I have yet to burn my first prom as I am still reading and learning, but I was wondering about the helpfulness of programs like Desktop Dyno. I know they give a really good graph as to what kind of power curve the engine makes based on the cam lobe timing events.
I was thinking this may be a (correct me if I am wrong here) useful tool for the spark tables? I am not entirely sure on any of this yet but I thought if you understood where the engine starts making power you could incororate that into something.
Not that programs like that are 100% accurate but I was thinking it could be a tool for tuning? kind of like on a real dyno?

 

I've used a bunch of simulation packages. My favorite is Virtual 4-stroke by Optimum Power. I don't think you'll be able to afford such software and for personal use you could never justify it's cost. The advantage of the software is that it's within 5% all around if you enter in all of the parameters correctly. I've seen it as close as 1% of actual but it likes to over exemplify the anti-tuning peaks of exhaust. ANYWAYS... Desktop Dyno is okay for figuring out where you're vol eff peaks. Other than that, it's just a toy for wishful thinking. There software is very good with the vol eff curve when using equal length exhaust primaries.
So take the vol eff peak and input that into your starting eprom. It's a big shortcut.

 

how do you mean to input the peak into my prom?

 

If you look at the VE tables there is a highest point, peak volumetric filling of the cylinders. Basically where your motor makes peak torque. Stock calibrations peak at lower RPM than say the zz4 or even a stock vette shortblock and a stealthram. The camshaft pretty much determines your peak volumetric efficiency and the rest of the parts resonate to either flatten your torque curve or peak it. With a v8 it's hard to get anything but a relatively flat torque curve. In a race engine you want maximum horsepower in your RPM range, hence the larger cams.... blah blah blah, back on topic.
If you use desktop dyno, use it with a grain of salt but it's useful in it's ability of determining the volumetric "curve" at 100-90kpa manifold pressure.

 

Programs like Desktop Dyno might be useful for infering WOT VE's as Jon said, but there's a lot more MAP columns on your tables than 100 kPa.

Also the VE's that are in your MAP tables are factored to suit the injector constant- they're not necessarily real VE's, although they could be.

John

 

Newbie deal here...
Where would one use the peak VE that DD2000 generates? Would it be used to change the VE% constants in the VE1 table? Honestly, how?

 

The dyno program creates a VE vs RPM curve. Plug those {scaled} values into your VE table(s) at 100KPa or the max shown KPa from the dyno program. Some will show the manifold pressure drop due to induction restriction. In the case of a '747 or '8746 both VE tables will need to be changed.

RBob.

 

Ok I am slightly confused. What exactly is represented for MAP in kpa? what is 20 and what is 100? Is it relative pressure? Or actual pressure? And what is the conversion to bar?

 

Okay...next question. i understand the concept behind the peak VE. How do I scale it into the BIN?

 

The MAP (manifold absolute pressure) is the pressure in the manifold in kPa. It is not relative pressure. 20 kPa MAP reading means there is a strong "Vacuum" in the intake (eg extreme closed throttle deceleration conditions). Under WOT conditions with no throttle body etc restrictions upstream of the MAP sensor, you should read atmo (100 kPa).

100 kPa is roughly 1 bar.

You need to use VE's that suit the Delco scales. For instance, an efficient race motor might have VE's of say 110% and you can't put this figure into a Delco VE table. So you might pick a max VE of say 85%, and multiply all your calculated VE's by 85/100 to {scale} them. This assumes that your mask's injector constant hasn't been based on this sort of {scaling} already.

I used to think this was a good idea, but there's more than the 100 kPa column to worry about, as I said above. You might as well guess the numbers in, or try to find VE's from a similar engine's BIN, then go for a careful drive and have Winaldl tell you what the correction factors should be for the entire table.

John

 

Engine Analyzer and Dragstrip Analyzer are both good programs.

 

I also vote for engine analyser and dragstrip analyser from performance trends.