DFCO vs ETC TP?

[DrX]

I have had DFCO disabled for AutoVE purposes but now that I look at the settings in the stock tune for my vehicle, it looks like it would have never kicked in anyway. The TP would never fall low enough to enable it. In my logs the lowest TP I see while in gear is 6% with the larger 90mm LS2 TB. I logged a stock 5.3 setup(78mm TB) and the lowest TP was 8%. I'll have to take a look at some other tunes, but unless I am missing something, it appears that DFCO is not really used on trucks. Is this correct? Here is my B3316:

http://i114.photobucket.com/albums/n241/TDOC2004/DFCOThrottle.jpg

[Tordne]

Do you log SAE.TP, and if so what does it report? Don;t see why DFCO wouldn't be used on trucks (generally)?

[DrX]

I have logs with SAE.TP and others with GM.ETCTP and they both look the same.

[Tordne]

:redface: I'm not familiar with ETC throttles, but I'd expect the values in that table would have to be greater than what is logged by SAE.TP to enable DFCO. You should be able to easily tell when it is active by the WBO2 AFR and the timing reduction.

[DrX]

:redface: I'm not familiar with ETC throttles, but I'd expect the values in that table would have to be greater than what is logged by SAE.TP to enable DFCO. You should be able to easily tell when it is active by the WBO2 AFR and the timing reduction.

It just seems curious that the stock B3316 table would have values that are lower than what a stock vehicle sees if it applies to ETC vehicles. My AFR always wants to go way lean on decel anyway unless I bump my VE table way up in the 30 kPa and below area. This is with DFCO "disabled" with respect to all of the enabler tables. I even played with trying to get the throttle closed as much as possible by knocking the cracker way down but it didn't seem to have much effect on decel AFR.

Does your TP fall to 0% on throttle release as you have the IAC motor? Do you see the lean on decel during AutoVE logging with your DFCO disabled?

[Tordne]

I find nothing in the factory calibrations strange anymore :)

My throttle is cable driven and absolutely falls to 0%. I don;t think the IAC has any effect on the TPS% as that is just based on the TPS voltage output and can be reset (somewhat). My IAC counts are low though, around 40 at idle though :)

Lean decel, I wish!! I have stock internals but installed SVO 42lb injectors that I have been getting to grips with of late. I have super rich (11-12:1 AFR) when off the throttle.

I recently installed the Fuel Pressure Sender setup and as a result have rescaled by IFR table to reflect actual/measured fuel pressure. Having done that, and having a RoadRunner I'm going to play with pulse widths again and see what I can do.

You may want to look at the Voltage Offset table in the High Vacuum cells. I have found that a difference of as little as 0.10 of a ms pulse width can make a big difference (from 14:1 to 17:1 AFR at idle for example). Especially with large injectors like the 42lb, or your 60's.

[DrX]

My throttle is cable driven and absolutely falls to 0%..

That's what I would expect and it seems that my B3316 would apply more to a cable-actuated setup.


Lean decel, I wish!! I have stock internals but installed SVO 42lb injectors that I have been getting to grips with of late. I have super rich (11-12:1 AFR) when off the throttle.

I recently installed the Fuel Pressure Sender setup and as a result have rescaled by IFR table to reflect actual/measured fuel pressure. Having done that, and having a RoadRunner I'm going to play with pulse widths again and see what I can do.

You may want to look at the Voltage Offset table in the High Vacuum cells. I have found that a difference of as little as 0.10 of a ms pulse width can make a big difference (from 14:1 to 17:1 AFR at idle for example). Especially with large injectors like the 42lb, or your 60's.

I saw the same lean swing with 42s(60psi) on decel. I have seen it mentioned that too much fuel can cause this as well?? So I tried bumping down the VE in this area to lower the pulse width with no effect except to go more lean. Could be that it was not enough but I also have some help from the boost/vac-referenced FPR cutting FP. Never had any idle issues. Haven't got to tinkering with minimum pulse width, etc. yet but others who are not boost-referenced have claimed to had problems getting it low enough with the 60s(43psi).

[Tordne]

I think the fuel system in the trucks being vacuum referenced with a return line are better than the cars :frown:... Wonder how costly and hard it would be to implement on my car...

[dfe1]

I have a 2002 Silverado 5.3 (which has ETC) and witht he stock DFCO settings, it almost never cut fuel on decel because the spark ramp-out rate was so slow. I quickened it up and now it goes into DFCO as soon as I get off the gas pedal (providing the other enablers are met). I'm with andrew-- nothing surprises me anymore with factory cals. They all seem to have been done by people on non-prescription pharmaceuticals.

[DrX]

I think the fuel system in the trucks being vacuum referenced with a return line are better than the cars :frown:... Wonder how costly and hard it would be to implement on my car...

Actually, my truck was also originally returnless.:frown: I modified the tank module and added a return line and external FPR at the rails.

Other options for FI guys might include:
1) Adding an external surge tank/pump/FPR setup. But you will lose the back pressure in the line from the main tank to the surge tank, thus disabling the venturi pump that keeps the bucket filled in the main tank and you still have to add a return to the tank module.
http://www.ls1turbo.com.au/fuel.htm

2) Adding an external booster pump for returnless systems with its own boost referenced controller. I don't think this will get your FP down below 60 psi at idle as minimun FP will still be determined by the in-tank setup. Might allow for smaller injectors though.
http://aeromotiveinc.com/pdetail.php?prod=32

3) Adding a fuel pump voltage booster.