Calculated new MAF Table
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Originally Posted by MNR-0
txhorns, not everyone is as patient or well versed as you in this area. For every success story like yours I hear 10 failures. While the technique you apply is simple the execution is not. For many, hours of logging, recal. and driving in different atmospheric conditions is just too much. Call me lazy if you like.
Ive tried your method and got some success, but it stuffed up too many other things in my tune - things like calculated cylinder fill, calculated transmission torque, calculated engine torque to name a few. With IFRs I can mod without having to readjust my MAF or VE every time.
Yup.
Yup. and Nup.
The problem is not airlflow. The problem is AFR.
If you are running SD WITHOUT a MAF then sure - I agree - get the VE right - its all about VE. If you run a bastardised MAF - then sure - I agree - get the MAF right - its all about MAF. Better to leave the MAF alone though
.
If you DO run a stock MAF - that device has been calibrated correctly in controlled conditions to generate the most stable average airflow reading possible. You will not do a better job by road tuning based on the residual LTFTs that are impacted by air density and temperature variations.
It's people who bastardise the MAF by pulling the laminar screen and porting the aerofoils that have changed the MAF performance and so a recal. is necessary.
Commanded AFR is a byproduct of airflow and injector pulsewidth calculations and rescaling the IFR will not cause fluctuating AFRs. If you have stable TRIMS you should get stable fuelling at WOT.
IFRs, however, will offset the actual AFR for a given commanded AFR - I agree with you on that - but so what? What happens if you reach a state where the actual AFR reads the Commanded AFR and you STILL have positive or unstable LTFTs?
The goal is not to get the commanded AFR reading actual AFR. It is what it is and will vary from car to car. You just need to know what the diferential is so you can begin making LINEAR adjustments.
Tuning is about maintaining the correct AFR for the intended engine load and RPM. Im glad it worked for you. Im glad it worked for me. If anything this debate has shown is that there are repurcussions with whatever you do and with whatever approach you adopt you need to be prepared to deal with the consequences.
Ive tried your method and got some success, but it stuffed up too many other things in my tune - things like calculated cylinder fill, calculated transmission torque, calculated engine torque to name a few. With IFRs I can mod without having to readjust my MAF or VE every time.
Yup.
Yup.
and Nup. The problem is not airlflow. The problem is AFR.
If you are running SD WITHOUT a MAF then sure - I agree - get the VE right - its all about VE. If you run a bastardised MAF - then sure - I agree - get the MAF right - its all about MAF. Better to leave the MAF alone though
.If you DO run a stock MAF - that device has been calibrated correctly in controlled conditions to generate the most stable average airflow reading possible. You will not do a better job by road tuning based on the residual LTFTs that are impacted by air density and temperature variations.
It's people who bastardise the MAF by pulling the laminar screen and porting the aerofoils that have changed the MAF performance and so a recal. is necessary.
Commanded AFR is a byproduct of airflow and injector pulsewidth calculations and rescaling the IFR will not cause fluctuating AFRs. If you have stable TRIMS you should get stable fuelling at WOT.
IFRs, however, will offset the actual AFR for a given commanded AFR - I agree with you on that - but so what? What happens if you reach a state where the actual AFR reads the Commanded AFR and you STILL have positive or unstable LTFTs?
The goal is not to get the commanded AFR reading actual AFR. It is what it is and will vary from car to car. You just need to know what the diferential is so you can begin making LINEAR adjustments.
Tuning is about maintaining the correct AFR for the intended engine load and RPM. Im glad it worked for you. Im glad it worked for me. If anything this debate has shown is that there are repurcussions with whatever you do and with whatever approach you adopt you need to be prepared to deal with the consequences.
Yup.
If your weather conditions, during use of the car, are not constant then the MAF is your friend.
AND the AirFlow commanded by the IAC Park effects the LTIT and STITs which effects AFR globally. Think about that....
It is so much easier to use a known maf curve from a vehicle that has more of a straight shot intake system right in front of the MAF, just like an aftermarket air lid on our cars. The stock air lid is oblong in shape and directs air differently across the MAF compared to an aftermarket airlid, therefore our MAF is no longer calibrated correctly from GM with an aftermarket airlid. The holden MAF table is pretty close to what our 98-02 f-body is with an aftermarket air lid. After a few minor adjustments it is nearly perfect and it sure as hell doesn't take huge logs worth of data to adjust.
