peak and hold current

[ElsmoortelG]

Hallo,

Can anybody tell me how long the peak current works with setting 2,5 A.
An about the Peak Hold Ratio (4)is this related to the time between peak and hold or the current ?

We used for injector 0 280 150 842 setting -0.1 as injector current but the injectors always fail after some time.
For the -0.1 setting there is mentioned 3ms peak and 1 amp hold.
What is the current of the peak value ? And what does no peak diag mean ?

If we change to 2,5 A injector current and a peak and hold ratio of 4 what is then the time of the peak current (ms)and what is the value of the hold current ?

Thanks

[DarrenR]

The current the injector draws rises from 0A when it is first turned on to it's maximum as the magnetic field builds. This takes around 2-3mS for most injectors. Given that the pintle moves before the maximum current draw is reached there is no need to saturate the coil to operate the injector.
The current the injector draws is monitored by the ECU and when the value you have set is reached it switches to the hold current (via PWMing the output). So with the 2.5A setting, the injector is turned on fully and the current drawn rises. When 2.5A is reached the output switches to a fast PWM with enough duty to hold 1/4 of the peak current (with 4:1 peak hold ratio), so 0.625A. The actual time it takes to reach 2.5A depends on the injectors inductance.

If the injector takes longer than 2mS to reach the peak current setting it switches to the hold current anyway and flags the peak not reached error, 'PEAK'.
Since some injectors need more time to build enough current to open the pintle, the minus current value is entered to make the ECU wait 4mS before changing to hold and flaging the error.

The Indy injectors use -0.1 as the setting as they are a little different to every other injector. They are turned on fully for 3mS before switching to a hold current of 1A. The peak not reached diagnostic is turned off for this as the ECU is running the injector for a time rather than waiting for it to draw the peak current.

I can't quite remember, isn't the indy injector an 839, not a 842??
I can tell you the correct setting to use for the 842 injector on monday. In what way do the injectors fail, blown coil??

[DarrenR]

I've just checked our documentation. Injector current of 2.5A and peak hold ratio of 4 are the correct settings for the Bosch 0 280 150 842 injectors.
Have you tried these settings? Do you get a 'PEAK' error?? What is your normal battery voltage and fuel pressure???
Using the -0.1 current setting shouldn't hurt the 842 injector, but does drive them harder than the 2.5A setting.

[ElsmoortelG]

No, I didn't have the chance to test these settings. I will test them next thursday.
About the failure on the injectors it differs :
- the injected quantity differs when tested on a bench
- the injector stays open from time to time

Normally these injectors are designed for CNG. We use them with standard unleaded petrol. Could this cause an issue ?
We have 13,5 V from the alternator.
Fuel pressure is 4,1 bar.