Single Cylinder Engines

General engine tech -- Drag Racing to Circle Track

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Bow
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Single Cylinder Engines

Post by Bow » Tue Mar 06, 2018 11:26 am

Hello,

I didn't know if this belongs in the actual Engine Tech Forum, so I'll post it here.

Have any of you all played with single cylinder, go kart type, engines?

I have been looking to modify the spare one I have just to see what it will do.

Basic Stock Engine information:

212 cc
Rated:
6.5hp @ 3600
8.1 ft.-lbs. @ 2500 RPM
Bore: 70mm
Stroke: 55mm
Compression Ratio: 8.5:1
OHV with a Hemi Head

I just finished building a Cyclekart (adult Go kart, styled like a racer from the 1920's), which is powered by one of these engines.
The Cyclekart weights 275lbs, the body is tube frame and fabric covering.

My engine is No longer stock and has been modified by:
Billet Aluminum Flywheel
Camshaft: .275" lift/ 230 duration @ .050" 104 L.S.A.
26lb valve Springs
Billet Connecting Rod that is 0.020" longer to 0 deck the piston
Mikuni VM22 carb
Longer intake runner Manifold
Longer header

The "Transmission" is a snowmobile style CVT setup and chain drive to the rear axle
So far, my first top speed run bagged 52.57 MPH, and i had to get out of it due to... traffic... but I'm pretty sure it has more in it..

So do any of you all ever play with small engines?
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Re: Single Cylinder Engines

Post by MichaelThompson » Tue Mar 06, 2018 8:51 pm

That's neat! I have been wanting to build a cycle kart but covered up with too many projects at the moment.

Have a couple go karts to fix up right now.

I assume you started with a Predator 212?

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Re: Single Cylinder Engines

Post by thatbikeguy » Wed Mar 07, 2018 12:42 pm

I build 2 strokes from 50cc(moped/scooter racing) to whatever the customer wants. I have built many kart engines beginning in the early '80s.

The kart looks terrific!!! What a fun project.

I am currently building a KTM 250 sx engine with a KTM big bore kit for a displacement of 293cc. It's for an 'Outlaw' shifter kart.

I mostly build 4 stroke DOHC inline fours for motorcycle roadracing and a few for drag racing.

I would like to buy a kart for chassis dyno purposes, but fitting different engines and clutch drive setups puts that notion beyond my patience level :D

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Re: Single Cylinder Engines

Post by mekilljoydammit » Wed Mar 07, 2018 2:50 pm

Ha, cool! Working on cyclekarts with my dad and working in the R&D lab for a company that makes, among other things, some of those little single cylinders. Actually after seeing some of the oddball flat track motorcycle races, I'm thinking of casting a hemi head with good ports for grins and building a frame to stick it in.

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Re: Single Cylinder Engines

Post by pcnsd » Thu Mar 08, 2018 10:58 pm

Can you post a picture(s) of the cylinder head and engine compartment with engine?. I would need more info to help. Con rod length for sure. Best bet based on what is posted is to drive the CR up. Speed is a matter of $, how fast can you afford to go? Understand that as you drive up HP beyond a certain point, if displacement stays the same, torque will fall. This will be an issue on a vehicle with significant mass.
- Paul

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Re: Single Cylinder Engines

Post by Bow » Sat Mar 10, 2018 2:52 pm

MichaelThompson wrote:
Tue Mar 06, 2018 8:51 pm
That's neat! I have been wanting to build a cycle kart but covered up with too many projects at the moment.

Have a couple go karts to fix up right now.

I assume you started with a Predator 212?

Thank you. it is a 2 year (on and off) Project.

Yes, started with the Predator 212 "Hemi Head" Model (#30636)

I am hoping to get Engine Pro in the Group Buy so I can start doing some simulation.

