dc_justin

iTrader: (13)

Damnit, you beat me to it.

Yep. In addition to using that table for lean cruise you can set up for a smoother transition into PE mode.


One thing I'd be concerned with regarding the Hex hack is this that was posted in the thread you linked:

NOTE: On ETC vehicles if you get the checksum wrong your PCM is toasted, chip off to recover it.

endo

Well now I need to go learn about the speed density stuff. Are there any negatives mileage-wise with going SD?

What's ETC stand for? Electronic traction control?

Flyer

iTrader: (1)

Electronic Throttle Control I think is what he meant.

HPT does offer some rewritten oS's for VE tuning. they do charge slightly for it though.

dc_justin

iTrader: (13)

Typically no. In fact, many people claim a mileage increase as well as increased drivability. If mapped out properly, your SD tune should be precisely the fueling that you will need to run the Air/fuel ratio that you want at any given rpm/load combination. One concern is though that an SD tune that is not perfect will be exaggerated by weather changes, so the more precise you can get it, the better. A wideband O2 sensor is necessary to get you to that point of perfection.

kbracing96

iTrader: (26)

Yep, and with the custom OS and a properly tuned VE table, you can comand A/F ratios that look like this And not even use PE.


I had a guy on the EFILive board hac me a stock OS, to enable lean cruise, but never used it, this seemed to work just fine and i need the extra tables in the COS 3 for my turbo

endo

I'll probably start with a stock hacked OS then, as this stuff is starting to get pretty darn expensive as is. Do want to do a wideband at some point, but not right out of the gate. Even though I live in a place without seasons, I often take the truck places where it's freezing, or through Nevada desert at 120*, or up to high altitudes (sig photo was taken at 11,300ft).

endo

And two more questions on this stuff....

With regard to the SD tune commanding the lean AFRs, is there an a second table somewhere to richen it up if ECT gets too high (like there is with factory lean cruise)?

Second question with regard to lean cruise OS hacking.... anyone know of any links describing how EFILive or HPTuners are storing their data (file format, which files do what, etc)? I've only been able to find the lean cruise bypass code in a raw PCM bin dump file, i.e., the 1,048,576 byte (exact 1MB) image of the PCM. The other piece of the puzzle I'm missing right now is where the check sum is stored and what algorithm is used to calculate it (or in the case of EFILive / HPTuners, is the software calculating the checksum just before it writes the PCM, such that I don't need to bother?)

Was really hoping ETC stood for something I didn't have on my truck. In any case though calculating the check sum shouldn't be too bad if I can be certain I know where it is and what algorithm is used. It will be easy to test to make sure I'm doing it right by trying whatever method is used against programs with valid checksums and making certain I get the same result.

dc_justin

iTrader: (13)

I'd be REAL careful about a lean cruise hack on an ETC vehicle (which you have). I don't think the high potential of a a fried PCM is worth the possible gain.

As for altitude changes, SD tune, by nature, is able to handle those effortlessly. Higher altitude = lower manifold pressure. Since fueling is determing via RPM and manifold pressure, altitude is not a concern.

endo

I'm not gonna go for this unless I've got all the information to make it work.. (Right now I'm not even close...still missing much critical info). Provided I know the location and algorithm of the checksum it shouldn't be hard to get it right though. I'll just grab a half dozen tunes from the web, calculate checksums for them and make certain the calculated checksum matches the provided checksum.

I'm still clueless as to even the file format of HPTuners/EFILive though, so I've got a ways to go on this.... the only place I've been able to locate the lean cruise avoidance code was in the raw PCM .bin file.

I'm still interested in an SD tune if it's the way to go. Just concerned that I'm looking at $890 for EFILive shipped + $200 for an LC-1. And to think I started out thinking this was going to be $500 (HPTuners std interface). (oh, and still on the fence about which (HPtunes vs. EFILive) to get).

PS, my math on the fuel economy gain is a bit skewed. It doesn't have to be profitable for me. Fewer stops at the gas station and spending money on anything but gas is worth a lot to me. Do appreciate the words of caution though, what I'm trying to do here might wind up being downright idiotic and you might well see a "OMG WTF my truck won't start" post from me in a month or two.

dc_justin

iTrader: (13)

You can do much better than that for EFI Live with an LC-1. If I remember correctly, $950 for both together, commercial version

Again though (I'm beating a dead horse here, I know), I just want to emphasize the danger of doing anything like that. The ETC system is finnicky, that's why they disable ETC mapping adjustments in the personal version. Improper adjustments can toast a PCM.

I'd really just stick to the Open Loop vs RPM/Map table in COS3+ personally Same effect + better PE transition (equivalent). Only downside is if your tune isn't spot on, you have no LTFTs and fueling may be off a bit.