ECU voltage compensations why?
25-10-2008, 10:08 AM
#1
ECU voltage compensations why?
Might be a daft question but why does the injector on time get adjusted by a set amount rather than a percentage?? 13v at idle .5 msecs is going to make a lot more difference than the same value at high boost?
And why does it add at all voltages, surely at one point no fuel needs adding and either side of that needs more or less?
And why does it add at all voltages, surely at one point no fuel needs adding and either side of that needs more or less?
Last edited by Martin-Hadland; 25-10-2008 at 10:22 AM.
25-10-2008, 10:12 AM
#2
Because its only during the opening of the injector that flow is effected by voltage, once the injector is fully open and just held there, the flow doesnt change.
So if the opening speed is reduced by lower voltage all we need to do is compensate for that, not change the value during the "held" state.
It adds at all voltages so that it can be capable of not overfuelling in a high voltage situation, if it flatlined after 13 volts or whatever, then it would go rich at 16v.
So if the opening speed is reduced by lower voltage all we need to do is compensate for that, not change the value during the "held" state.
It adds at all voltages so that it can be capable of not overfuelling in a high voltage situation, if it flatlined after 13 volts or whatever, then it would go rich at 16v.
25-10-2008, 10:20 AM
#4
Because its only during the opening of the injector that flow is effected by voltage, once the injector is fully open and just held there, the flow doesnt change.
So if the opening speed is reduced by lower voltage all we need to do is compensate for that, not change the value during the "held" state.
It adds at all voltages so that it can be capable of not overfuelling in a high voltage situation, if it flatlined after 13 volts or whatever, then it would go rich at 16v.
So if the opening speed is reduced by lower voltage all we need to do is compensate for that, not change the value during the "held" state.
It adds at all voltages so that it can be capable of not overfuelling in a high voltage situation, if it flatlined after 13 volts or whatever, then it would go rich at 16v.
25-10-2008, 10:33 AM
#11
Martin, setting this table up is actually one of the simplest tasks you will have as a mapper as it can be so easily simulated.
Run the ecu off an external variable voltage power supply.
Set the 13v point to 0.5 first as good starting point
Then record the AFR at idle.
Set the voltage to 12V and alter the compensation value until you have the same AFR again, then 11V etc
It needs doing on a per injector configuration basis, so it will only need to change if you change the injectors for another type or alter the fuel pressure.
It doesnt actually matter if when you do it the AFR is correct at the time or not, so you can do it before youve finished the rest of the mapping of the car, so its good one to get setup early on in the mapping process as it stops you getting spurious results during mapping.
Run the ecu off an external variable voltage power supply.
Set the 13v point to 0.5 first as good starting point
Then record the AFR at idle.
Set the voltage to 12V and alter the compensation value until you have the same AFR again, then 11V etc
It needs doing on a per injector configuration basis, so it will only need to change if you change the injectors for another type or alter the fuel pressure.
It doesnt actually matter if when you do it the AFR is correct at the time or not, so you can do it before youve finished the rest of the mapping of the car, so its good one to get setup early on in the mapping process as it stops you getting spurious results during mapping.
25-10-2008, 10:36 AM
#13
Martin, setting this table up is actually one of the simplest tasks you will have as a mapper as it can be so easily simulated.
Run the ecu off an external variable voltage power supply.
Set the 13v point to 0.5 first as good starting point
Then record the AFR at idle.
Set the voltage to 12V and alter the compensation value until you have the same AFR again, then 11V etc
It needs doing on a per injector basis, so it will only need to change if you change the injectors for another type.
It doesnt actually matter if when you do it the AFR is correct at the time or not, so you can do it before youve finished the rest of the mapping of the car, so its good one to get setup early on in the mapping process as it stops you getting spurious results during mapping.
Run the ecu off an external variable voltage power supply.
Set the 13v point to 0.5 first as good starting point
Then record the AFR at idle.
Set the voltage to 12V and alter the compensation value until you have the same AFR again, then 11V etc
It needs doing on a per injector basis, so it will only need to change if you change the injectors for another type.
It doesnt actually matter if when you do it the AFR is correct at the time or not, so you can do it before youve finished the rest of the mapping of the car, so its good one to get setup early on in the mapping process as it stops you getting spurious results during mapping.
25-10-2008, 10:43 AM
#16
PS
If you want to be safe on pretty much any injector you are likely to use in the mean time, set it to:
8 = 2
13 = 0.5
16 = 0.5
Then the worst that will happen is if you end up with a voltage problem in either direction the car will go rich, which is obviously preferable to lean.
If you want to be safe on pretty much any injector you are likely to use in the mean time, set it to:
8 = 2
13 = 0.5
16 = 0.5
Then the worst that will happen is if you end up with a voltage problem in either direction the car will go rich, which is obviously preferable to lean.
25-10-2008, 09:06 PM
#24
Too many posts.. I need a life!!
Join Date: Jul 2004
Location: norway
Posts: 868
Likes: 0
Received 0 Likes
on
0 Posts
25-10-2008, 09:51 PM
#37
