MAF trasfer table and AFR

[slow poke]

I'm starting to alter the MAF transfer function in PRP for my car. I have made changes and the AFR numbers are coming down closer to where they should be but they fluctuate sometime .5 to 1 AFR count at a specific MAF AD count.

How long should I hold the car at a specific RPM to datalog that RPM? I have been doing about 10-15sec steady loaded on the street.

How close should i get it 14.7? whats acceptable or best practice?

And, what is normal for the AFR while doing loaded part throttle MAF tuning should it hold like a rock at 14.7 at all MAF AD counts? or will it fluctuate like mine is doing while tuning?

Thanks

 

[01yellercobra]

It's always going to fluctuate. The O2s are always changing. IIRC mine would go from low 14's to low 15's.

 

[ZeroSVT]

The best way to dial in the MAF, is to lock the car into Open Loop. You can do this by setting Fuel Open Loop TP, TP_Counts to all 0's. Then Set part throttle base fuel table to 1.0 lambda. Then datalog the MAF AD counts and Lambda across the AD counts (part throttle) and make dial it in using the datalog as a reference.

Sorry for crappy typing, ipad is not best.

-Matt

 

[slow poke]

Thanks, I have do have it locked in open loop and have set the base fuel table to all 1's up to 3500rpm. I was just not sure how steady it should be as I have no prior reference.

 

[ZeroSVT]

Thanks, I have do have it locked in open loop and have set the base fuel table to all 1's up to 3500rpm. I was just not sure how steady it should be as I have no prior reference.

+/- .3 lambda is general for the entire curve. Continue up to 4500rpm

-Matt

 

[slow poke]

Thanks Matt, I know Lasota's book only mentions taking it to 3000rpm. Is it safe to go to 4500rpm at an with an AFR of 14.7?

Also, It has been running in the 17's before I go in and adjust the MAF table, Should I extrapolate to the Higher MAF AD counts before I log them as it has been trending lean?

My thought is this could safe time and be safer as it won't be as lean then

 

[ZeroSVT]

Thanks Matt, I know Lasota's book only mentions taking it to 3000rpm. Is it safe to go to 4500rpm at an with an AFR of 14.7?

Also, It has been running in the 17's before I go in and adjust the MAF table, Should I extrapolate to the Higher MAF AD counts before I log them as it has been trending lean?

My thought is this could safe time and be safer as it won't be as lean then

Yes it is safe to take it that high of RPM under light load (meaning no boost or stress on the engine, not volumetric load)

What are your car details? Specifically injectors and MAF setup?

-Matt
-

 

[slow poke]

Stock injectors, stock MAF with MAFia, BAP

running a ported blower, 2.8 upper, 4lb lower

So would the 4500rpm be a free rev or driven datalog?

 

[ZeroSVT]

Stock injectors, stock MAF with MAFia, BAP

running a ported blower, 2.8 upper, 4lb lower

So would the 4500rpm be a free rev or driven datalog?

Light load, so driven if thats your only choice. Dyno is the best of course.

Did you scale the following for the Mafia?
Fuel Injector Low Slope
Fuel Injector High Slope
Air Mass Displacement of one cylinder

-Matt

 

[slow poke]

Matt,

Driven on the road is the only choice, I dont have access to a dyno.

its a Lasota Base tune

I have the MAFia set on 2

I was considering scaling but was told by someone that it probably did not need it as my mods are so light

Should I have scaled those parameters? If so by what factor? PRP mentions .55 but that is a huge reduction

 

[ZeroSVT]

Matt,

Driven on the road is the only choice, I dont have access to a dyno.

its a Lasota Base tune

I have the MAFia set on 2

I was considering scaling but was told by someone that it probably did not need it as my mods are so light

Should I have scaled those parameters? If so by what factor? PRP mentions .55 but that is a huge reduction

For a setting of 2 you need to apply a correction of 24% or .76 to the FILS an FIHS... I dont know where .55 come from, but that would be closser to a setting of 3.

Cheers,
-Matt

 

[slow poke]

the .55 I think was just an example in his book as a starting point, for someone with more mods than me i guess.

I was wondering how that worked since I know the MAFia scales the MAF I was thinking what about other parameters.

so the 24% or .76 correction, do I need to apply it to any other varibles other than the FILS and FIHS you mantioned?

Thanks for the help!
Dave

 

[Don 95Vert]

If it is a LaSota base tune it is already adjusted for the MAF.ia on 2 if you stated you had the MAF.ia. If you are who I think you are, then it WAS done. Don't do it anymore than that or you will have a real mess. For loaded revs try to pause at a bunch of different levels. This is so much easier on the dyno though - not to mention safer. Usually, you are better off doing that part by re-enabling CL and using fuel trims. In OL you will never get it exactly to 14.7, it will fluctuate - and if you are in the USA, it is really 14.08, not 14.7, but your wideband thinks 14.08 is is 14.7, but that is a whole nother post...

 

[slow poke]

Hey Don,

I Appreciate it, I just wasnt sure and did not know if the scaling was performed. I will leave everything as is and yes I stated the MAFia being on board before I got the base tune.

