FAST O2 correction, Tip in & emissions

[clemsgn]

I'm trying to understand the tuning aspects of the FAST system a bit better. I realize the less O2 correction you have, the closer your tune will be and it will be easier for the ECU to achieve the target A/F ratio, but if you have a 15 or 20 % correction, is the ECU actually able to correct it enough ? I don't just mean at the track, but in everyday street cruising also.

Is the "actual A/F" ratio shown on the dashboard the corrected ratio or is it the figure before the ECU makes an adjustment ?
Is the "O2 correction %" on the dashboard the amount its trying to correct to, or the actual amount it's already made correction of ?

I have a Tip in problem only when warmed up. If I'm at a stop and quickly give it anywhere from a 1/4 - 1/2 throttle, she will bog and sometimes stall. It will also bog if cruising at 5 - 35 MPH at light throttle and then quickly give it a short pump of the throttle. I've played with the AE tables (adjusting them quite a bit richer than it was) and it's better than before, but it's still not right. I don't know if I'm getting close to being too rich now ? I think it has a 70 mm throttle body so when it opens, it probably needs quite a bit of fuel to make up for it. I just purchased this Turbo "T" a few weeks ago and it seems to run fine on the street with the calibration it had, except the bog. I've messed with the VE table to get the O2 correction as low as possible for street driving, but I read that "norbs" had to put the VE #'s at idle and around 100 kpa to around 70, to help with a bog. Mine were already in the high 60's in that area. Any suggestions ? I have a carburated 87 V-6 regal with no bog...I should be able to tune it out of a FI computer controlled turbo V-6 !!!

I just installed a cat to try to pass emissions. Any suggestions on tuning for this ? I've set Target A/F to 14.7 around the cruise RPM & load for the test (dyno in Mass) so I don't kill the cat. I tried to pass just the way I recieved it (without cat), but it failed by a small amount HC limit 2.00 - I had 2.53 NOX limit 3.00 - I had 3.26 it passed the CO w/ 26.95 on a 30.00 limit. Unfortunatly it has no EGR due to M&A heads. It has a 160 T-stat, but should I run it hot by increasing the fan on & off temps ?

Help or suggestions on any of the above would be appreciated !!
I can e.mail more details on the build-up or send a .GCT file to anyone that wants it.

Regards, Clem

 

[norbs]

caution..... long reply

I have never set the ve's cells at 70 around idle, you must be confused with someone else. Anyway, theres alot to fiddle with to get things right, so have patience, and try and do small changes first off. If the operational parameters are correct you should see idle numbers 20-35, and about 80-90 on the other ve nummbers at peak torque. If not your injector size or fuel pressure is way off from 43.5 psi.

Your best to get the engine warm to operating temperature, before doing any changes on the ve table. Since afterstart correction, and coolant temperature will be applied, when cold, making the ve table be off.


If your using the dos version, this is what i do......
drive the car around at slow speeds, without acceration, and use the L key and space bar to automatically get the ve table very close to the target a/f in your map. You must be in closed loop also, and press the space bar to bring the cursor into the active cell, then press the L key to apply the instant correction. Do this at different rpms, but try not to accelate much, since it will screw up the correction factor. On deaccelration you will get -25 % correction.


The o2 correction is the amount of fuel needed at an instant in time, to get the fuel ratio to the target fuel ratio, and it will change quite alot. The only thing which i have run into is that the o2 correction can show + and the a/f ratio can be showing overly rich from the target. It seems that there is some "lag"to the correction, but no one has really explained this in detail. The value you see is the actual correction applied, and it is effecting the fuel ratio you see. Some times to get a clearer picture, take the ecm out of closed loop, by unchecking the box. Do a pass at low boost and log the a/f, this will be the actual fuel ratio, with no correction factors confusing you.


YOu should adjust the acceleration enrichment to get rid of that tip in, play with the tps vs rate of change, do a quick log of the fuel ratio, tps, o2 correction, and actual a/f ratio. Do many logs of you stabbing the throttle, and watch the actual, a/f ratio. adjust the table, and note any differences, better or worse, if your stumble is caused by being way to lean or rich it will show up instantly in the log.


As for emissions, your best to tune to 14.8-.9and try that, set the timing to about 22 across the whole table and put the fan on temperature to 200. If it will idle in closed loop, without stalling, set the idle a/f to about 14.3, if it wont idle, go richer. Set closed loop high rpm 700 and and low rpm to about 600. This way it will stay in closed loop during the test.


As for setting the a/f table , i have found to be safe use 11.5 a/f over 20 psi boost, use 11.8 at 15 psi boost, and even 12.2-4 at 8 psi. If you set the a/f to 14.8 at cruise thats ok too, but remember if you use those numbers on idle to about 2000 rpm, the car will stumble, so you would want to be about 13.0 from idle to 2000 rpm.


thats it for now...

norbs

 

[clemsgn]

I'm sorry norbs, as I thought you were the one who wrote the "Unofficial Speed Pro Manual" . I saw your name in the address, but I guess you're just hosting it (for Troy K ?) and under "Tuning Tips & FAQ's" it says "he had to add fuel around 100kpa & idle to get rid of his stumble" .

