Combustion chamber turbulence

[gt350hr]

 THANK YOU to FrozenMerc for posting the youtube vid. I am old and 'may" have failing eyesight but that SURE looks like an explosion to me rather than a "controlled burn" as was suggested on another post here. Take that video and imagine domes in the path of the flame front and you can begin to understand why changes in timing are needed for various combinations. You can also get an idea of why spark plug location is critical.
   Randy

[frnkeore]

Who was it that did Bill Elliott's heads, in the '80's.

As I remember, he went from 2.19/2.25 intakes, down to about 2.06. He got about the same HP but, better fuel mileage, allowing fewer pit stops. I believe they where done in TX, somewhere.

    "Some" of them were done by Endyne , but not "all". Ernie is fairly vocal about how much Larry helped. There are other guys like Carl Foltz and Don Losito to name a couple , that are at LEAST as capable as Larry.
     Randy

If we are talking about the same guy and how influence he had in Bill's engines. Who was it that welded up the intakes and reduced the valve size?

[gt350hr]

   Frank ,
     I am not sure about Penske , I thought he was using someone else.  Endyne did "some" heads for the Elliotts. That is a fact. It is also a fact that Nascar teams are very secretive ( and were more so at that time) about development. What head they ran where and why or "if" is probably a question for Ernie.
     At this point in time the head being used was still a canted valve 351C style. Many builders ( Bud Moore rip for one) were "flairing" the area around the intake valve to improve flow. The Yates head which would follow years later employed a "flow designed" chamber as a result of some of this early work. Now the majority of "race heads" are similarly shaped.
   Randy

[Katz427]

Thank you Randy for filling in the history . I thought you would know the Endyne story. You also mentioned Losito. That name, was he responsible for the design of the D3 NASCAR cylinder head ? Seems I remember that name from a conversation, back before the D3 head was approved by NASCAR.

[frnkeore]

Randy, are you familiar with Bill's heads being welded up and smaller valves used?

 

[My427stang]

THANK YOU to FrozenMerc for posting the youtube vid. I am old and 'may" have failing eyesight but that SURE looks like an explosion to me rather than a "controlled burn" as was suggested on another post here. Take that video and imagine domes in the path of the flame front and you can begin to understand why changes in timing are needed for various combinations. You can also get an idea of why spark plug location is critical.
   Randy

It’s a burn buddy, heat expansion moves a piston, not an explosion. I promise, if it wasn’t your pistons would either break from the explosion or as the cylinder did around it. In fact the very discussion of flame travel, plug location and quench means we can control it

You could call it deflagration, which is often inaccurately described as a controlled explosion, but it’s really a discussion of rate of burn and a properly tuned engine just doesn’t burn uncontrollably

[blykins]

I think the lawnmower engine camera is still too fast.

Here’s something a little slower, in a chamber that’s more familiar to us....

https://m.youtube.com/watch?v=cy_yaAOKjA8

I think it’s easier to see “flame travel” in this video.

[Barry_R]

One thing to keep in mind while looking at the videos is the speed at which this stuff actually happens.  Some of the visual of the "burn" is likely to be an artifact of the filming process, similar to the images when looking at valve spring testing.  Like watching the herky/jerky movement of an "old time movie" played on the wrong equipment....changes in motion or position that are too fast for the imaging equipment to smoothly capture.

While Endyne's degree of responsibility for NASCAR and Pro Stock ports in that timeframe seems like it will always be shrouded in mystery and controversy, it is undeniable that port development went from a fairly simple "make it bigger" mind set to a far more sophisticated flow management philosophy over a comparatively short timeframe.  A valid comparison would be the abrupt move from flatheads to overhead valves, or carburetor to electronic fuel injection.  Since then we have returned to a more typical evolutionary progression of port development, aided by computerization, the availability of low cost flow equipment, and OEM work.