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Re: Single Cylinder Engines

Post by hoffman900 » Sat Mar 10, 2018 4:28 pm

I have a vintage 500cc Yamaha engine that is my pet project. The single cylinder stuff is fun because you can play engine R&D but you don't need multiple sets of everything. :shock:

Nick Smithberg (http://www.smithbergracing.com/) has played around with the hemi Predator head a little for fun and did the head for someone who has one on a drag mini bike that is really fast.
-Bob

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Re: Single Cylinder Engines

Post by Bow » Sat Mar 10, 2018 7:29 pm

Thank you everyone for the kind words. It is a hoot to drive.
My engine is modified way beyond what the Cyclekart Builders Gentlemen's Agreement allows, but I don't care... I built it for me, not them
pcnsd wrote:
Thu Mar 08, 2018 10:58 pm
Can you post a picture(s) of the cylinder head and engine compartment with engine?. I would need more info to help. Con rod length for sure. Best bet based on what is posted is to drive the CR up. Speed is a matter of $, how fast can you afford to go? Understand that as you drive up HP beyond a certain point, if displacement stays the same, torque will fall. This will be an issue on a vehicle with significant mass.
I understand speed vs $$!

Pics of the Head?
IMG_20171230_210436_512.jpg
IMG_20171230_210542_785.jpg
IMG_20171230_210554_791.jpg
This is not my actual head, it is a screen cap off You Tube. Same model
Hemi head.jpg
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Re: Single Cylinder Engines

Post by lefty o » Sat Mar 10, 2018 8:33 pm

last time was about 30 years ago, had a 67 polaris colt with a 1 cylinder. i prefer multiple cylinders now.

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Re: Single Cylinder Engines

Post by Bow » Sat Mar 10, 2018 11:53 pm

lefty o wrote:
Sat Mar 10, 2018 8:33 pm
last time was about 30 years ago, had a 67 polaris colt with a 1 cylinder. i prefer multiple cylinders now.
I can appreciate that... But singles are pretty inexpensive to play with...

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Re: Single Cylinder Engines

Post by pcnsd » Sun Mar 11, 2018 4:12 pm

I have run it through Pipemax and some spreadsheets, but I made some assumptions along the way and have some questions also
What prevents this thing from spinning faster? Is 4500 rpm within range or is there a governor of some type that limits RPM. If so, what is max RPM? Can it be defeated to get to 4500?
Are the peak torque and HP numbers from a stock motor or the suggestion of what you have now after mods?
Is 8.5:1 SCR stock or what you have with the longer connecting rod?
Do you have a tachometer on it?
- Paul

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Re: Single Cylinder Engines

Post by Bow » Mon Mar 12, 2018 11:01 am

pcnsd wrote:
Sun Mar 11, 2018 4:12 pm
I have run it through Pipemax and some spreadsheets, but I made some assumptions along the way and have some questions also
OK, thanks!

Let me see what I can answer:
What prevents this thing from spinning faster? Is 4500 rpm within range or is there a governor of some type that limits RPM. If so, what is max RPM? Can it be defeated to get to 4500?
Absolutely nothing now, I have pull the Governor out of the engine that limited it to 3600 - 3800 RPM. I have spun it to at least 5000 while driving it before the CVT goes into the overdrive and I watch the RPM drop below 4000.
With the stock valve springs it would start to float the valves around 5200 RPM, but I fixed that issue with the 26lb springs (as per the cam manufacturer suggestion).

The guys that race these engines in Go Karts say they can spin the 9000-10000 RPM if built correctly
Are the peak torque and HP numbers from a stock motor or the suggestion of what you have now after mods?
With it Governed at 3600 RPM are those advertised stock numbers
Is 8.5:1 SCR stock or what you have with the longer connecting rod?
Stock connecting rod (3.308") provided those SCR numbers. The rod I have installed is 3.328" which decks the stock flattop piston.

If it helps the Combustion chamber is 23cc
Do you have a tachometer on it?
Yes Sir. I'm running a Westach 2CT8-2 (0-8000 RPM)
It runs off the Magneto ground/kill switch lead and doesn't require a 12V source.
Image

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Re: Single Cylinder Engines

Post by mekilljoydammit » Tue Mar 13, 2018 9:12 am

Part of the trick with these things is that the ports are designed so that they can be die cast - so it's formed from the intersection of two cores that can be pulled out again. Really hurts things compared to a sand casting - there's no short side radius, as such.

