In cylinder turbulence/ burn rate

[automotivebreath]

Pinhead, I don't have experience with the grooved valves so I'm just stating my
gut feel. Formation of the flow cone around the valve is critical for cylinder
filling . It appears that his type of modification would have a impact on flow
in this critical area. To me it looks like it would add turbulence and hurt flow, I
could be wrong.

Here's another example claiming enhanced mixture motion at the valve that
enhance flow. May be something there?

"These dimples create a turbulent boundary layer that actually speeds up the
flow by adding energy to it via eddy currents. "

[Pinhead]

40% at low lift. It won't help nearly that much at full lift, but helps when the air/fuel has to slide by the valve when it first begins to open.

[big block fiero]

Well I will say that looks interesting, but I'm still skeptical. I dont think it would add huge flow but I would agree it probably helps vaporization.

I do a modification with a 1/8th inch drill bit that looks the same as that surface, but I do it to increase surface area to improove cooling in air cooled engines all thruout the cooling fins and jug.

it would be real easy for one of us to replicate with a drill bit then dyno. I'm willing to do it but I dont have time for at least three weeks.

Just for fun I'll tell my racing partners that I'm doing this to reduce valve weight and see what they say.

[big block fiero]

After much information sharing with darin morgan pertaining to wet flow testing I am getting more interested in testing this valve dimpling concept. The issue I originally had pertained to flow and I still dont believe there would be an airflow increase of 40% but there could be a sizable increase in horsepower nontheless due to the wetflow results.

[tommurphy73]

I read something on golf ball technology where they claim that hexagonal rather than round dimples give better results for distance . I wonder if the same is true regarding flow when used on something like a valve.

Regards
Tom

[rookie]

Did ya'll see Davids latest installment In cylinder Turbulance and Combustion Dynamics

Those valves remind me of golf balls, but I to have a hard time believing a 40% flow increase is possible, although you can bet when I get my mill set up I will find out.

[Pinhead]

Ok, I jumped the gun on the ST valves. I found some more info on thm and I have absolutely no idea where I got the 40% flow increase.

Scotts (ssheen at MPGResearch) said they give about a 5% increase of flow.
New Valves - Surface Turbulence - Turbobricks Forums

However, I still believe that the increase in air/fuel mixing would be the biggest advantage.

Originally Posted by scotts

With the valves they tune their engines for ~20% less fuel from normal for the given setup. If there was an issue with carbon effecting their efficiency, they would have to up the fuel as they became less efficient, which they have never had to do.

[MadBill]

The spark advance for best power (MBT) as RPM rises is determined by how fast the time available for combustion decreases vs. how much the ever-increasing turbulence speeds the burn. Typically from mid-RPMs up, the two are pretty much balanced, giving a fixed advance requirement.

On the detonation point, the missing factor is TIME. Once all the conditions of mixing, pressure and temperature have been met for detonation to occur, it DOESN'T! At least not for a short but critical delay period. If during this interval (which of course encompasses more crank degrees as the RPM increases) the normal flame front arrives in the subject region, no detonation occurs. For this reason, detonation is much more prevalent at low RPM.

[automotivebreath]

Originally Posted by MadBill

On the detonation point, the missing factor is TIME. Once all the conditions
mixing, pressure and temperature have been met for detonation to occur, it
DOESN'T! At least not for a short but critical delay period. If during this interval
(which of course encompasses more crank degrees as the RPM increases) the
normal flame front arrives in the subject region, no detonation occurs. or this
reason, detonation is much more prevalent at low RPM.

I confirm this to be true at the drag strip with testing. Auto-ignition first
shows up at launch when RPM (and flame speed) are at there lowest. Next
comes the bottom of high gear.

This adds another important factor to the equation, LOAD. At the initial
acceleration of launch, engine load is very high, again later at the high
gear shift.

[big block fiero]

pinging at maximum torque may be what you are refering to and if so I would agree to a point, depending on how this comparison is made and some other unknown factors.