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Check this out. For longevity, I'd stay below 2k for sure. With a 2.4 upper, stick with a 8.6 lower or smaller.
 

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The graph is based on a stock cube LSA motor. What kind of effects will a smaller cylinder bore have on the above weaponX graph? Will a 4" stroke smaller cylinder bores affect any of the variables with the WeaponX graph?
 

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The graph is based on a stock cube LSA motor. What kind of effects will a smaller cylinder bore have on the above weaponX graph? Will a 4" stroke smaller cylinder bores affect any of the variables with the WeaponX graph?
The supercharger rpm is based on pulley ratio and engine rpm not the engine its bolted to.

How much boost it makes is related to other factors like bore x stroke.
 

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Check this out. For longevity, I'd stay below 2k for sure. With a 2.4 upper, stick with a 8.6 lower or smaller.
That's actually what I used to pick the pulley combo. I wanted a near stock combo for break in and daily driving plus a max effort option for hero tune dyno and 1/4 mile (8 nozzle methanol).
 

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The supercharger rpm is based on pulley ratio and engine rpm not the engine its bolted to.

How much boost it makes is related to other factors like bore x stroke.
As usual. . .you are correct Matt..😉
It is the CFM Demand of the engine, versus the CFM the Supercharger can Supply.

The output volume of a 'Roots Style Supercharger' can be simply calculated.

While this formula is accurate, there is a limit to any given Superchargers
output, and then we also have to consider the heat generated by the SC.

=> (rpm of blower multiplied by the internal volume of the blower divided by 1728)

Where the value of 1728 is 12^3, or 12 inches (one foot) raised to the third power
or cubed, so that we now have, in this case, Cubic Inches.

An 1.9 Liter TVS Blower is equal to 116 cid,
or it's internal volume is equal to 116 cid.

What will be the calculated output volume of the above
blower, If the blower is spun to an rpm of 24000. . .

=> (116 * 24000 / 1728)= 1610 CFM <= Equals 'Hot Air' that must be
cooled by an efficient mass flow recovery system to be of any real use.

So, as Matt indicated above; a larger engine, spun to say 7000 rpm
will inhale more air then a smaller engine at the same engine rpm.

We established how to calculate the output volume (supply side),
given in CFM of a blower above.

To calculate how much an engine will inhale (demand side)
=> 100% Volumetric Efficiency is equal to (CID * RPM / 3456)

Where the value of 3456 is found to be double that of the 1728, because
a 4-Cycle Engine turns over twice, or 720° to fire all it's cylinders.

So, how much air (cfm) will a 376 cid engine require if spun to 7000 rpm. ..
=> (376 * 7000 / 3456)= 762 cfm.

If we simply divide 1610 by the value of 762, we find that
we 'Should Have' doubled the Volumetric Efficiency or (VE%)
but the engine won't double it's HP, as we must double the
'Density Ratio' in order to double the HP.

The Density Ratio seen at the output of the mass flow
recovery system will determine the temperature of the
air, and the air temperature will, in the end, define the
air density.

Also, as many cylinder head porters state:
Flow is simply the square root of pressure.

Same statement holds true for Supercharged Engines.

If the ABS or Absolute Pressure Ratio is 2.0, then
square root that and we have a value of 1.41.

Without considering temperatures here, we find that
we have increased the density ratio by a value of 41%
by doubling the pressure.

So, if we want to double the fwHP, we must then have a
Supercharger that flows 4X the VE% of the engines demand.

Then we square root the value of 4, and we get a value of 2.
So we now have the ability to double the fwHP of the engine.

-however-
How efficient is your mass flow recovery system?

-finally-
Boost Pressure as some call it, is simply. . .
'The Opposition To Flow', meaning something is
either too large, or something is too small within
the induction system and / or internal volume of
the engine at some(?) engine rpm.

Cheers,
RD
 
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If the ABS or Absolute Pressure Ratio is 2.0, then
square root that and we have a value of 1.41.

Cheers,
RD
Wouldnt the square root of 2.0 be 1? Not 1.41? What did I miss?

Second question, what do you estimate my power output on pump gas and E-85 to be with each of my uppers? My dyno guy said he likely couldnt get it below 600 if he tried (tame street tune) and 700+ on E-85 should be easy. Methanol might get us over 800?
 

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Apparently, pre-algebra.


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HA HA DERP

Should have focused on math instead of my cold pizza!
 

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#feelinggrateful
 

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Just for my old friend Karch, who has a love / hate affair with decimal points..LOL
It is exactly; 1.414213562

Or conversely, the value of 2, is equal to squaring the value of 1.414213562.

