IAT's and BEN

[Black02SS]

I don't know how to account for this, but when my IAT's get high my car runs extremely lean. When this happens, it is jacking up my BEN making it a PITA to tune. Is there a table that controls this or anything I can modify to cause this to stop? Would the IAT vs Spark cause the lean condition?

Chad

[GMPX]

Chad,

We are all seeing this, it's a pain alright, but no answer just yet apart from trying to keep intake temps down when logging, easier on a dyno, no so on the road.

Cheers,
Ross

[Dirk Diggler]

Zero out the IAT vs spark table for tuning purposes and that should stop what you are seeing

s a test yesterday I pulled 2* of timing from the HO and LO table and went out and logged. All my "BENS" went leaner about 3-4%. I then flashed back to the original tune and everything feel bacn into line. If you are seeing 113+* on the IAT you are a candidate for zeroing out this table. It will make your tuning experience more stable and wont have you wanting to set the car on fire ;)

[Black02SS]

I am going to try this here in a bit. I'll return with my results.

[Black02SS]

Ok, I made sure my IAT vs Spark was zero'd out today. Toady was freakishly hot. ECT's were in the 210* range (180* Normal). IAT's were anywhere from 110* up to 140+ (normal is 80-90*). Car still ran .5 lean it appears. I average 14.7 but today was in the 15.1-15.3 range. Is there a table that could be causing this that we don't yet have access to?

[Blacky]

Is there a table that could be causing this that we don't yet have access to?

If there is then I'm still looking for it...seriously, I am still trying to find a solution for this.

Paul

[Black02SS]

Thanks! If you come across it, let us know. :lol:

[jfpilla]

I don't know how to account for this, but when my IAT's get high my car runs extremely lean. When this happens, it is jacking up my BEN making it a PITA to tune. Is there a table that controls this or anything I can modify to cause this to stop? Would the IAT vs Spark cause the lean condition?

Chad

This may be a cause. At least when you take your foot off the gas. When IAT's go up the values used in the IAP table get lower. Lower values in that table increase airflow.

[Black02SS]

I'm sure that might be part of the problem, but I don't notice any of this when the IAT's are below 100*.

[bink]

As IAT increases the fuel (g/cyl) demand decreases. But the actual fuel provided (by the VE table) is static - if there isn't a separate " IAT - VE" correction table. Are the "Short Term Fuel Trims" the correction factor?

[Black02SS]

I can not answer that as I run a constant open loop and haven't had o2's for over a year. :)

[bink]

I can not answer that as I run a constant open loop and haven't had o2's for over a year. :)
Yeah ...that's why I asked. I haven't been closed loop for a long time. It seems like the correction would be the STFTs.

[bink]

Does the Holden GTS calibration have the O2s active??
Is it a Closed Loop Speed Density tune??

If not, then how does GM compensate for the IAT as far as a correction factor??

:?: :?:

[Blacky]

Does the Holden GTS calibration have the O2s active??
Is it a Closed Loop Speed Density tune??

If not, then how does GM compensate for the IAT as far as a correction factor??

:?: :?:

Technically its not a GM or GMH "factory" tune.
HSV make the GTS, they removed the MAF and retuned the PCM.
HSV work closely with GMH but I do not know how much sharing of tuning information goes on.

Anyway, the fuel trims (with the HSV stock tune) on my GTS were always around 5-10% positive. i.e. without the fuel trims I would have been running lean.
Right now I can't do any testing, it is having a cam transplant.

Paul

[Blacky]

As IAT increases the fuel (g/cyl) demand decreases. But the actual fuel provided (by the VE table) is static - if there isn't a separate " IAT - VE" correction table. Are the "Short Term Fuel Trims" the correction factor?

The PCM does calculate an adjsutment to the VE based on IAT as follows:

g/cyl = VE*MAP/charge_temp. (update: replaced sqrt(charge_temp) with just charge_temp.)
Ve is in g*K/kPa
MAP is in kPa
charge_temp is in degK

charge_temp is calculated as follows:
273.15+IAT+((ECT-IAT)*factor)
ECT is in degC
IAT is in degC
factor is a multiplier between 0 and 1.

At low airflow it is closer to 1 which weights the charge_temp in favour of ECT.
At high airflow (>150g/s) it is closer to 0 which weights the charge_temp in favour of IAT.
The factor is calibrated in a lookup table (not available in EFILive) that is indexed on airflow in g/s from 0 to 150g/s. Typical factor values are 0.8 for 0g/s down to 0.1 for 150g/s and above.

The theory being that heat (ECT) is transfered from the heads and manifold after the IAT has been measured and prior to the air entering the cylinder.

