AFR and Timing Tuning (02 Regal GS 223k!!!)

[PWNED]

I really don't know where to start on how to explain this car. Basically I bought the car from a friend and my mods are in the sig. Never seen a wideband in its life until today! Initially at wot it was running 10.6. Well I had to fix this. Now running 11.5-11.0 (redline)

Upon tuning I started seeing KR 2-4* 5200-6000rpm. I had the AFR's perfect 11.5-11.6 at wot. Now I started taking away timing to see if it would drop the KR down which at wot it was set to 13-14*. I dropped it down to 11-12* with no change at all. So I decided to add about 2% of fuel from 9500hz up. Initially its hits 11.6 and the closer to red line it gets its right around 11.0. With the timing untouched I get around 1* KR.

I will post up logs/tunes below. Now my previous gtp had an s1x cam and headers and running 18* timing at wot with a 11.3-11.5AFR.

Do I need headers to run a 11.5AFR and more timing? Or even rockers as well to get to 15* timing plus???? Is this a normal characteristic?

I spent a good 2hrs with the below logs/tunes. I wont post them all but I did 14 changes pretty much bit by bit.

----Note--- I have the wideband in the crossover pipe as there is a bung in it.

[PWNED]

Below are screen shots of what I can hopefully call progress.

Any help is appreciated!

First is the current tune

Second is the tune before me adding that 2% fuel.

Last is what I started with pretty much.

[Shane Hewitt]

Based on the assumption that you did these pulls on the same stretch of road, it would appear you picked up 13'ish whp, so progress for sure.

Regal.jpg

My experience with my own GTP taught me that a backpressure gauge is an invaluable tool with these cars. I too battled with ongoing KR issues until I finally stuck a backpressure gauge in one of my o2 sensor bungs & found that my Dynomax catback (basically a mandrel bent stock exhaust) was causing over 20 psi of backpressure! Upgrading to a 3 inch system resolved my problem.....backpressure & KR gone. I'm not suggesting that is the issue with your car, moreso suggesting to take some readings & make an educated decision on how to proceed further.

[PWNED]

Based on the assumption that you did these pulls on the same stretch of road, it would appear you picked up 13'ish whp, so progress for sure.

Regal.jpg

My experience with my own GTP taught me that a backpressure gauge is an invaluable tool with these cars. I too battled with ongoing KR issues until I finally stuck a backpressure gauge in one of my o2 sensor bungs & found that my Dynomax catback (basically a mandrel bent stock exhaust) was causing over 20 psi of backpressure! Upgrading to a 3 inch system resolved my problem.....backpressure & KR gone. I'm not suggesting that is the issue with your car, moreso suggesting to take some readings & make an educated decision on how to proceed further.

Yes it was the same stretch but depending which way will have an effect. Its the safest road with no homes by me. But I am running a stock muffler that has the seems blown out of it. I will try and target low 11s and get some timing in there along with placing the WB in the rear manifold rather than the crossover.

[PWNED]

Ok guys/gals we all know how I had the WB in the crossover pipe. With only minor changes from 7500-9500ish in the maf (1% more fuel was added) But initially beyond that I did not touch anything. Before I was hitting 11.1 afr in the crossover. Now in the rear manifold I hit 11.0. On the initial hit I get 11.8 afr and then taper to 11.0. With a few timing tweaks I am happy enough where it sits for what it is. I may or may not leave the lQ4 maf in (meaning if I go stock maf I need to redo everything, but by then I may just leave the stock maf table alone and tweak the IFR table if I get some insight on that)

[PWNED]

To add to my confusion

With these tables being 0'ed out does this mean I am never truly adding fuel in PE mode??

[PWNED]

I basically "hacked" the maf table to compensate for what I have 0'ed out. Is PE even functional now?

Trying to understand these tables is a bit confusing as for a v8 they have a PE vs RPM which is a super easy layout to modify unlike our cars.