At least that's the way my HP Calculator works..😂

Cheers,
RD
 

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I don’t have any hate affair with decimal points, I tend to watch significant digits, to be honest.

Fwiw, I use 1.414 for my casual calculations. I use 1.732 for sq root of 3.

Both are actually quite useful to remember, at least for me.

IE: how far is the throw from the foul pole to foul pole on a symmetrical baseball field with 330’ lines?

Answer: too far.

But, from third base to first it’s 90x1.4, about 127’.


Sent from my iPhone using Tapatalk
 

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Wouldn't the square root of 2.0 be 1? Not 1.41? What did I miss?

Second question, what do you estimate my power output on pump gas and E-85 to be with each of my uppers? My dyno guy said he likely couldn't get it below 600 if he tried (tame street tune) and 700+ on E-85 should be easy. Methanol might get us over 800?
I can usually estimate the fwHP / Output of an engine pretty close, if I am given all of the variables.
All I have, is what you put in your signature line, which does not include the CID of the Engine?

That's usually the first variable we need. . . .The Internal Volume of the engine, given in CID?
The second would be at what engine rpm will you shift at?

Those two values allow one to calculate the anticipated
'Volumetric Efficiency' for a given engine.

But one would 'Also' require many more values / inputs,
in order to calculate your fwHP with any accuracy.

-from your signature line-
1969 Chevelle RPM T-56 Magnum
L-76 block and heads, all forged Manley 4" H-beam long rod (ARP 2k) rotator (2618 pistons, tool steel top, ductile lower rings, filed 30)
ARP studded head and mains
BTR PDS Stage 4 cam, OEM stock (for now) LSA, Long tubes/X-pipe 3" mandrel SS

Cheers,
RD
 

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I can usually estimate the fwHP / Output of an engine pretty close, if I am given all of the variables.
All I have, is what you put in your signature line, which does not include the CID of the Engine?

That's usually the first variable we need. . . .The Internal Volume of the engine, given in CID?
The second would be at what engine rpm will you shift at?

Those two values allow one to calculate the anticipated
'Volumetric Efficiency' for a given engine.

But one would 'Also' require many more values / inputs,
in order to calculate your fwHP with any accuracy.

-from your signature line-
1969 Chevelle RPM T-56 Magnum
L-76 block and heads, all forged Manley 4" H-beam long rod (ARP 2k) rotator (2618 pistons, tool steel top, ductile lower rings, filed 30)
ARP studded head and mains
BTR PDS Stage 4 cam, OEM stock (for now) LSA, Long tubes/X-pipe 3" mandrel SS

Cheers,
RD
Sorry, I forget that the L-76 is an oddball, so most aren't familiar with it. Its a 6.0 aluminum so unless you sleeve them, boring should be kept to a minimum as the OEM sleeves are very thin. So we just honed 5 thou for cross hatch and check true (was a very low mileage motor from a wrecked G8). So with 4.005 and 4.0 stroke its 403 inches. Went with 11:1, zero decked with MLS 7 layer giving 40 quench. OEM size valves and factory cast rec ports; just went SS and Inconnel for durability, Ti locks and retainers. It's a 6.125 rod all forged Manley kit (H-beams) so it will handle higher rpms than those heads will likely permit, so I plan to let the dyno tell me the best shift point. I chose to run slightly high base CR to reduce the need of the blower to make the numbers I wanted. Since the LSA blowers are well known for creating a lot of heat once they get high up in revs. So E-85 primary, but will have flex fuel tune with GM sensor (running CTS-V ECM). So pump gas base tune, E-85 primary, and 8 nozzle meth setup for happy times (I don't want to run meth through the blower).

Cam is 235/252 .629"/.600" 119+5 according to BTR specs. It's on the large size for the stock heads, but I have a set of ARP 2000 head studs waiting for a set of better heads if the car doesn't run the numbers I hope. So I went up on the cam for that reason. But I now have an L-86 (big single) back up motor so, could go either way.

LSA is completely stock for now. Still need to order TB too now that I think about it...

Holley LS swap long tubes, 3" mandrel, X-pipe.

Sorry if I forgot anything, it's late! Lol
 

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I guess I should have stated im running Bosch ID1050x injectors but, have not yet installed the 8 methanol injectors (in the blower lid). I plan to have the brick reinforced as well.
 