[blykins]

One thing to keep in mind while looking at the videos is the speed at which this stuff actually happens.  Some of the visual of the "burn" is likely to be an artifact of the filming process, similar to the images when looking at valve spring testing.  Like watching the herky/jerky movement of an "old time movie" played on the wrong equipment....changes in motion or position that are too fast for the imaging equipment to smoothly capture.

While Endyne's degree of responsibility for NASCAR and Pro Stock ports in that timeframe seems like it will always be shrouded in mystery and controversy, it is undeniable that port development went from a fairly simple "make it bigger" mind set to a far more sophisticated flow management philosophy over a comparatively short timeframe.  A valid comparison would be the abrupt move from flatheads to overhead valves, or carburetor to electronic fuel injection.  Since then we have returned to a more typical evolutionary progression of port development, aided by computerization, the availability of low cost flow equipment, and OEM work.

Right.  We are splitting hairs by trying to quantify something that happens in a fraction of a fraction of a second.  It’s easy to get sucked up into semantics.

Ross and Randy are both saying the same thing, but Randy is looking at the big picture and Ross is zoomed in on a specific instant.  It is certainly an explosion if we step back and look at the overall scenario but we can also zoom in and control that explosion.  There is a flame travel and we can control where it goes and how quickly it goes there.

[DuckRyder]

Found a couple of pictures of MM "Surface Turbulence”. (if anyone cares)





Credit to 335ist : http://www.cardomain.com/ride/629515/1988-bmw-3-series/

Also a thread or two on turbo bricks:



Credit to Scott S : https://forums.tbforums.com/showthread.php?t=80786

This view is in contrast to the “port and polish” line of thought, in fact the core engine for the engine I had was a Hartge (IIRC) ported head and MM went trough the casting with the ST and had to replace the head (Which was a loss I’m sure, a Hartge head is rare and expensive)

I wish I had at least put the car on a chassis dyno, it was fast though...

Id be interested to hear any thoughts on this...

[My427stang]

One thing to keep in mind while looking at the videos is the speed at which this stuff actually happens.  Some of the visual of the "burn" is likely to be an artifact of the filming process, similar to the images when looking at valve spring testing.  Like watching the herky/jerky movement of an "old time movie" played on the wrong equipment....changes in motion or position that are too fast for the imaging equipment to smoothly capture.

While Endyne's degree of responsibility for NASCAR and Pro Stock ports in that timeframe seems like it will always be shrouded in mystery and controversy, it is undeniable that port development went from a fairly simple "make it bigger" mind set to a far more sophisticated flow management philosophy over a comparatively short timeframe.  A valid comparison would be the abrupt move from flatheads to overhead valves, or carburetor to electronic fuel injection.  Since then we have returned to a more typical evolutionary progression of port development, aided by computerization, the availability of low cost flow equipment, and OEM work.

Right.  We are splitting hairs by trying to quantify something that happens in a fraction of a fraction of a second.  It’s easy to get sucked up into semantics.

Ross and Randy are both saying the same thing, but Randy is looking at the big picture and Ross is zoomed in on a specific instant.  It is certainly an explosion if we step back and look at the overall scenario but we can also zoom in and control that explosion.  There is a flame travel and we can control where it goes and how quickly it goes there.

I believe that Randy and I agree on what happens in a chamber in general, and I also think we agree on what needs to happen and what can go wrong.  However, I am not thinking about instant versus big picture.  I am looking at it as something controllable, not violent and not unbounded.  Fast, yes, but, controllable.

I spent 20 minutes verifying the behavior of explosion,detonation and deflagration, but decided not to be catty. In the end, the terms overlap,  but in the end remember, the space shuttle exploded, Pintos exploded, Chevy truck side impact...explosion.  I am not so simple I cannot adjust thinking for a wider range of any definition, but I visualize the rapid burn in those pictures, not an explosion and CERTAINLY a controlled burn.  If it wasn't controlled, the basic premise of chamber design and tuning would not exist.

