burn slots in squish area ?

[Nick Campagna]

Instead of a groove, would a head quench surface that was not parallel to the deck surface be as effective ? Basically, taper the thickness of the head quench deck from the edge of the cylinder to the interior of the chamber so the quench space is not formed by two parallel surfaces. Make the quench a wedge with the deep portion at the chamber interior. ??

[Lasse]

Originally Posted by Nick Campagna

Instead of a groove, would a head quench surface that was not parallel to the deck surface be as effective ? Basically, taper the thickness of the head quench deck from the edge of the cylinder to the interior of the chamber so the quench space is not formed by two parallel surfaces. Make the quench a wedge with the deep portion at the chamber interior. ??

I think groove is only emptying channel for quench area. With groove you can make sharp gas stream to combustion chamber and you can direct that stream where you want. Sharp, high velocity stream will improve turbulence in combustion chamber.

If you make quench pad in wedge form, you actually lower velocity of quench effect. This is allmost same thing, if you add quench clearance.

This is only my opinion. Others, if you see this thing otherwise, tell your opinion.

[MAP]

Greetings,

I hope I'm not pushing the matter of using CFD too much, but my opinion is that the complexity of the matter demands it. We'd also need to gain an understanding of the reaction loading imposed on the piston as a function of how the charge is compressed in this area.

Clearly, we're not violating conservation of energy here - if you put a lot of kinetic energy into the air/fuel mixture, you have to pay the utility bill somewhere. This has to be figured in the overall consideration.

Best,
Mark

[stevek]

I'd be happy to donate CPU cycles if you setup the software and meshes.

I agree that CFD would be an excellent way to 'look into' what is going on, but I don't have any CFD software on hand (Fluent would be nice).

[MAP]

Hi Stevek,

The meshing part per se is pretty straightforward. For a 3-D model like this, mighty time-consuming (I think you need to model the whole combustion chamber, valve, and port, and then iterate the model through some kind of a time-step simulation,) but still fundamentally straightforward. Many packages nowadays will even auto-mesh the model. But, I have no personal access to a good CFD package for doing non-work related investigations. The good stuff, as far as I know, is mighty expensive for a seat license.

So, not trying to cop-out on a reasonable offer, but I need to pass. Is there someone reading here, who has the time and the software and motivation to do this, but doesn't need to do it for an employer? Or is this, I fear, like asking someone to design a rocket to go to the moon, that doesn't work for NASA? (Chuckle.)

Thanks,
Mark

[automotivebreath]

Hi stevek,
I was involved from a distance with a groove dyno test a few years back. See the
attached link. My involvement was with groove location, size and shape; not the
actual testing. The results were less than spectacular, thats why I recommended
getting very familiar with combustion, abnormal combustion and combustion
efficiencies before testing. I hope I didn't come across wrong questing your knowledge
and or abilities, thats not the intent.

The one thing that I found unusual about this test was the high levels of soot on the
combustion surfaces, nothing like what I see during disassemble. I suppose this could
have been related to the Klotz HiTRATE used as a octane boost in lieu of lead to
eliminate the possibility of lead fouling of the O2 sensor.

Any way you might fine this interesting.

revsearch grooves

[automotivebreath]

Hi Nick,
This picture is from a Harley Davidson running taper squish like you describe. I have
the same question as you, can we expect the same results with taper squish vs.
grooves. In the picture combustion appears incomplete, however the owners say it
the best way to go; I'm undecided.

[KLR142]

Finally got around to reading this whole thread... Been keeping up with the topic on my Volvo forum, Turbobricks.com where we have an extended length discussion/disagreement about these interesting things.

I haven't seen it mentioned much on here, but another benefit of the grooves aside from cleaner, more complete combustion at lower rpm, smoother running, less detonation prone, is the fact that your lean running limits raise up a bit as well. We have a couple of Volvo guys with programmable engine management, and one of them has pointed out that he is able to cruise without issue in the 17-18:1 range even! This goes along with the topics regarding lean burn, where the two main ingredients are a good jet of mixture through the spark gap and lots of spark energy...

Anyway, I'm sold and my next/first low budget, decent performance head for my lowly Volvo 244 will include a groove layout of some sort, a compression increase of around 1 point to 10.8:1 or so, along with bigger valves and some minor port work. Still undecided on groove layout, keep going back and forth, and trying to figure which squish pad to put 1/2 grooves in. And tight squish, which sometimes is not recommended with grooving. It's been said that grooving works best with a larger piston-head gap, in the .060-.080" range, if I remember correctly.

Someone posted some very interesting stuff over there today, TEST RESULTS! Now, they're awesome test results, but it really begs the question of taking it a step further and actually trying to take advantage of some of the noted benefits to grooving by upping the compression and such.

SOMENDER-SINGH.com - Herning Analysis
Garrett Robert Herning - Projects; Singh Test Results, AutoTronixs, LLC

If you have way too much time on your hands, here's the link to the main topic on the Volvo forum: Somender singhs groove theory tried. - Turbobricks Forums

Cheers,
Kyle

[Pinhead]

I see all of these pictures of high compression pistons with deep valve relievs and sharp edges around them... Other than obviously taking away some compression, why doesn't anyone radius them dang edges?