For anyone who's interested in modeling some basic induction, exhaust, or cam modifications for their engines, I figured I'd post a quick, basic "how to".

This is using the freely available, but "dated" and fairly basic "DesktopDyno2000" software. Better and more accurate tools are available, as are newer versions of DesktopDyno, but not for free.

1. Download DesktopDyno 2000 here: http://carprogrammer.com/Z28/PCM/Too...0(selfzip).exe
2. Install the software using the wizard (click "next" as fast as you can)

3. Launch the software (navigate to the default install folder of c:\Dyno2000, or your custom install folder, and launch "Dyno2000.exe")- create a shortcut of your own, if desired because the installer doesn't seem to create one

4. Configure basic Short Block info; examples for an SBC 350:
a. Block: Chevy, 8 Cylinder SB, 350 (or 383) -it will then automatically fill in Bore, Stroke, Cylinders, & Volumes for you; if your engine is overbored, just update the "Bore" value and click the Green check-box (you have to do this every time you make a change in the tool to get it to accept the value)

5. Add your Cylinder Head info: for this you can use the really generic default values (pretty worthless, IMHO), or click on "Airflow File" and then navigate to the "flw_Files" sub-folder under the c:\Dyno2000 folder and selection from a list of common heads, OR you can just Google search for the Airflow #'s for your head at each various lift #. For the newest generation of heads or anything ported, you will need to use the custom airflow profile method-enter it by clicking on "Cylinder Heads", then selecting "Custom Port Flow" at the bottom:
a. add a description for your Airflow file (ex: "Profiler 185cc 23 Deg")
b. Change the intake and exhaust valve diameters to reflect the head that you'd like to model (ex: 2.02" intake 1.6" exhaust) Note: You can also select an airflow file here to view the flow data at each lift to ensure that the saved data matches the airflow of your heads.
c. Change the Pressure Drop for the intake and exhaust columns to 28 inches H20, as this is generally what most head airflow testing is done at (no the tool doesn't add this as the default for some crazy reason)
d. Set the # of Data Points: Look at your Airflow chart for your head and count how many different CFM and lift values are provided and change the "data points" value at the top to reflect this (if your airflow chart includes flow at 0.200, 0.400, 0.500, 0.600" lift then entre "4" so that you can enter all 4 data points) Note: to decrease the # of data points you will need to delete the data in teh additional fields
e. Enter each intake lift value and flow CFM under the "intake valve" section and the exhaust lift and flow CFM under the "exhaust valve" section- Then Save this profile into the flow files folder for future usage and click "OK" to apply the flow data
f. Notice that the intake and exhaust valve size information from the airflow file did not automatically apply under "Cylinder Heads" -again select your intake and exhaust valves (ex: 2.02", 1.6")

6. Enter your Compression Ratio manually into the tool; you may use the drop-down or simply type in a custom CR such as "10.2:1"; no, the tool won't calculate your static CR for you. Use another web-based tool to obtain your static CR, if you don't already know it. Here's a free calculator that will give you both your static and dynamic (adjusted for cam intake close event) compression ratio: https://www.jeepstrokers.com/forum/calculator/

7. Enter your Induction data:
a. Select the rated CFM for your carb and whether it's a 2BBL or 4BBL from the "Induction Flow" drop-down; I believe the Corvette Quadrajet's are 750CFM
b. Select your manifold type (Single Plane, Dual Plane, Tunnel Ram, TPI, etc...)

8. Enter your Exhaust data:
a. IMHO, the only confusing part in this drop-down is the DesktopDyno definition of "small tube vs. large tube" headers; they're not talking about length but the diameter. I looked up the definition at one point and I think it was related to the ratio between the intake valve diameter and the inside diameter of the header's primary tubes (can't remember all the details). For a typical max intake valve of 2.02" on a head for a 4" bore block, I think 1 5/8" or less was considered "small tube" and greater than that was "large tube".

9. Enter your Cam data: Much like the Cylinder Head section, you can select from the super generic and not particularly useful default drop downs, or you can select cam data from a list of built-in cam data files that are found in the "Some_Xta_Cam_Files" sub-folder under the parent "c:\dyno2000" folder, OR you can enter custom cam data (my preference). This part is particularly confusing, but important: to enter custom cam spec data, click on the icon in the toolbar that looks roughly like a cam; if you "mouse-over" it, it will say "Cam Math":
a. Enter your LSA in "Lobe Centerline Angle" (in cam degrees) & your cam's intake centerline (in crank degrees) in "Intake Centerline" -this is the amount of advance or regard that's "ground-in" to the cam. If there's no advance or retard ground-in, then this should be the same as the LSA. To convert from cam degrees to crank degrees just multiply the advance / retard by 2. (Example: A cam with a 110 LSA with 2 crank degrees of advance built in: Lobe Centerline Angle = 110, Intake Centerline 108)
b. Enter the Intake Duration @ 0.050" and the Exhaust Duration @ 0.050" Note: The tool will let you enter the seat-to-seat duration or duration at any lift of your choosing, but that makes the instructions here difficult to describe so I'm sticking to 0.050" durations for these instructions.
c. Enter the Intake & Exhaust max valve lift (Note: Not the cam lobe's lift but the actual valve lift after adjusting for the rocker ratio.) If you need to convert the valve lift to account for larger ratio rockers, use this simple calculator from Wallace Racing: http://www.wallaceracing.com/rockercalc.php
d. Click Apply to be taken back to the main screen
e. Select your lifter type (solid flat tappet, hydraulic flat tappet, roller)
f. For "Cam Specs @" select "0.050-Lift"


Now you can look at the simulated torque / hp curves, or click the "table" view to get the numeric values.

