Ok. Peak flow cfm doesn't mean as much as cfm where the cams spend most of there time in mid lift and duration. You are right about high flow numbers dont always mean more power. An automotive engine still makes more power with more cylinder pressure, just as a single or any other internal combustion engine does. IF you have air/fuel coming into the combustion chamber and have a slight restriction at the exhaust, you are not going to see the power you could if it was unrestricted. That is what I am saying. In a turbo application volume is not the best way of spooling the turbine. You would want more pressure to turn the turbine so it wont lag. You still would want a little volume but pressure is going to spool it up quicker. Alot of the has to do where the turbo is placed also. The farther the turbo is away from the exhaust port the less pressure it has against it in a givin amount of time. Hence turbo lag.

 

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Every internal combustion engine benefits from cylinder pressure. A multi-cylinder motor has the benefit of other cylinders being in their powerstroke while some are in their intake stroke and others are in their exhaust stroke.

Lets say you have two cylinders on their powerstroke while two are on their intake stroke, how much harder will that motor be sucking air in than a single that can only rely on the inertia that is left over from the powerstroke to suck air in on the intake?

This makes every aspect of preserving cylinder pressure of huge importance to how the single cylinder motor revs and what power it makes.............including proper exhaust port sizing. On a N/A motor, if the exhast ports are opened up too much to the point of compromising cylinder pressure (specifically bottom end), smaller head pipes can actually be an improvement...........but it has to be at the head pipe. A pee shooter or a quiet core putting the restriction at the end of the pipe will exacerbate the problem.


I simply noticed a generalization being applied in a turbo application from non-turbo experiences that is not true in all cases but was presented as though it were........so I thought I would share a few things to consider. [img]i/expressions/face-icon-small-smile.gif[/img]


Btw, I buy my exhaust gaskets from Ron Wood.

 

Oh so that is why more cylinder make more power then less cylinders do.....[img]i/expressions/face-icon-small-disgusted.gif[/img]. Yes smaller head pipes can help performance, but restriction in those headpipes from the outlet of the exhaust port is hurting performance. On the same note smaller headpipes can also hurt performance to. Single cylinder motors still have inertia also, just not as much as a multi cylinder motor would. Which I am sure you know this. In Scoobys application he is not going to want any restrictions going into that turbo. Especially since where it is placed.

 

I agree! [img]i/expressions/face-icon-small-smile.gif[/img]

 

Ive always been told that bigger is not always better.....but that remains to be seen.

 

So what are the best ways to create cylinder pressure? Other than the obvious?

 

Goodsound - What specific things are you referring to when you say "the obvious" ?

 

I was once told that its not the size of the wand, its the magic of the magician.[img]i/expressions/face-icon-small-wink.gif[/img] She was trying to make me feel better.[img]i/expressions/face-icon-small-blush.gif[/img]

 

Big'un, I think you misunderstood her...............big is good! [img]i/expressions/face-icon-small-wink.gif[/img] I don't know what that says about the "Magic" tho...... lol


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