More quench talk for you.

And thank you for the post.

Tapered quench for NA

I found this posted on Speed talk and would like to hear the opinions of others on here. https://www.speed-talk.com/forum/viewtopic.php?f=1&t=56349 Specifically what do you think a tapered squish would do for a naturally aspirated methanol injected (mfi) BBC? Would it hurt it or help it. Say a...

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Is that the same thing as softening the chamber?

 

Anyone with some experience in boost here that wants to comment? Kind of interesting. I'm running a thicker head gasket to drop compression. I'm sure it is far from ideal quench. Wonder if tapering could improve performance and remove enough volume to go with a more common and thinner head gasket? Practically speaking, it would be a good thing if I could get into a thickness that was common enough that it was stocked and not special order.

 

I was running a sbe LS 5.3 turbo charged on E85. Flat top with 799 heads. Pushed that combo to mid 5.60s at 3400 pounds per class rules. Hurt several rod n pistons. The pistons always suffered damage in the quench area. I put a 7° softening on the chambers and ran low to mid 5.50s and rarely hurt anything. These motors where 10:1 then 9.7:1 after softening.

Another good video.

 

Third G, running .051" HG?

 

LS9 gasket #12622033 I've used .054" has the number. On the SBE deals the piston has typically been out of the hole .005" ish. FYI Current motor "not SBE" I'm using the smaller bore BTR gasket.

 

I'm at .066" with my gen 1. I'm guessing that other thicknesses are perhaps in stock.

 

So dumb questions. Should the taper extend consistently all the way to the edge of the cylinder? Or....should there be tapering off as you approach the edge? If the chamber has flat/quench on both sides, should they both be tapered out? If I am explaining my question properly.

 

I have understood and have always done .200 less than bore. That leaves a .100 perimeter of flat in the quench. This hand job left about the above dimensions and works well. I have patterns for the diameter and the angle. The tapper is to the center not a flat ramp. Then smooth the edges. Note this picture was not with the LS9 gasket.

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It should be an outward spiraling parabolic curve or conical cut that tapers all quench surfaces to that contour as the tool gets shallower the perimeter of the chamber and I would stop it .075 - .125ish from any O-ring or Hoop location so the gasket is not compromised. The thickness of gasket or piston to deck distance has basically no help in curbing detonation. I have seen it tested with flat top pistons as much as .125" in the hole and detonation was just as bad as zero deck with neither being softened. We always saw the damage start in the quench pad areas of the head and that was what zeroed us into what was needed to stop it. It would cause pitting on a billet head but the hard anodized pistons would show no damage. Other than the bent rods at every teardown it would have been even harder to diagnose. I give the credit to Alan Johnson for the solution and it was his heads we were working with. This was around 2008 when we finally figured it out with Alan's help. Basically without killing all the compression try to cut a hemispherical chamber in the wedge design. It's usually around 5° - 7° taper that seems to be enough to be effective. This is a AJPE billet SBC head that is what I would consider perfect and the best I have seen. These chambers are still only 56cc. We have discussed this several times in the past if you want to check the database for more info.

 

It should be an outward spiraling parabolic curve or conical cut that tapers all quench surfaces to that contour as the tool gets shallower the perimeter of the chamber and I would stop it .075 - .125ish from any O-ring or Hoop location so the gasket is not compromised. The thickness of gasket or piston to deck distance has basically no help in curbing detonation. I have seen it tested with flat top pistons as much as .125" in the hole and detonation was just as bad as zero deck with neither being softened. We always saw the damage start in the quench pad areas of the head and that was what zeroed us into what was needed to stop it. It would cause pitting on a billet head but the hard anodized pistons would show no damage. Other than the bent rods at every teardown it would have been even harder to diagnose. I give the credit to Alan Johnson for the solution and it was his heads we were working with. This was around 2008 when we finally figured it out with Alan's help. Basically without killing all the compression try to cut a hemispherical chamber in the wedge design. It's usually around 5° - 7° taper that seems to be enough to be effective. This is a AJPE billet SBC head that is what I would consider perfect and the best I have seen. These chambers are still only 56cc. We have discussed this several times in the past if you want to check the database for more info.
View attachment 252488

Great picture and explanation. I do wonder how much volume was removed from that chamber. Visually is just looks like the best that can be done for a 23 degree head to prevent detonation.

