ECMlink need some dead time/global fuel setting help...

[Turbocharged]

I finally got my LTFT's to level off. During cruise LTFT are at about +2% and at idle 0%. The problem is that Im at -21% with 100 dead time on my PTE 680's. From the equation provided by DSMlink, Im supposed to be closer to -34% with a dead time of around 240. I have an unhacked MAF with the screw untampered with and a 3kgt vr4 fuel pump. I do not know my fuel pressure.

What could be causing this? The car runs fine, although it seems to be running rich under WOT. The a/f ratio under WOT is 8.2:1 and my o2 voltages are at .92-.94. Why am I so rich under WOT and so lean at cruise and idle?

 

[Turbocharged]

Nobody has experienced this before? Could a boost leak cause this drastic of fuel trim problems? Also, how are LTFT determined by the ECU?

 

[Blk_99gst]

I finally got my LTFT's to level off. During cruise LTFT are at about +2% and at idle 0%.

That's good.

=TurbochargedThe problem is that Im at -21% with 100 dead time on my PTE 680's. From the equation provided by DSMlink, Im supposed to be closer to -34% with a dead time of around 240.

You'll have to explain this to those of us who don't have dsmlink. "What's" at -21%, the compensation factor? Most of us 2g's can't see dead time, so it means very little to us. I don't know how you would go about raising it to 240. Did you ever run the -34% number like the equation said? What were your fuel trims like when you did that. (the -34% number).

What could be causing this? The car runs fine, although it seems to be running rich under WOT. The a/f ratio under WOT is 8.2:1 and my o2 voltages are at .92-.94. Why am I so rich under WOT and so lean at cruise and idle?

What's the problem? You're fuel trims are fine, meaning that you are tuned for low speed/crusing. Just because you don't fit into an equation perfectly doesn't mean you are out of tune.

If it's rich at WOT, then you have to lean out WOT. I assume with dsmlink that idle,cruise,and wot can all be tuned separately. I don't think I would trust the estimated air fuel ratio dsmlink gives you. It's just an estimate. O2 voltages of .92 and .94 are good, but you know you can't tune off o2 voltage alone. And you have the GREATEST thing to tune wot for anyway, 2g knock on dsmlink. I would just tune wot runs based on that.

 

[Rob10_99]

Deadtime is how long the injector is not seeing any power to let the pintle, disc, or ball close.
I have a set of "reman" injectors, just stocks which were set to 950cc's(denso), and I'm having issues finding the right deadtime as well.
For my setup I'm using -55% and a deadtime of 235u right now. Its running decent but could be better.

 

[1992awdlaser]

Your global should be -31% and deadtime should be 315. You NEED to make sure the fuel pressure is 43 with the vacuum line disconnected. If your fuel pressure is off that could be the reason your global isn't correct.

Low fuel pressure would be able to cause a lean condition. The global setting tells the fuel injector how long to stay open. Obviously since the injectors are bigger than stock they will flow more in the same amount of time. This is why the global setting is negative, so it tells the injectors to stay open for less time. The smaller the number the longer the injector will stay open. -21% would be for injectors that flow approximately 575cc. So, if the fuel pressure is low and causing a lean condition you could get rid of the lean condition by changing the global setting to a smaller number(like you have). This would cause the injectors to stay open longer than they should which would cause them to spray more fuel which would make up for the lack of fuel pressure.

What kind of air/fuel ratio were and are you seeing? Why don't you post up a log on link forums?

 

[1992awdlaser]

You'll have to explain this to those of us who don't have dsmlink. "What's" at -21%, the compensation factor? Most of us 2g's can't see dead time, so it means very little to us. I don't know how you would go about raising it to 240. Did you ever run the -34% number like the equation said? What were your fuel trims like when you did that. (the -34% number).

The global setting is for how long the injectors should stay open based on their size compared to stock. The equation is stock injectors/your injectors -1=global setting. So we will just use 750's, 450/750=.6-1= -.40. So the global for 750's would be -40%. The car doesn't see deadtime, you can just adjust it with dsmlink. Here is a screenshot of where you adjust your global and deadtime http://dsmlink.com/images/screenshots/fuel.gif

 

[droppinbottom]

^^ I agree completley with that statement on how things should work. I had a problem with getting mine correct when I first ordered link so I took it to a friend of mine who really knows his stuff when it comes to tuning. He told me that sometimes in the real world the formulas dont always work and reason can vary from injector to injector. IE injectors have a +/- tolerance in how much they flow. For example say you got two injectors that flow 690 and one that flows 680 and one that flows 670, All these injectors would still be classified as 680's even though they flow different amounts of fuel, they still fall within manufacture specs. One way I was told to test this is to get motor warmed up, pull of on road where you can do a wot pull and change plugs to 4 brand new ones. Make a wot pull, shut it down asap then pull plugs and inspect for rich or lean on each plug(or you can have them flow balanced but that costs money)

Either way set your global correctly by the formula given above and then keep adjusting deadtime untill you get it right.

 

[1992awdlaser]

Yeah I didn't really mention anything about the deadtime because half the time the deadtime they give is close to what it should be but not exact.