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TimoL

Using different ECU for injector dead time testing

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I just bought JECS 1000cc side feed injectors for my 99 WRX but the seller could not provide any dead time values.

So I build a test bench for testing injector dead times. The setup:

-Adjustable fuel pressure reg, 2 - 9 Bar

-Adjustable voltage supply, 9 - 15V, 36 A

-MS2 based ECU

 

But I started thinking that maybe I should not do this with other ECU than the one I actually use on my car (Link G4+ WRX Ver5/6) with these injectors?

 

I plan to get fairly accurate data for dead time and possibly short pulse width, but I have no experience of the latter.

 

On the other hand, wiring the Link G4+ to my test bench should not be very hard. AFAIK only 8 wires would need to be connected:

-12V (batt)

-12V (switched)

-GND

-Inj 1, 2 ,3 &4

-Inj common (+12V)

 

-Timo

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Yes, I highly suggest you use the Link for this test as I suspect our injector driver circuits are probably different than a MS2 and this can have quite an effect on dead times.  

See this post here for a bit of an idea how another user tested deadtime and short pulse width adder  (Roman is user @Davidv on the Link forum):  https://oldschool.co.nz/index.php?/topic/21624-romans-beams-3sge-toyota-carina/&do=findComment&comment=1688039  Im sure he had a similar post on this forum but I cant find it.

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Thank you for your input Adamw.

 

I am going to use the Link ECU for the dead time testing. I took a look at PCLink manual and it seems that I can test only one injector at a time and only using injector channel 1 because I need the advanced mode. Is it right? It's not really a problem, I was just hoping to be able to test all 4 injectors at the same time.

 

Also I'm not certain as how to wire the ECU. The installation manual has at least some of the pins explained. Based on the manual I would wire the ECU like this. Is this correct? And how do I wire the injector +, just straight to +12V?

image.png.c6ec68591fcd0457f01d38de005d712f.png

 

-Timo

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Here's a more detailed post about how I tested deadtimes:

https://www.hpacademy.com/forum/general-tuning-discussion/show/calculating-deadtimes-with-a-link-g4-and-injector-test-bench

I made an extension lead for injector 1 so I could use the ECU in my car, the fuel pump thats in my car, the FPR that's in my car, etc etc so every variable is as close to actual use as possible.

Then I just made the ECU vary supplied voltage by using a battery charger connected to battery, and used different combination of accessories on and off to get the voltage to where I wanted to test it.
 

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18 hours ago, TimoL said:

I am going to use the Link ECU for the dead time testing. I took a look at PCLink manual and it seems that I can test only one injector at a time and only using injector channel 1 because I need the advanced mode. Is it right? It's not really a problem, I was just hoping to be able to test all 4 injectors at the same time.

You only need to test one injector for deadtime and SPWA, they should all be the same.

 

18 hours ago, TimoL said:

Also I'm not certain as how to wire the ECU.

Yes, your proposed wiring is fine.  The injector + should be connected to the same +12V source as pin B136-8 so it is seeing the same voltage as the ecu.

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8 hours ago, Davidv said:

Here's a more detailed post about how I tested deadtimes:

https://www.hpacademy.com/forum/general-tuning-discussion/show/calculating-deadtimes-with-a-link-g4-and-injector-test-bench

I made an extension lead for injector 1 so I could use the ECU in my car, the fuel pump thats in my car, the FPR that's in my car, etc etc so every variable is as close to actual use as possible.

Then I just made the ECU vary supplied voltage by using a battery charger connected to battery, and used different combination of accessories on and off to get the voltage to where I wanted to test it.
 

Thanks for sharing the link David, that's a great write up BTW. Since I will be using the Link ECU for driving the injectors and the voltage reported by the ECU for cal table x-axis, I believe it should be accurate enough. Also, the same fuel pressure sensor (connected to the ECU on both cases) will be used for the testing.

 

-Timo

3 hours ago, Adamw said:

You only need to test one injector for deadtime and SPWA, they should all be the same.

 

Yes, your proposed wiring is fine.  The injector + should be connected to the same +12V source as pin B136-8 so it is seeing the same voltage as the ecu.

Yes, they should be the same. I'm actually more concerned about the flow rate differences between the injectors. The seller claims that they are flow matched but I paid 140€ for a set of 4. You know, you get what you pay for...

I confirmed the wiring by measuring those pins from stock ECU while it was powered on. The wiring seems to work on the test bench. I could not do any tests yet, because the test bench fuel pump was shot. I believe it to be because it was used with ethanol and then stored dry (=corrosion?).

I will be posting results soon as I have some.

 

-Timo

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Finally had the time to finish the tests. Results are in the attached spreadsheet, feel free to use for your own measurements. It's not really clean and has a lot of unnecessary data, I just like to calculate things...

Here's what I found:

The dead time has some variation between injectors, lowest being 0,715 ms and highest 0,812 ms (at 14,0V, 350 kPa). The average was 0,763 ms for all injectors. I also measured the dead time using a MS2 based ECU and got an average result of 0,80 ms (also at 14V, 350 kPa).

image.png.b9f741e664d3e503319e61c3cfd4b037.png

 

Overall, the dead time is pretty much what I expected for these injectors. I only used one injector (Inj4) for measuring dead time at different voltages. I only went down to 10 Volts on the test bench and extrapolated the low end.

image.png.e6164e15d881fbfd0802ace32bdd01cb.png


-Timo

deadTimes.ods

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I also ran some tests on very low pulse widths to find how the injectors behaved in the non-linear range.

image.png.54c9f3db588e0218325cc7048d0b1d64.png

 

All of the injectors have a similar curve for low PW linearity but the peaks reside at different ms. The peak will be flattened (if not removed all together) when you calculate average for all of the injectors.

Since the low PW adder is same for all injectors you would need a low PW (and dead time) matched set of injectors to have full benefit from the low PW calibration table.  But since these are 1000 cc injectors, I expect to be operating in linear range and the low PW calibration will not be needed. Interesting results nonetheless.

image.png.1e565e55b9696675ffead81753e7eaaf.png

I could not wrap my head around how to calculate the low adder table but I think what's all that about. To visualize it:

image.png.7ddc797985b87c6c3edbbe45ed6759e9.png

 

The blue line represents the expected flow per millisecond and red actual flow. For example to find out the needed PW addition at 0,625 ms you would measure the distance from "the expected flow" line at that x-coordinate to the x-coordinate where the actual flow has the same flow value. I've marked these distances with green lines to the chart. Is this how the short PW adder works?

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