virtual dyno software


Staff member
you might want to spend a few bucks and play with one or more of these software programs as they can teach you a good deal.
If you take the time to read carefully, and take a couple dozen posted dyno results , read up on the parts used and carefully research data like compression,flow numbers cam duration,etc.
if you use VALID data and correctly fill the blanks

the PEAK torque and hp numbers,
the soft ware predicts are frequently with-in 5%-7% of what the engine actually produces.

but, as always the rule still applies garbage data in=garbage data out
to get fairly competent at using dyno software ID strongly suggest you take the effort to..

find a dozen old,posted engine dyno print-outs that come with the details on the parts used listed,in the engine build. you then fill in the data on your software program and get the predicted results, youll generally find you need to go back and verify data and only once you get a good feel for the process and find out that theres frequently data you either forgot to ask or inclued or you ignored that will effect the results.
now working with the known existing dyno results, and then finding the software prediction may not always match might seem to be backwards, but its going to have a very valid result in that it forces you to ask questions and look for answers you otherwise might never think about,that do effect the predicted software results.
yes once your familiar with what data actually matters and how critical it is to enter valid info youll see a distinct patern emerge and you learn that you can't assume data

Programs like that are great for getting an idea of how small changes will affect an engines performance, but do not place much stock in them as to real world dyno numbers as there are far too many un known variables where they assume things that might not be true in your case,. They make for a great tool to cross check changes on the computer though. If you are looking for some basic information on how changing LSA compression ratios or carb size or head flow, or to verify likely results from a cam advance, or swapping cams etc.. and potentially how those proposed changes may alter your potential power curve and have realistic cylinder head flow numbers to input into the software, they can be a useful tool.

if you have a time slip from the local track and
know your cars weight with you in it,
you can get an idea of your cars
your flywheel hp
(which is what the virtual dyno software predicts)
will generally be 17%-20% higher, so subtract that from the hp used in the weight/hp et prediction calculators to get semi valid answers

17%-20% lower with the drive train losses math calculators.htm

you want details and input data, well heres what you want, (above) its a P.I.T.A, to enter all the requested info but the results are detailed ... uct/186011

BTW PROGRAMS LIKE DD2000 is fun to play with but its hardly exact., if you want more reliable answers you need more exact data and a better program, but calculations get far more complicated and your going to need far more exact info fed in to get better answers

here if you want more precise guess work from software






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Staff member
Ive got several software dyno programs and Ive often compared results, between desk top dyno , and several other programs
comparing each other software result and engine dyno results
is by far the easiest to use and reasonably accurate for a basic quick bargain basement program at predicting peak hp and rpm levels
ENGINE ANALYZER PRO 3.9 is much more detailed and accurate, but it requires a ton of good accurate info, before it will even give a reasonably close guess
if you don,t know all the cam, head flow, cpr , runner size,vacuum readings, header config etc, I don,t expect ea-pro to give good results, but with it its more accurate


Staff member
I was playing with CamQuest by Compcams and decided to play with a few numbers. Could this be correct? Using the same heads 049 w/ 2.19 intake and 1.88 exhaust and the same camshaft, Hydraulic Roller Magnum 290HR. Heads are ported and polished.

402 cubic inch 640 hp / 592 tq
4.125 bore
3.760 stroke
38.3 cc pistons (10.5 CR)
640 hp / 592 tq


496 cubic inch 631 hp / 645 tq
4.310 bore
4.250 stroke
18 cc pistons (10.5 CR)
631 hp / 645 tq
Is is possible to get nearly the same horsepower in a smaller cubic inch engine? Looks like the only thing coming up short would be the torque by 53 ft/lbs.

Input data:
Exhaust - Large tube headers w/ mufflers
Induction - Carb/EFI (900 cfm)
Manifold - Dual Plane Max-Flow


its possible but its NOT reasonable,theres a rough guide you can use if you find obviously questionable results from software dynos ,youll generally find your engine will produce about 1-1.25 ft lbs of torque PER CUBIC INCH of displacement,at about 80% of max rpm, horsepower will depend on several factors but lets look at the formula for hp
torque x rpm /5252=hp
so if you made lets say
1.1 ft lbs of torque at a semi reasonable max piston speed for a street car combo of 4000 feet per minute
we find the 402 spinning at 6400rpm and the 496 spinning at 5650rpm
plug in the formula and we get
402 x 6400rpm x 1.1=538hp/442 ft lbs
496 x 5650rpm x 1.1-587hp/545 ft lbs

now obviously you can, boost both results but those are about the median results youll see from those engine displacements using basically common aftermarket, or re-worked stock components on an engine thats still built for street use


Staff member
heres a simple FREE cam selection program,
just for grins put your car and engine info into this program, and don,t lie, and see what cam it suggests

trust me, its nothing personal, I don,t know you and I sure don,t mean to offend,when i say (don,t lie) its just that most guys have a strong tendency to fill software question check marks or select factors, from the menus that they (WISH) they had or (INTEND TOO) install (SOON) rather than what they (ACTUALLY ) are working with when using that software, and that always results in the wrong answers Ive had dozens of guys I know use it and when I ask them what their choices were almost all the newer guys tend to fill out at least a few of the choices that way


Staff member
tailloring engine power to meet you needs is simple if you know what engine performance parts to change. These car racing tips apply to all engine performance parts regardless if you have a Ford Mustang, Chevy Camaro, Corvette, hot rods or roadster. So use these horsepower tips to pick the right engine performance parts to fit your needs.