If I build an engine for someone, I promise I am avoiding every sense of the term explosion, except maybe a rapid expansion of gas, but even then I am bending to be as much a gentleman as a knuckle-dragger like me can. 

I have no desire to "win" but jumped in a few posts above because this was sort of a poke from a conversation I thought we had already ended by agreeing to not completely agree. 

[gt350hr]

THANK YOU to FrozenMerc for posting the youtube vid. I am old and 'may" have failing eyesight but that SURE looks like an explosion to me rather than a "controlled burn" as was suggested on another post here. Take that video and imagine domes in the path of the flame front and you can begin to understand why changes in timing are needed for various combinations. You can also get an idea of why spark plug location is critical.
   Randy

It’s a burn buddy, heat expansion moves a piston, not an explosion. I promise, if it wasn’t your pistons would either break from the explosion or as the cylinder did around it. In fact the very discussion of flame travel, plug location and quench means we can control it

You could call it deflagration, which is often inaccurately described as a controlled explosion, but it’s really a discussion of rate of burn and a properly tuned engine just doesn’t burn uncontrollably

    Ross ,
      You are 100% correct that heat expansion moves a piston , even in a steam engine! NEVER an argument there! I guess I'm so old that I still remember the teachings of how a four cycle engine's operation was described "suck , squeeze, BANG, blow".  We know we are talking about the SAME thing and it's important that everyone viewing understand it is simply how "I" describe it versus how you do. My interpretation is certainly open to debate. I've been wrong before . There is no win or lose here as there is no contest and nothing to gain. Just a couple of very experienced guys airing their thoughts. I hope the viewers see that and not two kids throwing sand in the sand box.
    Randy

[gt350hr]

   DuckRyder,
       I've seen that group of modifications and also dimples ( swirl quench) as it became termed."To ME" ( I have to say that because it is my opinion ONLY) those modifications that are developed on a flow bench , don't "always" show up as a power improvement. My statement  ( here I go again putting a target on) is based on flow bench testing being done without a "valve in motion" and an unrealistic source of vacuum or pressure being used ( lack of a piston in motion) I am NOT saying a flow bench is useless at ALL. We came out of the stone age by using them. Big , smooth, shiny , ports of the '60s don't compare to modern ports developed by use of the flow bench. A flow bench ( in my eyes) is a relative tuning aid and I say that because airflow gains on the flow bench don't "always" assure dyno HP or lower ET's. When someone develops a way to test with a piston and valve in motion , then we will be on to reality. That would allow changes like rod to stroke to be measured for flow changes.
   When modifications like your pictures show do make gains it is impressive.
    Randy

[RustyCrankshaft]

It's somewhat uncommon to see at anything less than at the OEM level in most gas applications, but pretty common in diesels is to install pressure transducers and watch actual cylinder pressure. Doesn't matter if you call it a burn or explosion, what matters is the resulting cylinder pressure curve is controllable and within a range that the hard parts will tolerate. Watching the pressure grafs you can certainly tell when you've gone too far into "explosion" range and start seeing big spikes in cylinder pressure rather than a nice curve.

I'm not 100% sure what equipment the OEM's use. When I was messing around with it I cut up a pair of generic SBC heads on a 350 when I was messing around with it.

On some of the diesel's I worked on it was a service manual "tuneup" to measure each cylinder and adjust fuel to each cylinder to balance the engine. But we're talking stationary stuff here. Still, the perspective watching actual cylinder pressure and how it changes based on RPM and timing, etc. is interesting.

[gt350hr]

  Loss of controlled burn or pressure spikes often compromise the fasteners and "lift" the head off of the block and or gasket , usually resulting in gasket failure. We used to think of it as poor gaskets but now realize it it poor "burn management" LOL. If the fasteners aren't compromised , the next sacrificial part is the piston which more often than not is blamed but not the actual problem.
    Randy