Unstable AFR during crusing

[Ram Air IV]

Hi ! New with tuning. I have a LQ9 in my Firebird -68. When I cruise at low speed and low load (TP 5-15%) the AFR (WBO2 LC-1) bounce between 12-18. This occurs even if I don´t move the throttle. Both narrowband O2-sensors are new. The LTFT for both banks shows -14,8% during long periods. Could some one give me a hint. The engine is stock except Long tube headers and deleted cats.

[WeathermanShawn]

I would give a little more details on your tune. Preferably attach a copy for readers to look over. Are you running SD or MAF? I know you are attempting to run Closed-Loop, but you might want to take a look at your DTC's. You are so rich it is throwing DTC codes.

Post up a tune and we can take a look..

[Ram Air IV]

Some more information.
First of all, I use the original tune from the Cadillac Escalade, so I am running MAF-mode.
My DTC is 0172 and 0175 (system to rich I think). I will post my tune when I am back home later to day.

[Xman]

Your MAF needs to be calibrated. B5001 I assume that since this is a transplant into a different vehicle that you rerouted the air intake thereby modified the air flow thru the MAF.

This will cause your trims to be off and you will have several issues as a result even if your VE is perfect.

[redhardsupra]

Sometimes reasons for 'scattered' AFR are rather prosaic: clean your airbox/airfilter first, and then log again, see if it got any better. I know it sounds very silly, but you'd be surprised how much that helps.

[Ram Air IV]

So if I need to calibrate my MAF, how do I do that ?
What is B5001?
Here is my tune if it could help,
Thanks all / Magnus

[WeathermanShawn]

I scanned over your tune briefly. Something seems amiss with your Injector Flow Rate B4001.

On the MAF, there are hundreds of threads on it. Check these two links first:http://forum.efilive.com/search.php?searchid=37904 & http:///download.efilive.com/Tutorials/PDF/Calc.VE Tuning Tutorial.pdf. (http://download.efilive.com/Tutorials/PDF/Calc.VE%20Tuning%20Tutorial.pdf)

After you do some reading and more logging, or if you really get stuck..feel free to post up.

Good luck..

[joecar]

Hi Magnus, welcome to the forum :cheers:

Do you have a manifold referenced fuel pressure regulator...?

Which injectors do you have...?

Since your MAF/intake plumbing is different than the vehicle the .tun file is for, you should correct the MAF table as suggested above...
to do this, follow the Auto VE tutorial, but with MAF enabled and B0120 set to zero, and of course create a B5001 look-alike map (copy/paste the map labels from B5001).

[Ram Air IV]

Thanks all, I will study the Auto VE tuning tuturial.
Joecar, I running the Corvette 2001 filter/pressure regulator.
My injectors are from a LS1 2001.

[joecar]

So, your FPR is with the fuel pump in the fuel tank (i.e. not at the fuel rail)...?

If so you need to use the B4001 IFR table from a stock LS1 file, see below (from www.holdencrazy.com (http://www.holdencrazy.com) see stock 2001/2002 Camaro/Firebird files).

The stock 2001/2002 IFR table requires fuel rail pressure to be at 58 psi; if yours is not 58 psi then you need to recalculate the IFR using your actual pressure (see the spreadsheet at the following link).

Calculating-Injector-Flow-rate (http://forum.efilive.com/showthread.php?4821-Calculating-Injector-Flow-rate)


2001/2002 LS1 IFR B4001 (copy, then paste-with-labels):


LABELS Injector Flow Rate (Grams/Second)
Manifold Vacuum kPa {link: GM.MANVAC} Value
0 3.617188
5 3.640625
10 3.664063
15 3.687500
20 3.710938
25 3.726563
30 3.750000
35 3.773438
40 3.796875
45 3.812500
50 3.835938
55 3.859375
60 3.882813
65 3.898438
70 3.921875
75 3.945313
80 3.960938

[5.7ute]

You definately need some tuning to get the airmass calculations correct.
The reason for the fluctuation in the AFR is the STFT's doing there job. They are real aggressive in some areas & not too bad in others which I would put down to the different CL modes as well as the corrections needed to hit the switching voltage.

[Ram Air IV]

Yes, the FPR is at the fuel tank. I think I should mount a pressure gauge at the fuel rail so I can verify the actual pressure. Thank you Joecar.

[WeathermanShawn]

Changing the Injector Values to the proper flow rate will probably solve your LTFT issue. You still need to 'calibrate' the MAF, but your original Injector flow rate of 3.1797 vs the correct LS1 flow rate is about a 17% difference. About the same value your LTFT's were off.

