IHADAV8.com - Turbo Buick Tech, and Nonsense
Tech Area => General Buick Tech => Topic started by: good2win22 on May 30 2014, 12:02:38 PM
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Does anyone have or can anyone point me in the direction of a chart with stock intake and exhaust CFM numbers? I am sitting here at work pondering the gains of the a particular aluminum head. I have a copy of it's flow numbers at varying stages of lift but I can't locate anything on a stock head. Wouldn't it be nice to have my own flow bench.....
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The aluminum provides much more than just additional flow. You are able to use higher compression ratio and additional timing to gain power with an aluminum head and its detonation resistance.
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cfm isn't everything, a better designed/modified port will lend itself to velocity over cfm; a better designed naturally aspirated air pump will effectively respond better to boost conditions.
But, here you go (a little down the page): http://users.erols.com/srweiss/tablehdc.htm#Buick (http://users.erols.com/srweiss/tablehdc.htm#Buick)
And yes, those are some of the shittiest production flow numbers in history. I recently drove a stock N/A 3.8L Buick V6 (because I own it) and it was the worst motoring experience of my life. I will always maintain what a crappy engine these are without a turbocharged band-aid...
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That's exactly what I was hoping to find! Thanks motorhead! BTW, was looking at a wagon about a month ago and it was sold before I could make an offer. Always enjoy reading your build.
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The aluminum provides much more than just additional flow. You are able to use higher compression ratio and additional timing to gain power with an aluminum head and its detonation resistance.
Not so....:)
All things being equal, the aluminum head will produce less power than the cast iron head due to its poor thermal efficiency when it comes to the combustion process.
The real benefit of aluminum is lightweight and ease of repair. Of course, as we cannot buy an iron head with the port size of an aftermarket aluminum head, that breaks the "all things being equal" :)
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Iron might have thermal efficiency, but I still say the aluminum has more detonation resistance allowing additional compression and timing. Then there's that weight savings thing you mentioned.
The decision becomes are you going fast or are you going long?
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Once you raise the compression to make up for the lost heat, then you lose any perceived detonation resistance. The old rule of thumb that one raises the CR one point to make up for the power lsot from using aluminum works pretty well.
Now if you play with cam timing in order to affect dynamic cylinder pressure, you add another variable.
Modern heads may use swirl and chamber design to allow even more compression but that has nothing to do with the material.
Detonation is the auto-ignition of the end gasses in the chamber as opposed to ignition caused by the flame front started by the plug firing. It is affected by mixture distribution and temperature as well as fuel resistance to auto-ignition.
Aluminum retains less heat in the chamber and thus makes less power unless compensated for by timing, compression, or boost.
yes, one can run more compression but only to the point that one gets back to the heat retained by a cast iron chamber- being able to increase compression does not allow us to exceed that of the iron unless we change other variables as some modern engines do :)
I have learned to believe in science as I got older
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Having to increase compression to get back to even also increases the parasitic pumping losses too.
Plus aluminum conducts more combustion heat into the waterjacket... . and we all know you have to have a $10,000 custom radiator to start with. :D