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Re: Single Cylinder Engines

Post by Bow » Tue Mar 13, 2018 4:33 pm

Interesting thought, and that makes sense, especially for mass production

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Re: Single Cylinder Engines

Post by pcnsd » Tue Mar 13, 2018 9:20 pm

Here is a screenshot of your baseline data in Pipemax. It is pretty close to the suggested stock output. This is crankshaft HP.
Predator212 base.png
Here is a screenshot of about where I think you are now. The full data will follow the photo. Some things to note: Both valve are small for the bore, the intake valve in particular. I think you are in the area of 45-50 CFM max @ 28" H2O. My spreadsheet suggest you might get close to 70 cfm using the stock valve with porting. I will have some more later.
Predator212 changes.png
12.915 Cubic Inches @ 4750 RPM with 100.00 % Volumetric Efficiency PerCent

Required Intake Flow CFM @28 in. = 45.5 to 48.2 at .249 inch Valve Lift
Required Exhaust Flow CFM @28 in. = 39.0 to 42.3 at .205 inch Valve Lift

350 RPM/Sec Dyno Test Lowest Low Average Best
Peak HorsePower 9.3 9.5 9.6 9.7
Peak Torque Lbs-Ft 11.3 11.6 11.7 11.9

HorsePower per CID 0.718 0.733 0.742 0.752
Torque per Cubic Inch 0.875 0.898 0.910 0.921
BMEP in psi 132.0 135.5 137.2 138.9
Carb CFM at 1.5 in Hg. 18 20 21 22

Recommended Intake Valve Lift to prevent Choke = .249 Lift @ 4750 RPM
Recommended Exhaust Valve Lift to prevent Choke = .205 Lift @ 4750 RPM
Recommended Minimum Normal Maximum Time-Area-Duration Lifts
Intake Valve Lift = 0.2211 0.2490 0.2739 0.2895 0.3052 0.3208
Exhaust Valve Lift = 0.1882 0.2046 0.2250 0.2376 0.2525 0.2674
IntOpen= 11.00 IntClose= 39.00 ExhOpen= 39.00 ExhClose= 11.00
Intake Duration @ .050 = 230.00 Exhaust Duration @ .050 = 230.00
Intake CenterLine = 104.00 Exhaust CenterLine = 104.00
Compression Duration= 141.00 Power Duration = 141.00
OverLap Duration = 22.00 Lobe Separation Angle (LSA)= 104.00
Camshaft Straight Up = 0.00 degrees Cylinder Ignition Interval= 720 deg.

-- Operating RPM Ranges of various Components --
Best estimate RPM operating range from all Components = 2826 to 4826
Intake Flow CFM @28inches RPM Range from Flow CFM only = 2735 to 4735
Intake and Exhaust Systems operating RPM Range = 2996 to 4996
Intake and Exhaust Time-Area operating RPM Range = 3004 to 5004
Camshaft's Intake and Exhaust Lobes operating RPM range = 3072 to 5072
Intake Valve Curtain Time-Area at 0.275 Lift RPM Range = 3245 to 5245
Exhaust Valve Curtain Time-Area at 0.275 Lift RPM Range = 4385 to 6385

Intake Valve Close RPM = 5166 Exhaust Valve Open RPM = 4792
Intake System RPM = 4839 Exhaust System RPM = 5152
Intake Time-Area RPM = 4512 Exhaust Time-Area RPM = 5497
Intake Mach Z-Factor = 0.439552 Exhaust Mach Z-Factor = 0.474841
Intake Z-Factor Lift = 0.251826 Exhaust Z-Factor Lift = 0.197850

Curtain Area -to- Valve Area Convergence Intake Valve Lift inch= .266
Curtain Area -to- Valve Area Convergence Exhaust Valve Lift inch= .246

Target EGT= 1457.3 degrees F at end of 4 second 600 RPM/Sec Dyno accel. test
Octane (R+M)/2 Method = 87.8 to 88.9 Octane required range
Air Standard Efficiency = 58.05735 % for 8.500:1 Compression Ratio

