I do understand what you said. I never asked about idle we were trying to figure out cruise... but in any case, I will richen it up a little bit at idle. What is the best way to accomlish that? I would say Individual Cyl. Fuel Trims (at idle) right? The only other way to do it would be through the VE tables but I still can't get a straight answer on when the PCM refers to the ve tables...

 

would consider doing this at part throttle as well. the wilder the camshaft the more likely it is you will have to use open loop to get the AF's where you want them or the engine likes them.

 

^ why would he need to do that though? a 115 lsa camshaft is not exactly "wild" lol.

 

use the MAf table

 

Yea I don't think it's really as bad as you think. The car seems to run pretty good with my wideband hovering around the 14.3-15.2 range. When I made a thread about running full time in open loop the people that replied knocked that idea down... to me it would seem easier to keep the car in PE mode and fine tune the A/F ratio so the car won't have to think. The only problem I could forsee is some freak lean incident that would be uncorrectable by the o2 sensors. How many of you guys actually run open loop all the time??? I might just try that depending on the input I get.

As for the MAF tables... I would read the hz off the scanner and then increase the g/s in the idle range? That would tell the computer that when the MAF reads that certain frequency, it is actually pulling in more air than the original table right? These tables are only used in closed loop correct?

Sorry for hijacking.

 

No hz reading, you read g/s from the scan tool and then raise or lower the values in that range. The points have to form a smooth curve though or it will run like crap, so use the graph mode and don't just change a few values by a lot.

And no the MAF tables is used all the time (not just in closed loop).

 

I see. So say I was bringing in "X" g/s at idle. To add more fuel I would see what part of the table that value is closest to and increase it to add more gas? or decrease it? I'd think that by saying at the same frequency it is bring in "Y" amount more air so more gas is necessary.

I am going to make a poll about open loop vs. closed loop.

 

Doubtful. I checked a lot of mechanical things and my BLM split is pretty normal (like 5 or so most of the time). I tried a lot of different things in the tuning with no effect but I always noticed one thing happening consistently. When the surge came on stronger and stronger you could watch the integrator go lower and lower, the more fuel it would trim the worse the surge would become. Now, when I run open loop I notice my O2 voltage is hovering around low 900's ...which is obviously rich. This is what the O2 sensors see when I'm in closed loop so that is why I get the 108-116 BLM's. I have tried everything BUT limiting fuel trims and what not so that is why I'm now interested in that. BTW this thing runs smooth as butter in open loop. I need to try that max and min of 128 thing and see if it works any ....if it's in my version of LT1 Edit anywhere (don't remember anything like this). I do remember seeing "BLM = 128 at WOT, yes or no" ....which sounds like a BLM locker to me, so I'll be trying that if I go back to closed loop just to get the WOT more consistent. I wish I had more time .....

 

Charlie, the moral of this story is that getting the tune perfect is a pain in the ***. I wonder if I ask tunercat if its possible to add that feature of disabling learning in a certain range. That would be perfect.

How are you like the open loop tune? I made a poll thread to see how many people run open loop and closed loop because I'm really considering tuning in open loop all the time.

 

Absolutely no comparison. This thing runs WAY better in open loop, practically drives like stock with this 220/226/112+6 .544/.544 cam and 265/195 Lloyd heads. Gas mileage appears to suffer some albeit merely by observation. Idle is much stronger and it doesn't have the tendency to want to stall as you let out the clutch with no throttle, it will just grunt forward and dip down about 100 rpm. Even driving at the absolute lightest throttle positions possible (like steady 10 MPH in 1st or 2nd gear for example) there is nary a hint of surge, you would maybe guess there's a teenie tiny little cam in it that's just barely over stock.

For the next week or so it looks like we'll have nothing but precipitation in this area, so I am not driving the car. As soon as the sun comes back I will get it out and test PE vs RPM table to see if it is used in open loop (going to add a ton of fuel in there to see if it will go pig rich as soon as I give it some decent throttle %. If it is, I will likely run open loop via a leaned out MAF table in the cruise area. I plan to lean it out in small increments with a smooth curve until surge starts to come back, then add a small increment of fuel to knock the surge out. This way the engine gets what it wants, and I don't needlessly waste money on a dyno tune trying to get it to 14.7:1 when that's not really what it wants anyway. Chances are it will like an A/F of 13.5:1 or even richer due to the overlap dilluting the mixture (piston goes down in the bore while both, the intake and exhaust are open, bringing exhaust into the mixture). Extra fuel remedies this situation, giving more dynamic compression and smoothing things out, hence part of the reason my rich open loop tune is so much smoother. BTW I checked my plugs and they look normal, at least I think so, not gunked up and covered in soot or anything. I've only run it open loop 200-300 miles though.

All of this being said, if I can get it to run well in closed loop I'll probably go with it, I just have doubts about being able to get it to run this good. We'll see, I have lots to learn about manipulating the BLM's. If PE vs RPM isn't used in open loop forget it though, I will find a way to live with closed loop.

Doesn't it seem like this could be simpler?

 

Well said. Please post back and let me know how it goes. If I can't get my car right in closed loop, and you have success I will probably try open loop myself.

Question: If PE vs. RPM is not used in open loop, why does that matter? Can't you get the a/f ratio down using the open loop AFR table in the 95-100 kPa range? I don't see what the problem is, why do you need the PE table? Just leave everything alone and use the open loop AFR tables to get your fueling right. Ehh screw it no more assumptions. Let me know how it goes!!!

 

Thing is ... you can have some variances according to RPM...

You don't have an AFR vs RPM vs MAP table...

 

Today, I raised my threshold temp for closed loop up to 300 deg F. It definitely still uses the PE tables because in open loop at 13 psi boost and ~570 rwhp the A/F was 10.5/1.

Also, I did this because I've had a lean stumble for a long time, but only in closed loop. Running in open loop cured this.

How do you tune in open loop? AFR vs. Coolant vs. MAP? Or do you adjust the MAF table? Or is the the VE table?

Mike

 

Well Charlie it's been confirmed. From what I have read so far, the main tables used in an open loop tune would of coruse be open loop AFR for idle and part throttle, PE tables now that we know they are used for WOT, and MAF calibration tables for fine tuning. I think that since it's running in speed density mode, the VE tables will play a part but I really don't know too much about the VE tables. All I know is that with a larger cam, the volumetric efficiency goes up. By the same token, I'd figure that boost increases the volumetric efficiency? Yay or nay?

 

Sounds like it's pretty likely the table is used, but I'm not trusting that until I test it (may be other variables that affect it that we don't know of yet). My car's still up on jacks, just haven't had time to get to it and it's been raining anyway. The VE tables don't seem to be used on mine but I could be wrong, many say those tables aren't used on 94's unless the MAF fails. I don't have an AFR table in LT1 Edit, that must be a TunerCat only deal. You're right about the VE going up with a cam but that is in the area where it makes big power (4,500+), and yes, the blower increases the VE even more. Down at low rpm's the VE is reduced with a cam due to overlap not allowing a good cylinder fill, mid range is about the same due to offsetting variables, that's my understanding of it anyway. The centrifugal style blower cannot due much to make up for cam related VE drop at low revs since that type of blower doesn't produce much boost down low (unless it's pullied really high).