ProComp/Speedmaster aluminum heads

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318willrun said:
I mean, I'm willing to change my thinking, but somebody is going to have to offer some science. Nobody is arguing tire or balloon deflation with cooler temps = less pressure. Only explanation I'm seeing being offered is the process happens so fast that the drop in temp doesn't lose pressure???? Yet, heat crossovers are blocked and air gaps are used and the air moves MUCH faster through the intake which is feeding 8 cylinders than the air moves through a single cylinder on a 4 stroke.
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Temperature doesn't affect pressure, it affects density. Cool are is more dense than warm air.

The analogy of tires and balloons is flawed because the amount of air in the space hasn't changed, only the density. Now, with the reduced density, there is less volume, and less volume in a given space equals less pressure against the inside of the container it's in. This is why newer cars have nitrogen in the tires, it's less affected by temp changes and so the density isn't as affected and tires maintain a more equal pressure with changes in weather.

With engines, if it's normally aspirated, we tend to do things to try and keep the air cool to get a more dense intake charge. Hood scoops, cold air boxes, air gap intakes etc.

The other ways to increase the "density" is to use mechanical means, blowers, turbos, or chemical means, nitrous oxide etc.

The "cooling" of the heads is not going to matter since you're not "cooling" a flame. The burn is the burn and whatever made it into the chamber, is there to stay, until the valves open and let it out.


Science.... :)
 
Cuda416 said:
Temperature doesn't affect pressure, it affects density. Cool are is more dense than warm air.

The analogy of tires and balloons is flawed because the amount of air in the space hasn't changed, only the density. Now, with the reduced density, there is less volume, and less volume in a given space equals less pressure against the inside of the container it's in. This is why newer cars have nitrogen in the tires, it's less affected by temp changes and so the density isn't as affected and tires maintain a more equal pressure with changes in weather.

With engines, if it's normally aspirated, we tend to do things to try and keep the air cool to get a more dense intake charge. Hood scoops, cold air boxes, air gap intakes etc.

The other ways to increase the "density" is to use mechanical means, blowers, turbos, or chemical means, nitrous oxide etc.

The "cooling" of the heads is not going to matter since you're not "cooling" a flame. The burn is the burn and whatever made it into the chamber, is there to stay, until the valves open and let it out.


Science.... :)
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Agree with Sam, good post. I had considered fresh/cool air and hood scoops, etc. My way of thinking is once the valve is closed, the air in the cylinder, if ran cooler at that point (valve closed) would be less pressure. In other words, as the piston approaches the compression stroke, the cooler head would reduce density (like the tire) vs a hotter iron head. Certainly some flaw to the thought, but maybe a little truth to it as well....
 
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318willrun said:
Agree with Sam, good post. I had considered fresh/cool air and hood scoops, etc. My way of thinking is once the valve is closed, the air in the cylinder, if ran cooler at that point (valve closed) would be less pressure.
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Except that if it's cooler in the chamber, it was cooler before the chamber - which would mean more dense, which means more air/fuel in the chamber, which means more power.

I get what you were trying to say/ask, but it just doesn't/can't happen that way because the incoming air is almost always cooler than the engine induction components themselves, and so the charge mixture can only increase in temperature once it's through the manifold...

The physics of combustion mean that nearly all heat transfer is from the burning gasses themselves, because until the mixture ignites there's not enough convection for the incoming mixture to have any effect on the engine components, or for the engine components to have an effect on the mixture.
 
Phreakish said:
Except that if it's cooler in the chamber, it was cooler before the chamber - which would mean more dense, which means more air/fuel in the chamber, which means more power.

I get what you were trying to say/ask, but it just doesn't/can't happen that way because the incoming air is almost always cooler than the engine induction components themselves, and so the charge mixture can only increase in temperature once it's through the manifold...

The physics of combustion mean that nearly all heat transfer is from the burning gasses themselves, because until the mixture ignites there's not enough convection for the incoming mixture to have any effect on the engine components, or for the engine components to have an effect on the mixture.
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I guess this is the deepest I've ever thought into the theory as I've always ran iron heads on my old rides. I'm glad this conversation has happened, because I see my thoughts with aluminum heads had holes in it. :D Do not mistake this as I opposed aluminum heads, because I do not and may run some soon in my own future.

thanks to all that took the time to work through this conversation :)
 
318willrun said:
I guess this is the deepest I've ever thought into the theory as I've always ran iron heads on my old rides. I'm glad this conversation has happened, because I see my thoughts with aluminum heads had holes in it. :D Do not mistake this as I opposed aluminum heads, because I do not and may run some soon in my own future.

thanks to all that took the time to work through this conversation :)
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I'm no expert at all, and will also run alum heads in the future, but the whole iron/alum myths have always bugged me because so many things get repeated without backup info.

