4 Valve Head: Single Central Spark Plug vs Dual Spark Plugs

[hoffman900]

I really wish the NHRA would open up the rules on the Pro-Stock divisions. They both need a fresh shot in the arm. Make is displacement based and regulate some materials, spec the fuel, and then let them rip. No one would be able to afford it, but I like the idea of blank sheet designs that would probably look nothing like what you see currently.

Slightly off topic, but i agree completely. Opening the rules (thinner rule book) would encourage more innovation
in design and construction, and should be applied to many more classes of racing.

Technical advances are being made in many areas but usually do not flow down to the racer.
Improved metallurgy, new manufacturing methods (CNC, 3d printing, etc.), new coatings,
better fuels and lubes, computer controlled engines and transmissions,data loggers, aerodynamics,
and incredible simulation programs are available but seldom applied, often due to obsolete rules.

Cost is not the problem. We see multi-millionares who bitch about the cost of race gas from their
$650,000 motor homes. Same guys who charge $450 per hour in their practice but bitch
about a skilled mechanic asking for $100/hr to rebuild an $80,000 race engine.
Both skills took the same amount of training.

The problem is knowledge, or more correctly, the lack thereof.
Who reads SAE white papers, engineering textbooks, attends seminars?
Instead we read inaccurate magazine articles, listen to folklore, and watch YouTube for technical insight.

End of rant.

I agree 100% on all of this.

[David Redszus]

Thermal conductivity and heat absorbtion are two side of the same coin; they always come together.

Do I understand you correctly: Specific heat goes hand in hand with thermal conductivity for (solid) materials? So the higher the thermal conductivity the higher the specific heat and vice versa?

Never heard of that. Could you explain this more detailed please?

Material…..….Copper..….Alum……4130…..SS304….…Ti
Thermal cond…226……..…99……..…25…….…9.4…...…4.2
Spec Heat…….0.092…...0.230…..0.120…..0.120…..0.135
Density……....0.323….…0.098……0.283…..0.290……0.160

Aluminum appears to be the oddball material.

[BLSTIC]

[snip]
Honda: https://www.hondarandd.jp/point.php?pid=976&lang=en

[snip]

I can't comment on squish, but it's very clear they're both using in-cylinder tumble motion and DI to allow very high knock thresholds, which allows the high geometric compression ratio, which also makes for a more powerful and responsive engine, and are obviously doing it so it can have very good combustion at high rpm's and in Porsche's case, bore size, and being road race / road oriented engines, are probably have fantastic combustion at part throttle too.

The honda engine didn't have DI. But what it did have was some 10-15 degrees less ignition lead when the high tumble layout was introduced. And the port wasn't even properly modified, it relied entirely on bore shrouding and didn't even go as far to have a ski-ramp that's common on a few modern engines (like my favourite exercise in detonation resistance: the 9:1 compression, 30psi boost Mercedes M139).

It's also worth noting that the M139 chamber features a slight boss around the plug, projecting it another mm or so into the chamber. There are extra projection plugs available for many engines these days. Some of them are even side-gapped (the dual electrode ones like the BKR6EK) so that they don't actually project further in total, just the spark moves.

I was talking about the example engines having DI. I was letting the Honda paper speak for itself.

My bad, I misunderstood your meaning. It's a good read though, that paper.

I'd love to try that tumble port (or some variant of it) on a boosted car one day. Trading outright airflow for detonation resistance and efficiency isn't as much of a compromise with forced induction.

[MetricMuscle]

Not all squish surfaces are flat in the plane of the block deck. Often the dome of the piston and its
proximity to the chamber surface will provide the squish zone. Such designs change the squish direction significantly.
Mercedes did that as far back as 1970, and probably much earlier, and is commonly found in Porsche engines.

I found some folks doing this aftermarket for 4-stroke motorcycle engines but was a feature I wasn't going to attempt first time around. The plan is to use the OE flat top piston.

What is the goal for squish direction? Towards the spark plug? Towards another squish zone?

I found lots more discussion on angled squish in the 2-stroke forums but most 2T pistons I've seen are domed and the spark plug is located higher in the combustion chamber.

