Building your own kit to run on ethanol E85

crude vegetable oil, diester, bio-ethanol or other biofuels, or fuel of vegetable origin ...
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nlc
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by nlc » 16/11/09, 08:39

Ok for the changes, but there may have been simpler, and that allowed to keep the logic of a unit of enrichment = 5% of enrichment:

In timer.c / enrichment table, adding lines to reach up to 70% enrichment:

code: Select all

[...]
   { 11,  20 }, // 11/20  = 55% de carburant supplémentaire
   { 6,  10 }, // 6/10  = 60% de carburant supplémentaire
   { 11,  17 }, // 11/17  = 65% de carburant supplémentaire
   { 7,  10 }, // 7/10  = 70% de carburant supplémentaire


In timer.c / setInjectionParameters () function, we modify the table overflow check:

code: Select all

 // On limite à 70% par sécurité pour ne pas deborder du tableau de constantes
 if ( injectionValue > 14 )
     injectionValue = 14;


And so in ihm.c, rather than adding a variable starterBoostTmp I would rather do this:

code: Select all

BYTE _ihmInjectionValueGet ( void )
{
   // Retourne le pourcentage d'injection supplémentaire désiré par l'utilisateur
   
   // En mode SP95, pas d'enrichissement
   if ( mode == MODE_SP95 )
       return 0;

   // Dans les 3 premieres secondes après le démarrage de la carte, on
   // enrichit à 70% pour faciliter le demarrage du moteur
   if ( starterTmp > 7000 )
       return 14;

   // Durant le temps de starter qui reste, on
   // enrichit à 50% pour faciliter le demarrage du moteur
   if ( starterTmp )
       return 10;
   
   // Par sécurité, on limite à 50% d'enrichissement maximum
   if ( injectionValue > 10 )
       injectionValue = 10;
      
   return   injectionValue;
}
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latorsche
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by latorsche » 16/11/09, 23:29

It's good it's in the box : Cheesy: and I used the function greater than 7000 for 3 seconds which is much shorter than my hack (but good when I don't know we do as we can).
We will see here that it improves the start in cold weather against hot I think that we will have to wait 3 seconds to not drown the engine.
I already have the idea of ​​a starter management with 3 modes (without, with 50% and with 70% depending on the wait for the starter kick after switching on the ignition.)
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radi
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by radi » 28/12/10, 19:03

Hello,
I am new to the forum, I am 24 years old and electronic engineer.
I like electronics, mechanics, and when I can link the two it's a treat :). Here are for the presentations.

I watched carefully all the work done by NLC, it's good work, and I ask myself a few questions.

In the code, why put everything static (a function and a lot of variables)? I think it's a question of addressing the microphone and it requires less clock cycle, am I wrong?

Second remark, I thought it was necessary to have a driver to order a mosfet, it does not pull too much on the peak to connect it directly to the output through a resistor?
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nlc
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by nlc » 28/12/10, 20:11

Hi radi

radi wrote:Hello,
In the code, why put everything static (a function and a lot of variables)? I think it's a question of addressing the microphone and it requires less clock cycle, am I wrong?


No, nothing to do with clock cycles, it's just my ultra-square programming habit that I set up for big soft projects and that I also respect for small ones. The idea is based on the principle of object programming, namely that each of my C source files have their local variables and functions declared statically, so that they cannot be "seen" from the outside. The source file is therefore "a black box" seen from the outside. The gateway with the other parts of the program is only carried out by the function calls provided for that (APIs as we say).

radi wrote:Second remark, I thought it was necessary to have a driver to order a mosfet, it does not pull too much on the peak to connect it directly to the output through a resistor?


The driver is designed to manage the strong current pulses caused by the changes of state on the gate associated with the parasitic capacity of its gate.
They therefore make it possible to switch Mosfets faster and are therefore essential for non-negligible switching frequencies.
Here the switching frequencies of the mosfets are very low and therefore direct control by the PIC is sufficient. The PIC outputs are limited to 20mA, suddenly the speed of rise of the voltage Vgs and therefore the switching speed is limited by these 20mA but this switching speed is still measured in microseconds and the time in "linear" mode of the mosfet remains negligible compared to the ON / OFF switching frequency.
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radi
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by radi » 28/12/10, 23:10

Thank you for this additional information.

Another point, the injector is an inductive element, when the mos is opened, this must create a fairly large overvoltage given that the current no longer has a "path" to flow.
Would it be advantageous to add a freewheeling diode in parallel with the injector so as to avoid the problem?
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nlc
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by nlc » 29/12/10, 09:28

In principle it would be necessary, yes, but to demagnetize the injector as quickly as possible (when the computer stops piloting it has to close as quickly as possible), you must allow the voltage to rise as high as possible before the current is not making its way.
And in this case the current makes its way directly into the mosfet, we use the avalanche effect of this one: at the opening of the mosfet its voltage Vds exceeds the maximum admissible voltage and the mosfet becomes conductive. Seen from the outside it looks like a zener effect.
On the other hand, you must be careful to use mosfets which support this somewhat special use and check the characteristics of the avalanche effect in the doc.
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radi
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by radi » 29/12/10, 11:52

Ok. In fact I intend to make an E85 kit, and I did not know if I would take your mount and code but with a pic18F1220 or 1230 for example, because I have and I am more used to pic18, and that this one is compatible pin to pin, just the code has to adapt a little. I have MPLAB and the C18 compiler.

Otherwise I make a card that will take what you did, but with drivers and freewheeling diodes, add a temperature sensor to make the starter only if it is too cold, and add a connector to program and debug it pic (with an ICD2 programmer for example). And the ca would be with a slightly larger microphone, a PIC18F2420.
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nlc
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by nlc » 29/12/10, 11:59

Ah well there is only you who can decide what to do !!

For freewheeling diodes demagnetization will be too slow. If you put the oscilloscope on your injectors you will see that on the original computer there is also no freewheeling diode, the overvoltage when the injectors are cut off is around 80V.
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radi
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by radi » 01/01/11, 18:25

Suddenly, I think going on the layout that you have done, I hope to have time to do this during January.

In terms of reliability, have you been using it since 2008? So it's proven.
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nlc
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by nlc » 02/01/11, 11:18

I hardly use this car anymore but it still runs on ethanol, I never had a problem. I have had a lot of positive feedback by email too.
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