Hey Guys,

I've read a lot of different ways to tune open loop properly with a MAF setup, but everyone seems to have their own way. The car is an 89 Trans Am with Southbay 22lb Bosch injectors, 210/218 custom comp cam, cat delete with 2.5" Flowtech Terminator muffler, and a T56 swap. I've found out that the 22lb Bosch injectors flow more like the stock 19lbers. I'm running a modified 89 5.0 TPI 5 speed tune. Back when it was an auto I played with the auto MAF tables a bit to dial it in, but with the T56 I haven't needed to touch the MAF tables yet. In closed loop the car runs pretty well with the AFR fluctuating around 14.3-14.7 cruising around. However, in open loop even with the auto the AFR gauge reads about 15ish after starting up and quickly decays to full lean (18ish). I've tried changing the Startup Enrichment table and the Open Loop vs AFR % Change table. I've got it richened up to like 13.5, but at times it still does it's own thing and will peg full lean.

Also it has an AE issue that is a little more prominent than it was with the auto. When quickly shifting and getting back on the gas it will bog/hesitate a little bit and then pick right back up. The more throttle I give it, the worse it is. I've messed with LV8 Accel. Enrich Coolant Factor vs Coolant Temp and Acceleration Enrichment Factor vs Change in LV8. When giving it gas, the gauge will go lean (the throttle opening I presume?) and stay lean. With the adjustments I made, it still goes lean (throttle opening?) and then go to about 13.9 and back to cruise AFR. It still has the bog. This occurs in OL and CL. Even lightly giving it throttle, it jumps lean and then richens up.

As for PE, I've got it leaned out to about 12.3-12.7. It runs very well at WOT. It could use a bit of fine tuning there, but the PE tables are very intuitive.

Any input on tuning advice is greatly appreciated! I've read a lot on the forums so far and you guys are so helpful. My T56 swap was a breeze after looking around on here. It seems like there is a lot more information on SD stuff than MAF stuff and I'm struggling a little bit. Thank you!

-Tyler

 

what are the int and blm values doing to get to 14’s afr if open loop is that lean

primarily i like to tune the maf tables in open loop at operating temp. Once thats done, use the open loop vs coolant to adjust for cold start to warm up as colder engine will usually want to be richer. Then you have to mess with AE and PE

with a stick being directly coupled to drivetrain unlike the slip of a torque converter you may need a lot more AE adjustments and longer pulses and less decay rates. Not sure what tables they are id have to look to refresh my memory. Also may need some earlier pe enrichment to go along with it since load is increased with a stick.

i never looked at a 5 spd bin vs auto to know for sure but i did read of guys having much better luck on 350 cars with manuals when they tried the corvette manual trans based tunes.

 

Thanks for the response Orr89Rocz! I've noticed you have a lot of helpful input on the forums.

Anyways, I don't actually have any recent datalogs saved, but from what I remember, the INT was right around 128 and the BLMs were around 134-138 (14.7 roughly). I can submit my most recent bin and xdf if you wouldn't mind taking a look at it. Sorry I didn't mention, but it's also a 305 TPI, not a 350 car otherwise I would've tried a corvette bin w/modified spark table. All it has done is a 210/218 cam on a 112lsa, 22lb bosch injectors (flow like 19s), and an exhaust. I guess I didn't really think of the logic behind the stick vs torque converter.

 

The other thing that worries me is that if I changed the MAF tables for open loop, wouldn't my closed loop be too rich then?

 

No - closed loop only adjusts from the baseline established by the open loop. It will always target 14.7 (well - it will dither around 14.7) AFR. So if you move the open loop closer to 14.7, then closed loop will just not have to adjust as far.

I think the stumbling block is that you are looking at closed vs. open as entirely separate fueling models - while really one relies on the other. Open loop is the actual fuel or VE map. While closed loop is merely a function on top of the map that attempts to correct the actual AFR as measured by the O2 sensor back to 14.7 from wherever the open loop map currently has it.

And in effect, "open loop" is just the absence of the closed loop function. If there were no closed loop function, then you wouldn't have open loop - you would just have a fuel map. Both must exist for either one to have meaning as such.

GD

 

Still have A.I.R. pumping air into the exhaust in open loop?

 

Yes, my bird has the stock manifolds with the A.I.R tubes still hooked up.