When you review your engine's power curve and you feel that the power curve is too low on the graph, there are specific performance parts that can be changed in the engine that will move the whole power curve up or down on the graph. generally increasing the average rpm range and increasing effective air flow rates, or volumetric efficiency and compression increases thermal efficiency and power

you feel the need to move your engine's peak torque to a higher or lower RPM, try changing the cam, header lengths or the intake manifold runner lengths. Changing these performance parts in your engine may move the peak slightly higher or lower on the graph, but the major movement "rocks" the curve and moves the peak to the left or right on the graph.



your engine's torque curve falls off sharply as seen in the illustration above, then this is an indication that your engine can't breathe well enough, or your not controlling the valve train. This problem is typical of small carburetors, small valves,low duration cams, restrictive intakes or headers and divided intake manifold plenums. I t can also be caused by a low mechanical efficiency

Using your engine dyno software, you will notice that changing engine performance parts to improve the right side of the torque curve will also increase the peak horsepower and change the RPM of the peak horsepower.


Staff member
You should get one so the rest of us can borrow it !

I went to the AEM website and couldn't find anything about it. I searched on "dyno", but nothing. I wonder why they announce a product, but there is no info on their website ?


Staff member
BTW DD2000 is fun to play with but its hardly exact.
the most common question I get from people is how far apart are the results putting duplicate info in both software dyno programs, the answer would surprise most people, they generally show results in peak power and peak torque that are within 5%-7% of each other but thats about the only place the results are vaguely similar. and when you compare a real world dyno and use the two software programs compared to the dyno the real world results are generally in the area of 5% from the EA pro so they mat be good tools but they don,t give precise dependable results

one of the first things I did when I got my EA pro software was put in the specs of my old race car engines specs, and compare the results to the dyno sheet, then compare both to DD2000, as posted above I was rather pleased to find all three within 7% of each other so these software tools do provide you some insite

here if you want more precise guess work from software







I just inserted rather random info into my ENGINE ANALYZER PRO software on a potential engine combo SIMPLY TO GENERATE SOME FEED BACK to get it to print a suggestion report, so you can so you can see where the better software dyno software can lead you away from making mistakes in parts selection, but it also requires you to input a ton of correct data to get reasonable results

Analysis Report for Full Race Engine with Desired HP Peak at 6000 RPM

Peak Tq =598. @ 4500 RPM 1.06 Ft Lbs per CuIn
Peak HP =530. @ 5000 RPM .94 HP per CuIn

Maximum Exhaust System Backpressure 'Exh Pres' is 0 PSI.
This is typical for a race vehicle with Open Headers.

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 Intake Manifold Vacuum 'Int Vac' is 1.4 ''Hg.
This is somewhat high and is limiting air flow and HP.

Reduce Int Vac by specifying a larger Total CFM Rating in the
Intake Specs menu. Some classes of racing limit performance by
specifying a small Carb or a restrictor plate. In these cases,
you must try to improve performance with this small Total CFM Rating
or legally make small improvements in the Total CFM Rating of the
carburetor or throttle body, and any restrictor plate.

Maximum Volumetric Efficiency 'VE %' is 93.5 %.
This is somewhat low for 'non-supercharged' race engine. Typical
'non-supercharged', unlimited race engines have VEs of 100-135%.
Restricted race engines (small carb or restrictor plates) may have VEs
of only 75-90%.

Volumetric efficiency is the best measure of an engine's air flow
capability at a particular RPM. High VE is is critical to obtain
high torque and HP. See page 51 for a definition of volumetric
efficiency. Most all engine specs affect VE and the RPM at which
peak VE occurs. Generally, engine torque will peak close to the
RPM giving peak VE.

Maximum Fuel Flow 'Fuel Flow' is 283.1 lbs/hr GAS.
This is equal to 48.4 gallons per hour of fuel flow.
For an injected engine with one injector per cylinder, you will require
at least 35 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 Intake Valve Mach # 'MACH #' is .579
at your DESIRED HP PEAK RPM of 6000 RPM.
This is Very high and indicates you will need more Intake Valve
Diameter, Valve Flow Coef or higher CFM's in the Flow Table in the Head
Specs menu, or more intake cam profile (larger Duration, Lobe Lift or
Rocker Arm Ratio) in the Cam/Valve Train menu.

