove volume?

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Post by automotive breath » Wed Jun 21, 2006 10:05 am

Ron E wrote:OK, the mixture is squished toward the open chamber in typical chambers. you said you make the grooves as deep as possible. I'd guess that means you get as much volume as possible in the grooves. Do you feel that the mixture in the grooves is forced into the open chamber later,(beginning near the end of the normal squish) actually extending the turbulence "phase" of the cycle?

Do you possibly have any chambers showing how the burn-patterns have changed? Also, with the famaliar wash around the bore in typical 23° heads, are you purposely extending the grooves into this area?, or is more a function of groove volume?
I believe the flow in the grooves begins when normal squish flow begins and the grooves extend the squish action during the combustion phase as the piston approaches TDC.

The primary purpose of traditional squish design is to convert kinetic energy in the form of flow into turbulent energy. As the piston reaches top dead center of the compression stroke the air/fuel mixture located between the piston and the head is squished out and flows into the combustion chamber cavity, to some extent the energy is converted to turbulent flow.

With triditional squish designs, this conversion is much more effective at high RPM when the velocity of the piston is highest, that’s why we don’t advance the ignition timing as the engine RPM goes up. Without turbulence in the combustion chamber we would burn the mixture at the laminar burning rate which is ten to twenty times slower than the turbulent rate. This would make engines that rev higher than about 1500rpm nonexistence.

The grooves make up for the inadequacy of squish at lower engine speeds. With the grooves more of the energy of piston movement is converted to turbulence. In addition the altered squish flow follows the combustion chamber roof; I believe this is why engines with dome pistons respond to the modification so well.

These pictures are from a grooved high compression 355 bracket engine;
one year run time.

Image

Image

Ed-vancedEngines

Post by Ed-vancedEngines » Wed Jun 21, 2006 10:38 am

Man!
That is a great looking burn and it quenches right at the edge too. I do love the looks of that one.
Ed

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Post by Ron E » Wed Jun 21, 2006 12:04 pm

automotive breath wrote:I believe the flow in the grooves begins when normal squish flow begins and the grooves extend the squish action during the combustion phase as the piston approaches TDC.


The extended turbulence in lower RPM engines seems like a great benefit. It looks like a good approach to hi-load/low-RPM rattling. I have always had a lot more faith in chamber induced turbulence than the ramped port-floors and spirialed guide bosses, etc. And, in low RPM deals where real-time favors detonation, anything to extend the turbulence seems, and apparantly is a big plus. The piston looks very evenly covered especially considering the stock 23° valve location, low ports and a domed piston.

how are you determining the number and direction of the grooves? ( I realize it's not a very "friendly" A-B-A experiment.)

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Post by DavidNJ » Wed Jun 21, 2006 12:35 pm

Are there any online articles on turbulent deflagration? Wouldn't the grooves have more affect at higher speeds where increased rod stretch reduced the quench height? Do they require very tight piston to cylinder head clearances for a measurable effect?

I thought the limit on ignition timing was a function of excessive reverse piston thrust and/or excessive pressure near TDC leading to detonation.

Thanks,

David

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Post by automotive breath » Wed Jun 21, 2006 12:39 pm

Ron E wrote:[...The extended turbulence in lower RPM engines seems like a great benefit. It looks like a good approach to hi-load/low-RPM rattling. I have always had a lot more faith in chamber induced turbulence than the ramped port-floors and spirialed guide bosses, etc. And, in low RPM deals where real-time favors detonation, anything to extend the turbulence seems, and apparantly is a big plus....

how are you determining the number and direction of the grooves? ( I realize it's not a very "friendly" A-B-A experiment.)
We agree on port induced turbulence, this is usually done at the expense of volumetric efficiency, not good. I routinely remove swirl ramps in favor of improved cylinder filling. In addition when the turbulence is induced in the port there is plenty time for the energy to be absorbed by the viscosity of the air/fuel mixture.

I believe this design will prove to provide most benefits in low RPM applications, or in high RPM applications coming into the engines RPM range. It’s perfect for the hot rodder that routinely runs the engine out of the designed RPM range. At low RPM traditional squish action is inadequate resulting in slow burn rate; allowing plenty of time for end gas to absorb heat and build pressure, the result is detonation.

One question I have not been able to answer is; can engines benefit from increased turbulence intensity at high RPM? Is too much turbulence bad?

Evaluating improvements in combustion efficiency can be very difficult; it’s not clear cut like volumetric efficiency. Make no mistake the benefit is there, determining ideal groove number and placement will be a challenge. At this time I think it no more than best guess. The one thing I feel strongly about is aiming the groove between the valves, but you can see my latest layout veers from that.

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Post by SUPRSLO » Wed Jun 21, 2006 1:21 pm

Does anyone have any comment as to the possibility of the grooves allowing for the flame to expand into the areas between the quench pad of the head and the flat areas of the piston during intitial light off? I thought someone suggested this possibility in the last thread about these grooves and it seems nascar runs full dish pistons now and I was just guessing that this opening of the pathway of travel for the flame front maybe one of the reasons for the use of the full dish in nascar. Purely a guess and question though 8)
I love this stuff!!!!!!!!!!!

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