just to show something kind of cool....after running the motor with a 65mmTB (using the cfm numbers from the accufab in the FAQ) i ran the programs "analyser"(btw gained 2 peak hp and 1 peak ft/lb of torque with the mid)
this is what it spit out(i used a "desired hp peak at 5500rpm just for a reference)
Analysis Report for Mild Street Engine with Desired HP Peak at 5500 RPM
Peak Tq =299. @ 3200 RPM .99 Ft Lbs per CuIn
Peak HP =227. @ 4800 RPM .75 HP per CuIn
Maximum Exhaust System Backpressure 'Exh Pres' is 2.3 PSI.
This is typical for a mild street vehicle with a free flowing,
'production type' exhaust system.
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 121 lbs/hr GAS.
This is equal to 20.7 gallons per hour of fuel flow.
For an injected engine with one injector per cylinder, you will require
at least 15 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.
The Maximum Average Piston Speed 'PSN SP' is 2800 ft/min
at the Performance Calculations Maximum RPM of 5600 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 2500-2750 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.
The Intake Runner Velocity 'Avg In Vel' is 321 ft/sec
at your Desired HP Peak RPM of 5500 RPM.
Based on 'Simple Rules of Thumb' this is somewhat high and indicates you
may need a larger diameter intake port or manifold runner for less
restriction and better intake tuning.
Based on 'Simple Rules of Thumb', an Avg In Vel of about 230 ft/sec
should work well with the current specs. If the Avg In Vel is
approximately 30-80 Ft/Sec higher than this, you will likely improve
torque below this RPM, but lose some HP.
Based on 'Simple Rules of Thumb', good Inertia tuning should occur at 3900 RPM,
which is somewhat lower than your Desired HP Peak RPM of 5500 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.
Intake and/or Exhaust 'Valve Toss' is indicated at 1 RPM(s).
Valve Toss is the condition where there is insufficient valve spring
pressure to keep the lifter in contact with the cam. Valve Toss
causes severe stress and damage in the valve train and must be avoided.
Valve Toss can be avoided by reducing valve train weight,
going to gentler cam profiles (less lift for the same or less
duration), stiffer valve train components, or reducing the
engine's operating RPM range.
Maximum Knock Index is 2.4 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 69.4 %.
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
capability.
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.
Dynamic Compression Ratio is 6.83 .
This is somewhat low, as most engines (Mild Street, Street/Strip
or Race) usually end up in the range of 7 to 9. This can be increased
by increasing the engine's Compression Ratio spec or having the intake
valve close earlier. Earlier intake closing can be obtained by:
- Advancing the cam
- Closing up the lobe separation
- Smaller intake duration
- Smaller (earlier) intake centerline
- Smaller (earlier) intake closing event
End of Analysis Report
