what do you guys think of this? Part II

[Unkl Ian]

I had considered the possibility that the grooves influence flame travel.
The single groove heads seem to aim the groove at the spark plug.

But there is so much going on in terms of wet flow,
turbulence,quench,flame travel,etc,whos to say exactly what is happening.

The angle groove test should be interesting.
This is where a single cylinder,OHV,dyno test motor would be handy.

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When you say "full dish pistons in Nascar"
do you mean they are running zero quemch area ?

[Ed-vancedEngines]

I think he means that mush of the combustion prosess goes in in the head of the piston. not sure though.
Ed

[SUPRSLO]

I had considered the possibility that the grooves influence flame travel.
The single groove heads seem to aim the groove at the spark plug.

But there is so much going on in terms of wet flow,
turbulence,quench,flame travel,etc,whos to say exactly what is happening.

The angle groove test should be interesting.
This is where a single cylinder,OHV,dyno test motor would be handy.

-------------

When you say "full dish pistons in Nascar"
do you mean they are running zero quemch area ?

I've been told that nascar uses a full dish piston by a very knowledgeable source but it's certainly not "no quench design" as in the entire piston would be a hole or something, ha. I've not seen them myself though. Have you ever seen a cup piston? I was lead to believe that is is very similar to the pistons in my motor which are a turbo piston from weisco which is a full dish with valve reliefs cut in them.

http://www.wiseco.com/PDFs/Catalogs/AB05_chevy.pdf

Look at page 13 listed on the bottom right hand corner of each page and see the picture of the piston i'm talking about (by the description "reverse dome turbo duty"). That's what i've been told the nascar pistons look like.

I'm just taking a wild guess that with a piston like that, more area is available for flame travel to progress across during the progression of the flame front. With a tight quench area design is seems to me you'd be concentrating the majority of the flame and cylinder pressure in a smaller portion of the piston then in something which is pictured in that link and supposedly used in the cup cars.

[SUPRSLO]

I think he means that mush of the combustion prosess goes in in the head of the piston. not sure though.
Ed

Yes, exactly! But once again, it's more of a question then a suggestion.

[automotive breath]

...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. ...

I think the are using something like this:

[SUPRSLO]

...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. ...

I think the are using something like this:

Ahh, ok! Has anyone swapped in a piston like this vs. a more traditional tighter quench piston and compared results while maintaining the same compression ratio?

[beth]

...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. ...

I think the are using something like this:

Ahh, ok! Has anyone swapped in a piston like this vs. a more traditional tighter quench piston and compared results while maintaining the same compression ratio?

There is less pumping loss with this design.

[MadBill]

We used a set that looks just like a.b.'s picture (except for those scallops on what, the oil ring grooove? What's with them?) from Wiseco at their suggestion on a recent SB 2.2 build. Very pleased with the power, but it was the first build up of a "NASCAR used parts" engine and we have nothing to compare it with.

[Windsor377]

Those scallops just help channel the oil inside the piston skirt.

Has anyone tried the grove in a blown gas application?

Edit: Wingade can escape through there too...

[lil289]

Beth, what do you mean there is less pumping loss?

Thanks

[beth]

It takes power to "squish" air and fuel.

[SWR]

Has anyone tried the grove in a blown gas application?

Been there done that... not dynoed it yet though,but running on the streets it has lower exhaust temps than last year...by a considerable margin.

[MadBill]

Edit: Wingade can escape through there too...

Wingade? Do you mean windage? If so, there shouldn't be any to speak of in the thous. or two piston-to bore-gap unless the compression ring sealling is bad...

[automotive breath]

Here's a picture of the Brodix heads I mentioned. With tall domes I put the groove between the valves to assure the squish flow makes the trip over the dome. I thought about adding feeder grooves into the main groove but decided not to mutilate Lobe's prize possession.

[Windsor377]

Edit: Wingade can escape through there too...

Wingade? Do you mean windage? If so, there shouldn't be any to speak of in the thous. or two piston-to bore-gap unless the compression ring sealling is bad...

Yeah, wingade. You know that reverse pulse generated at the collector bearing.

Seriously though, where there is a reciprocating engine, there is windage. Introduce a power adder and there is more. I like to fight it with an external 5 stage SCP oil pump.