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Old 10-02-2006, 03:15 AM   #1
Spec C Wannabe
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Question Actual and Target A/F in comparison?

Since I don't have a wide band O2 to read actual A/F ratio, I just wonder by how much my Target A/F (those numbers found in the Lo Det Fuel Map) would differ from the actual.

I would like to ask you guys who tune yours with the WB O2 and can access to the fuel map to share your findings.

My car is pretty much ordinary Stage 2 (Up, Down, Catback, Inter hoses and Turbo Inlet pipe). NO modification was done to the intake system (well, except the turbo inlet pipe)

I've flashed my car with british version of PPP (my car is EURO version, by the way) and it runs very strong. I've been using OpenEcu programs such as Enginuity, EcuEdit, Tari ECUExplorer to tune my rom for the last six months. Mostly touched around the boost area. I use slow-but-sure philosophy to tune my car!

And now that I've got my boost dialled in, I would like to step further into Fuel and Ignition region.

I know that WB O2 and knock detector are needed to tune safely. Those instruments will come later when my fund is well replenished.

Fuel map in the PPP program is very rich, 10.5 -10.1 rich in the high-rev-high-load area. I have not yet really tweaked my Fuel and Ignition other than leaning out those nasty rich area by 0.06-0.21 point. At highest- load highest-rev point of the map now becomes 10.23 AFR.
Also, I've added, at low-load low- rev area, 0.35-0.70 degree of advance timing while reduced -0.7 degree in the knock-prone area of the Ignition Correction map.

As I said ealier, the car is running strong without any sign of knock (no audible knock, no negative Knock Correction, no knock signals, IAM stucks at 16) except very high speed runs on hot days (100+*F) or in the track that I would see IAM drop to 10-12 and then would bounce back the following days of normal driving.

I WILL NOT alter my fuel and ignition beyond this point if I don't get myself some proper tools. Changing these parameters without metering it properly is like playing russian roulette. And I have a heartache everytime I blindly change them.

For your information, the best gas I can access here is 95 octane which should equal to around 91-92 of US' (RON+MON)/2 rating. I live at the sea level, in the hot and humid climate, tropical style with average day time temp around 90-100*F.

If you've happened to have your car Wide Banded, please please share your experience.

Thanks in advance for your answers.
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Old 10-02-2006, 07:30 AM   #2
qoncept
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The numbers don't really mean anything. The only thing you can say for certain is that the AFR is proportional to the "target" AFR in the tables. I honestly don't know why the fuel table is set up the way it is -- it's very misleading. It would have made more sense just to make the values a number from 0-255.
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Old 10-02-2006, 08:15 AM   #3
TheMadScientist
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Originally Posted by qoncept View Post
The numbers don't really mean anything. The only thing you can say for certain is that the AFR is proportional to the "target" AFR in the tables. I honestly don't know why the fuel table is set up the way it is -- it's very misleading. It would have made more sense just to make the values a number from 0-255.
The better your MAF calibration the closer the target numbers in the map will be to accual AFR's. If you have a stock airbox the AFR targets should be close, most of the ones I have seen will be a couple of tenths to 0.8 AFR richer than what you put in the table. I would not take that as correct for "your" car and would all ways double check the AFR with a WBO2.

TMS
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Old 10-03-2006, 06:18 AM   #4
Spec C Wannabe
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Originally Posted by TheMadScientist View Post
The better your MAF calibration the closer the target numbers in the map will be to accual AFR's. If you have a stock airbox the AFR targets should be close, most of the ones I have seen will be a couple of tenths to 0.8 AFR richer than what you put in the table. I would not take that as correct for "your" car and would all ways double check the AFR with a WBO2.

TMS
My intake system is very stock except Turbo Inlet Pipe. My MAF scaling map is left untouched. And looking from STFT is almost 0% and LTFT is around -1.5 to -2.

So, most of your cases, The actual is "richer" than Target?

Last edited by Spec C Wannabe; 10-03-2006 at 06:19 AM. Reason: typo
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Old 10-03-2006, 09:46 AM   #5
akira02rex
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Quote:
Originally Posted by TheMadScientist View Post
The better your MAF calibration the closer the target numbers in the map will be to accual AFR's. If you have a stock airbox the AFR targets should be close, most of the ones I have seen will be a couple of tenths to 0.8 AFR richer than what you put in the table. I would not take that as correct for "your" car and would all ways double check the AFR with a WBO2.

