Hi guys, I'm running a 6E MAF setup with a Stealth Ram on my flat tappet hydraulic cammed 327. I have enough overlap with this cam (.462"/.482", 219/229@0.05, 275 adv duration, 112 CL) that the narrow band O2 sensor is absolutely useless at idle. It reads nearly 0.00 mV unless I richen the idle so much that the car barely runs. It will max out the BLMs unless I play with the O2 upper/lower/cross point bounds in the 6E code in Tunerpro.

I just realized that there is a minimum LV8 to update BLM in Tunerpro for the 6E. I haven't logged in a really long time, but I thing that my idle was around 45 LV8. If I set the BLM minimum update to 50 LV8, then can't I just use the MAF tables around idle to tune my idle AFR to what I want, without it trying to make the BLM run away and over richen? I get a lean O2 CEL after prolonged idling (more than a few minutes), which goes away once I am above idle and the O2 is swinging happily again. If I have the BLM locked out because the minimum Lv8is above what my idle is, will I still get a lean CEL at idle, or no? Has anyone ever used the minimum LV8 to update BLM to tune idle issues before with a big cam?

 

I believe all that does is "update" the BLM for block learning. It doesn't cause the ECM to remain in open loop; it just won't learn.

Give it a try and you will see if your scan tool goes closed loop after a period of time.

FYI, I have a friend with much larger solid roller cam with a 110* LSA and we had no problems running closed loop. I cannot recall if he is running a heated O2 sensor though. We did have to message the lower MAF tables though.

 

I have the same problem in closed loop at idle with 6E, the blms are pegged at 160 until I give it gas. Any time other than idle, it drives fine.

I think running open loop might be the cure.

 

Thanks guys. I think ROLLER is the answer for me. The hydraulic cam profile is so lazy that the O2 sensor is not happy with it. THere is no amount of "massaging" my MAF tables that will make the O2 read normally at idle. If I crank the fuel way, way up I can get it to read nonzero values at idle, and I can mess with the O2 bounds so it looks like it gets cross counts, but the engine will be so rich that it will die idling on me. It is a brand new AC Delco 3 wire heated AFS 73 sensor, in long tube headers with verified no exhaust leaks.

 

Are you using Highway Mode? It is open loop. Why not zero out all the spark tables for highway mode, set it to go into highway mode at 0 mph, get rid of the delay timer, change the maximum allowed time for much longer, drop the minimum RPM down real low, then have it set the maximum LV8 so that LV8s above idle (open throttle) disable it. You can adjust the highway a/f ratio vs. LV8. You now have an open loop idle that you can control the A/F mixture at idle.

I never had trouble with the cam in my old 312, because I had an Innovative LC1 Wideband. Use the narrow-band output to match the stock narrow-band sensor.

 

Fast355, that is a great idea. However, I need Highway mode. I run 15.5:1 with the 327 and around 42 timing and it is very happy. What I may try, is your suggestion, just to see if I can get the idle to not smell so damn rich. If I can, then I will curse a lot and have to come up with a new plan. Would I be nuts if I used the highway mode idle to play with target AFR's, and then used a vac. gage to keep trial-and-error adjusting the idle AFR until I get best vacuum at my desired idle speed? Kinda like setting the idle on a carb. Since I don't have a wideband yet!

 

Hi guys, I set the min blm update Lv8 to 50 and drove around. The car runs fine, idles fine. The idle still smells awful and leaves that terrible burned smell on your clothes, that will linger for days until they are washed. Of course even a WB O2 won't be accurate with this cam at idle so not having one is really not hampering my idle tuning progress. I guess I can play with the MAF tables now that the O2 is not going to be adjusting the idle. Effectively I do have an "open loop" idle. The car goes closed loop normally like it always did, but now it will only have 128 BLMs in the idle region (below 50 LV8). Not a bad start.

 

Oh man, I'm a dumb ***. I found out after going back to Tunerpro, that the maximum value it can store for minimum LV8 to update BLM is 12.29 (even when I typed 50 in there). So this does not give me enough room to lock my idle region as 128. No wonder the car did not idle any different after my change. Stupid friekin friekin friekin cam that I should not have installed. I guess I can go back to messing with the MAF tables, making my fuel trim such that I assume the BLM will max out (I capped it at 140) because the O2 is unhappy. Then if I just turn the rich/lean exhaust CEL flag off I won't get the annoying CEL during prolonged idling. Stupid friekin friekin flat tappet cam!!