------- Piston Motion Data -------
Average Piston Speed (FPM)= 1713.96 in Feet Per Minute
Maximum Piston Speed (FPM)= 2834.091 occurs at 73.41637 Degrees ATDC
Piston Depth at 73.416 degree ATDC= 0.9404 inches Cylinder Volume= 91.9 CC
Maximum TDC Rod Tension GForce= 920.7334 G's
Maximum BDC Rod Compression GForce= 466.7104 G's

----- Engine Design Specifications -----
( English Units ) ( per each Valve Sq.Inch area )
Engine Size CID = 12.915 Intake Valve Net Area = 0.868
CID per Cylinder = 12.915 Intake Valve Dia. Area = 0.887
Rod/Stroke Ratio = 1.528 Intake Valve Stem Area = 0.019
Bore/Stroke Ratio = 1.273 Exhaust Valve Net Area = 0.741
Int Valve/Bore Ratio = 0.386 Exhaust Valve Dia. Area = 0.760
Exh Valve/Bore Ratio = 0.357 Exhaust Valve Stem Area = 0.019
Exh/Int Valve Ratio = 0.926 Exh/Int Valve Area Ratio = 0.857
Intake Valve L/D Ratio= .259 Exhaust Valve L/D Ratio= .279
CFM/Sq.Inch = 51.2 to 54.3 CFM/Sq.Inch =54.3 to 55.4

Intake Valve Margin CC's Exhaust Valve Margin CC's
1.00 CC = 0.0688 1.00 CC = 0.0802
0.50 CC = 0.0344 0.50 CC = 0.0401
0.25 CC = 0.0172 0.25 CC = 0.0201
0.10 CC = 0.0069 0.10 CC = 0.0080

- Induction System Tuned Lengths - ( Cylinder Head Port + Manifold Runner )
1st Harmonic= 42.228 (usually this Length is never used)
2nd Harmonic= 23.967 (some Sprint Engines and Factory OEM's w/Injectors)
3rd Harmonic= 16.732 (ProStock or Comp SheetMetal Intake • best overall HP )
4th Harmonic= 13.170 (Single-plane Intakes , less Peak Torque • good HP )
5th Harmonic= 10.685 (Torque is reduced, even though Tuned Length)
6th Harmonic= 8.990 (Torque is reduced, even though Tuned Length)
7th Harmonic= 7.758 (Torque is greatly reduced, even though Tuned Length)
8th Harmonic= 6.824 (Torque is greatly reduced, even though Tuned Length)
Note> 2nd and 3rd Harmonics typically create the most Peak Torque
4th Harmonic is used to package Induction System underneath Hood

Plenum Runner Minimum Recommended Entry Area = 0.485 to 0.546 Sq.Inch
Plenum Runner Average Recommended Entry Area = 0.558 Sq.Inch
Plenum Runner Maximum Recommended Entry Area = 0.570 to 0.674 Sq.Inch

Minimum Plenum Volume CC = 23.5 ( typically for Single-Plane Intakes )
Minimum Plenum Volume CID= 1.4 ( typically for Single-Plane Intakes )
Maximum Plenum Volume CC = 211.6 ( typically for Tunnel Ram Intakes )
Maximum Plenum Volume CID= 12.9 ( typically for Tunnel Ram Intakes )

--- Cross-Sectional Areas at various Intake Port Velocities (@ 28 in.) ---
119 FPS at Intake Valve Curtain Area= 0.918 sq.in. at .275 Lift
123 FPS at Intake Valve OD Area and at Convergence Lift = .266
152 FPS 90% PerCent Rule Seat-Throat Velocity CSA= 0.719 sq.in.
--- 4750 RPM Intake Cross-sectional areas in Square Inches ---
350 FPS CSA= 0.312 Port has Sonic-Choke with HP Loss ( too fast FPS )
330 FPS CSA= 0.331 Port may have Sonic-Choke with HP Loss ( too fast FPS )
311 FPS CSA= 0.351 Highest useable Port velocity ( possible HP loss )
300 FPS CSA= 0.364 Smallest Port CSA ( Hi Velocity FPS • good TQ and HP )
285 FPS CSA= 0.383 Smallest Port CSA ( very good TQ and HP combination )
260 FPS CSA= 0.420 Recommended average Intake Port CSA (very good TQ and HP)
250 FPS CSA= 0.437 Largest recommended average Intake Port CSA ( good HP )
240 FPS CSA= 0.455 Largest recommended average Intake Port CSA (less Peak TQ)
235 FPS CSA= 0.464 Largest recommended Intake Port Gasket Entry area CSA
225 FPS CSA= 0.485 Largest Intake Port Gasket Entry CSA ( Slow FPS )
215 FPS CSA= 0.508 Possible Torque Loss with Reversion ( Slow FPS )
210 FPS CSA= 0.520 Torque Loss + Reversion possibility ( too slow FPS )
200 FPS CSA= 0.546 Torque Loss + Reversion possibility ( too slow FPS )
Note : these are calculated average Port cross-sectional areas and FPS