These are the stock files below. With a little reading in the hpt help I am still a bit confused.

--Power Enrich Fuel Adder vs. Throttle Position Sensor-- This table adds to the base AFR in relation to throttle position. It is generally used to lean the fuel at smaller throttle settings.

--Power Enrich Fuel Adder vs. RPM vs. Time-- This table adds to the base AFR in relation to RPM and time in PE mode. It is used to provide additional RPM and time based enrichment and is similar to the PE vs RPM table on V8 engines, but with an additional time component. Remember, this value adds to the Base PE AFR so positive numbers here are leaner and negative numbers are richer.

Enrichment Rate: This is the rate at which Fuel is added to reach the desired enrichment value. The smaller this value is, the slower the VCM will reach the desired PE AFR. For instance if your non pe commanded EQ ratio is 1.0 and your pe commanded EQ ratio is 1.300 and your enrichment rate is set to .3 it would take 1 step ~10ms for most pcms to reach full PE.

In stock form we have a commanded afr of 12.4 at operating temp which is lean. Now in the Fuel Adder vs. TPS we have 0 after 70% so it does not lean anything out. What if I left the stock values up to 15 tps %, will this net me better mpg's at all? Should I really be touching this area at all? Next we have the Power Enrich Fuel Adder vs. RPM vs. Time. This is super confusing due to the layout and not understanding the numbers. We can all agree that from the factory the cars run rich for safety. With that being in mind it is right around 10.8 afr at wot I would guess. We have that 12.4 commanded afr and according to the chart a -1.000 to -3.000 in the 5600-6400rpm to make things richer. Do these numbers have an actual value meaning? How will I know exactly which area to have a + or - number in the correct column according to seconds? I would like to put my stock maf back in with table, leave it alone and tune this table instead. Will fuel trims be affected by this table when not in PE? Will some maf tweaking still need to be done in the lower half to compensate?

[Shane Hewitt]

As it is set up right now (AFR22.hpt), any time the conditions to enable PE are met the car is commanding an air/fuel ratio of 11.5:1, as none of the other adders are modifying that value....which is fine for now.

Now by looking at your config file, I'm guessing that you are simply modifying your MAF table to get your desired air/fuel ratios?

If that is the case, there is a better way!

Here is the config I use when tuning these cars.

GTP.cfg

Histogram #10 is your best friend. It compares what the commanded air/fuel ratio is to what the measured air/fuel ratio is in each of the cells in your MAF table & provides you with an error % (air/fuel ratio error). Load this config & go for a nice long drive to get lots of data (you may need to substitute whatever wideband you are using in place of my PLX). Before you start logging, go into the VCM Controls tab in the scanner & click on the Fuel & Spark tab & then click the Closed Loop Off button, & the Reset Fuel Trims button.....this is essential or you will be chasing your tail. Once you have lots of cell hits in all the cells, highlight the entire histogram, right click & copy. Go to your MAF table in the editor, highlight the entire table, paste special, & multiply by %. This will modify your entire MAF table by the error percentage you recorded (I normally like to smooth this at least once at this point). Flash this to the car & you are done with the MAF. Now the air/fuel ratio that the pcm is commanding is going to be extremely close to what you are going to observe with your wideband.

Once this is done, if you want to richen the car up from say 11.5 to 11.2....simply change the value in your PE Fuel Base, & what you will observe on your wideband will be extremely close to what you are commanding. So much simpler than trying to manipulate your MAF to try to achieve your desired air/fuel ratios.

Once this is done & commanded vs actual are actually matching, now you can start monkeying around with the adder tables & achieve predictable results.

[PWNED]

As it is set up right now (AFR22.hpt), any time the conditions to enable PE are met the car is commanding an air/fuel ratio of 11.5:1, as none of the other adders are modifying that value....which is fine for now.

Now by looking at your config file, I'm guessing that you are simply modifying your MAF table to get your desired air/fuel ratios?

