FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: allrightmike on November 07, 2019, 07:46:31 AM
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As I understand it combustion chamber turbulence (call it CCT) helps promote flame propagation and reduces total spark advance requirements. Barney Navarro once told me that flathead Fords only wanted 18-22 degrees total because they had an extremely turbulent chamber. This leads to my question, modern chamber and coordinating piston shapes seem to have very little squish area which would tend to create less turbulence thus slower flame travel thus more spark advance requirement. I know that this is not the case so how do these modern designs create such rapid flame travel?
Mike.
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The chamber design is everything in modern engines. The chambers are designed to produce a swirl effect as the intake charge enters the chamber/cylinder. Look closely at the contour of the chamber around the intake valve, where the intake charge enters the chamber, and you'll see flow "directors" that promote that swirl. If you look at modern heads for the FE, most incorporate these more modern designs into them, at least to the degree that the intake port allows. Oil jets for piston cooling also help a great deal in controlling heat and hot spots in modern combustion chambers, as well as the increased heat transfer that aluminum heads promote.
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Modern piston shapes have changed to enhance the swirl effect noted by cjshaker. Older chambers HAD to have squish pads to limit detonation and they had virtually no swirl.
Randy
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The old Flathead may have had alot of turbulence in the combustion chamber, but the flame front also had a very long distance to travel compared to OHV engines. That long travel distance promotes poor combustion and un-even burning.
https://www.youtube.com/watch?v=jdW1t8r8qYc (https://www.youtube.com/watch?v=jdW1t8r8qYc)
(https://i.imgur.com/kAktAtf.gif?noredirect)
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When I retired about 7 years ago, the buzz word was "tumble". A lot of CFD work on computers to design a port where the air literally "tumbled" down the port, and into the cylinder. It is all about breaking the fuel molecules down as small as possible so when the chemical reaction is initiated, the combustion is complete, and what doesn't burn is handled by the catalyst. Let me say , I've seen the time from open chambers, to air injection 2 cycle, to tumble ports, with the end game being to "of course" (eliminate pollution) improve efficiency.
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I think maybe Randy probably has a recollection of a company called Endyn and an aerospace engineer who if memory serves me named Larry Widmer. Larry was promoting a "soft chamber" with a fair amount of swirl for Ford NASCAR program. As I remember Ford engineers thought pretty highly of Larry's work. This was back in the 1980's. Larry and his company were in California.
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Concerning the flathead chamber, about 3/4 of the area above the piston is quench so maybe not so large a chamber as it might appear
Mike..
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It's still up http://www.theoldone.com tells Larry's story with his theory on chamber, port design and the boss 429 Pro stock program in the 1980's. An interesting read.
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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.
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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.
I thought Ernie Elliott did them.........
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When I was into BMW’s Jim Rowe of Metric Mechanic promoted turbulence, I actually had one of his first 2.9 Hi Flow ST engines (I came by it used) and it ran good.
https://metricmechanic.com/
While I longer see all the information on his website about it, he cut crescent shaped grooves in the ports to cause what he called “surface turbulence” they even would do the intake and exhaust manifolds...
I always wondered what that treatment would do for a hot rod v8...
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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.
I thought Ernie Elliott did them.........
No, not in the '80's, when Bill was winning all the races.
Bill's team tried to keep the guy hidden, as long as possible. It's my recollection, the they would not, tell Ford or any other team, what they were doing.
Again, as I remember, Penske also used the same guy for his NASCAR, AMC program.
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I think maybe Randy probably has a recollection of a company called Endyn and an aerospace engineer who if memory serves me named Larry Widmer. Larry was promoting a "soft chamber" with a fair amount of swirl for Ford NASCAR program. As I remember Ford engineers thought pretty highly of Larry's work. This was back in the 1980's. Larry and his company were in California.
Texas. Larry is ahead of his time for sure. Those who he helped with initial concepts , took the information and did their own take on it.
