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Old 09-05-2013, 11:50 AM   #40 (permalink)
t vago
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Quote:
Originally Posted by AndrzejM View Post
Now I get it To get the atmospheric pressure you can read it before starting the engine or anytime when engine is not spinning (EOC), using engine's MAP sensor. Then remember its value to have a decent reading of the absolute pressure.
I do that now. If the engine is not running, and the vehicle is not moving, I use P(MAP) as P(baro). Unfortunately, due to the way my 2nd stage filter operates, it takes a few seconds for the reading to build up when the engine is not running. I will have to fix that. Maybe move the 2nd stage out of the master timer (what I've lately come to think of the timer2 overflow interrupt) and into the ADC interrupt, right after the 1st stage filter.

The 2nd stage operates either once per injector firing, or twice a second - whichever is faster.

Quote:
Originally Posted by AndrzejM View Post
It shouldn't vary from the absolute pressure much, unless you're traveling long distance or in mountains. But I'm sure that will be a good starting point for you, to get correct readings of the fuel pressure.
I do travel many hills on my commute, and my work and my house are at different elevations. It's not much (14.6 psia vs 14.3 psia), but it is enough.

Quote:
Originally Posted by AndrzejM View Post
Don't worry it's perfectly normal I remember when I was changing my MPGuino code (based on metric "Canadian" version), and everything looked just fine on my tedt Guino, untill I havent uploaded the code to MPGuino mounted in the Berta. It's good to have many copies of the code and make a new one after any major change. But I'm sure you know that
It's just annoying, is all. To pour all that work of one day into modifying the code, only to have it just sit there with a blank screen, when you knew for a fact it worked well only a few hours before, and when you are not able to test the code immediately because the MPGuino itself is not readily available, that well and truly sucks.

I have archived previous days' coding effort since 15 July. It's good to have, in order to revert back some change, or even just to copy code I thought I didn't need, only to find I needed it after all.

Quote:
Originally Posted by AndrzejM View Post
Anyway it's a really great job and I'll be honered to be your beta tester
Thanks again. Hopefully, I'll have the code posted here today or tomorrow.

Quote:
Originally Posted by AndrzejM View Post
Engine Off Coasting... Engine is not spinning Of course you need to wait a few seconds to get accurate readings, but that shouldn't be a problem
Unfortunately, the MPGuino is not equipped to even be able to tell whether the engine is actually not spinning. With only a fuel injector sense and a VSS sense (and a MAP sense for my code), you can't really tell for certain whether the engine is actually stopped. All it can tell you is whether fuel injectors are firing or not. As I have an automatic, my engine will continue to spin, due to the torque converter coupling, as I am coasting in DFCO, which is a form of EOC. There is no fuel being injected, so the engine is technically off, but it is still spinning.

Now, you can certainly guess if the engine is not spinning, by examining the MAP reading to see if P(MAP) is below some threshold value, which is what I can do in the meantime.

With the addition of a barometric sensor, it becomes fairly easy to tell. If P(MAP) = P(baro) and there are no fuel injector pulses being sensed, then it's pretty obvious that the engine is not spinning.
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