t vago's MPGuino workspace thread, continued

[josemapiro]

Hi t vago
Yes these lcds seem to be very interesting because part of the work is done by it through the processor and internal memory it has.
With it you can create more attractive and easy to see menus.

Thanks
José Rodrigues

[t vago]

After a bit of a hiatus, I have started work again on modifying the MPGuino code.

Added the #ifdef bugfix that was posted earlier this year. Completed a substantial re-write of fuel injector open time SWEET64 calculations, to support microseconds per gallon and fuel injector delay stored parameters calculations. Added skybolt's updated doOutputJSON() routine, and am scratching my head at the digitalWrite commands. Also scratching my head at the reverse-engineered acceleration test flag values.

[josemapiro]

Hi t vago
It's good to see you're back at work.

Thanks
José Rodrigues

[josemapiro]

I've been seeing some ideas for LCD Nextion and created these two images to give you an idea.
The text is in Portuguese, but I think you can get an idea.

UploadDeImagens.com.br - Menu_consumo.png

UploadDeImagens.com.br - Menu_grafico.png


José Rodrigues

[josemapiro]

Hi t vago

I wanted to do some coastdown testing but I need your help.
First as this topic is very technical the translation does not always represent what it is actually transmitting to me, that's why I asked if it's possible that I try to explain myself in the less technical way, maybe this way the translation will be easier.

For the coastdown test it takes 3 values.
1st vehicle frontal area I already have.
2nd Density of the air, this value as you get it, there is some site where you can see this value or it is through calculations. I have tried several sites of Weather but do not have this value.
3rd period between samples, what is the value that you think is most appropriate for these tests.

What is the procedure for getting the results, what kind of road is the most suitable for the test and what values can I get, just to get an idea if I'm not doing something wrong.

Thanks
José Rodrigues

[t vago]

Originally Posted by josemapiro

Hi t vago

I wanted to do some coastdown testing but I need your help.
First as this topic is very technical the translation does not always represent what it is actually transmitting to me, that's why I asked if it's possible that I try to explain myself in the less technical way, maybe this way the translation will be easier.

For the coastdown test it takes 3 values.
1st vehicle frontal area I already have.
2nd Density of the air, this value as you get it, there is some site where you can see this value or it is through calculations. I have tried several sites of Weather but do not have this value.
3rd period between samples, what is the value that you think is most appropriate for these tests.

What is the procedure for getting the results, what kind of road is the most suitable for the test and what values can I get, just to get an idea if I'm not doing something wrong.

Thanks
José Rodrigues

The second parameter, air density, can be found from converting barometric pressure and outside air temperature, to density. Link here -> How to Calculate Air Density - Fly Me to the Moon

The third, period between samples, is a good guess. I would pick once every 5 seconds.

You'll want to find a nice, smooth, flat section of road. No bumps, dips, humps, potholes, inclines, or anything else that might interfere with the coastdown itself.

Keep in mind that coastdown doesn't work yet because it isn't fully coded. I have yet to program a matrix equation solver. I also have to figure out how I am going to account for vehicle lift at higher speeds.

[josemapiro]

Hi t vago
Thank you the website is perfect for the calculation.
In relation to the test, the speed at which the test should be performed is important?
Should it be the same speed or should it be with different speeds?
What is the speed range that you think is the most suitable for the test?

Thanks
José Rodrigues

[josemapiro]

Hi t vago
I know the value will be given by the code, but what the (Cv) means the other two I know, this is that I could not find out what it is.
(Cd) - Coefficient of drag
(Crr) - Coefficient of rolling resistance
(Cv) - ?

Thanks
José Rodrigues

[josemapiro]

This is the video of the Nextion project that I have been working on.
The motions are not the best because the program where this simulation was done requires some features that the computer I'm using does not have it, but you can get an idea of the project.

www.youtube.com/watch?v=RpUdmRpKA6k

José Rodrigues

[t vago]

Originally Posted by josemapiro

Hi t vago
Thank you the website is perfect for the calculation.
In relation to the test, the speed at which the test should be performed is important?
Should it be the same speed or should it be with different speeds?
What is the speed range that you think is the most suitable for the test?

I think that should be a low-speed test, at about 40 or so km/h. This should be used primarily to determine the coefficient of rolling resistance. Aerodynamic drag, viscous drag, and lift should not factor in during low-speed testing.

Originally Posted by josemapiro

Hi t vago
I know the value will be given by the code, but what the (Cv) means the other two I know, this is that I could not find out what it is.
(Cd) - Coefficient of drag
(Crr) - Coefficient of rolling resistance
(Cv) - ?

That would be viscous drag, which apparently is not accounted for anywhere else in literature discussing how to perform coastdown testing. Likewise, aerodynamic lift is not accounted for anywhere else. I think that viscous drag may not matter too much, and might even be a negative number for newer cars. I simply don't know.

As for determining lift and coefficient of drag, that will prove to be tricky as both are functions of the square of velocity. Both terms only show up under moderate to high speeds. I think lift shows up at a higher speed than drag, though. Again, I simply don't know for sure.