Originally Posted by MNR-0
Tuning is about maintaining the correct AFR for the intended engine load and RPM. Im glad it worked for you. Im glad it worked for me. If anything this debate has shown is that there are repurcussions with whatever you do and with whatever approach you adopt you need to be prepared to deal with the consequences.
As far as the MAF goes, even stock, unmodified MAF housings may need recalibration for let's say like someone who's done headers and a cam. You can log VE airmass calcs vs MAF airmass calcs and see that due to the change in engine dynamics, there is an airflow discrepancy. And you are most definitely right about recalibrating the MAF for modified/aftermarket MAFs b/c of the change in volume flow. But perhaps some people have taken all this the wrong way. I think if you're on a stock motor with boltons, and stock MAF leave it alone. If you do internal, and/or MAF mods then most certainly you will need recalibration. I have this problem that I assume everyone has my same setup
But for highly modded cars, aligning reported airflow with what the motor's operation suggests is a good idea to keep fueling consistent.I guess if your happy with obtaining the AFR you seek by playing with IFRs then go for it, it's almost like carb tuning if you ask me, but EFI gives us all the tools and calculations to measure air, pressure, temps and so forth to get the correct amount of fuel. And to those who disagree I'm not trying to be judgemental, just providing discussion that's all. Patience was a great virtue in learning all this, but without research how do we learn anything? I think my patience has paid off and now that I have a deeper understanding of all this, perhaps I can sift out all the finer points to aid others in the tuning process!
Last edited by txhorns281; Mar 7, 2005 at 09:47 AM.
Originally Posted by Nic00Z28M6
It is so much easier to use a known maf curve from a vehicle that has more of a straight shot intake system right in front of the MAF, just like an aftermarket air lid on our cars. The stock air lid is oblong in shape and directs air differently across the MAF compared to an aftermarket airlid, therefore our MAF is no longer calibrated correctly from GM with an aftermarket airlid. The holden MAF table is pretty close to what our 98-02 f-body is with an aftermarket air lid. After a few minor adjustments it is nearly perfect and it sure as hell doesn't take huge logs worth of data to adjust.
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txhorns281, its great talking to you about this as I do appreciate the efforts you have undergone to make sense of it all.
another_user, I can feel your frustrations. All I will say is that it is much easier to recalibrate a constant than a variable. The reciprocal interactions a MAF has with other systems makes tuning the curve a nightmare.
Overall, I would much rather lose the MAF and go MAFless than recalibrate it. Leave it stock and use IFRs or lose it and attack the VE. Its MAF or MAFless, no in between. That's what I recommend.
another_user, I can feel your frustrations. All I will say is that it is much easier to recalibrate a constant than a variable. The reciprocal interactions a MAF has with other systems makes tuning the curve a nightmare.
Overall, I would much rather lose the MAF and go MAFless than recalibrate it. Leave it stock and use IFRs or lose it and attack the VE. Its MAF or MAFless, no in between. That's what I recommend.
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Well, I need to go look over my logs, but I have had really good (fairly consistent it seems) luck using an 04 Z06 MAF table and shifting the cells to the left to change the curve. Every shift seems to be worth about 5% FTs...maybe a little more. Like I said...I still need to sit down with my logs. The results seem a LOT more reliable than our calculated from scratch tables. You would think that this would be the same as scaling your MAF table by x percent, but I don't think it works that way. I need to sit down and compare the two, but I think that scaling the MAF table may not be as good as shifting the cells. Just my thoughts for today. I will post some more reliable information while nobody is looking at work tomorrow.
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Originally Posted by Another_User
The results seem a LOT more reliable than our calculated from scratch tables. You would think that this would be the same as scaling your MAF table by x percent, but I don't think it works that way.
I think it CAN work that way - if your VE table is solid.
But then that would mean the MAF table is solid too.
