Why is it important to get the A/F right on when the Fast system will correct it for you on a run? If you have it set for a certain boost then you turn the boost up or down the ratio will be off from that perfect setting, will it not? Is there power to be had for zero corrections by the Fast in closed loop? I am talking about corrections in the 5 to 10 percent range
A/F correction
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Ricky Trussell
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My understanding is the 02 correction will be slower so you want it doing as little work as possible. It seems to me looking at my logs that the 02 correction lags which makes swings. 5% correction would not be something I would worry about though. If you are that close take your time trying to get it lower.
Turning boost up puts the reading in a higher KPA so you will need to tune that area.
Turning boost up puts the reading in a higher KPA so you will need to tune that area.
BoostKillsStres
TIRE-FRYER VIA HAIR-DRYER
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Well having a perfect fuel curve would be, well perfect, but thats basically impossible because of many factors which will have an effect on A/F consisting of but not limited to: timing, engine temp, air temp, humidity, altitude, boost, intake air temp and so on. Thats where the wideband is a fantastic piece of equipment for helping to make automatic corrections based on those variables and showing you those corrections made so you can then correct your base tables.
You want a base fuel curve as close as possible obviously so the WB doesn't have to make large corrections. Think of it this way, if the WB is having to make a 20% correction at one point in the map then gets to a point where 0% correction or even negative correction is needed, well your going to have a transition period where the WB correction is removed which is a period of time where you'd be better off with a more consistant and correct base table so the A/F would stay closer to the target. So you do have something to gain with smaller WB corrections to the base tables, aka fewer transitional corrections periods. Not to mention the WB correction process is a toss up between being able to make fast corrections to get to target quickly to protect parts and being able to make small corrections once on target to maintain the target.
As for different boost levels or octane levels I would imagine more than one program would be suggested, low boost street octane and high boost race octane and anything inbetween depending of course on how you like to and mostly drive the car.
my 2 cents.
HTH
You want a base fuel curve as close as possible obviously so the WB doesn't have to make large corrections. Think of it this way, if the WB is having to make a 20% correction at one point in the map then gets to a point where 0% correction or even negative correction is needed, well your going to have a transition period where the WB correction is removed which is a period of time where you'd be better off with a more consistant and correct base table so the A/F would stay closer to the target. So you do have something to gain with smaller WB corrections to the base tables, aka fewer transitional corrections periods. Not to mention the WB correction process is a toss up between being able to make fast corrections to get to target quickly to protect parts and being able to make small corrections once on target to maintain the target.
As for different boost levels or octane levels I would imagine more than one program would be suggested, low boost street octane and high boost race octane and anything inbetween depending of course on how you like to and mostly drive the car.
my 2 cents.
HTH
Boost thanks that makes sense. Since there are so many factors that affect the perfect tune as you mentioned, it seems impossible to have that tune for more then 1 run. All the variables that affect the tune will change from run to run? The next time you race at a different track or day wont that near perfect tune be out of wack each time? Seems like the tune is an ongoing process that is as much a part of each pass as the components on your car? That explains why my tune looks off each time I run the car on different days and tracks.
BoostKillsStres
TIRE-FRYER VIA HAIR-DRYER
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RT, Well the tune is a never ending process but once you get a good base WOT full load tune at a particular boost level the WB correction should be in a small % range so then only minor adjustments should be needed and a bit of work needed tuning higher kpa regions as Ricky said for higher boost levels. Boosted applications just impart more variables into the mix and of course TR people are pretty much after all the boost they can get with the small cubic inches anyway. I'm fixing to start tuning my WB chip on a friends upcoming install of a 274 inch non stage engine w/ fully ported M&A's and a BBT70 in his street T so thats gonna be a blast. 
ski_dwn_it
Member
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- May 3, 2005
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- 96
Just went through this with my tune on my car.
Although its not fast, but DFI I used the following to get mine on.
Make a pass. Come back and make new log with just in 3rd gear. Overlay this information and see what corrections are being made. Use that percent so .92 o2 correction for particular cell. I would take (cell value x .92) = new value. I did this for each of cells used for the run. Repeated each time and now the correction is VERY minimal. ~1-2% for each run.
Now more specific to the topic. Advantages of having as little of correction as possible. I race at MANY different tracks at different elevations. And also as many of you experience, at much different DAs. The system works perfectly to give me my desired AFR every run no matter what the DA or track I am at.
I can't really say for absolute sure the car is running any quicker, even moving from stock ECM, but the car is definately more predictable. Predictable in the sense now that I do not see as much swing in the ETs from day to day or through the day as DA changes.
I guess the way I look at it is you have a very capable system that can deliver near dead on AFRs with VERY VERY little effort to get perfect. Why not take advantage of it. I was able to get mine within 5% in the first 4 runs of having the system using the above method. And withing 1-2% with a few more passes. Since then with much different track conditions I have seen as much at 8% correction but the ETs are where I predicted them to be. In my book that is about as good as it gets.