--- Cross-Sectional Areas at various Exhaust Port Velocities (@ 28 in.) ---
110 FPS at Exhaust Valve Curtain Area= 0.850 sq.in. at .275 Lift
123 FPS at Exhaust Valve OD Area and at Convergence Lift = .246
152 FPS 90% PerCent Rule Seat-Throat Velocity CSA= 0.616 sq.in. at 4750 RPM
--- 4750 RPM Exhaust Cross-sectional areas in Square Inches ---
435 FPS CSA= 0.215 Sonic Choke at Throat Area (too fast FPS velocity)
380 FPS CSA= 0.246 Sonic Choke at Throat Area (possibly too fast FPS)
350 FPS CSA= 0.267 Exhaust Port has Sonic-Choke with HP Loss (too fast)
330 FPS CSA= 0.284 Exhaust Port has Sonic-Choke with HP Loss (too fast)
311 FPS CSA= 0.301 smallest Exhaust Port ( very high velocity FPS )
300 FPS CSA= 0.312 smallest recommended Exhaust Port (Hi velocity)
285 FPS CSA= 0.329 smallest recommended Exhaust Port (Hi velocity)
265 FPS CSA= 0.353 Recommended average Exhaust Port CSA
250 FPS CSA= 0.375 Recommended average Exhaust Port gasket area
240 FPS CSA= 0.390 Recommended largest Exhaust Port gasket area
225 FPS CSA= 0.416 Largest Exhaust Port Exit gasket area (Slow FPS)
210 FPS CSA= 0.446 Largest Exhaust Port Exit gasket area (Slow FPS)
190 FPS CSA= 0.493 Torque Loss + Reversion + Scavenging loss (too slow FPS)
180 FPS CSA= 0.520 Torque Loss + Reversion + Scavenging loss (too slow FPS)
Note : these are calculated average Port cross-sectional areas and FPS

Valve Intake Exhaust Curtain Area Cross-Sect Area Minimum Flow
Lift Choke Choke Square Inches 280FPS 280FPS CFM @ 28 In
inches RPM RPM Intake Exhaust Intake Exhaust Int Exh
.050 954 1161 0.167 0.155 0.078 0.067 9.1 7.8
.075 1431 1741 0.250 0.232 0.117 0.101 13.7 11.7
.100 1907 2322 0.334 0.309 0.157 0.134 18.3 15.7
.125 2384 2902 0.417 0.386 0.196 0.168 22.8 19.6
.150 2861 3483 0.501 0.464 0.235 0.201 27.4 23.5
.175 3338 4063 0.584 0.541 0.274 0.235 32.0 27.4
.200 3815 4643 0.668 0.618 0.313 0.269 36.5 31.3
.225 4292 5224 0.751 0.696 0.352 0.302 41.1 35.2
.250 4768 5804 0.835 0.773 0.391 0.336 45.6 39.2
.275 5245 6385 0.918 0.850 0.430 0.369 50.2 43.1
.300 5722 6965 1.002 0.927 0.470 0.403 54.8 47.0
.325 6199 7546 1.085 1.005 0.509 0.436 59.3 50.9
.350 6676 8126 1.169 1.082 0.548 0.470 63.9 54.8
.375 7153 8706 1.252 1.159 0.587 0.504 68.5 58.7
.400 7629 9287 1.336 1.237 0.626 0.537 73.0 62.7