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From: Va. beach,Va
Originally Posted by txhorns281
However, there are a multitude of things that are DEPENDANT on the IFRs. Changing IFRs have global effects too which cause funny things like commanding an certain AFR but not achieving it. If your VE fueling tables are all mapped out correctly, then the one thing the MAF is dependant on is correct, therefore allowing you to calibrate it properly. This is b/c VE calcs must include an airflow aspect, otherwise fueling would be totally screwed if our MAFs failed. Since we can measure that airflow aspect, we can align our MAFs to report true combustable airflow measurements from 0 mph all the way up to whatever you feel like topping out at and for all rpms.
Always change IFR = always BS to your PCM about what you really are pushing
Never change MAF = never change the device that deals DIRECTLY with what the problem is here... airflow.
MAF calibration does not pick up a change in air volume when we deal with ported/aftermarket MAFs since it is not adaptive. When we mod, we not only change air velocity but also air volume. These sensors have the ability to be accurate so long as they know what to be accurate about. So what we're doing is measuring and redefining the airflow as the motor requests and uses. You can see graphically, at least in my case, that after all my mods, my motor uses about 20-30% more airflow than what the MAF is reporting. I could actually breakdown how much % off my stock calibration was at each individual MAF calibration point but that would take a lot more space than I already have. With this kind of precision, why not use the MAF for what it's for and tell it correctly what kind of airflow it will expect to see through its calibration?
Even if we're not 100% totally on, it seems like scaling IFRs is like throwing fuel in to compensate for extra airflow, but there's no airflow data to really target from. You add fuel or subtract fuel to produce whatever AFR you want, despite what the PCM commands and all this while making your PCM think it's got bigger/smaller juicers. Why not work with readily available data? I used to get IFRs scaled around before I knew too much about this stuff and the one thing i look back and remember is that yes my car put out 13.0 AFR on the dyno, but my PCM was commanding 11.7. So it sounds more like scaling IFRs is the "make it work" solution here. Now when i command 13.0, i get 13.0, or 12.5 or whatever I want. No guess work anymore, just tell it to do and it does. Stock GM 26#er IFRs and my car runs smooth, makes awesome power, and the EFI responds to command and correction as it should. Also, my MAF reports almost exactly the airflow the VE calcs come up with during combustion so there's no fueling confusion there since even if it's a biased decision b/w MAF or SD, they both show the same airflow.
Can I make it work? I did and it worked VERY VERY well, while being VERY VERY easy too
Always change IFR = always BS to your PCM about what you really are pushing
Never change MAF = never change the device that deals DIRECTLY with what the problem is here... airflow.
MAF calibration does not pick up a change in air volume when we deal with ported/aftermarket MAFs since it is not adaptive. When we mod, we not only change air velocity but also air volume. These sensors have the ability to be accurate so long as they know what to be accurate about. So what we're doing is measuring and redefining the airflow as the motor requests and uses. You can see graphically, at least in my case, that after all my mods, my motor uses about 20-30% more airflow than what the MAF is reporting. I could actually breakdown how much % off my stock calibration was at each individual MAF calibration point but that would take a lot more space than I already have. With this kind of precision, why not use the MAF for what it's for and tell it correctly what kind of airflow it will expect to see through its calibration?
Even if we're not 100% totally on, it seems like scaling IFRs is like throwing fuel in to compensate for extra airflow, but there's no airflow data to really target from. You add fuel or subtract fuel to produce whatever AFR you want, despite what the PCM commands and all this while making your PCM think it's got bigger/smaller juicers. Why not work with readily available data? I used to get IFRs scaled around before I knew too much about this stuff and the one thing i look back and remember is that yes my car put out 13.0 AFR on the dyno, but my PCM was commanding 11.7. So it sounds more like scaling IFRs is the "make it work" solution here. Now when i command 13.0, i get 13.0, or 12.5 or whatever I want. No guess work anymore, just tell it to do and it does. Stock GM 26#er IFRs and my car runs smooth, makes awesome power, and the EFI responds to command and correction as it should. Also, my MAF reports almost exactly the airflow the VE calcs come up with during combustion so there's no fueling confusion there since even if it's a biased decision b/w MAF or SD, they both show the same airflow.
Can I make it work? I did and it worked VERY VERY well, while being VERY VERY easy too
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Originally Posted by Bink
Why not??
I think it CAN work that way - if your VE table is solid.
But then that would mean the MAF table is solid too.