Regards
Paul

[turboberserker]

Hmmm. I've been having a temp related (as best I can tell at this point) issue with surging at idle where the otherwise stable AFR ranges from 12 - 18AFR in the worst cases. I've been tweaking and tweaking and tweaking idle settings, and have gotten it some what better, but when the IAT, ECT and Trans temps go up (as the do in FL summer traffic), I get this weird surging.

Could these issues be related?

[Black02SS]

I think they could be. I have noticed that with the AC on and when the IAT temps get higher, the car will lean out and sometimes the timing differs even though the IAT Spark table has been zero'd out in my car. I noticed today that with my AC on and the IAT temps in the 90*'s, my timing rose. :?

[bink]

As IAT increases the fuel (g/cyl) demand decreases. But the actual fuel provided (by the VE table) is static - if there isn't a separate " IAT - VE" correction table. Are the "Short Term Fuel Trims" the correction factor?

The PCM does calculate an adjsutment to the VE based on IAT as follows:

g/cyl = VE*MAP/charge_temp. (update: replaced sqrt(charge_temp) with just charge_temp.)
Ve is in g*K/kPa
MAP is in kPa
charge_temp is in degK

charge_temp is calculated as follows:
273.15+IAT+((ECT-IAT)*factor)
ECT is in degC
IAT is in degC
factor is a multiplier between 0 and 1.

At low airflow it is closer to 1 which weights the charge_temp in favour of ECT.
At high airflow (>150g/s) it is closer to 0 which weights the charge_temp in favour of IAT.
The factor is calibrated in a lookup table (not available in EFILive) that is indexed on airflow in g/s from 0 to 150g/s. Typical factor values are 0.8 for 0g/s down to 0.1 for 150g/s and above.

The theory being that heat (ECT) is transfered from the heads and manifold after the IAT has been measured and prior to the air entering the cylinder.

Regards
Paul

Too funny :lol: I looked all over for a reason to use the sqrt of T. :lol:

So at idle the factor/value is greatest. As we sit still and the IAT raises the g/cyl value drops. Lower g/cyl ....less fuel -> Lean. Makes sense.

Can we change the Look-up table factors, at low g/sec, to something less extreme?


black02ss - makes sense that your timing would change as the "reported" g/cyl dropped (via the above calc and lookup table). Seems like spark would drop tho...unless the PCM compensated to prevent a stall and bumped IAC...that would prolly boost the timing?? Just a thought.
Happy 4th!!!

Cheers,
joel

[jfpilla]

As IAT increases the fuel (g/cyl) demand decreases. But the actual fuel provided (by the VE table) is static - if there isn't a separate " IAT - VE" correction table. Are the "Short Term Fuel Trims" the correction factor?

The PCM does calculate an adjsutment to the VE based on IAT as follows:

g/cyl = VE*MAP/charge_temp. (update: replaced sqrt(charge_temp) with just charge_temp.)
Ve is in g*K/kPa
MAP is in kPa
charge_temp is in degK

charge_temp is calculated as follows:
273.15+IAT+((ECT-IAT)*factor)
ECT is in degC
IAT is in degC
factor is a multiplier between 0 and 1.

At low airflow it is closer to 1 which weights the charge_temp in favour of ECT.
At high airflow (>150g/s) it is closer to 0 which weights the charge_temp in favour of IAT.
The factor is calibrated in a lookup table (not available in EFILive) that is indexed on airflow in g/s from 0 to 150g/s. Typical factor values are 0.8 for 0g/s down to 0.1 for 150g/s and above.

The theory being that heat (ECT) is transfered from the heads and manifold after the IAT has been measured and prior to the air entering the cylinder.

Regards
Paul

Too funny :lol: I looked all over for a reason to use the sqrt of T. :lol:

So at idle the factor/value is greatest. As we sit still and the IAT raises the g/cyl value drops. Lower g/cyl ....less fuel -> Lean. Makes sense.

>>>>>Joel, Getting back to the IAP table. As IAT increases the values used get lower. Those values report that less air is being used and causes the TB to allow more air=leaner. What do you think?

Can we change the Look-up table factors, at low g/sec, to something less extreme?


black02ss - makes sense that your timing would change as the "reported" g/cyl dropped (via the above calc and lookup table). Seems like spark would drop tho...unless the PCM compensated to prevent a stall and bumped IAC...that would prolly boost the timing?? Just a thought.
Happy 4th!!!

>>>>>Another possibility. If the ECT spark table had been pulling timing then the ECT increased and stopped pulling timing, making it look as if timing had been added. :shock:
Joe
Cheers,
joel

[Blacky]

I'm adding the factor table to EFILive...
Paul

[Black02SS]

:mrgreen:

[Blacky]

Chad, here's the table from the *.tun file you sent.
Paul

[bink]

>>>>>Joel, Getting back to the IAP table. As IAT increases the values used get lower. Those values report that less air is being used and causes the TB to allow more air=leaner. What do you think?





