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Inj. dead times and fuel pressure


revmesh
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Hi fellow tuners, I'm afraid that i need assistance with setting the injector dead times to my ecu. I have set the fuel pressure to 55psi with the fuel regulator vacuum line disconnected. When it's connected and engine idling, the fuel pressure is about 40psi. So my question is, when i key-in the dead times, should it be based on the "base pressure" or the pressure i'm idling with the vacuum line connected? I have attached the dead times table from the injector manufacturer. Thank you very much for your time. 

PL1200 LATENCY.pdf

Edited by revmesh
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You set it to the base pressure. 

That said i would make a 3d deadtime table and copy that entire table in

Also hook up a fuelpressuresensor and you are golden

thanks, but why make a 3d table (is it to get the interpolation data?) and  can i do it in excel?

Note if you see a 15 psi change when you connect your manifold reference something is wrong. Most engines will idle about 50kpa below atmosphere so I would only expect to see a ~8 psi drop.

thanks man, i shall look in to it

 

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You use a 3d table because injector deadtimes vary not only with voltage but also with pressure. Now, without a fuelpressure sensor there would be no point in using the 3d table but i suggest you do get one and use it.

You would be suprised to see how much the differential fuel pressure (the relation between fuelrail pressure and intake manifoldpressure (This is the base pressure you set the regulator at)) changes. You would think it stays at the set basepressure but thats not the case.

So one upside with running one is the ecu can look up the correct deadtime based on both voltage AND differential fuel pressure (DFP).

Another one is the ECU can compensate the injetor pulsewith based on DFP which meens the VE table is more correct. ALSO and more important the ecu can compensate should your fuelpressure drop for some reason and make sure you dont run lean (or rich in case of raised pressure)

Third you can have the ECU trigger a limiter based on DFP. Like if a pump starts to go bad it can save your engine.

Why would you do it in Excel? You got all the data right there in that file you posted. Just type it into the deadtime table. Takes 5 minutes.

Edited by Steve
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