One other thing is I like the fact that once I get the AFR dialed in, I can change the spark advance and know that I am still getting the same AFR, granted with some extra correction, but the AFR is spot on. This allow 1 dimensional changes to be made. Unlike with the stock ECM if you add timing you may see the AFR lean out. So was the gain or loss from adding the timing or leaning it out. With the DFI I know the reason cause their was only 1 true change.
I want to get to a dyno cause I think that will be super easy to see what the car wants. My plan of attack would be. Run the car for a baseline. Then add fuel across the boards. Areas of the RPM range that benefit from the added fuel, keep the new setting in those areas. Do this several times and you would quickly discover the best AFR for different RPM ranges your motor likes. You can do the same with spark adance and work between fuel and spark for fine tuning of power. It makes it MUCH MUCH easier.
I personally was a HUGE advocate of the stock ECMs and still think they have their place and have tune MANY MANY very fast n/a setups on stock ECMs, but these aftermarket ones are SO much easier to dial in.
Although its not fast, but DFI I used the following to get mine on.
Make a pass. Come back and make new log with just in 3rd gear. Overlay this information and see what corrections are being made. Use that percent so .92 o2 correction for particular cell. I would take (cell value x .92) = new value. I did this for each of cells used for the run. Repeated each time and now the correction is VERY minimal. ~1-2% for each run.
Now more specific to the topic. Advantages of having as little of correction as possible. I race at MANY different tracks at different elevations. And also as many of you experience, at much different DAs. The system works perfectly to give me my desired AFR every run no matter what the DA or track I am at.
I can't really say for absolute sure the car is running any quicker, even moving from stock ECM, but the car is definately more predictable. Predictable in the sense now that I do not see as much swing in the ETs from day to day or through the day as DA changes.
I guess the way I look at it is you have a very capable system that can deliver near dead on AFRs with VERY VERY little effort to get perfect. Why not take advantage of it. I was able to get mine within 5% in the first 4 runs of having the system using the above method. And withing 1-2% with a few more passes. Since then with much different track conditions I have seen as much at 8% correction but the ETs are where I predicted them to be. In my book that is about as good as it gets.
One other thing is I like the fact that once I get the AFR dialed in, I can change the spark advance and know that I am still getting the same AFR, granted with some extra correction, but the AFR is spot on. This allow 1 dimensional changes to be made. Unlike with the stock ECM if you add timing you may see the AFR lean out. So was the gain or loss from adding the timing or leaning it out. With the DFI I know the reason cause their was only 1 true change.
I want to get to a dyno cause I think that will be super easy to see what the car wants. My plan of attack would be. Run the car for a baseline. Then add fuel across the boards. Areas of the RPM range that benefit from the added fuel, keep the new setting in those areas. Do this several times and you would quickly discover the best AFR for different RPM ranges your motor likes. You can do the same with spark adance and work between fuel and spark for fine tuning of power. It makes it MUCH MUCH easier.
I personally was a HUGE advocate of the stock ECMs and still think they have their place and have tune MANY MANY very fast n/a setups on stock ECMs, but these aftermarket ones are SO much easier to dial in.
Let's look a worst-case scenario.
The low end of your VE table requires a lot of extra fuel added (i.e. the VE tables make your engine run lean), and the high end of your table requires fuel to be taken out.
As you go through the bottom of the RPM range, your O2 correction will add fuel. Then as your RPMs increase, fuel will be taken away. Then comes the shift point- here is the problem. Since the RPMs drop rapidly from 6000 to 3500 RPM (or whatever) and the WB is removing a lot of fuel, you will be in a situation where you have a VE table that is making your car lean, and an O2 correction that is pulling out even more fuel- the O2 correction hasn't yet reacted to the lean condition, so it is still pulling out fuel from the high RPM range.
I don't have to tell you what running THAT lean will do to your motor!
Remember that the WB is a reactionary device, and makes changes based on what was happeneing at a previous point in time, not the present.
There are other dynamic conditions that will also cause problems with your fuel curve. Take the time to get your VE tables close.
-Bob Cunningham
The low end of your VE table requires a lot of extra fuel added (i.e. the VE tables make your engine run lean), and the high end of your table requires fuel to be taken out.
As you go through the bottom of the RPM range, your O2 correction will add fuel. Then as your RPMs increase, fuel will be taken away. Then comes the shift point- here is the problem. Since the RPMs drop rapidly from 6000 to 3500 RPM (or whatever) and the WB is removing a lot of fuel, you will be in a situation where you have a VE table that is making your car lean, and an O2 correction that is pulling out even more fuel- the O2 correction hasn't yet reacted to the lean condition, so it is still pulling out fuel from the high RPM range.
I don't have to tell you what running THAT lean will do to your motor!
Remember that the WB is a reactionary device, and makes changes based on what was happeneing at a previous point in time, not the present.
There are other dynamic conditions that will also cause problems with your fuel curve. Take the time to get your VE tables close.
-Bob Cunningham