[MetricMuscle]

What about Singh Grooves or the like?

[hoffman900]

What about Singh Grooves or the like?

Just no. Maybe they help in an exceptionally rare case, but, 99.9% of the time look to OEM designs of the last ten years and NASCAR designs for 2 valve applications (OEM level / financed development where they are just as focused on combustion efficiency as much as power).

Honda in that white paper I linked shows exactly the taper needed to do what you need it to do.

Remember, reverse squish is what everyone also needs to be thinking about.

[ptuomov]

What about Singh Grooves or the like?

Can you put an exhaust anti-reversion device inside a Singh groove?

[BLSTIC]

What about Singh Grooves or the like?

Can you put an exhaust anti-reversion device inside a Singh groove?

I have no idea what to think of this statement.

Also I thought Singh grooves were more like some kind of imitation tapered squish than anything, allowing the burn to continue into the squish pad area while the piston is nearer tdc than without them, but also without losing squish pad area.

[ptuomov]

What about Singh Grooves or the like?

Can you put an exhaust anti-reversion device inside a Singh groove?

I have no idea what to think of this statement.

It was just a joke about various designs like Singh grooves, exhaust wave termination boxes, exhaust anti reversion valves, etc. that car factories never employ but hobbyists continue to be fascinated about. An attempt at comic relief, in other words.

[BLSTIC]

Ah I suspected, but I'm about as socially aware as a brick while conversing through text. I really need some kind of automatic emoticon injection in my browser.

Nothing wrong with a bit of anti reversion... Done properly

[MetricMuscle]

It was just a joke about various designs like Singh grooves, exhaust wave termination boxes, exhaust anti reversion valves, etc. that car factories never employ but hobbyists continue to be fascinated about. An attempt at comic relief, in other words.

Me too! I do realize Singh Grooves conjure up more heated discussions but wanted to find more info on Squish Direction and how best to go about it since, if I understand correctly, it can negate the need for a centrally located spark plug not to mention a few other advantages.

Actually, the squish velocity and direction will produce the largest component of turbulence and thus control
flame speed and combustion angle (or time).

Can you put an exhaust anti-reversion device inside a Singh groove?

This largely depends on what color power band you are running.

[MetricMuscle]

Honda in that white paper I linked shows exactly the taper needed to do what you need it to do.

Which white paper? I read through the one about the 110cc engine but don't recall any discussion of taper.

It was just a joke about various designs like Singh grooves, exhaust wave termination boxes, exhaust anti reversion valves, etc. that car factories never employ but hobbyists continue to be fascinated about. An attempt at comic relief, in other words.

I do respect that OEMs have spent lots more money and done lots more work to develop reliable proven designs but then again, this is what Nissan/INFINITI thinks is a proper exhaust manifold for my car....

[hoffman900]

I mean, they’re also trying to make a profit and not chase every last bit of power, and make it all so some person can assemble 30 of them a day. Apples to oranges.

From a combustion standpoint, it’s hard to look past what they are doing, especially in the last 5 years.

[ptuomov]

I mean, they’re also trying to make a profit and not chase every last bit of power, and make it all so some person can assemble 30 of them a day. Apples to oranges. From a combustion standpoint, it’s hard to look past what they are doing, especially in the last 5 years.

If you look at a production car that retails for $100k today, it’s extraordinarily difficult to find parts that could easily be made much better. BMW exhausts, for example, are perfect.

[elle]

Thermal conductivity and heat absorbtion are two side of the same coin; they always come together.

Do I understand you correctly: Specific heat goes hand in hand with thermal conductivity for (solid) materials? So the higher the thermal conductivity the higher the specific heat and vice versa?

Never heard of that. Could you explain this more detailed please?

Material…..….Copper..….Alum……4130…..SS304….…Ti
Thermal cond…226……..…99……..…25…….…9.4…...…4.2
Spec Heat…….0.092…...0.230…..0.120…..0.120…..0.135
Density……....0.323….…0.098……0.283…..0.290……0.160

Aluminum appears to be the oddball material.

Ok? What units are these numbers in?