Anyone done/doing/using one? I decided to go ahead with tuning the car completely in open loop, and then possibly later adding closed-loop logic back on top of it. I guess I just didn't like knowing the car was reliant on being in closed loop to be fueled properly. Not to mention, at low RPM and higher load the car wasn't being very "friendly" either -- I had nearly eliminated my off-idle hesitation with VE tuning, but it never really went away.

So, a couple weeks ago I simply unplugged the O2 sensors without touching the tune. The car instantaneously started running pretty rich (ie. cruising at 13.0:1, WOT under 10.0:1). Well, confirms that I definitely am pretty far off on my tune At least the off-idle hesitation went away .. completely ... Got started on tweaking, starting from a fresh unedited BIN. Nailed in the idle, and went to work. First things first, I completely zeroed the PE table -- concentrating ONLY on part-throttle tuning. After three or four BINs I now cruise around 14.2:1 and it richens up to the mid-low 13's when you ease into the throttle. I'm actually impressed how easy it was to get this close, this fast. The A/F ratio doesn't exactly track the desired ratio displayed with the scan tool yet though -- I'm about a half point richer than the PCM reports, on average. Once I get this nailed down "close enough" (ie. +/- 0.2:1) I'll start working on the VE table for the areas that don't match up well.

After this is all done, doing the PE table will be child's play. Once completed, I may or may not add the O2 sensors back into the mix. So far, the car has been running better and better in open loop that I'm still on the fence.

 

How about gas mileage. And what wideband system are you running

 

Too early to tell on gas mileage -- I'll report back after I get the tune as close as possible and go through a couple tanks of gas. With the previous closed loop tune, I average around 12-13 MPG on my daily commutes (23 miles each way, 40 minute drive time, stop light traffic with mostly 45MPH speed limits).

For the wideband, I'm running a TechEdge 1.0 in the passenger side header.

 

Your PT tune was off do you know why you were going down the wrong path

 

whats your combo brains? year, cam, heads, gears, auto/manual youve probaly mentioned it a million times in other posts but for us newbies maybe fill us in on how big of a cam your running that youve decided open loop is better for you.

Thanks
Bill

 

Ummm. punctuation?

1. Yes, my PT tune was off -- that was the whole purpose of going through this little exercise.
2. Yes, I'm fairly certain as to why, and I think I'm on the right track since I was able to pretty quickly correct it.

Update: Flash file number four, (#3 for today) and now cruising at 14.7:1 +/- 0.1 at anything over 1600 RPM. Idles at 14.8-14.9:1 and immediately transitions down into the 13's with throttle/load. PCM desired A/F matches wideband pretty darned close. Turned PE back on, albeit with a lot less fuel being added. WOT A/F around 13.5, gotta add some fuel back in.

 

BTW -- my setup is as follows:

370cid iron block, 4.030" bore, JE flat tops w/ 2cc reliefs, .012 out of the hole, Lunati H-beams, stock crank.
OLD *** stage II heads (2.02/1.57), flow about what the current "budget" stage II heads flow.
238/240 .605/.609 112+2 Comp Cam, PRE blue stripe 26918 valve springs , 7.350" pushrods, Comp R lifters.
Hooker headers, LS6 intake, yadda yadda. .. basic junk...
Six speed car, Moser 12 bolt, Denny's driveshaft, 4.11 gears.
NXL kit, not used much -- still on the first bottle
Car weighs in at a portly 3720lbs. with me in it (and I weigh 165).

 

m6 im assuming?

 

Why did you zero out your PE table to begin with? Not sure I understand that part since it doesn't have anything to do with the PT tune right?

 

It was a case of "remove as many variables as possible" .. I added it back in for the drive home from work today, and it reacts exactly as expected with one exception. I didn't see the PCM's desired AFR PID include PE fuel -- it would remain constant as you added throttle.

 

So this is an open-loop, but still MAF-based
tune I take it?

Any plans to unplug the MAF next and go for
bare open loop speed-density? Go, Tarzan!

 

Brains is too smart for that.

joel

 

Its definitely still MAF-based. Since I'm going through the motions, it probably would make sense to tune w/o the MAF and get the entire tune as close as humanly possible. I'd hate for the car to drive like total crap should I ever toast a MAF. Its a bit of work, but I'm seeing good results so its worth it.

 

So you tweaked the A/F ratio using the ve table or the desired A/F ratio tables?

 

Both ... I started with a stock VE table, and stock A/F ratio tables. I moved the injector flow rate table around until I got close to the indicated AFR. Then I tweaked the desired A/F ratio tables more to my liking. Then I started tweaking the VE table to get the desired A/F to match my actual A/F.