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Sorry, I forget that the L-76 is an oddball, so most aren't familiar with it. Its a 6.0 aluminum so unless you sleeve them, boring should be kept to a minimum as the OEM sleeves are very thin. So we just honed 5 thou for cross hatch and check true (was a very low mileage motor from a wrecked G8). So with 4.005 and 4.0 stroke its 403 inches. Went with 11:1, zero decked with MLS 7 layer giving 40 quench. OEM size valves and factory cast rec ports; just went SS and Inconnel for durability, Ti locks and retainers. It's a 6.125 rod all forged Manley kit (H-beams) so it will handle higher rpms than those heads will likely permit, so I plan to let the dyno tell me the best shift point. I chose to run slightly high base CR to reduce the need of the blower to make the numbers I wanted. Since the LSA blowers are well known for creating a lot of heat once they get high up in revs. So E-85 primary, but will have flex fuel tune with GM sensor (running CTS-V ECM). So pump gas base tune, E-85 primary, and 8 nozzle meth setup for happy times (I don't want to run meth through the blower).

Cam is 235/252 .629"/.600" 119+5 according to BTR specs. It's on the large size for the stock heads, but I have a set of ARP 2000 head studs waiting for a set of better heads if the car doesn't run the numbers I hope. So I went up on the cam for that reason. But I now have an L-86 (big single) back up motor so, could go either way.

LSA is completely stock for now. Still need to order TB too now that I think about it...

Holley LS swap long tubes, 3" mandrel, X-pipe.

Sorry if I forgot anything, it's late! Lol
You wrote:
"so I plan to let the dyno tell me the best shift point."

'You also wrote:
"Cam is 235/252 .629"/.600" 119+5 according to BTR specs. It's on the large size for the stock heads"

First, you decide how much HP you desire, and then the engine rpm
will determine how much piston speed the engine develops. The higher
the piston speed, the higher the depression will be across the intake valve.
The above defines the 'Engine Flow (CFM) Demand'.

Once you have that info, you then will understand how much the cylinder heads 'Must' flow.
Now you now how large the camshaft must be.
The above defines the 'Engines Induction System (CFM) Supply Side'.

Also, heads that flow too little, will require a larger camshaft, not a smaller one.

An 403 CID Engine will make about 820 fwHP to 835 fwHP, 'IF' the cylinder fill equals 100%.

Small TVS Roots Style Blowers don't help to achieve that in any significant manner.
Proper piston speed, and the correct induction system requirements / scaling must be met first.

Then you add the correct size TVS Roots Blower and you generate more torque
at lower engine RPM, which is relevant to the Absolute, or (ABS) Pressure Ratio.

If the blower can also generate sufficient output at the shift rpm,
then your HP will also increase accordingly. But that is not what
we have with these small 1.9L TVS Blowers.

The CFM or Mass flow rate of the engine correlates with the Torque Curve.
In fact, they are pretty much the same. . . . .

820 fwHP will require about 1230 cfm.

That tells one that the heads must flow. . .
=> (1230 / 4 / 0.87)= 353 CFM, at or before convergence lift on these engines.

-in general-
A 235° camshaft can flow sufficient air, if the cylinder heads are scaled properly.
The same 235° cam will be insufficient, if the cylinder heads are not scaled properly.

All of the above is predicated on the the area of the piston, as well as the engine rpm.
Square root the area of the piston, and that would be the valve area required to begin with.

Any compromise, must then be compensated for via the camshaft.

Your piston has 12.60 Sq." of area.

=> (12.60^0.5 equals 3.55 Sq.".
Where raising the value of 12.60 to 0.5, is the same as taking the square root of that value.

A 2.165" valve has an area of 3.68 Sq.".

Again, it is all about 'Scaling'. . . .

Any Torque or HP values I give are always based on 'Gasoline' unless otherwise stated.

Cheers,
RD
 
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Your piston has 12.60 Sq." of area.

=> (12.60^0.5 equals 3.55 Sq.".
Where raising the value of 12.60 to 0.5, is the same as taking the square root of that value.

A 2.165" valve has an area of 3.68 Sq.".
Cheers,
RD
Ok so if I understand correctly, your post says that my intake valves are more than large enough for the piston area, but you are unsure if the heads port volume (CFM) is large enough to make the estimated 1230 cfm required to meet the "820 fwHP to 835 fwHP" capability based on displacement, correct?
 

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Ok so if I understand correctly, your post says that my intake valves are more than large enough for the piston area, but you are unsure if the heads port volume (CFM) is large enough to make the estimated 1230 cfm required to meet the "820 fwHP to 835 fwHP" capability based on displacement, correct?
Are you running a 2.165" intake valve?
If so, it's going to be shrouded and won't flow well with your 4.005" bore.

