Quench grooves

[bigblockfiero]

Again, every time grooves are tested at wide open throttle (and that is every time) there are no noticable gains so that is discouraging to many that would consider useing them, read the thread.

many of the chambers out there will see no grooving gains at all, even at part throttle.

lets just start a list of the engines that will see a more noticable part throttle gain for those that havent read the thread----------- SBC, SBF, SBmopar, BBmopar, BBoldsmobile, BBpontiac, BBbuick, BBcadillac------------ and then there is the list that help to a lesser degree.

Post a chamber pick and I will catagorize it.

I heard that KIA is considering or going to use chamber grooves but I don't know where ive heard this.

I will post up factory groove picks of a four valve head when I find it in all my shit somewhere, I dont think it was a benefit for them but they did it.

[Kohburn]

so are you saying the only ones that noticed a gain at partial throttle were large diameter cyclinders? the gain was relative to the surface area? or was it because those engines tyically ran lower compression?

the lack of WOT gains might deter people looking for performance on race engines, but partial throtle gains especially at lower rpm are very important to daily drivers

[The Dark Side of Will]

From earlier in this thread, he said that it helps chambers with large quench pads. Most modern chambers are for smaller bores and have 4 valves... this means that they have comparatively little quench area.

ALSO, in the combustion terms, quench grooves would be like quench volume and top ring land volume... within the groove there will be poor combustion, which contributes to carbon monoxide and unburned hydrocarbon emissions. I think that the volume of a groove would add SIGNIFICANTLY to the quench/ring land volume, hurting the engine's emissions numbers, especially at cold start, so I don't think OE's will ever do it for that reason.

ALSO, direct injection obviates the need for quench grooves because, especially in lean burn mode with fuel injected on the compression stroke, it guarantees that the charge around the plug is rich enough to light and smoothly distributed WITHOUT quench grooves.

I think that quench grooves probably are the most help to older chambers that don't have the benefit of CFD design, but may not be applicable at the OE level.

IOW, I think that they work, but are probably an "Engine Masters" technology that's not necessarily applicable to modern production engines.

And by "modern" I mean modern. The chamber design on the <'99 Northstars for instance is 18 years old or more. It's not modern anymore. Modern means GM's high feature V6's, direct injected Ecotec, Nissan VQ engines, VW/Audi FSI engines, etc.

[bigblockfiero]

so are you saying the only ones that noticed a gain at partial throttle were large diameter cyclinders? the gain was relative to the surface area? or was it because those engines tyically ran lower compression?

the lack of WOT gains might deter people looking for performance on race engines, but partial throtle gains especially at lower rpm are very important to daily drivers

One of the inefficiencies that grooves improve on is (as will said) a large quench area percentage-----per the total cylinder diameter area and that quench area located all on one side of the chamber (one quench area) rather then part on each side of the chamber (two quench areas). BUT the foregoing inefficiency scenario is in conjunction with its quench location being at the intake valve short turn radius AND that large single quench area then being on the opposite chamber side as the spark plug. If all this is true of your chambers then you have a perfect worst case scenario that quench grooves will noticeably improve at part throttle.

KOHBURN WROTE the lack of WOT gains might deter people looking for performance on race engines, but partial throttle gains especially at lower rpm are very important to daily drivers. :thumbleft:

This all is very hard to explain and I explain it just a bit better each time I try. My above description is about the best I've done so far in just one paragraph and yet it still kind of sucks.

[bigblockfiero]

ALSO, direct injection obviates the need for quench grooves because, especially in lean burn mode with fuel injected on the compression stroke, it guarantees that the charge around the plug is rich enough to light and smoothly distributed WITHOUT quench grooves.

This would generally be true but we still need fresh oxygen near the plug as well, rather then just residual exhaust gas. ANOTHER WARDS the fresh oxygen is located at the intake valve short-turn radius (at part throttle). Aside from all this I know the direct injection makes it light off better at part throttle (like chamber grooves do).

[The Dark Side of Will]

GM's done a tremendous amount of CFD to shape the chambers and piston tops of the DI engines. The pistons have raised "craters" on the domes to trap a donut of good mixture around the spark plug during lean burn operation. Also, the variable intake & exhaust cam phasing lets them very precisely control internal EGR to make sure that the donut of mixture is a donut of clean mixture.

[bigblockfiero]

ALSO, in the combustion terms, quench grooves would be like quench volume and top ring land volume... within the groove there will be poor combustion, which contributes to carbon monoxide and unburned hydrocarbon emissions. I think that the volume of a groove would add SIGNIFICANTLY to the quench/ring land volume, hurting the engine's emissions numbers, especially at cold start, so I don't think OE's will ever do it for that reason.

Top ring land CLEARANCE VOLUME is actually a fair percent of the total chamber volume when the piston is at TDC of the compression stroke------So yes its an important consideration and another good reason not to put more then one groove per chamber but------ I think the burn improvement more then offsets any emission losses and the groove reduces chamber shadowing similar to the way a piston fire slot does. Flame travels threw the groove for a more direct path to the far side of the chamber which can only help to more quickly burn everything over there.

Ive not purposely tested the groove emissions but I have run a such car threw government testing for license tabs and got a perfect score of zero.

[bigblockfiero]

If you see a grooving guy on the net named automotivebreath (randy) I can tell you by his drag racing experience that his sixty foots are better with chamber grooves because of his increased throttle response, clean running wile staging, and bottom end grunt. What is also interesting and validating is that if he leaves on a stutter box, with VS without grooves, then there is no grooving improvement difference, this is because in this scenario the throttle is already opened during staging.