[Stan Weiss]

Originally Posted by i82much

how does a smaller engine running at a higher RPM react differently to plenum size than a bigger engine at a lower RPM?

If we have two 600 HP engines, say a 455 peaking at 6000 RPM and a 535 peaking at 5400 RPM, does the 535 see a benefit going to a bigger plenum that the 455 does not see? And if so, why?

I am not answering your question, just looking at your question a little differently. At 100% VE a 535 @ 5400 RPM will want the same mass air flow as the 455 @ 6349 RPM. Now they will only produce the same HP if they can both produce the same BSAC numbers

Stan

[i82much]

Originally Posted by Stan Weiss

I am not answering your question, just looking at your question a little differently. At 100% VE a 535 @ 5400 RPM will want the same mass air flow as the 455 @ 6349 RPM. Now they will only produce the same HP if they can both produce the same BSAC numbers

Stan

Thanks Stan. I understand that part. What i don't understand is that there seems to be a theory that a bigger engine wants a bigger plenum. But what I don't understand is why the plenum cares whether it is a big engine sucking slowly on it or a small engine sucking quickly on it, if that makes any sense.

I'm sure there is a more artful way to phrase that concept but it's not coming to me at the moment

[Stan Weiss]

Originally Posted by i82much

Thanks Stan. I understand that part. What i don't understand is that there seems to be a theory that a bigger engine wants a bigger plenum. But what I don't understand is why the plenum cares whether it is a big engine sucking slowly on it or a small engine sucking quickly on it, if that makes any sense.

I'm sure there is a more artful way to phrase that concept but it's not coming to me at the moment

I can not say about plenum size, but I can say about cylinder head flow and carb size. My software produces these same results, but more people know Larry's software, so I am showing those results.

Stan

[i82much]

Originally Posted by Stan Weiss

I can not say about plenum size, but I can say about cylinder head flow and carb size. My software produces these same results, but more people know Larry's software, so I am showing those results.

Stan

That's interesting, so it looks like you can make 600 hp with a 275 cfm head assuming you use a really long duration cam, if I am reading that right.

[Stan Weiss]

Originally Posted by i82much

That's interesting, so it looks like you can make 600 hp with a 275 cfm head assuming you use a really long duration cam, if I am reading that right.

No. I read in an old input file I had for a 535 @ 7400 RPM and didn't optimize the cam for these engines. Pipe Max works differently and doen't use the cam to come up with the HP number. But yes it is saying for the best build you can make about 2.2 HP per 1 cfm of cylinder head air flow.

Stan

[i82much]

Originally Posted by Stan Weiss

No. I read in an old input file I had for a 535 @ 7400 RPM and didn't optimize the cam for these engines. Pipe Max works differently and doen't use the cam to come up with the HP number. But yes it is saying for the best build you can make about 2.2 HP per 1 cfm of cylinder head air flow.

Stan

gotcha, thanks!

[Gach]

There’s all kinds of software out there, but the real software is the guys out there who make the real hp. The amateur software builders can only surmise. How it all works.

[PAUL K]

Originally Posted by i82much

That's interesting, so it looks like you can make 600 hp with a 275 cfm head assuming you use a really long duration cam, if I am reading that right.

One could make 600 HP with a stock iron head that flows 220 cfm or at least come darn close.