>>>>>Another possibility. If the ECT spark table had been pulling timing then the ECT increased and stopped pulling timing, making it look as if timing had been added. :shock:
Joe
Cheers,



Joe - I only know what I've seen with my car. You guys have had a lot of experience with Y and Fbods. I wasn't sure if the IAC-Park table functioned the same for the Fbod (Black02SS). Seems like the gurus always say the IAC-Park table is ONLY used to reset the IAC after a major transieny/change.
Of course I know that I can, and have , calibrated my IAC Park table so that DynAir correlates to MAF - MANY Thanks to you and Nick! :mrgreen:


I don't understand why the PCM would stop pulling Timing, via ECT spark table, if the ECT or IAT (IAT Table) are the same or higher?? Won't be the first time you have to elaborate so that i "get it" :lol:

[jfpilla]

>>>>>Joel, Getting back to the IAP table. As IAT increases the values used get lower. Those values report that less air is being used and causes the TB to allow more air=leaner. What do you think?





>>>>>Another possibility. If the ECT spark table had been pulling timing then the ECT increased and stopped pulling timing, making it look as if timing had been added. :shock:
Joe
Cheers,



Joe - I only know what I've seen with my car. You guys have had a lot of experience with Y and Fbods. I wasn't sure if the IAC-Park table functioned the same for the Fbod (Black02SS). Seems like the gurus always say the IAC-Park table is ONLY used to reset the IAC after a major transieny/change.
Of course I know that I can, and have , calibrated my IAC Park table so that DynAir correlates to MAF - MANY Thanks to you and Nick! :mrgreen:


I don't understand why the PCM would stop pulling Timing, via ECT spark table, if the ECT or IAT (IAT Table) are the same or higher?? Won't be the first time you have to elaborate so that i "get it" :lol:

I have also been able to use IAP to match values. I think IAP's impact when we take our foot off the gas. However, we have also seen some situations where matching did not work. There must be something we don't know. Could be as simple as how well the voltage for the TB has been set.

Regarding timing, if you look at the Spark ECT table it pulls timing up to 75C and adds nothing up tp 105C (in your car and mine, at least). Since we don't know what temps are being run normally for the cars in question, I threw this up as a possibility.
Frankly, I think it's a none issue at part throttle. We have no way of knowing what will help the car run smoothly at part throttle other than SOP using BI-D controls.
There is another table that has an impact. "Fuel MixtureSpark Correction" comes into play on A4's. I "0'd" mine and will use the dyno to get the timing needed for best power.
What you guys have discussed is very interesting. It helps explain some of what is seen happening in our logging.
I also love the link feature. It has enabled me to see the affect of some different conditions.
PS the engine is together and should go in next week. Should know soon if the sensors fit under the headers. I'm confident they will work and can be sensitized properly, if needed.

[Black02SS]

That table is already "0'd" out on my car from the factory. :( Weird stuff is going on with my car. I think she is mad at me. I logged every single spark pid today and guess what, NOTHING extra is showing up except for the idle correction. IAT, ECT, TC, CAT, etc. all show a 0 on the log. I didn't mess too much with the car today as it is pretty warm and the IAT's are in the 130* range. I even disabled spark smoothing to see if that had any effect to no avail.

[Black02SS]

Here are two screen shots from the same tune, but different IAT"s. The first pic represents a IAT average of 91*.

http://home.insightbb.com/~black02ss/IATAVG91.JPG

Second shows the same tune, but IAT's averaging 110* (max was 122*)

http://home.insightbb.com/~black02ss/IATAVG110.JPG

All the timing tables are zero'd out as well.

[MN C5]

That table is already "0'd" out on my car from the factory. :( Weird stuff is going on with my car. I think she is mad at me. I logged every single spark pid today and guess what, NOTHING extra is showing up except for the idle correction. IAT, ECT, TC, CAT, etc. all show a 0 on the log. I didn't mess too much with the car today as it is pretty warm and the IAT's are in the 130* range. I even disabled spark smoothing to see if that had any effect to no avail.

Don't you want a 1 value vs a Zero for ECT vs IAT ?

[Black02SS]

Are you refering to the fuel Air Spark Correction table?

[MN C5]

No the Charge Air Temp Blending Table. I though thats what you were refering to. Where a factor closer to 1 favors ECT and a factor closer to 0 favors IAT at high are flow.

Sorry if I missed what you were refering to.

[Black02SS]

:lol: Start talking about tables and we get kinda confused easily. We don't have access to that table as of yet. Mine is how you see it in Pauls post as I haven't had the opportunity to alter it. When it becomes available, I will tinker with it and see how it reacts.