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 4250 ft/min
at your DESIRED HP PEAK RPM of 6000 RPM.
This is EXTREMELY high, requiring strong, light reciprocating parts.

The Maximum Average Piston Speed 'PSN SP' is 4604 ft/min
at the Performance Calculations Maximum RPM of 6500 RPM.
This is EXTREMELY high (if you want to run this entire speed range),
requiring light, high strength reciprocating components.

A race engine should limit PSN SP to a range of 4500-6000 ft/min. (Race
engines on the 'leading edge' of technology are running up to 7500
ft/min.) To run over 2750 ft/min requires 'better than production'
parts. To run at 4500 ft/min or higher, you will need 'state of the
art' reciprocating components (connecting rods & bolts, pistons, etc.)
like those present in Drag Racing's Pro Stock class or Formula 1.
These components must be both extremely light and strong.

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
reciprocating 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

Based on 'Simple Rules of Thumb', good Inertia tuning should occur at 5500 RPM,
which is close to your Desired HP Peak RPM of 6000 RPM.
Since this RPM is about where the HP peak should occur, peak HP
should be good. If you specify longer and/or smaller diameter intake
runners, you may gain Peak Torque and lose some Peak HP.

Maximum Intake Inertia Tuning Pressure 'In Tune Pres' is 3.4 ''Hg
This is Very low for a race engine and will limit Tq & HP.
Typical race engines will show 6-10'' of 'In Tune Pres'.

Intake Inertia Tuning Pressure 'In Tune Pres' has a significant impact
on engine performance. It improves with different Manifold Types or
Runner Flow Coef in the Intake System menu. It is also affected by
many other engine variables including intake runner dimensions, the cam
profile and timing, flow capability of the heads, and exhaust system

Maximum Knock Index is 1.4 which indicates detonation
(spark knock, ping, etc.) may occur.
You may want to 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 operate with a Knock Index less than 1. (A Knock
Index between 1 and 2 is the 'gray area' where the program is not sure
if detonation will occur or not.)

You can reduce the likelihood of detonation, by increasing FUEL
OCTANE or DEW POINT (humidity), or reducing INTAKE AIR TEMP 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 66.1 %.
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 %:
CFM in the Exhaust Flow Table in the Head Specs menu.
- Increase the Exhaust Duration .050'', Max Lobe Lift and/or ROCKER
You can reduce VALVE EXH/INT % by changing other specs, but that may
also reduce performance.

Estimated Idle Vacuum 'Idle Vacuum' is 11.8 ''Hg.
This is somewhat high and would provide for a relatively smooth
idle. However, for a race engine, it may be indicating the cam
does not have sufficient overlap which may limit full throttle
torque and HP.

To reduce idle vacuum for possibly better full power performance,
increase cam overlap by specifying a higher Duration @ .050'' for
both the Intake or Exhaust in the Cam/Valve Train menu.

End of Analysis Report


The Grumpy Grease Monkey mechanical engineer.
Staff member

this is a good value for the price

THE most common mistake, most guys make when doing calculations is use of the wrong data , you may have sellected two 750cfm carbs on a tunnel ram and expect them to flow 1500 cfm, but the fact is each of the two carbs now shares a comon plenum on one engine so the vacume each individual carb venturies sees is reduced significantly, OR
if you were to sellect individual runner mechanical or EFI stack injection, when you select
"Individual Runner fuel injection"in the calculation , each runner feeds a single cylinder, again this fails to use the correct calculation, individual runners acting as a ram tub must be significantly larger because they induce a pulsed or ram, inertial flow.
you can,t use the carb cfm, info, thats simply failing to use the correct flow calculations

this is the result of failing to realize each
Individual Runner,
easily flows easily 320cfm to 450 cfm
(depending on each individual ram tube and throttle bore size )
UNLIKE a carburator which will have a listed
(and basically useless flow rating)

thus the minimum CFM youll use in the calculations is more than likely in the 320 x 8 or 2560cfm-to-3600 cfm flow range
so put 2600 cfm in for a SBC and 3200 CFM in for a BBC individual runner FUEL INJECTION INTAKE CONFIG

heses a typical chart showing SBC intake gasket sizes
notice 1.3 x 2.31 is the largest size thats roughly 3 sq inches

trust me the larger bore flows significantly more air


but remember
GARBAGE DATA IN times software manipulation= GARBAGE INFO OUT
I found this software I purchased to be rather helpful, but be aware its a P.I.T.A. to find and enter all the data it requestsm while rather precise its time consuming and a bit aggravating, and since its at least 12 years old its surely been replaced with better software by now, even though mine has several expensive software upgrades

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