That should solve a lot of your problems.
Sounds like an interesting build you have going on. Good luck with your project..:cheers:

[joecar]

Very nice looking car :cheers:

[Ram Air IV]

Thank you all, what would I do without you. I think I understand what is wrong.

[Ram Air IV]

I have now investigated the part no. on my injectors, they are from 97-98.
When I bought my LQ9 engine the intake was replaced with a LS1 intake with injector part 12554271 (flow# 28,5).
Is it possible that the FPR is different on the Escalade compare with the Camaro/Corvette. Did the Escalade FPR have a feed back for manifold pressure?
If so it should explain why my B4001 was a flat line at 3,1797.

[joecar]

The trucks usually have manifold reference/feedback into the FPR. <-- this is certainly why your B4001 is flat.

The 1997 Corvette had manifold-reference, the 1998+ Corvette did not.

The 1998-2002 Camaro/Firebird did not.

[joecar]

If your injectors flow 28.5 lb/hr at 58 psi, then you can enter these values into the spreadsheet (see Calculating-Injector-Flow-rate (http://forum.efilive.com/showthread.php?4821-Calculating-Injector-Flow-rate)).

Or you could use an 2001/2002 LS1 IFR table, but if you do calculate it anyway to sanity check it.

[Ram Air IV]

Bingo ! Thanks, I will change the B4001 and then do a new scanning of the AFR/LTFT.

[Ram Air IV]

Yes, I did see the spreadsheet. I will read that thoroughly.

[Ram Air IV]

I have now changed the B4001 to the LS1 2002 and it improved my LTFT/AFR. I now running LTFT at -1,6 - -5.0%. I will calibrate my MAF during the weekend.
Thanks / Magnus

[joecar]

Good job :cheers:

Post logs when you have a spare moment.

[Ram Air IV]

Here is the log. Please comment !

[joecar]

Ok, LTFT's are much tighter now.

B5913,14 have timing values that are too low... you should be able to run with timing tables from 2001/2002 Camaro/Firebird (without getting any knock).

B5932,33 also look low to me.

Set B3609 to all zeroes.
Set B0701 to disable.
Set D0960,1,2 to all 100% (otherwise it interferes with the PT up/down tables and the WOT tables).

Try D1108,9,10 set to 0.25s, see what it feels like.

If you drive around in Manual 3rd, you can lock the TCC in 3rd gear, if you like.

Check G1206,7... do you have mechanical cable throttle, or electronic throttle...?

[joecar]

O2 sensors seem to be slow in switching, maybe because car needs to be driven more/harder... :) ...these engines like to be driven agressively... :)

Take some more logs, drive along at cruising speed, and then open up throttle a few times, keep safe/legal.

There might be some dynamic/transient fueling adjustment required, but I can't tell, need more logs.

Is there a way to obtain cold air ("Ram Air")...?
Which intake manifold do you have...?
Which exhaust components...?
What is vehicle mass...?

[joecar]

Nice car... :cheers: what is the color...?

Post pics when you have spare time (do any of us have spare time...? :) )

[joecar]

Do you have 1 or 2 coolant fans...?

Do you have AIR and EGR...?

[Ram Air IV]

Hi, nice information.
I running Electronic throttle, LS1 intake (will be changed to LS6 during the winter), I have tuned long tub headers (1 3/4") with one 2,5" inch muffler for each bank. Car mass is 3400 lb. Today I am using 1 16" fan but the cars electric system is ready for 2 fans so I will change that in the future. I do not have AIR and EGR. I am planning for cold air intake (Yes, the car should have Ram Air !!!)

What should I check about the G1206,7 ?

And last, The color is Plum Crazy Metallic (Dodge HEMI color from 1970). I fell for the name of the color, so I painted it.....

I will post some picture later to day. Thank you for all help.

[Ram Air IV]

Ok, so here are some picture of my ride. It is a -68 that has been my since 1988. I did the engine swap 2 years ago. After that I have made a new electric system for the car and new harness for the engine. Both front and rear suspension are improved, the leaf springs are replaced with 4-Link/Coil-overs. I have enlarged the rear wheelhouse so it can shelter 325/50-15 tires (soon changed to 335/35-17). It is fun :grin:!!!

[WeathermanShawn]

Thats a really sweet ride!

Always wanted to do a project like you have done. Of course if you don't already have the car, it takes some money and time.

