Inliners International Forums General Discussion Engines "desktop dyno" or other software recommendation?

I'm looking to buy a new engine calculator program, I have an ancient Desktop Dyno, but install has become a PITA, requires a phone call every time, and it's got a number of annoyances.

I know I cannot get "real" numbers from a program like this; I use it mostly for what-if's and A vs B, and look for relative changes and shapes of curves, not X ftlb at Y RPM.

Of course I have to enter my own engine specs, nothing i care about is in the libraries (too old!).

Anyone use and trust any of this stuff?

The main problem with any of those programs is they only offer modern cylinder head port and chamber configurations. This is fine if your doing a simulation for a SBC or BBC or any IR runner style head. But it is almost useless when trying to use it for a siamese port head because there is no direct comparison between this type of port to any other port selection to chose from in those software packages. Also, it is nearly the same when constructing a Flathead style port or chamber vs. the modern OHV layout the software is designed to use. So if your intention is to use it for older vintage engines that have siamese ports or L-Head style heads none of the software packages will give you any realistic ideas of any gains or losses and would be a waste of money to invest in. That software just isn't designed around those types of engines or parameters.

Yeah, as I figured. But since things like head flow are constants for a given chunk of iron, i would be using it more for what-ifs surrounding camming and general behavior around flow restrictions. Not so much to design an engine, but to see the effects of changes in duration etc.

Yep, one of my engines of concern is siamesed port (trough intake too).

Do you think it's a total waste of time even for my intended uses?

You wouldn't really be comparing apples to apples with using software designed to be used with IR head configurations on a siamese port head. You are assuming that changes that improve or hurt an IR headed engine will do the same with a siamese headed engine. I wouldn't pay full price for any software, I would see if you could find a used copy on ebay for a lot less. But again, since it wouldn't be an apples to apples comparison, it might lead you to false conclusions that over time you might actually begin to believe.

X2 - siamese behaves differently. Bell says that the siamese intake port area should be slightly larger than the intake valve area. Example: a 235 with 1-7/8" valve is 2.76 in., which is impossible to cut into any 235 head casting.
The behavioral difference will also vary based on the firing order separation between cylinders: in an L6 the #3 & 4 have equal 360-360° intervals, the others have 240-480° split.
Even more difference for an L4 because the interval is much larger.

The typical siamese port does have an advantage: the cross-sectional area between the seats is huge compared to the bowl in an IR port, but the entry shape is poor.

Hey, I have an engine simulation program by Lotus Engineering. But I've never seen it for sale anywhere. It is ment to be used by EOMs and I got a license via my employer.

With the program you 'build' a model of the engine and it will calculate the performance based on how much air is drawn into the engine. You have to exactly program the dimension and shape of parts like the inlet manifold and it will based on that calculate the flow resistance of the system. so no need to know all the cfm's.

I did some simulations on a 270 GMC engine (which has siamese ports as well) and it worked out quite well. I 'build' the stock engine with the data I had available and corrected the simulation to the know performance curves. Then I 'mounted' tuning parts to see what they would bring in hp.

I could do the simulation for you. the only thing is that I would need a LOT of data from your engine. You may even need to take stuff apart to measure all the diameters, volumes, curves etc. Is your engine stock? and do you have a performance curve to check the 'base' engine's simulation results?