TMS
That isn't totally true at all, there is missing information there. I have a completely stock airbox and my AFRs are different than target values.
Your injector scaling plays a big part in the correlation as well.
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Old 10-04-2006, 12:03 AM   #6
Spec C Wannabe
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My assumptions:

Stock injectors

Stock Intake system

Stock MAF Scaling map

Stock pump and regulator

Fresh Fuel filter Fresh Air Filter

Could target be close to actual
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Old 10-05-2006, 09:22 AM   #7
ride5000
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Quote:
Originally Posted by akira02rex View Post
That isn't totally true at all, there is missing information there. I have a completely stock airbox and my AFRs are different than target values.
Your injector scaling plays a big part in the correlation as well.
actually i have found that with proper injector scaling the corrections to the mafv-g/s table are minimal, and once done DO align the target and tailpipe afrs.
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Old 10-06-2006, 07:43 AM   #8
xolosis
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Okay what happens when you through a Fuel Pressure Regulator into the mix. I'm running stock box with turbo inlet and at idle my trims a on 0 give or take -/+ 0.5% with AFR's right on 14.7. However at medium to WOT the AFR's dip into the mid 9's with a Wideband 02. Does this suggest I need to scale the MAF to compensate?

Something is not right?
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Old 10-06-2006, 08:43 AM   #9
ride5000
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Originally Posted by xolosis View Post
Okay what happens when you through a Fuel Pressure Regulator into the mix. I'm running stock box with turbo inlet and at idle my trims a on 0 give or take -/+ 0.5% with AFR's right on 14.7. However at medium to WOT the AFR's dip into the mid 9's with a Wideband 02. Does this suggest I need to scale the MAF to compensate?

Something is not right?
first you need to make sure that there are no other corrections taking effect. for example there is a MAP based fuel correction in my ecu.

once you're sure of that, drive your car on an image for a while. at least a few days. make sure that LTFT has settled down, and that it's close to zero.

now, if you wanted to correct your translation table, correlate the rich-regions with specific mafvs. make very small changes to the translation table (ie, 1%) at one time. resist the urge to interpolate the changes to other mafv. this is an iterative process that must be repeated again and again.

having said that, is it possible that when rpms rise, and fuel pump duty goes up, that you're overdriving the oem fpr? and when this occurs, rail pressure rises, fuel delivery rate increases, and afrs shift rich? sure. there have even been reports of it happening. i can't really comment on that because it's been years since i've run on it! i know that on my car i see zero change in afr as the pump duty changes, but i'm running an aeromotive.

if this is indeed what's happening, then making the changes to mafv-g/s is NOT the best place to correct for it. in my oem ecu there is yet another fuel correction table, and that is RPM based. since the fuel pump duty is rpm based as well this is the best place to make your correction.

i used xmlwrite to scrape these map locations/definitions off my rom.

hth
ken
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Old 10-06-2006, 09:28 PM   #10
xolosis
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Originally Posted by ride5000 View Post

having said that, is it possible that when rpms rise, and fuel pump duty goes up, that you're overdriving the oem fpr? and when this occurs, rail pressure rises, fuel delivery rate increases, and afrs shift rich? sure. there have even been reports of it happening.
I believe this is the problem I'm experiencing. At idle and light throttle AFR's han9 around the 14.7 region. Mid to WOT and it goes pig rich.

What other Fuel compensation should I be looking for? Name of the maps would help.

BTW I tried 2 things last night which are totally seperate to eachother.

1. Rescaling the MAF which fixed my rich connection and I as seeing AFR's at 10:8 - 11.0 at WOT and car felt great. However when I returned home A/F Learning at idle was showing +14.85 so looks like it was ajusting due to what I took out of the MAF Scaling.

2. Rescaled the Fuel Enrichment Map - Took -17% and didn't make a difference. Actually it dipped into the high 8's.

Maybe I should be looking and my MAF sensor. Could need a clean or replacement?

This is tough!
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