************** Metric Units ******************

0.2116 Liters @ 4750 RPM with 100.00 % Volumetric Efficiency PerCent

Required Intake Flow L/S @ 7 kPa = 21.5 to 22.7 at 6.326 MM Valve Lift
Required Exhaust Flow L/S @ 7 kPa = 18.4 to 19.9 at 5.197 MM Valve Lift

350 RPM/Sec Dyno Test Lowest Low Average Best
Peak KiloWatts 6.9 7.1 7.1 7.2
Peak Torque Ntn-Meter 15.3 15.7 15.9 16.1

Kilowatts per Liter 32.7 33.3 33.8 34.2
Torque N/M per Liter 72.4 74.3 75.3 76.2
BMEP in kPa 910.1 934.0 946.0 958.0
Carb L/S at 38.1 MM Hg 8 9 10 10

Recommended Intake Valve Lift to prevent Choke = 6.326 MM Lift @ 4750 RPM
Recommended Exhaust Valve Lift to prevent Choke = 5.197 MM Lift @ 4750 RPM
Recommended Minimum Normal Maximum Time-Area-Duration Lifts
Intake Valve Lift = 5.6158 6.3256 6.9581 7.3539 7.7515 8.1490
Exhaust Valve Lift = 4.7808 5.1966 5.7162 6.0356 6.4134 6.7913
IntOpen= 11.00 IntClose= 39.00 ExhOpen= 39.00 ExhClose= 11.00
Intake Duration @ 1.27 = 230.00 Exhaust Duration @ 1.27 = 230.00
Intake CenterLine = 104.00 Exhaust CenterLine = 104.00
Compression Duration= 141.00 Power Duration = 141.00
OverLap Duration = 22.00 Lobe Center Angle (LCA)= 104.00
Camshaft Straight Up = 0.00 degrees Cylinder Firing Interval= 720 degrees

------- Operating RPM Ranges of various Components -------
Best estimate RPM operating range from all Components = 2826 to 4826
Intake Flow CFM @ 7 kPa RPM Range from Flow CFM only = 2735 to 4735
Intake and Exhaust Systems operating RPM Range = 2996 to 4996
Intake and Exhaust Time-Area operating RPM Range = 3004 to 5004
Camshaft's Intake and Exhaust Lobes operating RPM range = 3072 to 5072
Intake Valve Curtain Time-Area at 6.985 Lift RPM Range = 3245 to 5245
Exhaust Valve Curtain Time-Area at 6.985 Lift RPM Range = 4385 to 6385

Intake Valve Close RPM = 5166 Exhaust Valve Open RPM = 4792
Intake System RPM = 4839 Exhaust System RPM = 5152
Intake Time-Area RPM = 4512 Exhaust Time-Area RPM = 5497
Intake Mach Z-Factor = 0.439552 Exhaust Mach Z-Factor = 0.474841
Intake Z-Factor Lift = 6.396392 Exhaust Z-Factor Lift = 5.025399

Curtain Area -to- Valve Area Convergence Intake Valve Lift MM= 6.750
Curtain Area -to- Valve Area Convergence Exhaust Valve Lift MM= 6.248

Target EGT= 791.8 degrees C at end of 4 second 600 RPM/Sec Dyno accel. test
Octane (R+M)/2 Method = 87.8 to 88.9 Octane required range
Air Standard Efficiency = 58.05735 % for 8.500:1 Compression Ratio

------- Piston Motion Data -------
Average Piston Speed (M/S)= 8.7069 in Meters per Second
Maximum Piston Speed (M/S)= 14.3972 occurs at 73.41637 Degrees ATDC
Piston Depth at 73.4164 degree ATDC= 23.88712 MM Cylinder Volume= 91.9 CC
Maximum TDC Rod Tension GForce= 920.7334 G's
Maximum BDC Rod Compression GForce= 466.7104 G's

