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Richie-Van-GTi

Injector dead time

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Richie-Van-GTi

Sorry still learning, is this a fixed value for specific injectors or can it vary by installation?

I see on my ecu software there is a graph where the dead time drops based on voltage but once at 12v it flattens out.

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petert

Injector dead time varies between injectors. Your injector supplier should be able to supply values of dead time vrs voltage vrs pressure. Motec has a large library.

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Thijs_Rallye
4 hours ago, petert said:

Motec has a large library.

Are those freely accessible or do you need a Motec license to access that database?

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Richie-Van-GTi

Cannot find the dead times for them after hours of searching.

Anyone know 0280 150 762 (1.9 mi16)

The mapper has put values in for the current injectors (211 standard 1.6 injectors) although not sure if they are accurate.

 

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petert

Are you tuning via VE or msec?

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Thijs_Rallye
Posted (edited)

Funnily enough I had sent an email to Bosch last Wednesday asking about deadtimes (Totzeit in German) and I was surprised that I have received an answer this morning already.

So it might be worth to just send them an email via their contact form.

 

As far as I knew the 702 were fitted to the Mi16 engines and the 045 are nowadays sold as their replacements. The latter I have been using for quite a while now in my 205 with XU9JAZ.

 

EV_Daten_Herr_Rallye.pdf

0280156045 - Berechnung Spannungsabhängigkeit V offset ts.pdf

0280150702 - Berechnu ng Spannungsabhängigkeit V offset ts.pdf

Edited by Thijs_Rallye
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Richie-Van-GTi
2 hours ago, petert said:

Are you tuning via VE or msec?

They have done it with msec. I can convert to VE but since its going back to them i would rather leave as is

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petert

I don't think it matters so much then.  Definitely if VE, so you get 100 at max/peak torque.

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Richie-Van-GTi
Just now, petert said:

I don't think it matters so much then.  Definitely if VE, so you get 100 at max/peak torque.

I need to rescale the fuel table for an injector change which will introduce errors if i dont account for dead time change.

 

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Richie-Van-GTi

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Thijs_Rallye

I've compiled a small google document in which anyone who wants can add data to it. (I hope, first time using google docs) It would be nice to have some additions to the application list.

 

https://docs.google.com/spreadsheets/d/1lNsjX6I0NY70CLLa25-HLHfcbb-EhxRoDQ-UxZd2rPs/edit?usp=sharing

 

 

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petert

Well done.

I'm in a similar position. I upgraded the injectors a few ago but didn't adjust the dead times. The VE numbers were still ok, but definitely on the low side. ie idle is 30. I was going to enter the correct numbers and head back to the dyno, then we had the crash. Changing the dead times will affect the tune, so you'll be back to the dyno anyway. I'd probably just fit new injectors and get it tuned again in VE mode, minimising the trips to the dyno. Or am I missing something?

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Richie-Van-GTi
7 hours ago, petert said:

Well done.

I'm in a similar position. I upgraded the injectors a few ago but didn't adjust the dead times. The VE numbers were still ok, but definitely on the low side. ie idle is 30. I was going to enter the correct numbers and head back to the dyno, then we had the crash. Changing the dead times will affect the tune, so you'll be back to the dyno anyway. I'd probably just fit new injectors and get it tuned again in VE mode, minimising the trips to the dyno. Or am I missing something?

No, its going back on the dyno regardless as its only tuned to a driveable state as the cam was just not working with the set up.

My plan is to use the car a little bit, just for some local meets etc whilst its summer. Ideally with the new injectors so i know everything is working correctly. Then i will swap the cam and take it back to the dyno on a trailer and have the correct final mapping done.

Although i am tempted to try the new cam and see if i can tweak the current map enough myself to make it safe to drive before it goes back.

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Richie-Van-GTi

I think i know how to change the injectors and table.

Its currently tuned in ms and the dead time is set at 1ms. The actual dead time according to bosch is 1.34.

So if i add the difference of .34 across the table and update the dead time, then make sure the engine volume and injector flow are correct before converting to VE i should get sensible values.

Then i can change the injector flowrate and dead times to suit the new injectors and it should be pretty much right.

 

Does that sound right?

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Thijs_Rallye

Doesn't the ECU have a dedicated map where you can fill in the dead times? The dead times vary with voltage.

 

Afaik the VE should remain the same, regardless of what injector one uses. The VE table is basically the model of how the engine breathes. As long as nothing is changed to intake / exhaust or cam timing this should remain the same.

 

The ECU uses the VE map (dead times, injector flow, coolant temperature, and IAT to some degree) to calculate the amount of fuel that needs to be injected to obtain your target AFR / lambda. The only control the ECU has is opening the injector for a certain amount of time, hence the milliseconds. The dead times basically "calibrate" these times to the general map.

So if the ECU knows it needs 5 ms of injection time* to obtain the right AFR / lambda based on the target map and volumetric efficiency map, the dead times are added for opening and subtracted in case of closing.

 

*The 5 ms of injection timing assumes instant opening and instant closing of the injector.

 

That is at least how I think it works.

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Richie-Van-GTi

Yes there is a small table for the dead times expressed as ms/volts

Currently the graph used is pretty much 1ms for the entire table. Since the actual value should be 1.34 at 14v which is what it runs at then it means the mapper has put that .34 into the current tuning, which he has done in ms. So if i add the .34 to the dead time and remove it from the entire table it should in essence be the same amount of fuel being delivered.

If i then make sure the flowrate is set correctly and convert to VE i should have a simpler map to change the injectors as its then just change the flowrate and dead time to the new injectors.

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petert

It also depends on whether it’s sequential or multipoint/batch. Sequential has only one dead time per cycle, whereas multipoint has two.

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Richie-Van-GTi
Posted (edited)
1 hour ago, petert said:

It also depends on whether it’s sequential or multipoint/batch. Sequential has only one dead time per cycle, whereas multipoint has two.

Alternate firing in pairs, current is doubled on the ECU

Edited by Richie-Van-GTi

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