If that is the case, there is a better way!

Here is the config I use when tuning these cars.

GTP.cfg

Histogram #10 is your best friend. It compares what the commanded air/fuel ratio is to what the measured air/fuel ratio is in each of the cells in your MAF table & provides you with an error % (air/fuel ratio error). Load this config & go for a nice long drive to get lots of data (you may need to substitute whatever wideband you are using in place of my PLX). Before you start logging, go into the VCM Controls tab in the scanner & click on the Fuel & Spark tab & then click the Closed Loop Off button, & the Reset Fuel Trims button.....this is essential or you will be chasing your tail. Once you have lots of cell hits in all the cells, highlight the entire histogram, right click & copy. Go to your MAF table in the editor, highlight the entire table, paste special, & multiply by %. This will modify your entire MAF table by the error percentage you recorded (I normally like to smooth this at least once at this point). Flash this to the car & you are done with the MAF. Now the air/fuel ratio that the pcm is commanding is going to be extremely close to what you are going to observe with your wideband.

Once this is done, if you want to richen the car up from say 11.5 to 11.2....simply change the value in your PE Fuel Base, & what you will observe on your wideband will be extremely close to what you are commanding. So much simpler than trying to manipulate your MAF to try to achieve your desired air/fuel ratios.

Once this is done & commanded vs actual are actually matching, now you can start monkeying around with the adder tables & achieve predictable results.

Correct I am modifying the maf to get the desired afr under wot. This sounds like a much simpler way. I will want say a 15 minute log? Do I want from idle all the way to wot ? Will letting off the accelerator screw things up? What about when I am in cruise, will the 14.7 get screwy? I know there must be a table for this that I don't want to touch. In doing so will it bring my fuel trims right in?

[Shane Hewitt]

Correct I am modifying the maf to get the desired afr under wot. This sounds like a much simpler way.

I will want say a 15 minute log? The more hits you can get in each cell the better the average will be......the more data the better.

Do I want from idle all the way to wot ? Yes, you want to cover the entire MAF table.

Will letting off the accelerator screw things up? DFCO can have an impact. Flashing a file to disable it prior to doing this will resolve that

What about when I am in cruise, will the 14.7 get screwy? The actual air/fuel ratio being commanded doesn't really matter as the histogram is looking at the error between what was commanded & what was observed.

I know there must be a table for this that I don't want to touch. In doing so will it bring my fuel trims right in?

Your fuel trims will be very close afterwards.

[PWNED]

Your fuel trims will be very close afterwards.

Will letting off the accelerator mess with anything? I could have sworn when a maf calibration is done that that can screw things up (but is not done the way you are stating as you don't want to hit PE)

With your way I am just going to drive in the city (stop and go), on the highway and do some wot runs all in one scan?

As it is in cruise I think my trims were close to +/- 4 But letting off the gas the ltft will go to -17. At idle and city driving (low tps) around -7 ltft and at wot the st/lf lock at 0.

[MMGT1]

Look at a scan you have that includes "coastdown"... in table view you will see the "Fuel Trim Cell" you are in while in DFCO. Take note of which cell that is. Then in your histogram filter that PID so it is ignored in the scan play back. Set the number of cell hits required to 50 or more for accurate results. Apply the error by % half as the guys have said and in just a couple of goes you will have your MAF dead on. Drive for a good 25 min to a half hour to acquire good data before making changes. Also, make sure the car is at full operating temp before you start to scan.

[PWNED]

Look at a scan you have that includes "coastdown"... in table view you will see the "Fuel Trim Cell" you are in while in DFCO. Take note of which cell that is. Then in your histogram filter that PID so it is ignored in the scan play back. Set the number of cell hits required to 50 or more for accurate results. Apply the error by % half as the guys have said and in just a couple of goes you will have your MAF dead on. Drive for a good 25 min to a half hour to acquire good data before making changes. Also, make sure the car is at full operating temp before you start to scan.