 

Thank you GeneralDisorder,
Coincidentally I'm currently enrolled in a technical college class where we're talking about Open Loop and Closed Loop systems. For one of our labs, I tried setting up the values in closed loop and it didn't work too well, but when I set up the values in open loop and connected closed loop, it worked . I probably should've put two and two together.

So my approach should roughly be like this?:
1. Lock car in Open Loop
2. Tune MAF tables at operating temperature to 14.7:1
3. Adjust Open Loop AFR % Change vs Coolant temperature respective to AFR and colder temps. (What is an ideal starting point for colder temps like 60F? 13.5-14?)
4. Enable Closed Loop
5. Adjust AE tables (Any input on what tables to start with? There are a lot of AE related tables in the 6E mask. What should my AFR gauge do when giving it throttle? Should it shoot lean quickly as the throttle is opened and then go to the AFR the "pump shot" gives or should it just stay exactly the same value it was when I was cruising?)

I'd like to thank everyone for putting their input in with MAF tuning. I'm sure this thread will help others out too.

 

Update:

I had the chance to try tuning the car in open loop. I reset all of the open loop tables I changed along with the AE tables. I had my dad drive the car around while I rode shotgun with the laptop and the Ostrich 2.0. I messed around with the MAF tables until I got most of the 1-2 tables around 14.7-15.5ish. Around the 20 g/s areas in the bottom of MAF 1 and the top of MAF 2 I had to up the scalars 2 or 3 notches. Either way, it wasn't running insanely lean (18) anymore. For some of the higher g/s areas it was around 13.5ish which I thought was fine for heavier throttle stuff. WOT still is about 12.3-12.6 from messing with the PE tables. After all of these changes, I enabled closed loop. To my surprise, the INT was roughly 128 most of the time (14.3-14.7 on my WB), but the BLMs were now in the 114 area besides the idle (128). Later I had to go to work and when my dad pulled the car into the garage, the WB was reading 13.3ish and went to 14.7 as he was moving it in. The temperature was a notch or so above 100F. I'll need to see how it does on a cold start. On the bright side, he said it started really well and it wasn't surging or missing.

I was kinda surprised with it correcting for a rich condition now. Any thoughts guys?

Thanks!

 

Another thing I thought of doing is replacing the oxygen sensor. I don't like to throw parts at things, but the car has 58k miles and I'm sure the O2 has never been replaced. I'm sure it's not as accurate as it once was.

 

Check your system voltage on startup vs. hot idle and you will probably need to make changes to the injector voltage compensation to even out the fluctuations. The Bosch DIII injectors are a pain to get the voltage compensation correct with. One of the reasons I demand injectors with compensation values included.

GD

 

I have messed with the injector voltage tables a little bit after looking at the Bosch D3 Sticky. However, before I even fired up the car with the T56, I had already done that. Something tells me that the injector constant is the one to blame considering I tuned the MAF tables in open loop to 14.7-15.5 and now the BLMs are saying it's correcting for a rich condition. I don't think my injectors flow like 22lbs or even 19lbs. I may start with my original base tune and drive around changing the constant to get roughly 128BLMs. After that, I may try adjusting the MAF tables in open loop again. Does my situation seem weird?

 

That doesnt seem right to me but if wideband is saying 14.5 plus or minus a few tenths, i would leave that alone. Leave injectors what they are. You can maybe try adjusting the o2 sensor rich lean swing points. It may be targeting leaner than stoich.

do you still have AIR enabled and functioning?

 

I'm just as confused haha. The AIR is still enabled as I'm running factory manifolds. If I were to start again with the factory 5 speed tune, but putting 22lb injectors in the tune, it would run even leaner right? When I drove it today I noticed that if I gave it a little gas cruising, the gauge would jump to around 17:1 and it would have no power until it came back to around 14.4. This was in closed loop. This might be an AE problem. I was kind of thinking starting with the factory 5 speed tune, setting the injector constant lower than what I have it (19lbs), and then tuning it open loop again. I figure if the closed loop BLMs are more accurate, open loop should be as well.

I'm not exactly sure how it's running rich now considering I tuned the MAF tables in open loop to 14.7-15.5. You'd think it should be pretty close.

 

Another side note:

Should I have zeroed out the PE table and open loop AFR table when tuning the MAF tables in open loop? Would having those tables "enabled" mess up the MAF tuning?

 

I dont see changing injector constant doing anything different than what you already have.

i dont zero out pe or open loop. Suppose you could but its not necessary imo.