( Metric Units ) ( per each Valve Sq.CM area )
Engine Size Liters = 0.2116 Intake Valve Net Area = 5.601
CC per Cylinder = 211.645 Intake Valve Dia. Area = 5.726
Rod/Stroke Ratio = 1.528 Intake Valve Stem Area = 0.125
Bore/Stroke Ratio = 1.273 Exhaust Valve Net Area = 4.781
Int Valve/Bore Ratio = 0.386 Exhaust Valve Dia. Area = 4.906
Exh Valve/Bore Ratio = 0.357 Exhaust Valve Stem Area = 0.125
Exh/Int Valve Ratio = 0.926 Exh/Int Valve Area Ratio = 5.528
Intake Valve L/D Ratio= .259 Exhaust Valve L/D Ratio= .279
L/S/Sq.CM = 3.748 to 3.969 L/S/Sq.CM = 3.974 to 4.049

Intake Valve Margin CC's Exhaust Valve Margin CC's
1.00 CC = 0.0688 1.00 CC = 0.0802
0.50 CC = 0.0344 0.50 CC = 0.0401
0.25 CC = 0.0172 0.25 CC = 0.0201
0.10 CC = 0.0069 0.10 CC = 0.0080

- Induction System Tuned Lengths MM- ( Cylinder Head Port + Manifold Runner )
1st Harmonic= 1072.584 (usually this Length is never used)
2nd Harmonic= 608.764 (some Sprint Engines and Factory OEM's w/Injectors)
3rd Harmonic= 424.998 (ProStock or Comp SheetMetal Intake • best overall HP )
4th Harmonic= 334.509 (Single-plane Intakes , less Peak Torque • good HP )
5th Harmonic= 271.408 (Torque is reduced, even though Tuned Length)
6th Harmonic= 228.335 (Torque is reduced, even though Tuned Length)
7th Harmonic= 197.066 (Torque is greatly reduced, even though Tuned Length)
8th Harmonic= 173.326 (Torque is greatly reduced, even though Tuned Length)
Note> 2nd and 3rd Harmonics typically create the most Peak Torque
4th Harmonic is used to package Induction System underneath Hood

Plenum Runner Minimum Recommended Entry Area = 3.129 to 3.520 Sq.CM
Plenum Runner Average Recommended Entry Area = 3.598 Sq.CM
Plenum Runner Maximum Recommended Entry Area = 3.675 to 4.349 Sq.CM

Minimum Plenum Volume CC = 23.5 ( typically for Single-Plane Intakes )
Minimum Plenum Volume Liter= 0.0235 ( typically for Single-Plane Intakes )
Maximum Plenum Volume CC = 211.6 ( typically for Tunnel Ram Intakes )
Maximum Plenum Volume Liter= 0.212 ( typically for Tunnel Ram Intakes )

--- Cross-Sectional Areas at various Intake Port Velocities (@ 7 kPa) ---
36.221 MPS at Intake Valve Curtain Area= 8.618 Sq.CM. at 6.985 Lift
37.481 MPS at Intake Valve OD Area and at Convergence Lift = 6.750 MM
46.273 MPS 90% PerCent Rule Seat-Throat Velocity CSA= 4.638 Sq.CM.
--- 4750 RPM Intake Cross-sectional areas in Square CentiMeters ---
106.680 MPS CSA= 2.010 Port has Sonic-Choke with HP Loss ( too fast MPS )
100.584 MPS CSA= 2.134 Port may have Sonic-Choke with HP Loss (too fast MPS)
94.793 MPS CSA= 2.264 Highest useable Port velocity ( possible HP loss )
91.440 MPS CSA= 2.347 Smallest Port CSA ( Hi Velocity MPS • good TQ and HP)
86.868 MPS CSA= 2.470 Smallest Port CSA ( very good TQ and HP combination )
79.248 MPS CSA= 2.708 Recommended average Intake Port CSA • good TQ and HP
76.200 MPS CSA= 2.816 Largest recommended average Intake Port CSA • good HP
73.152 MPS CSA= 2.934 Largest recommended average Intake Port CSA • less TQ
71.628 MPS CSA= 2.996 Largest recommended Intake Port Gasket Entry CSA
68.885 MPS CSA= 3.129 Largest Intake Port Gasket Entry CSA ( Slow MPS )
65.532 MPS CSA= 3.275 Possible Torque Loss with Reversion ( Slow MPS )
64.008 MPS CSA= 3.353 Torque Loss + Reversion possibility ( too slow MPS )
60.960 MPS CSA= 3.520 Torque Loss + Reversion possibility ( too slow MPS )
Note : these are calculated average Port cross-sectional areas and MPS