Randy
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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
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So, Randy, was it Larry Widmer that was doing Bill's heads, back in the 80's and also Penske's AMC project?
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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
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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?
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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
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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.
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Randy, are you familiar with Bill's heads being welded up and smaller valves used?
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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
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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.
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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.
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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.
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Found a couple of pictures of MM "Surface Turbulence”. (if anyone cares)
(http://carphotos.cardomain.com/ride_images/1/2519/301/6295150016_large.jpg)
(http://carphotos.cardomain.com/ride_images/1/2519/301/6295150007_large.jpg)
Credit to 335ist : http://www.cardomain.com/ride/629515/1988-bmw-3-series/
Also a thread or two on turbo bricks:
(http://www.sheenconsulting.com/car/pics/IntakeSTtop.JPG)
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...
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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.
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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
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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
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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.
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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
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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.
I used to be a Test Engineer at a snowmobile and ATV manufacturer. We used all piezo-electric pressure transducers to monitor cylinder/combustion pressure. Along with monitoring crank and cam position to the .01 of a degree, valve position with laser transducers to catch any valve float, and strain gages on each of the petals of the reed valves (2 strokes), it was amazing how much data you could gather. The flutter experienced by the reed valve petals on an 800 cc 2 stroke turning 10,000 on the pump always fascinated me. The fact that we could see that movement and graph it precisely in relation to crank position, cylinder pressure, injection timing, or any other wide variety of variables helped dial these engines in precisely.
It was not unusual to record data at 100,000 Hz or more to see exactly what was going on. Then again, these were $3,000 pressure transducers plugged into $80,000 Data Loggers running inside $3,000,000 AVL AC drive dyno cells. Definitely not your shade tree mechanic level stuff.
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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
You mean it's not always those "cheap" OEM torque to yield bolts that was the problem!!!??? If you are terrible at tuning use cheap head bolts LoL
I used to be a Test Engineer at a snowmobile and ATV manufacturer. We used all piezo-electric pressure transducers to monitor cylinder/combustion pressure. Along with monitoring crank and cam position to the .01 of a degree, valve position with laser transducers to catch any valve float, and strain gages on each of the petals of the reed valves (2 strokes), it was amazing how much data you could gather. The flutter experienced by the reed valve petals on an 800 cc 2 stroke turning 10,000 on the pump always fascinated me. The fact that we could see that movement and graph it precisely in relation to crank position, cylinder pressure, injection timing, or any other wide variety of variables helped dial these engines in precisely.
It was not unusual to record data at 100,000 Hz or more to see exactly what was going on. Then again, these were $3,000 pressure transducers plugged into $80,000 Data Loggers running inside $3,000,000 AVL AC drive dyno cells. Definitely not your shade tree mechanic level stuff.
I haven't data logged a 2 stroke and watched cylinder pressure and never had the stuff to watch the reed petals. All of that stuff I did mostly on diesels and a few push-rod V8's just for fun while I was figuring out how to run all the electronics. I did race snowmobiles and quads for a quite a long time and even without an impressive graph data logging the petals I have an enormous amount of respect for what those reed can do.
The pressure transducers I was using, I'm sure they're are better versions now, were also piezo's good to 5k psi but they had a very definite life span and it wasn't as long as you would want (at least not when you have to pay for em!).
But really, when you consider the cylinder pressure, temperatures and everything else that's going on in a push rod engine even at 5000 rpm it's pretty impressive on a basic level of what the material can handle. Especially when you compare it to what we had available 75 years ago, or even 20. I doubt many people driving their 100hp hotrod A or B model Ford's around would have thought it was common to see 500-700hp cars on the show room floor.
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https://www.youtube.com/watch?v=jdW1t8r8qYc
Here is a better slo mo Briggs and Scrapiron see thru head video. The alcohol one is pretty interesting, especially being such low compression.
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https://www.cycleworld.com/flat-head-motorcycle-engine-examined-kevin-cameron-top-dead-center//