Which Heads For 540 Sci
12-06-2011, 09:30 AM
#62
http://www.youtube.com/user/valakora.../2/F9i6EMDNAc0
The same holds true for exhaust ports. From the flow bench I learned the bbc choke is at the flange. If the port is correct, the area at the flange could be increased to accomidate a header size of 2.250+ and flow 340+ cfm maintaining the 1.880 exhaust valve (.800 lift without a cheater pipe). My guess is that is too much export for a 540 ci marine engine that runs 5700 rpm. So, if I had my way I would shrink that port and valve size to fit the engine. I have had reputible builders tell me "the flow bench doesent mean anything". Personnaly I question if they know how to use it properly.
12-06-2011, 10:56 AM
#63
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I have been following this thread and reading carefully and I feel a lot of valid agument has been made here and that not all cylinder heads flow "just" air the same or as effective.
As a cylinder head manufacturer and self taught designer and cylinder head engineer I have also learned that one must also carefully look at what the air/fuel mixtures "wet flow" do in the intake systems, intake port and entry and distribution in the cylinder and combustion chamber.
All this talk and comparison of flow numbers, velocity, port size, valve size, head pipes and such when considered and compared only from the standpoint of dry air cfm is a bit misleading and over simplification.
We all know we can't burn just air in an engine and make power! Does not really matter how much or how fast we put just air into or out of an engine, we have got to mix fuel in this airstream and flow and we've got to suck or pack it into the chamber in its most efficient distribution, compress it and burn it properly to extract the best power and torque!
This is why many tend to discount just flowbench testing and comparison of cylinder head designs and flow results as it can be shown many times that the highest flowing ports and such in cylinder heads do not always deliver the best end result.
That being said, it is obvious that one can tweak and maximize cylinder head air flows but without looking at air/fuel mixture flows one can not always acheive the best result with just dry air flow.
Raylar did some wet flow testing on our first iterations of heads and we learned a lot more than we really wanted to know. Trust me , it ain't easy making cylinder heads really work on a running engine, just a lot of dyno time and engine testing to achive the better results.
I know wet flow testing system upgrades to existing flow benches are avaialble as well as the software support, but then you get into cylinder, piston, combustion chamber variations, temperature differentials and WHEW! it gets complicated!
My point here is let's not get so air flow competition oriented that we forget there are some pretty big other factors that make for real "volumetric efficency" and that is one of the places where real useable power comes from.
Just my two cents here.
Best Regards,
Ray @ Raylar
As a cylinder head manufacturer and self taught designer and cylinder head engineer I have also learned that one must also carefully look at what the air/fuel mixtures "wet flow" do in the intake systems, intake port and entry and distribution in the cylinder and combustion chamber.
All this talk and comparison of flow numbers, velocity, port size, valve size, head pipes and such when considered and compared only from the standpoint of dry air cfm is a bit misleading and over simplification.
We all know we can't burn just air in an engine and make power! Does not really matter how much or how fast we put just air into or out of an engine, we have got to mix fuel in this airstream and flow and we've got to suck or pack it into the chamber in its most efficient distribution, compress it and burn it properly to extract the best power and torque!
This is why many tend to discount just flowbench testing and comparison of cylinder head designs and flow results as it can be shown many times that the highest flowing ports and such in cylinder heads do not always deliver the best end result.
That being said, it is obvious that one can tweak and maximize cylinder head air flows but without looking at air/fuel mixture flows one can not always acheive the best result with just dry air flow.
Raylar did some wet flow testing on our first iterations of heads and we learned a lot more than we really wanted to know. Trust me , it ain't easy making cylinder heads really work on a running engine, just a lot of dyno time and engine testing to achive the better results.
I know wet flow testing system upgrades to existing flow benches are avaialble as well as the software support, but then you get into cylinder, piston, combustion chamber variations, temperature differentials and WHEW! it gets complicated!
My point here is let's not get so air flow competition oriented that we forget there are some pretty big other factors that make for real "volumetric efficency" and that is one of the places where real useable power comes from.
Just my two cents here.
Best Regards,
Ray @ Raylar
Last edited by Raylar; 12-07-2011 at 01:01 AM.
12-06-2011, 11:35 AM
#64
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Good post Ray.
This is the reason it is very difficult and certainly not a cost effective proposition to try and improve upon a thoroughly researched with state of the art equipment, and big budget, head design and cnc program.
It's relatively easy to improve performance on an iron production casting because they weren't designed with maximum performance in mind.
This is the reason it is very difficult and certainly not a cost effective proposition to try and improve upon a thoroughly researched with state of the art equipment, and big budget, head design and cnc program.
It's relatively easy to improve performance on an iron production casting because they weren't designed with maximum performance in mind.
12-08-2011, 01:19 PM
#65
I don't know much about 4-stroke head porting, but I do know(I use that term loosely) a couple good 2-stroke snowmobile engine experts and what they can do with cylinder/case/head porting is amazing!
The only way a cnc port job could compare to the work they do is if they were the ones that did the programming!
Maybe it's apples to oranges but the basic desired end result seems to be the same, pump more air through an engine, which in turn increases power.
The only way a cnc port job could compare to the work they do is if they were the ones that did the programming!
Maybe it's apples to oranges but the basic desired end result seems to be the same, pump more air through an engine, which in turn increases power.
