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Engine Masters rod ratio test results

General engine tech -- Drag Racing to Circle Track

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Stan Weiss
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Joined: Tue Feb 20, 2007 1:31 pm
Location: Philadelphia, PA

Re: Engine Masters rod ratio test results

Post by Stan Weiss » Wed Mar 18, 2020 3:47 pm

Since my calculations are not exactly the same as the chart for the Loads I here is what I get and also the 500 ci Pro Stock. For the 500 ci engine I used the same ring and ros bearing weight as the NASCAR engine.

Stan

Bore_=_3.858268___Stroke_=_1.565748___Rod_Length_=_4.015748___RPM_=_20000
Piston_Weight_=_295.0___Rod_Weight_=_311.0
Small_End_Rod_Weight_=_85.0___Big_End_Rod_Weight_=_226.0
Rod_CG_/_Distance_from_Small_End_=_2.918196
Crankpin_/_Rod_Big_End_Acceleration_=_286172.4
Crankpin_/_Rod_Big_End_Rotational_Force_=_4431.643

____________Reciprocating____Total_____Piston_Side___Piston______Crank_Pin__Instantaneous
Crank_Angle____Force_________Force________Force__Inertia_Force__Tangent_Force__Torque
__Degree_______Pounds________Pounds_______Pounds______Pounds_______Pounds___FT-Pounds
___.000______8904.100_____13335.744_________.000____6912.394_________.000________.000

=======================

Bore_=_4.185___Stroke_=_3.25___Rod_Length_=_6.2___RPM_=_10000
Piston_Weight_=_500.0___Rod_Weight_=_564.0
Small_End_Rod_Weight_=_140.0___Big_End_Rod_Weight_=_424.0
Rod_CG_/_Distance_from_Small_End_=_4.660993
Crankpin_/_Rod_Big_End_Acceleration_=_148500.9
Crankpin_/_Rod_Big_End_Rotational_Force_=_4314.432

____________Reciprocating____Total_____Piston_Side___Piston______Crank_Pin__Instantaneous
Crank_Angle____Force_________Force________Force__Inertia_Force__Tangent_Force__Torque
__Degree_______Pounds________Pounds_______Pounds______Pounds_______Pounds___FT-Pounds
___.000______8219.218_____12533.651_________.000____6421.264_________.000________.000

=======================

Bore_=_4.73___Stroke_=_3.555___Rod_Length_=_6.05___RPM_=_11500
Piston_Weight_=_615.0___Rod_Weight_=_519.0
Small_End_Rod_Weight_=_160.0___Big_End_Rod_Weight_=_359.0
Rod_CG_/_Distance_from_Small_End_=_4.184875
Crankpin_/_Rod_Big_End_Acceleration_=_214823.2
Crankpin_/_Rod_Big_End_Rotational_Force_=_5284.504

____________Reciprocating____Total_____Piston_Side___Piston______Crank_Pin__Instantaneous
Crank_Angle____Force_________Force________Force__Inertia_Force__Tangent_Force__Torque
__Degree_______Pounds________Pounds_______Pounds______Pounds_______Pounds___FT-Pounds
___.000_____14759.757_____20044.261_________.000___11712.581_________.000________.000
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David Redszus
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Re: Engine Masters rod ratio test results

Post by David Redszus » Wed Mar 18, 2020 4:36 pm

Stan Weiss wrote:
Wed Mar 18, 2020 1:16 pm
David Redszus wrote:
Wed Mar 18, 2020 12:37 pm
Stan Weiss wrote:
Wed Mar 18, 2020 12:32 am
David,
What would the numbers look like for a 3.555" with a 6.050" rod turning 11500 RPM. If it matters a bore of 4.73" (499.74 ci) This would be the old carb NHRA Pro Stocker engine. Remember have a min piston and rod weight rule.

Stan

Hemi_PS_Block.gif
3.55/6.050 = rod ratio 1.70......................11500rpm
Axial peak inertial G force, tension .............8636
Axial peak inertial G force, compression.......-4756
Axial resultant force, tension N..................37760
Axial resultant force, compression N...........-59797
Inertial side Thrust friction N......................7906
Inertial side AntiThrust friction N................-7906
Resultant side Thrust friction N...................9343
Resultant side AntiThrust friction N.............-8729
Mean piston speed m/s............................34.23
Max piston speed m/s..............................56.68

For accurate side force values, we would need piston weights and
combustion gas pressure curves. The above are based on typical SBC.

Does anyone wonder why they change pistons quite frequently?
David,
"Does anyone wonder why they change pistons quite frequently?"

Where did you hear this?

Stan
Most recently (20 minutes ago) from an engineer at Mahle Motorsports. Their recommendation
is for a mean piston speed limit of 25 m/s; as speed increases, piston life is shortened.
Typical ProStock piston life is about half of a season, sometimes less.

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