I understand the ease and safety of the dyno but I have been able to gather some data up to about 3000rpm and at 500rpm intervals below the 3000rpm

My question is how long do I hold it at the RPM to get accurate data for that RPM, I have been holding for 10-15sec, is that long enough?

with each successive MAF AD count I am running in the upper 16's - low 17's before adjustment.

 

[01yellercobra]

You can look at the tune history and see what's been changed. You'll be able to see what was scaled. I usually hold the rpms for a few seconds. I think 10 is plenty.

 

[ZeroSVT]

In OL you will never get it exactly to 14.7, it will fluctuate - and if you are in the USA, it is really 14.08, not 14.7, but your wideband thinks 14.08 is is 14.7, but that is a whole nother post...

I'm not sure I understand what you're saying here.

Stoich
E0 = 14.68
E10 = 14.13

A good median would to have the car setup for 14.4 which would be a good 2-3% median correction depending on fuel used.

Why would the wideband think 14.08 is 14.7? AFR is always AFR its not a calculation against a value, however, if you are using lambda, thats another story.

Tuning MAF by fuel trims is a dirty way of doing it, you are relying on calculation rather than result.

Cheers,
-Matt

 

[ZeroSVT]

with each successive MAF AD count I am running in the upper 16's - low 17's before adjustment.

If its that way across the entire range, Add 13% to the entire MAFXF. Then work your way from there.

I also agree that 10 seconds is plenty.. what you really want ot see is the stabilized "step" on the datalog

-Matt

 

[Don 95Vert]

I'm not sure I understand what you're saying here.

Stoich
E0 = 14.68
E10 = 14.13

I should say, read the book! HAHA! Ford uses 14.64 as stoich for gasoline and 14.08 as stoich for E10. So it is a good idea to use those when tuning Fords, since Ford uses those values. Most widebands in the price range that most people can afford - with a couple exceptions - are calibrated for stoich being 14.7. Since this is just an internal calculation based on Lambda, all is not lost. Because really when you see 14.7 on a non-adjustable wideband, you can figure it must be Lambda 1.0 - and it does not matter what fuel is used, that is stoich. Even if the stoich is actually 14.08, or 9.76, it doesn't matter, you still look for 14.7. The key is Lambda and Lambda 1.0 equals 14.7 via the manufacturer's internal calculation. The sensor itself switches around the stoich point of whatever fuel is being used, it does not care what it is, it just knows what stoich is and then the electronics calculate that data and report to you what you see. Using Lambda to tune eliminates this confusion. And, calculations are being made whether you use fuel trims or not - and using them at some point in the process will be a good double check on your cheap (compared to a 6k lab grade Horiba) wideband and will tell you if all is well with your 02 sensors when they start working again. Of course 2011+ with wideband sensors from the factory are a bit different.

 

[ZeroSVT]

I should say, read the book! Ford uses 14.64 as stoich for gasoline and 14.08 as stoich for E10. So it is a good idea to use those when tuning Fords, since Ford uses those values. Most widebands in the price range that most people can afford - with a couple exceptions - are calibrated for stoich being 14.7. Since this is just an internal calculation based on Lambda, all is not lost. Because really when you see 14.7 on a non-adjustable wideband, you can figure it must be Lambda 1.0 - and it does not matter what fuel is used, that is stoich. Even if the stoich is actually 14.08, or 9.76, it doesn't matter, you still look for 14.7. The key is Lambda and Lambda 1.0 equals 14.7 via the manufacturer's internal calculation. The sensor itself switches around the stoich point of whatever fuel is being used, it does not care what it is, it just knows what stoich is and then the electronics calculate that data and report to you what you see. Using Lambda to tune eliminates this confusion. And, calculations are being made whether you use fuel trims or not - and using them at some point in the process will be a good double check on your cheap (compared to a 6k lab grade Horiba) wideband and will tell you if all is well with your 02 sensors when they start working again. Of course 2011+ with wideband sensors from the factory are a bit different.

I have read you book actually

(See EDIT below)Could you give me an example of a Wideband that is specifically calibrated for 14.7? Every aftermarket wideband we have tinkered with is calibrated for range +/- 2.5(ish)%

I don't agree that you can figure that 14.7 is 1.0 on a non adjustable wideband. Does this wideband show lambda? (Maybe its just a cheap wideband thing?) EDIT: Apparently there are meters out there that only show AFR (stupid). So you can correct this though, its called Meter correction factor.

Meter Correction = 14.7 x Target λ Value

I do agree cross referencing the STFT after you build out your MAF is not a bad idea

It's debatable what the official number is internally, we all have our opinion. However, there is some Math that comes into play here to get politically correct.

For example providing that you are after Blend AFR at E10.
Blend AFR (x) = (0.10 x E85 A/F Ratio) + (0.90 X Petrol A/F Ratio)
x = (0.10 x 9.765) + (0.90 x 14.7)
x = 14.20 to be politically correct by math

or if tuning for a AFR other than stoich

λ = (Desired A/F ratio) ÷ (Stoichiometric A/F Ratio)

Then goes the fancy chemical engineers with the Residual exhaust oxygen and hydrocarbons and A/F measured different places, temperatures, vs petrol makeup blah blah blah... Ugh, I need to change jobs, anyone need a good Janitor?

Cheers,
-Matt