Analysis Report for Mild Street Engine with Desired HP Peak at 6500 RPM
Maximum Exhaust System Backpressure ‘Exh Pres’ is 0 PSI.
This is low for a street vehicle with a full exhaust
system. This is simulating either an extremely free flowing exhaust
system or open headers or open exhaust manifolds. This may be
illegally loud for street operation.
Typical ranges of Exhaust System Backpressure are listed on page
32 in the User's Manual. You can lower the Back pressure by
increasing CFM Rating in the Exhaust Specs menu or specifying
Open Headers. Lowering the CFM Rating will simulate a quieter,
more restrictive exhaust system. Most dyno tests are done with
Open Headers, which are simulated by selecting Open Headers.
Maximum Fuel Flow ‘Fuel Flow’ is 226.65 lbs/hr GAS.
This is equal to 38.8 gallons per hour of fuel flow.
For an injected engine with one injector per cylinder, you will require
at least 19 lbs/hr injectors.
Fuel Flow will only change if air flow changes or you select a
different type of fuel. The Engine Analyzer Pro assumes 12.5:1
A/F for gasoline and 5:1 for alcohol (methanol) for all
conditions. You can not richen or lean out the fuel mixture.
Mechanical Efficiency ‘Mech Eff’ is 76.3 %
at the current Peak HP RPM of 6500 RPM.
This is Very low and represents a real power loss in this
engine’s current operating range. This can be improved by paying
close attention to details in the Short Block Specs menu.
Mechanical Efficiency can be improved by:
- Reducing piston skirt size or piston ring tension
- Minimizing 'power robbing' accessories
- Reducing crankcase windage
- Reducing stroke
- Reducing valve spring loads
- Reducing the engine's operating RPM range
The Intake Valve Mach # ‘MACH #’ is .304
at your DESIRED HP PEAK RPM of 6500 RPM.
This is low and indicates perhaps too much intake cam duration.
MACH # is the BEST INDICATOR of the usable RPM range of this
engine with the current cam & head specs. Air flow and performance
drop rapidly (the engine 'runs out of breath') when the MACH # goes
over approximately .55 for low RPM engines or .45 for high RPM
MACH # is explained on page 53 in the User's Manual. You can
lower the MACH # by specifying larger VALVE DIAMETER, VALVE FLOW
COEF, or higher CFMs in the Intake Flow Table in the Head Specs menu,
or larger Intake Duration .050'' and MAX LOBE LIFT in the Cam/Valve
Train menu. MACH # is also affected by Runner Diameter and Runner Flow
FLOW COEF in the Intake Specs menu, but to a lesser extent.
The Average Piston Speed ‘PSN SP’ is 2990 ft/min
at your DESIRED HP PEAK RPM of 6500 RPM.
This is somewhat high, requiring strong, light reciprocating parts.
The Maximum Average Piston Speed ‘PSN SP’ is 2990 ft/min
at the Performance Calculations Maximum RPM of 6500 RPM.
This is somewhat high (if you want to run this entire speed range),
requiring light, high strength reciprocating components.
A mild street engine should limit PSN SP to a range of 2500-3000 ft/min
with production quality rods. To run at 2750 ft/min or higher, you will
need ‘better than production’ reciprocating components (connecting rods
& bolts, pistons, etc.).
PSN SP (average piston speed in ft/min) and PSN GS (peak piston Gs)
are indicators of how severely you are stressing the engine's
rotating components. To lower PSN SP and PSN GS, you must shorten
the piston STROKE or design the engine for a lower RPM range.
See pages 53, 54 and 160 in the manual.
Maintaining low PSN SP and PSN GS are critical for ‘keeping the engine
together’. OVER-REVVING PARTS BEYOND THEIR INTENDED LIMIT IS UNSAFE
FOR THE ENGINE, YOURSELF AND BYSTANDERS.
Based on ‘Simple Rules of Thumb’, good Inertia tuning should occur at 5300 RPM,
which is somewhat lower than your Desired HP Peak RPM of 6500 RPM.
This RPM is about where the torque peak should occur and should pro-
duce good peak torque. You may want to try shorter and/or larger diameter
intake runners to gain Peak HP, but likely losing some Peak Torque.
Maximum Knock Index is 2.9 which indicates detonation
(spark knock, ping, etc.) is Very likely to occur.
You should try a higher Octane fuel, lower Compression Ratio, to
reduce the possibility of detonation. You can also try specifying
a spark curve with less advance which will likely hurt performance, but
allow this engine to safely operate with a Knock Index less than 2.
You can reduce the likelihood of detonation, by increasing FUEL
OCTANE or DEW POINT (humidity), or reducing INTAKE AIR TEMP or
COOLANT TEMP in the CALCULATE PERFORMANCE CONDITIONS menu, or
reducing COMPRESSION RATIO in the BASE ENGINE menu. Also, anything
which reduces performance, or shifts the performance curve to a
higher RPM range will also reduce the likelihood of detonation. You
can also specify a spark curve with less spark retard than what the
engine is currently running. See Spark Advnc in the results.
Retarding Spark Advnc is not necessarily a 'bad thing'. The best
performance for a particular RPM range and FUEL OCTANE may come with
retarded spark. Just be sure to retard spark in the actual engine
to avoid detonation which will cause engine damage.
Also, retarding the spark curve usually increases exhaust temperatures,
which can damage exhaust valves, turbo turbines, etc.
The % Exhaust to Intake Flow Capacity ‘VALVE EXH/INT %’ is 64.8 %.
This is somewhat low, and indicates you could improve performance
by improving exhaust valve flow and exhaust cam profile. The most
common ‘rule of thumb’ is to design for around 75% EXH/INT flow
To increase VALVE EXH/INT %:
- Increase the EXHAUST VALVE DIAMETER and/or VALVE FLOW COEF and/or
CFM in the Exhaust Flow Table in the Head Specs menu.
- Increase the Exhaust Duration .050'', Max Lobe Lift and/or ROCKER
ARM RATIO in the CAM/VALVE TRAIN menu
You can reduce VALVE EXH/INT % by changing other specs, but that may
also reduce performance.
End of Analysis Report
Yes it was modelled with open headers.