Combustion is complicated, and alum vs iron definitely has an impact but it seems to be in different ways than 'common sense' would seem to suggest. I'm still digging through the occasional engineering or research paper where I can - always fascinating stuff to find.
 
Phreakish said:
I'm no expert at all, and will also run alum heads in the future, but the whole iron/alum myths have always bugged me because so many things get repeated without backup info.

Combustion is complicated, and alum vs iron definitely has an impact but it seems to be in different ways than 'common sense' would seem to suggest. I'm still digging through the occasional engineering or research paper where I can - always fascinating stuff to find.
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100% agree.
 
http://web.mit.edu/2.61/www/Lecture notes/Lec. 18 Heat transf.pdf

Here's at least one of the items I found which I've found interesting. Note that the aluminum head ran cooler, but that both materials remain below ignition temperature. That the spark plug tip and the exhaust valve are the hottest items in the chamber and so likely the greatest contributors to pre-ignition.

Also, the lower running temp of the alum cylinder head suggests that the reduced thermal resistance doesn't result in more heat extracted but instead in a lower surface temperature of the combustion chamber. At least that's my take-away..
 
And let's remember that an IC engine, in its best form is about 28-30% efficient. You can get a couple of points better but its costly.

The biggest loss of heat (power) is the exhaust. I remember my first data logger. I forget the brand but I had EGT's and all the rest. At that time...the sampling rate was 5 times a second!!! 5 times a second. At the time that was pretty good. A few short years later a sampling rate of 100 times a second was easy.

I mention this because it's relevant. This is because if you think about it, if you divide a second into five segments, and then understand that once you sample the data there is a huge gap in time until the next sample. Let me see if I can show this in text.

Let's make a dot the sample point and a dash the time in between the sample points. Sooooo...

.----.----.----.----.

That is five samples per second. What do you see??? Huge gaps between samples. That is all time the computer isn't getting information.

Now think about sampling 100 times a second and how much less time you have between samples. I'm looking at a data logger that can sample two hundred times a second.

My car at that time was a 9.80ish car. At 5 samples a second you only get 50 samples per run! That ain't much. If it was sampling 100 times per second, you'd get 1000 data points per run.

I said all that to say this:

The rate of change of almost any function you can measure happens so quick that transient response time is critical. IOW's things happen so fast that one system can't overcome another. As in, the rate of temperature change happens so quickly that even the head can't reject the heat fast enough to affect detonation resistance. I hope that makes sense.

Another thing I learned when I started data logging was even with relatively quick sampling rates, some other limits were expose. Such as transient response time of the EGT probes. Those damn things respond so slow it's almost useless to use them for anything other that cylinder to cylinder balance, and that can take you right down a rabbit hole all by itself. You make changes based on those slow buggers and you'll be sorry.

I also learned that when running alcohol (it happens on gasoline too but you have to be real rich to see it) if you get too far to the rich side the exhaust gas temp will go through the roof. I think the highest EGT's I'd seen on my junk was like 1660 or so. The headers should have melted off the car, the plug should have been missing it's ground wire and much more.

What happens when you get too rich the fuel doesn't get burned before the exhaust valve opens and that combustion continues into the exhaust pipe. It makes you think you are lean but you are pig rich and adding fuel makes it worse. That's just one more way a measuring tool can screw you if you aren't thinking about the entire process.

Slow ignition timing does the same thing.

Funny story. A customer had a friend who was running an ex Pro Stock Truck in Comp Eliminator. He called me from the pits and said my buddy has EGT's that are going through the roof and he's deathly afraid to lean it out as he can't afford to kill his engine.

I forget what engine it was but it was a Dodge. Anyway, I said what does he have for timing and jets? The timing was 24 degrees total and I forget the jets, but they were way too big. I said tell him to drop 4 jet sizes and put the total timing to 30 degrees. Make a pass and check the EGT's.

He was scared but he did it. Temps started dropping like a rock. He eventually got to 32 total and ended up dropping 8 jet sizes.

You can get real crossed up in a New York second of you ain't careful.
 