You should be proud of your accomplishments. Hopefully you will get the minor tuning problems worked out.
Good luck..:cheers:

[joecar]

Very nice and clean car :cheers:

[Ram Air IV]

Thank you. I have a new tune. Tested it and made a scan file. More response at WOT, works much better. If you have time, please comment.

[WeathermanShawn]

RamAir:

You are picking up some significant Knock retard (KR), even during PE Mode.

I am would change B3616 to something far more conservative. It is taking too long in the combustion process for the fuel to cool the cylinders at your current 90% TPS Mode. You might want to look at your Hot PE Mode too (just in case).

Here is an example of the current B3616 I am running..

Edit: It is hard to tell from the Log is that is 'real' KR or false. It almost looks like you had a one loud bang (mechanical?). For now I would assume combustion-related KR..Do you hear Knocking?

[Ram Air IV]

Thanks Shawn for your observation. Could you please explain the function of the B3616 and if I change the B3615 should I use the same value.
Thanks / Magnus

Also, I did not hear any knock but on the other hand it is hard to hear in a 40 year old car, it is a lot of noise .....

[joecar]

B3616: when the throttle position (TP) reaches this value, the PE table B3618 becomes active.
B3615: same as B3616, but for hot mode (see B3614,B3619-B3626).

See post #4 here: Summary-Notes (http://forum.efilive.com/showthread.php?14188-Summary-Notes)

When you open the throttle some amount, the load on the engine is increased, and to help the engine to accelerate it needs a richer mixture...

B3616 enables B3618 which provides the richer mixture.

Be careful though, if B3618 is way too rich then the engine may bog down with rich misfire (too much fuel)...

with your wideband AFR 12.6 is sufficiently rich to be safe from knock and is suitable for making torque at higher load/airmass.

Always keep an eye/ear open for knock when accelerating.

[WeathermanShawn]

As Joe stated it is all a delicate balance.

I am not convinced from your log that is is necessarily 'detonation', but in any case it is pulling timing as a protective measure. So you have to figure it out.

You can pick a more conservative PE Table..say a 2002 LS1 Camaro and look over their PE Enablers. By 4000 RPM it seems like you would want it to engage PE by 50% TPS (IMO).

The Hot Mode is just protection. If your engine temperature climbed past the threshold and you hit PE, obviously fueling would be even more critical. It is very rarely used (hopefully never).

If after adding fuel, it still indicates KR..it is always possible their is a drive-train noise that is mimicking KR. That will take some more work to figure out.

Good luck.

[joecar]

From post #32...

Good log, lots of data :cheers:

[Ram Air IV]

Thank you Joe and Shawn. Now I understund the function of the Power enrichment. I have now changed the B3616 to the LS1 Camaro 2002. I will down load the new tuning to the PCM and make a new log. The car runs much better now. Have a nice weekend.

[joecar]

What do you have for PCV system...?

Can you check past the throttle body for presence of oil in intake manifold...

Does valvetrain make noise...?

Can you hear audible knock...?

Are motor mounts new...?

Does exhaust header hit car anywhere...?

[joecar]

You may have a little too much fuel at WOT/PE.

Are you below sea-level...? Your MAP sensor hits 104kPa.

Can you show a close up pic of your MAF plumbing.

[Ram Air IV]

PCV (Positive Crankcase Ventilation ?) The tubing from the left bank valvecover goes to the back of the intake just below the MAP-sensor (see picture).
There is no oil in the intake. I will check for mechanical noice in the valvetrain with the stethoscope. The motor mounts are new. I can´t see any spot where the headers hits the chassi.
How do I change the amount of fuel during WOT/PE
Stockholm is situated 150 feet above sea level. I will make a new log to night with the PE table from the Camaro LS1 2002.

[Ram Air IV]

I have now a new log and it still show knock retard during acceleration. It looks like it occurs when gearbox shifts to next gear. Any clue how I can eliminate this knock?

[WeathermanShawn]

What year/type of knock sensors do you have?

It does look like false knock. You get one massive 'event' then the KR slowly decreases (irregardless of your TPS becoming less).

There are techniques to 'desensitize' KR or at least lessen the degree and hasten the recovery. However, I would try to eliminate the mechanical source first. Either replace the KR sensors or suspect motor mounts or suspension as the culprit. Anywhere you have metal to metal contact.

What type of motor mounts and suspension bushings do you have?

[Ram Air IV]

I think it is the original knock sensors from 2002 (located under the intake). I am using the original Chevy SB rubber mounts. I have polyurethan busing in the suspension. I will try to attach some kind of stethoscope so it is possible to listen for mechanical noise.