I will try this after when I have a free day to do so. I am a bit confused but I will poke around and see. What is DFCO? With flashing a file to disable is this needed? Safe? Or just ignore? I have not seen "coastdown" before. Is this in the scanner histogram somewhere?

[MMGT1]

DFCO is when your PCM turns your engine into an air pump. Look at a scan where you are cruising along and then you let off the gas to begin breaking, you will see that your timing drops, fuel cuts and your reported AFR or Lambda pegs completely lean. When this happens you are in DFCO. While looking at that section in chart view for example, you can then open your table view and there is a PID called Fuel Cell that is running. Make a note of the Fuel Cell your car is in when DFCO is active. Then in the histogram that you are using to make fuel adjustments, you use the filter in settings to filter that cell from your scan. Once you filter that cell, your scan will not report any values when that cell is being referenced. This will keep the areas of your MAF/VE from being poisoned with inaccurate data. DFCO will make your scan look like you are dead lean and you will add a ton of fuel, then when you go through those cells when not in DFCO you will be so rich that you will flood your engine with fuel, possibly bad enough to actually wash down rings causing very serious engine damage. You really need to make sure DFCO is filtered from your scans, its an important one.

[PWNED]

DFCO is when your PCM turns your engine into an air pump. Look at a scan where you are cruising along and then you let off the gas to begin breaking, you will see that your timing drops, fuel cuts and your reported AFR or Lambda pegs completely lean. When this happens you are in DFCO. While looking at that section in chart view for example, you can then open your table view and there is a PID called Fuel Cell that is running. Make a note of the Fuel Cell your car is in when DFCO is active. Then in the histogram that you are using to make fuel adjustments, you use the filter in settings to filter that cell from your scan. Once you filter that cell, your scan will not report any values when that cell is being referenced. This will keep the areas of your MAF/VE from being poisoned with inaccurate data. DFCO will make your scan look like you are dead lean and you will add a ton of fuel, then when you go through those cells when not in DFCO you will be so rich that you will flood your engine with fuel, possibly bad enough to actually wash down rings causing very serious engine damage. You really need to make sure DFCO is filtered from your scans, its an important one.

Will the above config enable me to filter out what you are mentioning? Or does this have to be set up before hand.

[PWNED]

It has been very cold/bad weather so I have not been able to get the wideband on the car like instructed. I did how ever get a few scans (normal driving) no wot on my way to work (10 minutes).

Is there anyway to get my trims in check a little better as what is seen in the scan? To net me some better mpgs?

C1 is from yesterday (after the scan I removed 2% of fuel from 5200-2500hz) Today's scan is C2 showing if that change did anything to help until I get the wb on.

What is the best way to go about this? Trim the injector flow rate a little bit? Or just subtract fuel from the maf (I know I have an lq4) but compared to stock maf file mine is scaled down a noticeable amount.

There is my (regal1) histogram and the (gtp) supplied in an earlier post.

Can someone screenshot where the "coastdown" selection is in the fuel trim cell?

[gn2beatu]

You will not get better mpg's by trimming fuel unless your running open loop. The ECM will just compensate. Im not able to look at your tune/logs now but dont subtract fuel for mileage, you will just throw your trims off. Your long term fuel trims are off and you should get them dialed in. Once that is done you can run an open loop tune and lean out the areas in hwy mode to 16.1 AFR. Just know that you wont see much differance in mpg. Youd think youd get 10% better milleage due to the leaner mixture, but your actually better off keeping closed loop and running more timing in light throttle areas. Believe it or not, these cars like close to if not up to 40 degrees of timing in light throttle kpa areas under 2500rpm. That is where you will see your milleage. You can also play with decel fuel cut and EGR to increase mpgs but wont see much as there are not allot of tables in the 3800 for the EGR to play with.

As to your WOT AFR, I agree with the other poster, these cars like 11.2 AFR.