--- Cross-Sectional Areas at various Exhaust Port Velocities (@ 7 kPa) ---
33.569 MPS at Exhaust Valve Curtain Area= 7.978 Sq.CM. at 6.985 Lift
37.526 MPS at Exhaust Valve OD Area and at Convergence Lift = 6.248 MM
46.329 MPS 90% PerCent Rule Seat-Throat Velocity CSA= 3.974 Sq.CM.
--- 4750 RPM Exhaust Cross-sectional areas in Square CentiMeters ---
132.588 MPS CSA= 1.389 Sonic Choke at Throat Area (too fast MPS velocity)
115.824 MPS CSA= 1.590 Sonic Choke at Throat Area (possibly too fast MPS)
106.680 MPS CSA= 1.724 Exhaust Port has Sonic-Choke with HP Loss (too fast)
100.584 MPS CSA= 1.830 Exhaust Port has Sonic-Choke with HP Loss (too fast)
94.793 MPS CSA= 1.942 smallest Exhaust Port ( very high velocity MPS )
91.440 MPS CSA= 2.013 smallest recommended Exhaust Port (Hi velocity)
86.868 MPS CSA= 2.119 smallest recommended Exhaust Port (Hi velocity)
80.772 MPS CSA= 2.279 Recommended average Exhaust Port CSA
76.200 MPS CSA= 2.416 Recommended average Exhaust Port gasket area
73.152 MPS CSA= 2.517 Recommended largest Exhaust Port gasket area
68.580 MPS CSA= 2.685 Largest Exhaust Port Exit gasket area (Slow MPS)
64.008 MPS CSA= 2.876 Largest Exhaust Port Exit gasket area (Slow MPS)
57.912 MPS CSA= 3.179 Torque Loss + Reversion + Scavenging loss (Slow)
54.864 MPS CSA= 3.356 Torque Loss + Reversion + Scavenging loss (Slow)
Note : these are calculated average Port cross-sectional areas and MPS

Valve Intake Exhaust Curtain Area Cross-Sect Area Minimum Flow
Lift Choke Choke Square CM 85.3MPS 85.3MPS L/S @ 7 kPa
MM RPM RPM Intake Exhaust Intake Exhaust Int Exh
1.270 954 1161 1.077 0.997 0.505 0.433 4.3 3.7
1.905 1431 1741 1.616 1.496 0.757 0.650 6.5 5.5
2.540 1907 2322 2.155 1.994 1.010 0.866 8.6 7.4
3.175 2384 2902 2.693 2.493 1.262 1.083 10.8 9.2
3.810 2861 3483 3.232 2.992 1.515 1.299 12.9 11.1
4.445 3338 4063 3.770 3.490 1.767 1.516 15.1 12.9
5.080 3815 4643 4.309 3.989 2.019 1.733 17.2 14.8
5.715 4292 5224 4.848 4.487 2.272 1.949 19.4 16.6
6.350 4768 5804 5.386 4.986 2.524 2.166 21.5 18.5
6.985 5245 6385 5.925 5.485 2.777 2.382 23.7 20.3
7.620 5722 6965 6.464 5.983 3.029 2.599 25.9 22.2
8.255 6199 7546 7.002 6.482 3.282 2.815 28.0 24.0
8.890 6676 8126 7.541 6.980 3.534 3.032 30.2 25.9
9.525 7153 8706 8.079 7.479 3.786 3.248 32.3 27.7
10.160 7629 9287 8.618 7.978 4.039 3.465 34.5 29.6

L/S = Liters per Second CM = CentiMeters kPa = KiloPascals
MM = MilliMeters M/S = Meters per Second Square CM = Square CentiMeters
MPS = Meters per Second CC = Cubic CentiMeters CSA = Cross-sectional Area
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- Paul

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