Ok so I've burned about 15 chips so far for the 730 ECM. Well, I got fairly close after the last batch. Most of the lower RPM's were within .8% each way. Most of the crusing RPM's 2000-2800 were within 3%. I was pretty excited. I'm finally getting the hng of this. After driving about 200 miles I hooked up datamaster again to take some more readings to burn another chip and I find that my idle is now 18% lean and most of the other places are at least 5.5% lean. Now I did have that exhaust leak near the O2 sensor last time but I took care of that and it's maxing out the BLM's plus I seem to be retaining the very improved gas miliage I began to realize when I fixed the exhaust leak. So I don't think it's the exhaust leak again.

Now does the computer run strictly off those tables or does it have a learning function that will alter the tables after so much driving. Nothing has been changed since I took the last readings so maybe that was part of it "learing my driving style"? I'm just taking stabs in th dark I really don't know what is going on here. If some of you guys could sheld some light on this I would really appriciate it. Thanks

Jim

 

See: Part throttle tuning (no PE) in the sticky post area. Read it as many times as it takes to understand it as it is your best shot at getting the VE knowledge. As to why things may have changed, most likely your initial data run was too short. BLM changes may take a bit. Also, so that you understand, a 128 BLM and a 128 INT is 14.7:1 AFR in closed loop. A 150 BLM and a 130 INT is 14.7:1 AFR in closed loop. The reason for trying to acheive 128, 128 is for maximum ecm adjustment and easier tuning at WOT. To sort of answer one of your questions about what tables the ecm uses is in what situation it's in. The VE table is combined with whatever other "situation" may be present as in AE (pump shot) or cold start or WOT. However, only in closed loop will corrections to the VE table be made and what effect, if any, do the "situations" do to the BLM is beyond me.

 

I realize it takes time for tem to adjust. I drove out to Riverside (about 130 miles roundtrip and toke readingd for the first hour solid. never whent outside of about 4.3% either way. It looks like its doing the same thing it was before (gas milage went to ****.) so I guess I have to go back to tracking down the problem. I'll let you guys know if I find anything.

As far as the article goes I have read it more times then I care to remember and I think I have a pretty good handle on how the table itself works and how to tune it, etc., but I was just confused on how it would just start dumping fuel into the engine for no apparent reason (I'm sure there is a reason though, there always is)Thanks

Jim

 

Well, I guess it was the exhaust again. Some how it was getting air near the O2 sensor. I don't get it, a brand new gasket and I tightened the bolts untill I thought they might break. But anyway it seems things are better again.

 

And from the stock exhaust manifolds, too. Man, I've had better luck with headers! Well, just keep at it.

 

I have a set of Edelbrock headers. Thats what is giving me all the problems. The pipe that runs under the oil pan does not cleanly mate up to the driver side header and it is leaking on the oil pan side. (If you know what I mean, kinda hard to explain.) They moved the O2 sensor to right above where the 2 pipes meet, so a small exahust leak turns into a huge fuel problem. Like I said in my other post after I fixed it the first time I gained about 6-8 mpg, wnet from about 110 miles per tank to about 160-180.