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Discussion Starter #1
I'm building a test rig to measure injector deadtimes and I understand that the flyback diode used can influence this so the test setup should match whatever the actual ECU is using.

Looks like the injectors are driven by an ST microelectronics A2C11827-BD / ATM36N and I assume that this includes a zener diode for the flyback but I can't find a datasheet anywhere to confirm that or the diode's voltage.

Is anyone here familiar with this part or know where I can find a datasheet?
 

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Discussion Starter #4
I am curious why? What do you hope to learn?
I hope to learn the deadtimes of the Bosch 0280155832 injectors that I swapped in while diagnosing a rough idle.
The -832 injectors improved the idle but it's still not perfect. They did transform the general smoothness, low rpm torque and throttle response though so I'm curious whether the remaining roughness in the idle can be at least partially attributed to the -832 injectors having different deadtimes.

I measured 0.65ms with one of the stock 0280150792 injectors at 5bar and 14V which is a bit higher than the 0.53ms the DME has. I figure the difference could be due to the the injector, the test fluid I'm using, or different flyback control compared to the DME, so I'd like to eliminate at least one of those variables.
 

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It takes time for the injector to open and also to close maybe that is considered by the DME. Injectors are pretty complex things, flow rates are a little mind boggling, like more pressure does not really mean more fuel always and how the heck does one put out more fuel at a duty cycle of 98% than it does at 100%? Why did you not just replace with stock injectors? It is one thing to change injectors when you go forced air, but if you are stock why not stock injectors?
 

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The flyback diode will only have an impact on closing times. Not so much for opening times. At low duty cycles at least.
 

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Discussion Starter #7
Why did you not just replace with stock injectors?
Because stock injectors are $$$ and used ones will be 20-25 years old. I could get a set of 8 of the -832 injectors for the price of two used stock injectors. Bear in mind this was just to test a theory, I don't plan to run with these long term.

I'd actually ruled out the injectors a while back because I swapped the injectors between banks and since the pattern of INPA's 'run unrest' didn't change I figured it wasn't injectors, but after reading another thread on this board related to a failed injector causing misfire where moving the injector didn't move the misfire I thought it was worth looking into again.

Anyway, I guess I'll have to put the oscilloscope on the car and see if I can figure out the flyback characteristics that way.
 

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Discussion Starter #8
Looks like I was mistaken on the injector driver, seems to be a Harris DPS326718 on the MSS52?
 

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Looks like I was mistaken on the injector driver, seems to be a Harris DPS326718 on the MSS52?
I believe that is correct for the MSS52 and MSS54 non-HP. MSS54HP switched to the ATM36 / ATM36N

I haven't found datasheets or any of the above
 

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Discussion Starter #10
I measured the voltage between the injector pins on the DME and ground and it looks like the clamp voltage is ~50V.

941998


Put a 51V Zener in my test rig and flowed at 7.8, 10, 12, 14, and 16V and 5bar pressure. Measured Deadtimes are slightly higher than those in the DME.

Guess the test fluid is another variable, I'm using stoddard solvent which is probably more viscous than gasoline?

How do you handle injector dead times when changing injectors for superchargers etc.?
 
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