Competition Would there be any interest in an aluminum cylinder head?

[Forrest Nearing]

HEH!



I had one of those - and I gotta tell ya, I want to be standing WAYYYYyyyy back when a competition Cummins hits the same RPM as a well modded LS1! :-laf :-laf

just saying those ports flow a lot of CFM, but the engines still have great low end due to the ports ability to maintain good velocity at lower CFM demands.

 

[jvjump]

We have motor spinning 6,000 + rpm! And spike higher with no load! I belive that is in LS1 range!

 

[Gary - K7GLD]

just saying those ports flow a lot of CFM, but the engines still have great low end due to the ports ability to maintain good velocity at lower CFM demands.

Let's put this back into the perspective stated earlier - do those LS1's also have the cam overlap suggested - and are they using forced induction?

We have motor spinning 6,000 + rpm! And spike higher with no load! I belive that is in LS1 range!

Perhaps in the range of a STOCK, non turboed LS1...



And what are the full details of that engine you speak of, what valve overlap, and how much "not to be bragged about" boost at power peak?



Keep focused, that MY point in this discussion is my challenge to the suggestion that significant measurable BOOST is undesirable, "Nothing to be bragged about", in a competition engine, and that lots of valve overlap to purge cylinders, plus improved head flow rates are PREFFERED over boost if a choice is to be made.



All my earlier exposure to the theory of intake/exhaust flow in engines has been that valve overlap is a potentially useful tool that encourages improved total charge flow thru an engine as it operates, providing cylinder scavenging and enhancing cylinder filling as the exhaust valve closes and provides a small degree of artificial forced induction/cylinder pressure due entirely to the increased flow rate/speed created by valve overlap.



That's on a NORMALLY aspirated engine!



Things supposedly are different on a forced induction - turbocharged or supercharged - engine. Good flow rates thru use of intake/exhaust manifolds, as well as intake/exhaust head ports are certainly still good to have - as well perhaps as a relatively SMALL degree of valve overlap - but with the characteristic benefit provided by forced induction, large amounts of valve overlap for cylinder filling is not only largely unnecessary, it can actually bleed off a large degree of the desired cylinder charging and volume of additional charge mass the forced induction was installed for in the FIRST place!



Sorta like designing a big balloon with an included extra hole to bleed off that "undesirable" pressurized air we just worked so hard to get inside! :-laf

 

[DCreed]

what happened to this project????

 

[Forrest Nearing]

Let's put this back into the perspective stated earlier - do those LS1's also have the cam overlap suggested - and are they using forced induction?







Perhaps in the range of a STOCK, non turboed LS1...



And what are the full details of that engine you speak of, what valve overlap, and how much "not to be bragged about" boost at power peak?



Keep focused, that MY point in this discussion is my challenge to the suggestion that significant measurable BOOST is undesirable, "Nothing to be bragged about", in a competition engine, and that lots of valve overlap to purge cylinders, plus improved head flow rates are PREFFERED over boost if a choice is to be made.



All my earlier exposure to the theory of intake/exhaust flow in engines has been that valve overlap is a potentially useful tool that encourages improved total charge flow thru an engine as it operates, providing cylinder scavenging and enhancing cylinder filling as the exhaust valve closes and provides a small degree of artificial forced induction/cylinder pressure due entirely to the increased flow rate/speed created by valve overlap.



That's on a NORMALLY aspirated engine!



Things supposedly are different on a forced induction - turbocharged or supercharged - engine. Good flow rates thru use of intake/exhaust manifolds, as well as intake/exhaust head ports are certainly still good to have - as well perhaps as a relatively SMALL degree of valve overlap - but with the characteristic benefit provided by forced induction, large amounts of valve overlap for cylinder filling is not only largely unnecessary, it can actually bleed off a large degree of the desired cylinder charging and volume of additional charge mass the forced induction was installed for in the FIRST place!



Sorta like designing a big balloon with an included extra hole to bleed off that "undesirable" pressurized air we just worked so hard to get inside! :-laf

I know plenty of people with turbo LS1's, and they run great. with our RPM requirements, we would run considerably less (or zero) cam overlap

 

[Timebomb]

I have asked this question befor with no avail. Anyone know the specs on a stock 12v Cam ?

 

[kbbt]

what happened to this project????

Would like to know too.

 

[NoSeeUm]

<snip>



Keep focused, that MY point in this discussion is my challenge to the suggestion that significant measurable BOOST is undesirable, "Nothing to be bragged about", in a competition engine, and that lots of valve overlap to purge cylinders, plus improved head flow rates are PREFFERED over boost if a choice is to be made.



All my earlier exposure to the theory of intake/exhaust flow in engines has been that valve overlap is a potentially useful tool that encourages improved total charge flow thru an engine as it operates, providing cylinder scavenging and enhancing cylinder filling as the exhaust valve closes and provides a small degree of artificial forced induction/cylinder pressure due entirely to the increased flow rate/speed created by valve overlap.



That's on a NORMALLY aspirated engine!



Things supposedly are different on a forced induction - turbocharged or supercharged - engine. <snip>

Comp is closer to being right. You need to think in terms pounds (moles) of air vice pounds per square inch of air. I am sure you realize that pressure is due to the effect of restriction (headloss). It also means that in many cases a maximum pressure directly relates to a minimum flow rate. In Comp's explanation, I believe he simply was trying to say that less restriction results in lower boost even while increasing the flow rate.



I don't believe Comp was refering to any type of scavenging. I believe he was refering to the density of the air charge, the pounds of air in the cylinder, precisely when the piston is at BDC and the intake valve closes. The air charge available for combustion.



In any instance, it is always the displacing action of the piston with increasing cylinder volume not the applied pressure of the air that allows the combustion chamber to fill. The amount of air that gets in the cylinder is a function of volumetry efficientcy (VE) of the intake path. The pounds of air that get into the cylinder is a function of the VE and the air density. Comp also mentioned that with the compressor possibly running at a higher eficientcy, due to the lower boost, then the air temperature would be lower and that the air density would be higher for a given value of boost.



***** Back on track *****



Morse, you still mulling this over? I am still interested in your progress.



Jim