This is the point that I like to save the over-all Dyno results using the file menu's Save-As option and I will save the files with long filenames that show all the major parameters "350 Profiler 185cc DualPlane Headers Lunati 262 Cam 440hp_5,600 470 ftlbs_4,500".

Then I'll play around with different cams or messing with the advance/ retard or changing the induction or the exhaust to just get an idea of what the changes will do.


Once you've got DesktopDyno down, using CompCam's CamQuest software (http://www.compcams.com/v002/Softwar...itle=CamQuest6) is a breeze. It seems to be built upon a much newer version of DesktopDyno except that you can only really pick CompCams and it automates much of configuration of the tool.


Adam

 

Interesting. The dual plane manifold model must be super restrictive, knocked off 80+hp... A fun toy, but not sure how useful it truly is? Mine also seemed more accurate using the seat to seat duration instead of the .050"? Again, a huge difference in numbers between those two.

 

I go into it treating it like a wheel dyno: understanding that it's probably not an actual, numerical representation of the engine, but being able to model changes and what it does to the curve (HP vs. Torque trade offs, RPM for peak torque vs. peak HP, do I see a big change or a small change? etc...).


A guy on the ThirdGen forums who really knows what he's doing modeled my combo in EA Pro and came out decently close to the DesktopDyno results, anyway.


Obviously, the tool doesn't take into account intake air temp, actual cam lobe profiles, friction, or air velocity; things that can significantly matter, but it's free so I don't expect a ton.


Adam

 

I've got the new program and it's a blast. It's also easy to use and has most cams already installed. Thanks for the right up.

Even if these programs aren't super accurate, using the same base data for your motor and just changing the cam will show you how the different cams will effect your motor and which will be in the range you want. Once I get my 327 built I'm going to get it dynoed and then figure out how close this is to reality

 

I used an active pressure wave simulator software for years called Dynomation. It simulates the engine running. You can see how even minor changes in intake and exhaust track effect the pressure waves and inertia and how that affects power and torque curves.

As in all software you need to make a correlation between the simulations and real world dyno testing. I did this and found I needed to tweak the inputs a little to make the dyno and the simulator end with the same results. Once I did it was invaluable for building combinations in the software instead of experimenting on the dyno, especially on separate runner designs I was working on. Dynomation would make accurate simulations that would bare out on the dyno.

Mike

 

I've had Desktop Dyno and Dyno Sym software for years, though I haven't used it in a while. Your accuracy depends on the detail of your entry info. If you get within 5% of on your actual engine, consider that excellent results. One way to test is to "dry run" by inputting a known engine combo and checking the results against the actual engine HP and TQ.......see how close it actually gets....you may have to tweak your input info a little to get it to match....and then you can more accurately input your desired combo since you now have a more accurate measuring stick.

 

Out of curiosity, I tried it out again with my truck engine instead of the Vette engine. The truck engine has actually been on an engine dyno - I run it on LPG (propane) so I had it run in on the dyno to help seat the rings. It seems more accurate, but again I needed to use the seat to seat duration rather than the @0.050" - I suspect this is probably due to it being older software, and not accurately reproducing a modern hydraulic roller grind. Dual plane vs single plane was much less an issue though - I suspect the simulation badly hurts dual plane figures once you get a little over 400hp.

Fwiw, Vette engine - 388 (0.060" over) sbc stroker, ported Edelbrock RPM heads (and intake), 238/242@0.050 (300/304 seat to seat) Crane hydraulic roller with .558" lift, 11.1:1 compression. Never been dynoed, but pulls hard past 7,000, and I believe it makes close to 500hp based on performance tests.

Truck engine - 393 Ford Cleveland stroker (4.020" bore, 3.875" stroke), 2v heads with 4v valves, Performer RPM intake, dual Impco 425 carbs (though engine dynoed on petrol), 222/222@0.050 (276/276 seat to seat) Crow hydraulic roller cam with .568" lift, 10.2:1 compression ratio. Made 417hp and 472 ft/lb of torque on the engine dyno, made over 400ft/lb from start of pull at 2500rpm through to 5400rpm, was still making nearly 400hp at 6000rpm (end of pull). Awesome truck engine, will tow anything (fitted in a 1979 Ford F250).

 

So how come this software seems to think single plane intakes are far superior to dual plane?


I plugged in my motor (350, 9:1, Brodix IK200 heads, Lunati 268 cam, Edelbrock Performer RPM intake) and when I switched the intake to a single plane, it says I would pick up about 25 horsepower and some torque too, and not just at peak power!

 

The software sees the dual plane intake as a huge restriction, doesn't take into consideration that an RPM Air Gap is better than the plain stock intake. Exhaust is skewed the same way, mufflers are considered restrictive, not free flowing. Take this into consideration and input a better intake and exhaust (according to the software) and your accuracy will be better.

 

This is why Dynomation is far superior to any static software. It is very similar to what the OEM's use to design engines. You input the intake tracks actual dimensions as well as the exhaust. You can also input cam doctor files so you have the actual cam profile inputted. You have lots more info to put in to get data out. Then the program runs like the engine is actually running. It gives you readouts on wave shape and timing, port air speed and inertia, piston speed, cylinder pressure, as well as the torque and horsepower curves. Very powerful software. it's not cheap though.

I've used many static programs, but never really impressed by any.

Mike

 

Yeah, Dynomation is definitely the way to go for more accurate simulations.