Help Me Understand INT

[jmgtp]

What I think I know:

- 128 is optimal, meaning the computer isnt adding or subtracting fuel
- Above 128 adding fuel
- Below 128 subtracting fuel
- INT is locked at 128 on a cold engine for X amount of time until the o2 is responsive

Here are some examples of what it does on a 10 or so mile drive once INT is active:

-maintaining about 40mph on level ground, 6% throttle INT value 110-115

-easy acceleration from 33-55 mph, throttle steady at 20%:
MPH RPM INT
33 1750 124
40 2125 155
50 2650 132
55 2950 117

-deceleration sometimes makes the INT go crazy, I've seen it dip into the 70s when throttle is 0% and other times it stays around 128.

I guess I just don't understand what is the proper way for the INT to behave? Are these wide variations normal? I'd think a well tuned car wouldn't deviate from 128 too much. I'm even more blown away to think of how one tunes for the correct INT given the enormous combination of possible throttle/engine vac/rpm.

Other issue:
I'm still having a code 43 issue as well... the CEL comes and goes but never when the engine is up to temp. It usually happens at startup of a cold engine (maybe 1 in 10 starts) and there is no driveability issue. But, sometimes it happens on a warming up engine, like today I had 120* on the temp gauge (aftermarket, accurate) and the CEL came on at a stop light and the idle roughened up and dipped low but didnt stall. Check engine light went out before the traffic light turned green and the idle cleared up and no probs the rest of the way home. CPS is a few years old as is the wiring from CPS to ign module, coils and ignition module from late model 3400. I've swapped coils/ign module with another set and condition persists. I've suspected the knock sensor but I'll pick up less than a dozen knock counts on a normal drive (WOT is a diff story it'll detect about a hundred and pull massive amounts of spark on a jounce to 60). Sometimes it goes a week without a problem. But when it happens in traffic and the engine feels like it might quit it scares me.

[Superdave]

we don't tune with the integrator.. we tune to the BLM..

the INT is the short term correction, it reacts to the o2 voltage very fast. Sometimes you can use that to fix AE issues but overall watching the BLM's is what's done. BLM is the long term fuel correction, those will always change a little from 126-130 but should stay around 128. Going lower indicates a rich condition and higher indicates a lean condition.


furthermore, in PE mode the BLM and INT lock to 128 and the computer relies on the VE tables for fueling.



43 Electronic Spark Control (ECS) circuit or Knock sensor (KS) circuit Check wiring and connectors form the knock sensor to the ESC controller or ECM for an open or short to ground; if necessary, reroute the harness away from other wires suck as spark plugs, etc. Replace the knock sensor

[jmgtp]

Thanks Superdave.... I knew INT was short term but I didn't think it should have such large variations. My BLM is 128 so I suppose my part throttle tune is doing ok.

How does one determine how to smooth out idle a bit on a modded car? What factors should I be looking at? I have no headwork and a factory bottom end but cam timing, intake manifolds, throttle body, exhaust - etc are all non stock and the end result is a very rough lopey idle, probably mostly from the cam timing. I know I can't expect it to be smooth as stock but I think it can be improved some through spark/fuel changes. Is it just guessing/experimenting or is there some logic to it?

I think I'll replace the knock sensor and even the wiring. I wasn't sure if code 43 was a definite knock sensor issue or if it could pertain to faulty coils, ignition module or hall effect sensor.

thanks again!

[pocket-rocket]

One thing that can put a band-aid on it is to raise your idle speed.

[Superdave]

Yep, to correct mine i upped the idle speed and reduced idle spark timing.. that helped alot. This year i also built some hybrid lifters which seem to have really helped the idle since they don't fully pump up till over 1500 or so RPM. That won't help you though.. lol

[jmgtp]

I'd hate to bump the idle speed up only because the getrag already doesnt like going into 1st gear and more revs means more works for it to do between clutch disengagement and going into 1st.

I'm still a ways out from attempting to change anything. I'm getting my datalogging in still.

[SappySE107]

I keep my BLM locked at 128 and watch the INT values only. Otherwise its more math to deal with. Gearing will change your INT values and the manual trans is impossible to have all fueling dead on.

[jmgtp]

Replaced the knock sensor last night. The rubber insert on the old sensor was decayed and the end coming out of the rubber crooked.

Idle is smoother. How I don't know but my steering wheel isn't hopping up and down a half inch anymore. It never registered knock at idle on TunerPro so I don't think it should have had any impact. Nothing else was changed. I didn't pull the battery or do an idle relearn. I only replaced the sensor and cleared the trouble code with TunerPro.

I logged 2 WOT bursts to redline in 1st, 2nd gear. Much fewer knock counts, only a total of 20 whereas before it would be well over 100 and it has midgrade in it now not premium. It pulled minimal spark a few times, 3-4 degrees I think. I wonder if it would have knock at all now running premium. And I will continue to wonder since I can't afford premium nor full throttle. I'm running one of the chips that Ben sells on the store. Can I run low grade gas without a problem? Again I don't plan on full throttle, more like as little throttle as possible. I'm going for mileage not power right now.

Sounds like there is two schools of thought on fuel tuning, one looking at BLM and the other INT. I'm still fuzzy on all of this. At part throttle when the ecm is using o2 data is it able to compensate fuel quickly and accurately enough to be near perfect?

[Joseph Upson]

I keep my BLM locked at 128 and watch the INT values only. Otherwise its more math to deal with. Gearing will change your INT values and the manual trans is impossible to have all fueling dead on.

I got the same impression from my ALDL monitoring, that the integrator is a better value to tune to since it responds so quickly. In my observations the BLM doesn't change fast enough or much although my INT is bottoming out at certain points indicating immediately the AFR is to rich.

[pocket-rocket]

I've run regular in mine and hardly seen any knock on my scans. I also can't afford WOT all the time, so that is what my truck is for :P

[Superdave]

you shouldn't get any knock counts.. lol


I usually get a few while starting the car and i get a few if i hit the rev limiter when the engine goes lean. I run 89 with 10% corn @ 9.8:1 scr...

I did use the INT this weekend to re-tune my idle VE, Joseph is right.. it is much faster reacting to VE table changes. If you can get someone else to drive your car while you tune with the INT that's great.. shouldn't take long to dial in the tables. I still prefer to use the BLM's though since i'm usually the one driving and i can use the datalogs to graph the BLM's and MAP loads more accuretly.

in the end, whatever works best for you.

[pocket-rocket]

Given the rarity and cost of 284's I don't let anyone else drive my car... lol. Well, I've let a handful of people on this board that I trust drive it, and that is it, lol. Ben has my tune really dialed in well. I think for 10 minutes of scans and getting on it about 33% of the time in the whole drive, I had around 10 counts of knock total. I would have to go over them to be sure, but I know it is extremely low.

[SappySE107]

GM Top Engine Cleaner might go a long way to reducing KR.

Lock your BLM at 128 and tune with the INT alone (as long as you aren't off the charts). Its the way to go cause BLM is so slow. Set the min int to 50 and max to 200. If your BLM isn't 110 or 150, you should be ok to lock it. I prefer to get the BLM in the high 11x to low 140s range or better first. Beats adding BLM and INT, then dividing by 2. Thats all BLM is doing with the INT anyway.