I think it CAN work that way - if your VE table is solid.
But then that would mean the MAF table is solid too.
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From: Lower Alabama
My calculations with a home ported TB,MTI lid w/K&N and stock screened MAF look very similar to the Monaro values. All else being equal wouldnt I be much better off using these values in place of my stock 2002 LS1 Values?
And everyone talks about the weather changing VE tables day to day. Doesnt this happen in stock form as well? Is it that big of a deal if you can at least get it fairly close on a mild temp day or have a cold weather and hot weather tune? I dont mind using a tune for 2 different temps but anymore than that is a little excessive.
And everyone talks about the weather changing VE tables day to day. Doesnt this happen in stock form as well? Is it that big of a deal if you can at least get it fairly close on a mild temp day or have a cold weather and hot weather tune? I dont mind using a tune for 2 different temps but anymore than that is a little excessive.
Originally Posted by way2slow
My calculations with a home ported TB,MTI lid w/K&N and stock screened MAF look very similar to the Monaro values. All else being equal wouldnt I be much better off using these values in place of my stock 2002 LS1 Values?
And everyone talks about the weather changing VE tables day to day. Doesnt this happen in stock form as well? Is it that big of a deal if you can at least get it fairly close on a mild temp day or have a cold weather and hot weather tune? I dont mind using a tune for 2 different temps but anymore than that is a little excessive.
And everyone talks about the weather changing VE tables day to day. Doesnt this happen in stock form as well? Is it that big of a deal if you can at least get it fairly close on a mild temp day or have a cold weather and hot weather tune? I dont mind using a tune for 2 different temps but anymore than that is a little excessive.
Good find. Anybody have a monaro table? I have them all but the gto/holden.
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Originally Posted by SmokingWS6
Good find. Anybody have a monaro table? I have them all but the gto/holden.
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From: Australia
Originally Posted by Rays C5
I am on the fence with discussions from both of you... When lowering ifr to make richer does it also in essence actually make my stock 28 lb. injectors smaller causing them to max out sooner?
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Originally Posted by Another_User
PM me and I can send, or you can get the whole tune off of horist's site. I noticed with the lid and stock MAF it was really close to the Holden table with one cell shift to the left on my car.
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Originally Posted by Another_User
Well I got to thinking about it...how does a MAF translator work? I would bet (not knowing the electronics) that it shifts the frequency right? Not scale the entire table. I will try to make another run tonight. I have gotten a lot close by shifting the Z06 table than any of my other tuning attempts.
There are more reverberations with scaling the MAF - within the system.
Scaling the MAF is a factoring of overall airflow - Not a Calibration deficiency.
Hope this helps some. FWIW.
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So whats the scoop guys? Did ya'll decide that the theory about rescaling the MAF based on Dynamic Air Flow and MAF HZ wasn't a valid theory and are back to contimplating other theories?
I think I agree on one thing that the end goal is a specified AFR for a given set of conditions and there are several ways to get to that goal. So now all we have to do is find the best way to reach our goal right?
I think I agree on one thing that the end goal is a specified AFR for a given set of conditions and there are several ways to get to that goal. So now all we have to do is find the best way to reach our goal right?
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From: Lower Alabama
Has anyone looked at what a professional tuner does? Do they rely on MAF changes with a stock MAF or IFRs? Both? I dont want to take the easy way out but I want a reliable tune also.
(EDIT) I just had a thought. In my case my MAF values look extremely similar to the Monaro values. Could I use this as well as an IFR adjustment. This way I would be tweaking the IFRs less and using a MAF table that was at least calculated for a MAF at some point. Or is this just complicating matters?
(EDIT) I just had a thought. In my case my MAF values look extremely similar to the Monaro values. Could I use this as well as an IFR adjustment. This way I would be tweaking the IFRs less and using a MAF table that was at least calculated for a MAF at some point. Or is this just complicating matters?
Last edited by way2slow; Mar 9, 2005 at 09:32 AM.
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Originally Posted by RedHardSupra
using IFR to manipulate airflow is like using MAF to adjust for new injectors
IFR is MAP based (Fuelflow).
MAF is g/sec (g/cyl, AirFlow).
IFR is like rejetting a carb. FWIW.