Hey guys,

I know that part of my question has been answered before on here, such as how the distributor spark advance setting should match the bin setting etc..

Well my distributor was set to 10*, and the BIN has been set at 6* for the past two years... It ran good.. Not really rich or lean anywhere for part throttle/cruise, idle was another story.. and WOT i don't know i don't have a WB (yet).

Now, yesterday I changed the BIN setting to 10* to match the Distributor setting. Then, not surprisingly, things changed, not too drastic, but noticeable. The whole RPM range became rich all over the place, ranging from 118 to 124, but overall just alot richer than it was before (125/126 etc.) More importantly, the car feels quite a bit slower than before, it's very noticeable, especially acceleration.

Now that the BIN base setting matches the distributor, I started adjusting the fuel tables to get everything back to 128, which I did pretty good.

My question is, since my engine ran way better before I changed it in the bin, how did that change affect everything else? My GUESS is that it pulled 4* timing accross the whole range, which would explain the sudden richness all over the place.. If that IS true, shouldn't I just add 4* timing to every number in the spark table? Or is that a recipe for disaster?

 

Yes, with the 4* adjustment to the base timing setting, you have pulled 4* globally from the timing tables.

If you added 4* to the spark tables, that would get you very close to what you had before, if not the same.

 

Awesome! That's what I'll do now and re-adjust for all the fuel that I pulled.. Thanks!

 

I presume no big change in environmental temps nor change in atmospheric pressure

 

Assuming no other changes in temps/weather conditions as mentioned above, 4 deg timing can make a big difference in performance. Even idle to part throttle driving can feel better with 4 deg more timing.

The car probably liked that advance, so I'd give it 4 deg to entire spark table and put the fuel settings back to where you had them.

 

Done. It definitely liked 4 degrees more advance! Pulls MUCH harder with no knocks that I can see at any rpm..

Now, back to square 1 with fuel/timing (sigh). Sucks cuz I had to store it today

Thanks guys!

 

Oh, and to respond further, temperature has gotten maybe slightly colder but nothing too drastic (a couple of degrees celcius colder). Also, is it worth it to increase timing at idle? I do have a larger cam than stock (dont know the specs), but it seems to idle strangely now at 1* more timing at 800rpm and at 32/48/64/80/96.. it was a bit rich at idle so that's why i increased the timing by 1* at this LV/RPM. Should I just lower fuel at that g/sec rather than add timing to get it at 128BLM?

 

what LV8 is it idling at? You commanding 800 rpm idle? More timing generally helps idle, unless its overly rich and it will surge around abit.

 

Hey Orr, it's idling around 55-70 LV8. I am commanding 700-750RPM which it gets when closed loop comes in (which is very rare, and I found out that I need to change it to a 3 wire! DOH!) It surges more now than it did before it seems.. How can I tell if it's too lean at idle? Solely through BLM's?

Oh, and commanding, do you mean by setting this in the table: Idle RPM vs Coolant temp?

 

Yes, idle rpm vs coolant. Warm/hot engine will idle lower rpm and should show less LV8 than a cool/cold start.

BLM's can give an idea if your lean. That and the INT values..If your cam is pretty big you could have false readings due to valve overlap and some fresh air getting into the exhaust. You can still try to tweak MAF table 1 around where the car currently idles at. Example, if you idle at 10 grams/sec and you think its rich, go to table 1 and find where 10 grams/sec is. It may be between 2 voltage values. In stock 89 ARAP bins, in MAF table 1, 0.73 volts shows 8.36 g/s. 0.91 volts shows 10.87. If you idle at 10 and need to lean it out, go to 0.91 volts and make that 10.87 say 10.5. Then go to 0.73 volts and make that 8.36 an 8.00. Restart after disconnecting ECM power for a min or so, and see what it does then.

Do the same thing if its lean but increase the grams/sec values. You can use BLM/INT's to show rich/lean and also try checking spark plugs. If you have a fresh plug available, put it in and let car idle for a few min while warm. Turn car off and pull the spark plug. Color/pattern on the plug will show whats goin on in there.

Another trick for idle timing that can help is to hook vacuum gauge up to the plenum. Tune air fuel and timing til you get the most stable idle and most vacuum on the gauge. A good 5-10 deg timing difference can show a huge difference in vacuum, several inches of Hg. LV8 may also read lower with better tuned idle and proper timing.

 

I idle around 8 - 8.5g/sec.. it's pretty consistent... around 700-750RPMs.

I have tried that tactic of changing the value closest to the g/sec in MAF table 1. Specifically, the two you mention, mine were slightly higher at 8.7 and 11.3 roughly. I lowered these as my idle was rich, to about 8.3 and 11. I guess what was taking me for a ride was the O2 sensor being messed up and going back to open, sometimes i would not notice it enter open loop and the idle numbers would change considerably. I never had any knock counts so atleast that's good.. I know if BLM's are lower than 128 it's rich and ECM is adding fuel, and the opposite is for when it is lean.. But for INT's, what does its operation do?

I read that article on how to fix big cam overlap.. A bit confusing, I still don't understand it. Except that I tried my best to get it to idle right. The whole notion of the BLM falsely reporting numbers makes me worried that I took out fuel for nothing or something along those lines.. I guess I'm too paranoid! :P

For the idle rpm vs coolant table, i set the lowest RPM to 700, so it averages around 700-750 around operating temperature (my fans are set from 170 to 190*F).

 

INT's work the same as BLMs but faster since its a short term fuel term. If BLM goes lower than 128 its sensing motor is rich and ECM should remove fuel. You should see INT go higher than 128 meaning its leaning the system out.

Just give the motor the timing and fueling it wants at idle so that its happy. Check the plugs to verify. THen worry about BLMs etc. If the motor is happy at a certain idle point but BLMs are saying different, I wouldnt worry too much unless you want to. Another thing you can try is force open loop and tune open loop AFR/MAF fuel tables while checking plugs to first stabilize idle. Then set closed loop conditions.

If your Open loop is close, then closed loop wont have to make much if any adjustment to the fueling so it should remain stabilized.

 

And to tune open loop i'll need a WB02 sensor or is there a way to tune it with a NBO2?

 

Correct. Plug color can be done but is not practical. But why cant you tune CL with NB? Before I had a WB I tuned my CL to a decent level and my WOT commanded to 12.3 showed up at 12.0 on dyno. AE I pretty much did seat of pants starting lean on AE and working up to a nice transition in daily driving. past 2 years I seldom used WB for datalogging. I do have a A/F gauge in car but seldom looked at it. this summer nitrous went on so a diff story now.

 

No. The NB o2's are just too limited in resolution @ the A/F ratio of WOT
&
They are excluded from OL calcs. no o2 is pretty much the definition of OL.

Just so I don't start the same old discussion (argument), I'll say there is more to OL & CL & o2's than that simple statement.

 

Hey Orr,

Just took the car out so tuning begins again!

I know you've previously mentioned on here that it is possible to know what the AF ratio is based on the mv of the O2 sensor, just to confirm, was the middle point 450mv, and higher means that it's lean, and lower means that it's rich?

Thanks!

 

Higher o2 mv indicate rich, lower lean.

 

ok thanks XCH3NO2!

 

For wot i've seen around 900mv as high 12's to 1 air fuel. much higher than 900 it starts getting into the 11's to 1 and 10's to 1 quickly. Like 950 is high 10's to 1. Its a weird scale.

 

and 900mv is ideal for WOT, correct?

 

Found a site that explains alot of O2 stuff! And there's a little graph if you scroll down that shows what AF ratio is at which volts!

http://www.aa1car.com/library/o2sensor.htm