Big differences in the camshaft requirements for an NA Engine, Centrifugal Blower and an DD / PD Blower.
I have not watched the video.
Time vs. Money
Videos, as are the magazine articles, are always compromised in some way or another.
Blades just went from 625 HP to 710 HP with a change in heads.
Blades, correct me if I am wrong, but I believe that was the only change you made. . . Correct!
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-as a general guideline-
For every CFM of air your engine inhales, your engine will produce ~1.0 fwHP.
-as a general guideline-
Your torque curve pretty much gives you a look at the CFM Flow Rate / Mass Flow Rate
that your engine is consuming. Piston Speed / Motion, is demanding a specific CFM at various crank angles, and the question becomes. . . Can your induction system 'Supply It'?
Peak Volumetric Efficiency (VE%) is found at Peak Torque Engine RPM.
As your Engine RPM is increased, you will understand that even
though the CFM Flow Rate / Mass Flow Rate is increased after
peak torque rpm, the Mass Flow Rates VE% is 'Decreasing'.
-in general-
PD / DD Blowers make huge torque improvements at lower engine rpm.
As the speed of the blower is increased, they become very inefficient.
Therefore, they are not the best blower to use to maximize fwHP
Expanding on what other forum members have stated above;
Our engine platform uses a small blower and a small TB.
Therefore, our engine platforms are running in a restricted form.
Therefore, torque will not be compromised, but fwHP will be.
Couple the two statements above, and one realizes why our dyno
charts show almost equal 'Peak Torque' and 'Peak HP' numbers.
Couple the above with Random's comment about requiring a
numerically higher LSA / LCA (Lobe Center Angle) value as we
simply can't afford to blow the mass charge out the exhaust side.
If this were not the case, we could run more positive overlap,
run a smaller exhaust valve allowing us to run a larger intake
valve, if we moved the valve guides. We could also open the
exhaust valve a little later.
As it is, we have a low compression / low efficiency engine.
This means the 'Burn Angle' is slow. Opening the exhaust
valve early to compensate for the zero overlap requirement
means we are not burning all the fuel, as the burn angle
is so slow.
I am not going to attempt to go into depth here regarding the
various porting techniques regarding NA or any of the varying
FI methods, but later I will touch on how I approach building
an engine for a PD / DD Blower.
In my opinion, they would all require a different cylinder head!
So, reducing this all down; both the cylinder head and the
camshaft requirements would be different regarding all of
the variations seen regarding the various blowers.
In the case of the PD / DD applications; since these blowers
won't hold a high pressure ratio, then we must pay attention
regarding valve size to bore size ratios, where we need to put
the maximum sized intake valve we can into the engine, which
is very similar to how we approach the building of an NA Engine.
At what engine rpm will we be shifting at?
We then extrapolate what the piston speed is.
That delivers to us the Piston CFM Demand at any
crank angle if desired, or we simply work with the
'Mean Piston CFM'.
Now we must look at the 'Supply Side'. . .
This leads us to what the bore size too valve size relationship
must be. This then tells one what size the port / runner must
be, and then that tells one what the camshaft requirements
must be. We do this after we verify the cylinder head flow
on the bench.
Most likely none of that was done within this video, and it
appears from the comments within this thread that the
video has served to complicate, rather than clarify. . . .
Again, nothing new as 'Time is Money'..
Cheers,
RD
