Help with building your Speeduino, installing it, getting it to run etc.
User avatar
By PSIG
#48818
There are various ways to manipulate the numbers, as they are all multipliers in the PW calculation. First you should consider that you told it you had 6 cylinders and 6 injectors on 750cc and 4S, so it's calculating for that, but only using half the fuel flow (injectors) on half the displacement, but every stroke. You can change injector size, displacement, or manually enter a new Req_fuel value, for examples. I find R_f almost always needs manual manipulation, as it is only a calc based on estimates, and rarely spot-on.

For that example, I run the engine to fully warmed, and run different low-load table areas which should be 14.7 everywhere by the calculator. It won't be. I find the trend of Lambda (generally rich or lean overall), and adjust R_f to bring the table generally towards the calculated target, without changing VE values. Now the table more approximates the intended AFR/Lambda the calculator produced. Begin VE tuning, which should be much closer than it started with.

Likewise (or in addition), I may change the R_f in order to increase low-PW resolution and control, and other purposes. So don't let it bother you if you want to try almost any manipulation in order to find suitable ways to correct for estimates and errors or to work-around other issues. You can always go back with a click.

David
By kettlekev
#48846
David

So understanding the VE is just a starter for testing and the injector time is just an estimate based on the engine specs.

In the image below, is the red circled number the on the VE table uses? and can I manually set that? Or is it another number?
reqdfuel.PNG
reqdfuel.PNG (38.99 KiB) Viewed 3858 times
Cheers

Kev
User avatar
By PSIG
#48926
It can be changed by any of the methods I described. Don't get silly with this, as your other estimates may be even worse (such as the VE table), but the point being that it is another way to manipulate, experiment or correct the calculations for PW. More tools.
By kettlekev
#48930
David,

I appreciate these are just tools and estimates but my main question was of the two numbers in the 'calculate required fuel' box, is it the one I ringed that controls the VE table (or is it something else) and if I manually change it, will that number be used as the base for the VE?
By LPG2CV
#48932
the one with ms (milliseconds) is used in calcs
The top one is the value you enter, and the ms one changes depending of the number of squirts per cycle.
Change squirts and watch it change.
User avatar
By PSIG
#48933
Kev, they are all components of the calculation. The top R_f number is the base number, and the lower one is divided if you use multiple injections. This can be important as a tool to see if you're getting too close to uncontrollably small values. The Calculations.dash dashboard I mentioned before is a good way to see the relationships of the factors in the PW calc, and you can "see" where things are odd, or short, excessive, or just weird.

See the image for an example of how the numbers fall-in, how they are multiplied against each other, and that each is its own factor in the final PW determination. I think it's awesome that you are seeking understanding that goes far beyond just knowing. I hope it helps.

David

Load the Calculations.dash file from your firmware package into TS for real-time values:
Calculations-dash img.png
Calculations-dash img.png (208.61 KiB) Viewed 3804 times
By kettlekev
#48938
Brilliant! Thanks guys.

Your patience is much appreciated!

No matter how much reading there is to do, little bits of knowledge like these open the doors. Understanding is everything....

:D
By bfinney
#48982
kettlekev
The formula for REQ_FUEL is = Displacement / # cylinders * air density / AFR / injector flow rate / # squirts with conversion factors to get the resultant value in milliseconds. Note: for air density TunerStudio is using the value at 25 deg C / 77 deg F = 0.0739085 lb / cu ft . I determined this by solving the equation for air density with the calculated REQ_FUEL from TunerStudio.

As an example I'm in the USA and use english units, my project values are displacement 290 cu in, 4 cylinders, 14.7 AFR and 21.5 lb/hr injectors 2 squirts (4 cycle), the equation becomes 290 (cu in) / 4 / 1728 (cu in / cu ft) * 0.0739085 (lb / cu ft) / 14.7 / 21.5 (lb hr) * / 2 (squirts / cycle) * 3600000 ( millisecond / hour ) = 17.6 ms (Note: my max RPM is 2800, large displacement slow turning).

Gasoline weighs approximately 6 lb per US gallon, 1 lb/hr = 10.51 cc/min, 1 cu in = 16.387 cc

I'm not sure why you can't do 3 cylinder with 3 injectors, after looking at the code a 3 cylinder engine will have 3 injector and 3 ignition events regardless of 2 cycle or 4 cycle or spark mode unless I'm missing something.


PSIG
How do you load the Calculations.dash file, I haven't been able to figure it out, Note I'm currently using the free version of TunerStudio, thanks.
Attachments
Screenshot from 2021-03-13 22-29-35.png
Screenshot from 2021-03-13 22-29-35.png (101.54 KiB) Viewed 3720 times
User avatar
By PSIG
#48989
bfinney wrote: Sun Mar 14, 2021 8:22 am How do you load the Calculations.dash file, I haven't been able to figure it out, Note I'm currently using the free version of TunerStudio, thanks.
I don't recall all of the differences between free and registered versions; but right-click anywhere on the gauge dash, and see if you have the option to Load / Save > Load Dashboard, as in the image below. It does not need to be connected.
TS_Load_Dashboard.jpg
TS_Load_Dashboard.jpg (107.97 KiB) Viewed 3701 times
By bfinney
#48994
Thanks PSIG, in your image where LOAD/SAVE is mine has LOAD DEFAULT GAUGES. I couldn't find anything in the documentation for TunerStudio about it.

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