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yellow rose said:
And let's remember that an IC engine, in its best form is about 28-30% efficient. You can get a couple of points better but its costly.

The biggest loss of heat (power) is the exhaust. I remember my first data logger. I forget the brand but I had EGT's and all the rest. At that time...the sampling rate was 5 times a second!!! 5 times a second. At the time that was pretty good. A few short years later a sampling rate of 100 times a second was easy.

I mention this because it's relevant. This is because if you think about it, if you divide a second into five segments, and then understand that once you sample the data there is a huge gap in time until the next sample. Let me see if I can show this in text.

Let's make a dot the sample point and a dash the time in between the sample points. Sooooo...

.----.----.----.----.

That is five samples per second. What do you see??? Huge gaps between samples. That is all time the computer isn't getting information.

Now think about sampling 100 times a second and how much less time you have between samples. I'm looking at a data logger that can sample two hundred times a second.

My car at that time was a 9.80ish car. At 5 samples a second you only get 50 samples per run! That ain't much. If it was sampling 100 times per second, you'd get 1000 data points per run.

I said all that to say this:

The rate of change of almost any function you can measure happens so quick that transient response time is critical. IOW's things happen so fast that one system can't overcome another. As in, the rate of temperature change happens so quickly that even the head can't reject the heat fast enough to affect detonation resistance. I hope that makes sense.

Another thing I learned when I started data logging was even with relatively quick sampling rates, some other limits were expose. Such as transient response time of the EGT probes. Those damn things respond so slow it's almost useless to use them for anything other that cylinder to cylinder balance, and that can take you right down a rabbit hole all by itself. You make changes based on those slow buggers and you'll be sorry.

I also learned that when running alcohol (it happens on gasoline too but you have to be real rich to see it) if you get too far to the rich side the exhaust gas temp will go through the roof. I think the highest EGT's I'd seen on my junk was like 1660 or so. The headers should have melted off the car, the plug should have been missing it's ground wire and much more.

What happens when you get too rich the fuel doesn't get burned before the exhaust valve opens and that combustion continues into the exhaust pipe. It makes you think you are lean but you are pig rich and adding fuel makes it worse. That's just one more way a measuring tool can screw you if you aren't thinking about the entire process.

Slow ignition timing does the same thing.

Funny story. A customer had a friend who was running an ex Pro Stock Truck in Comp Eliminator. He called me from the pits and said my buddy has EGT's that are going through the roof and he's deathly afraid to lean it out as he can't afford to kill his engine.

I forget what engine it was but it was a Dodge. Anyway, I said what does he have for timing and jets? The timing was 24 degrees total and I forget the jets, but they were way too big. I said tell him to drop 4 jet sizes and put the total timing to 30 degrees. Make a pass and check the EGT's.

He was scared but he did it. Temps started dropping like a rock. He eventually got to 32 total and ended up dropping 8 jet sizes.

You can get real crossed up in a New York second of you ain't careful.
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Holy AJ..!!...
 
Dam, it almost looks like I should be giving my cheap CNC flimsy Procomp heads away b4 they destroy my short block. They will be flopping around like a chicken with its head cut off. Kim
 
oldkimmer said:
Dam, it almost looks like I should be giving my cheap CNC flimsy Procomp heads away b4 they destroy my short block. They will be flopping around like a chicken with its head cut off. Kim
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drop one on the floor and it will hit ya in the nogg'n on the rebound! :eek:
 
j par said:
Well I remember what it was about when I asked it this morning but 318 has valves that will fly took the discussion off into his own world and now everybody is left wondering what this thread was all about...
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:eek::eek: I was right on Que !~~ Aluminum heads!!!!
 
oldkimmer said:
Dam, it almost looks like I should be giving my cheap CNC flimsy Procomp heads away b4 they destroy my short block. They will be flopping around like a chicken with its head cut off. Kim
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Then you can believe the hype like 318 has valves that will fly and think Promax is going to be better quality...
he's had laboratory core test done for evidence..
 
j par said:
Then you can believe the hype like 318 has valves that will fly and think Promax is going to be better quality...
he's had laboratory core test done for evidence..
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BWAHAHAHAA Jpeghasrubberheads!!!!!!! :D :D
 
yellow rose said:
Did you actually ask the question yet? I may have missed that post.
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give me a second I'll look back a few pages here it should be the first post or two today since a week ago...
it seems like I can't say anything anymore without 318 turning everything into a fiasco or basically spaghetti...(with ketchup)...
 
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