I've got the Windows version, but does the space bar & L key still work there ? I would guess you would have the VE table showing and then hit space & L , correct ?

I've tried to log the stumble, but right when I give it that quick stab, the A/F doesn't change much, but as the TPS is coming down, the A/F seems to spike down (rich) quickly and go back up. I'm guessing it's that lag you're talking about...I don't know ?

norbs, I would like to send you a GCT and a log or 2 for you to peek at, but I can't send attachments to this forum. How do you get that changed to allow it ? I could e.mail it to ya...let me know.

P.S. I'll send it to anyone else that wants to take a peek also. Let me know.

Thank You...Regards, Clem

 

[bobc455]

Originally posted by clemsgn
I realize the less O2 correction you have, the closer your tune will be and it will be easier for the ECU to achieve the target A/F ratio, but if you have a 15 or 20 % correction, is the ECU actually able to correct it enough ? I don't just mean at the track, but in everyday street cruising also.

Yes. Not an ideal way to run, but it will work. If you see those kinds of corrections, change your VE values until you have near-zero corrections (as best you can).

>>> Is the "actual A/F" ratio shown on the dashboard the corrected ratio or is it the figure before the ECU makes an adjustment ?

The "actual A/F" is what's seen by the O2 sensor, what is traveling down the tailpipe. It includes all adjustments.

>>> Is the "O2 correction %" on the dashboard the amount its trying to correct to, or the actual amount it's already made correction of ?

It is how much correction is currently being applied.

>>> I have a Tip in problem only when warmed up. If I'm at a stop and quickly give it anywhere from a 1/4 - 1/2 throttle, she will bog and sometimes stall. It will also bog if cruising at 5 - 35 MPH at light throttle and then quickly give it a short pump of the throttle. I've played with the AE tables (adjusting them quite a bit richer than it was) and it's better than before, but it's still not right.

That's what those tables are there for- hopefully you can tune most of the "bog" out. VE tables should also be pretty close, like Norbs says. (BTW I only use the "L" button when I'm way off, the fine-tuning is best done manually in my opinion).

>>> I just installed a cat to try to pass emissions. Any suggestions on tuning for this ? I've set Target A/F to 14.7 around the cruise RPM & load for the test (dyno in Mass) so I don't kill the cat. I tried to pass just the way I recieved it (without cat), but it failed by a small amount HC limit 2.00 - I had 2.53 NOX limit 3.00 - I had 3.26 it passed the CO w/ 26.95 on a 30.00 limit. Unfortunatly it has no EGR due to M&A heads. It has a 160 T-stat, but should I run it hot by increasing the fan on & off temps ?

Typically, HC means you are too rich, NOx can be a result of too much timing, and CO is too lean. Judging from those numbers, it sounds like you have a pretty inefficient combustion going on- I would put in a higher T-stat (or just the fan on/off), and maybe go to a hotter spark plug. Then of course change it all back after the test

-Bob C.

 

[ijames]

Clem, take a look at http://www.turbobuick.com/forums/showthread.php?s=&threadid=91105 from the emissions forum for a link to a nice chart showing the effect of afr on emissions.

 

[clemsgn]

Thanks everyone for your replies !

Thanks Carl, but I noticed that chart B-4 when you listed it for someone else...it's a great visual aid to get a handle on how they interact with each other...Actually I downloaded it so I wouldn't lose it.

As far as emissions go, I went to the testing station again today to make a diagnostic only test...I know the guy running the dyno. If I wanted to, he would "get it to pass" but I want to see if it will do it on it's own. I added the Cat for this test, raised the fan on/off temp to 195/190 and messed with A/F numbers a bit. Well it came close, so I'm going in the right direction.

These are my numbers from the 1st time on 7/31

tested limit result
HC 2.53 2.00 Fail
CO 26.95 30.00 Pass
Nox 3.26 3.00 Fail

Here are the #'s from today
HC 2.27 Fail
CO 18.45 Pass
Nox 2.07 Pass

As I said, I'm gettin close ! We ran out of time to try again.

My observations.... I think the slight bog I have may be hurtin the HC #'s . When he starts to accellerate on the dyno, the lean bog sends unburnt fuel out the exhaust. I've logged the tip in bog a few times and just after I stab the throttle, it shows rich, but I think it's the miss causing this.....Any comments ? ?

Later on I did some testing by lowering all the AE tables to 0 and then checked for the bog while in park at idle....It actually almost seemed the same as B-4. So I started to raise the AE vs TPS Rate and the AE vs MAP Rate slowly and it was a little better. Then I put the AE vs TPS position to 100% for TPS of 0% and 7% then it tapered down from there. This seemed the best so far, but it's still not right. I should be able to drive without acting like I have an egg under my right foot !!

Thanks again for the help
Regards, Clem