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need advice on adjusting injector latencies


subie368

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So I'm having some random hard starting issues with my infamous stage 3 tune and need some advice. My lv currently looks almost perfect and car is idling almost perfect for a Subaru. My car is starting fine every morning no matter the temp. But if I let it sit for an hour or 2 it cranks for 5 to 10sec and then fires and stumbles...almost stalls then smells terribly of gas and returns to normal idle. Occasionally it won't start without giving it slight throttle almost as if the injectors are dumping way to much fuel. My question is this...will adjusting my injector latencies based off my dw740 charts latencies that was in the box help my problem? Or am I asking for trouble messing with this now that the car actually runs good once warmed up and driving?? Seems to me the latencies that I'm currently running are way off from what the dw print out that cane with the injectors said. Also does anyone know the stock legacy gt latencies are for 05 models? I read mixed reviews that stock latencies work for dw740s? Any help is greatly appreciated!!
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I used the latency supplied with the injector flow chart and stock. Both were not even close.

 

I set my scaling to the average cc of all 4 and used .86 @ 14v to start. Using learning view I tweaked it from there. I ended up at .84. The I scaled the other voltage points to the same percentage of change from the 14v column.

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Tuner said that the injector latencies have absolutely no affect on starting which I think is bs. Here are my latencies I'm currently running for my dw740s.

 

[Table2D] volts 6.00 9.00 11.50 14.00 16.00

msec 5.70 2.05 1.16. 0.78. 0.62

 

now i just pulled out the flow chart that dw gave me with my injector purchase and the latencies are

 

Volts/Milli sec

 

7 3.3

8 2.7

9 2.3

10 2.0

11 1.8

12 1.6

13 1.5

14 1.4

15 1.3

16 1.2

17 1.1

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And could someone correct me if I'm.wrong but my conclusion on the latencies is that having a lower time in milliseconds that it takes to fully open an injector would use less fuel then a higher time rating in milliseconds and would keep the injector slightly open longer until its fully open using more feel? And when your cranking your engine your at 12v give or take slightly so if your milliseconds at 12v was lower there would be less fuel dumping into the engine on crank then there would be with a higher time in milliseconds corect? Obviously if my cars running the volts should be around 14v give or take and the car idles fine..so Im thinking I only need to adjust thev12v time??? What do you guys think or do I have it all wrong?
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I don't think latency impacts cranking much, if at all.

However there are some table dedicated to cranking, see the attached image.

You may need to turn up the User Level in RomRaider or EcuFlash to see these.

I have ID 1000s, so you might want to change yours only about half as much from stock.

 

Mine fires right up in the morning, but hot starts/restarts take just a little longer than I think they really should. There are some dedicated hot start tables, but they have not been discovered yet in any LGT/OBXT ROMs, as far as I know. Just fixing the regular cranking IPW tables will still make a big improvement, though.

CrankingIPW.thumb.PNG.5dd8fcc702057252ad57d52fa7ecd34e.PNG

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So assuming my latencies are good..how would I go about adjusting my injector pulse widths while cranking based of my issues??

 

Roughly speaking...

 

new pulse width = stock injector flow scaling / your injector flow scaling

 

So if your new injectors are twice as big as the old ones, the pulse width would be about half as much as before.

 

That doesn't take latency into account, but it'll get you close. I've found that a pretty wide range of cranking pulse widths will work pretty well anyway.

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would anyone be so kind to post up there pulse widths for 740 inj?? that would be greaaaatttllyyy appreciated. iv been trying to figure out this problem since august and shamar is no help keeps saying its not the tune.....
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no. To be honest with 740's you should have an issue with starting.... scale the maf and see if that helps. during a cold start the ecu is set to open loop fueling- I.E. really rich for warm-up idling.... if the engine is warm it should settle out right a way. The maf scaling will have an effect on both of these. but in order to scale the entire maf range, you need to adjust the open loop scale which should be confirmed via a wideband in terms of reaching your target AFR(in the open loop fueling table). regular driving and cruising off boost can be done without a wideband in terms of scaling by using the romraider maf tool in the logger....
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