dyeager535

Been dealing with this issue for awhile. Fuel pump hose went bad so chased that as a problem for a long time, now that it is fixed, the DFCO problem is more evident.

6E/modified APYP.

DFCO doesn't work. I'm not running AIR, EVAP, or EGR presently. No converter at present either.

When coasting, there is moderate backfiring from the exhaust, and it stinks as if running too rich. Everywhere else it runs good.

Would any of the modifications to the bin to "turn off" (or minimize the effects when commanded) AIR, EVAP or EGR have the potential to keep DFCO from being invoked? Depending on type of converter, I was wondering if somehow DFCO was tied into AIR for converter operation.

I want to put a muffler and converter back on the thing, but after the backfires that blew the last ones out due to the fuel issue (at least they were old) I'd rather get the DFCO problem fixed before I put any on...the light backfires are nowhere near the same, but I'm now averse to spending money and time putting a new converter and muffler on, only to blow them apart. Additionally, last time I was out I was doing a BUNCH of downhill...because I don't compression brake due to the smell, the front hubs got hot enough to literally smoke the wheel bearing grease.

RBob

iTrader: (1)

Have you checked the BIN values for DFCO against a data log? It may be that the vehicle parameters haven't been met for DFCO to kick in.

I've found that backfires in the exhaust on a lift is due to air leaking into the exhaust system.

RBob.

dyeager535

Rbob, thanks for the reply.

I'm probably going to take a "stock" APYP and transfer only my current fueling/timing data into it just to test and make sure something didn't get corrupted. This has been going on as long as I can remember, but not being driven very much, I haven't had the incentive to spend a ton of time working on it. This last time I really needed some engine braking is going to have me get to the root of the problem.

I've never "seen" DFCO work before, so I don't know what it looks like (except there is a DFCO off/on in the log that is always off) but I have assumed that O2 should go and stay lean as long as DFCO is working, correct?

RBob

iTrader: (1)

Yes, O2 should show dead lean on DFCO, and the injector PW going to zero.

RBob.

thewizard

iTrader: (43)

If I recall correctly timing reverts to 0* advance as well.

The simplest way to get it functioning is to play with the enable and disable LV8 parameters.

SbFormula

I believe timing does not revert to 0* advance but definitely pulls off. On my set up (305 TPI Speed Density, Manual Trans, 7730, Mask $8D, ATNX), in DFCO, the spark advance averages 5* less then what Close TPS Spark Advance calculation should be. So over 2800 rpm in DFCO, I get around 30*, 1600rpm and under around 15*, between 15* and 30* as RPM increases from 1600 rpm to 2800 rpm. I haven't found any table that can be modified for DFCO spark advance (using Tuner Cats RT), but I consistently get an average of 5* less than the Close TPS Spark Advance table taking into account the CT correction table. There must be something programmed somewhere for it though but I don't have access to the code.

My 2¢ worth is they did not want the spark advance to go to 0* in DFCO which would create a delay in the proper spark advance when you step back on the pedal, like going from 0* to 38* at 2800rpm. As far as I understand, the engine does not need any spark in DFCO anyway since no gas is present in the cylinder. But that is pure speculation based on my logical understanding of combustion engine and electronic fuel injection... ha ha ha!

And in the end all my ramble on won't fix dyeager535's problem!

thewizard

iTrader: (43)

Interesting; I'll check mine again to see out of curiosity.


I know the last OBD2 tuning I did showed 0*, but it was waste spark compression sense, so who knows the relevance of that.

RBob

iTrader: (1)

Be careful when comparing different EFI masks, they don't all do things the same way.

RBob.