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Davidv

Aggressive change in injector timing = missed inj events?

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I've got an injector timing table set to 240deg BTDC end of injection all the way through rev range.

With some changes to cam timing I decided to test 400deg btdc above 2200rpm / redo some testing at different angles.
And as soon as I make this change, when my car gets to that rpm where the injector timing advances a lot the car bucks and lurches and stutters. 
If from here, I set all of the timing to either 240 degrees or 400 degrees, its fine again. But when it's on that transition point, things get weird.
It seems more prominent at low load, I'm guessing because its an issue if start of injection is beyond a certain point? 

I suspect that an injector event gets skipped, the car hesitates and rpm drops and same thing happens again.
(It's a really aggressive lurching of the car, and definitely not just caused by the effect of different timing)
If I set the table to all 400 deg or all 240 deg the car drives smooth and fine.
I can supply logs and a basefile as an example if needed. 

Thanks
David

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Hi David,  If you want to email me your map that gives the stumble I will run it on the bench here with a scope connected to an injector output and see if I can capture if anything odd is happening.

NAjJcZt.png   It might be a couple of days before I get to it. 

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Hello, 

Give it results for this problem. I got all most the same problem. When I set 400° for all situations it robbing over 200kpa. When I set all to 300° the robbing comes earlier at 180kpa but work by 200kpa or higher. When I try to kompensate over pressure and rpm, the robbing coming one times earlier some times later.. I'm totally confused. 

I know it gives many meanings to this them, but maybe we can take meanings together. 

Greetings Benny 

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Hi Benny,

When David above reported this problem I set it up on the bench here and done a test while recording the injector pulses with an oscilloscope.  It appeared to work as expected with PW matching the commanded value and no "missed" events.  My feeling was it most likely was related to the timing of the injection event affecting the "puddle" or wall wetting effect so one intake cycle goes very lean.   I did send him a video of my test but I have since deleted it from my onedrive.

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He thanks Adam for the fast answer, great guy:)

Slowly I got the feeling that the injectors (siemens deka 630cc) on higher boost 200kpa are little bit on the limit. My fuel value are by 92% but my duty cycle shows 65% :huh:

I look for other injectors (Bosch 750cc) with direct datasheet and test it. I give feedback when it done. 

Greetings Benny 

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