Rule of thumb for a wedge engine is 52% of bore equals max
intake valve size when the valve to deck angle is about 20°.

So, (4.005 * 0.52)= 2.08" intake valve.

As you roll the head over, or reduce the valve to deck angle,
you can move that 52% up to about 53%.

This is one of the reasons the Mast Heads perform so well.

You have a 10.5° valve to deck angle, and a combustion chamber
that is well thought out, and where both combined, help to reduce
valve shrouding to a minimal.

Plus their large bore head had a 2.204" valve and
an intake runner volume of around 285CC.

Simply put; it's real difficult to make power with a roots blower
with a small valve and a small runner.

That's why the 388 CID Engines with those heads run so well.

For those that are new to this forum and don't know,
a 388 CID LSA can be built using a 4.125" bore.

Increase the piston area, as well as the intake valve size,
and you can increase the %VE at a higher engine rpm.

Think of it this way:
((Bore area) multiplied by engine rpm divided by 60 divided by two)
Where the value of 60 converts Minutes to Seconds.
Where the value of 2, gives us the number of intake strokes.

Let's take Jesse's 401 as an example:
Jesse's engines bore is 4.125"

Bore area then equals 13.36 Sq."
Shift RPM is 6800 RPM.

=> (6800 / 60 / 2)= 57 intake strokes per second.
=> (57 * 13.36)= 762 cfm, and equals the 'Mean CFM' value.
**Note; 762 cfm would produce about 510 fwHP

Now, the pistons 'Peak Speed' is approximately 1.57
times the mean value. This occurs at ~74° ATDC, where
we find the piston headed 'Downward' on the intake stroke.

So, understanding the above, we then can also 'Attempt' to
include for the impact on the induction system, surrounding
that additional piston speed / motion.

Where the value of 1.57 equals Pi divided by two. . .
=> (3.14 / 2)= 1.57

=> (762 * 1.57)= 1196 'Peak Potential' CFM <= This is what we
shoot for, but normally won't realize, unless / until the 'Piston Speed'
is sufficiently high that we can generate a sufficient depression
across the intake valve, for a sufficient period of time. . ..
which is determined by . . . ."Cam Duration", especially the IVC event!
** Note: 1196 cfm would produce about 802 fwHP

--next in line is the cylinder head flow and camshaft-
When the piston speed is sufficient, we can then
calculate what the heads must flow, as well as
integrate the cylinder head flow into the camshaft
requirements.

The above relates to an NA Engine.

The above calculations have also been made, assuming
gasoline of the correct quality is used.

With a roots blower, one can better the above,
but it takes a lot of attention to details. . . .

With a roots blower on 93 Octane, I believe that
Jesse made ~835 HP.

Jesse pays extreme attention to details, so
I chose Jesse's engine as the model to
use here.

Now, let's use the HP value, and attempt to determine
how many CFM his engine 'Inhaled' to make that HP. . .

=> (835 / 0.67 / 0.87)= 1432 cfm.
Where 0.67 is the %ASE.

Where 0.87 serves to note that the induction system
is assumed to sustain a ~13% loss.

Jesse's engine uses a 2.204" intake valve.

But I don't know the valve to deck angle,
but I think(?) they are around 11°.

Since Steve / Karch sells them, maybe he can let us know. . . .

Finally for the OP:
If Jesse's bore area is 4.125", and his intake valve has a diameter of 2.204".

Then his valve divided by his bore ratio is. . .
=> (2.204 / 4.125)= 53.4%


To move above that one must go to a 'Cross Flow'
and 'Splayed Valve' Cylinder Head, having a valve
to deck angle of about 8°, or even less.

Many NHRA Pro Stock Engines use a bore of 4.750"
Many also use an intake valve of ~2.555".

Eight degrees, and sometimes even less valve to deck angle.
=> (2.555 / 4.750)= 53.8%

If the valve to deck angle reaches 0°, then
the valve would be sticking straight up out
of the combustion chamber.

Hence, if the blocks center to centers are wide enough,
one could design a head, which would have little to
no valve shrouding.

Cheers,
RD
 
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Are you running a 2.165" intake valve?
If so, it's going to be shrouded and won't flow well with your 4.005" bore.

Cheers,
RD
I believe thats the stock valve size for L-76 Rectangle port heads no? We just replaced them with Stainless intake and Inconel exhaust of the same OEM size.
 
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