My 23 degree head years ago was rolled a bit and milled. The problem I may run into with softening is that the edge of the intake seat is already touching the deck so to speak. That makes it difficult to fall with taper from the quench area.

 

I'm not so sure quench is so great based on that design which is pretty sexy. The hemi motors don't seem to have any quench at all. With a nice "soft" chamber can so smooth out all the way to the bore edge with a flat top or small dome with a turbo e85 engine and just do away with the majority of quench? AJ is the man. I'm lucky enough to hang out at the digs and see some of his work up on the bench and it's amazing stuff!! those valve seats look pretty exotic

 

Thats the whole point, you don't want quench in a boosted wedge headed application. Yes you can try to do it in reverse with a full dish piston that uses a parabolic shaped dish. The problem is in most race applications you can't get enough compression ratio that way. Softening the quench pads is the most effective solution and you keep as much compression as possible. The pistons for that build actually have a slight dome to get it to 11.5CR even though its a 4.250" stroke. Again the Hemi is THE KING of boost for a reason. They are shit NA without quench pads like the Pro Stock hemi's ran and even then they needed almost another 1000rpm to be competitive with the current DRCE2 wedge heads. The 10,500rpm limit is why no one runs the Dodge or Ford hemi engines which are basically identical heads other than what they say on the valve covers. The G3 Hemi Eagle heads have two basically flat quench pads. The new Apache heads on the BGE engines and the Hellcat/Demon/SS have softened quench pads and I can post some pics of them later. These are the new heads for the 2500+ HP hemi project. I wanted as much tuning window as possible.

 

It has been discussed several times on here but I'll add this again. Just giving the quench pads more clearance is not the solution. It has to be angled in such a way that there are not parallel surfaces in the quench areas and they allow the air/fuel mixture to be pushed towards the center of the chamber without squeezing it between parallel surfaces as a NA engine does.

 

Bill 'Grumpy' Jenkins mentioned this in his book back in the early '80's - tapering the quench pad towards the roof of the chamber and putting a radius on it so that gases wouldn't get trapped in the quench area and cause secondary ignition.
Another low buck way to achieve a similar thing is to cut a couple of Singh grooves in the quench pad, these grooves allow the trapped gases to be evacuated from the quench area, a secondary benefit is that the squished out jets of fuel/air creates turbulence in the chamber which will allow a quicker burn .

 

This is just a rough example of a 4.5 inch bore with a 3 degree taper cut excluding the current chamber volume. This example would be like making a cut into a flat plate of aluminum.

Triangle Calculator

This free triangle calculator computes the edges, angles, area, height, perimeter, median, as well as other values and a diagram of the resulting triangle.

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A triangle with a 2.25 long side at a 3 degree angle will have a height of .118 inches

Cone Volume Calculator

The cone volume calculator determines a cone's volume and the volume of a truncated cone.

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An oblique cone with a height of .118 in and a radius of 2.25 in will have a volume of 10.251 cm³

There is not very much removed if my math is close and even less if you figure that the volume of the chamber where the cut goes thru has not been taking into consideration.

I am sure there are different ways to skin this cat.

 

At 4.155 bore it would be .109 high and = 8.073cc at 3 degrees

 

The AJPE head I posted as a wedge example is 13° valve angle and the intake valve is splayed towards the center of the bore. I would have to verify exact volume lost but I would say 10 cc - 12cc off the top of my head.

 

Thanks all. This seems pretty appealing actually.

 

When you have a chamber that looks like this (not mine but my deck nips the valve seats a hair, so even worse), how do you soften the side that is top on this picture? There may be a little room to let the quench blend into the exhaust seat, but very little for sure.

 

Also wondering, I can easily do this on my CNC, just unsure how the intake seat is addressed,

 

Surprised there aren't some chiming in on this.

 

Seams at what appears to be 23° and large valve you maybe screwed. Probably have to move to the piston to fix it.

 

You obviously can't cut into the valve seats. You do what you can and the alternative is to try and design the piston top to accomplish similar geometry. On some like a 23* SBC or 24* BBC head this can be a challenge to keep enough compression ratio. Ultimately you do the best you can using what you have to work with. Everything is a tradeoff in engine building, finding the best balance is the key to success.