Using VCM Scanner to check AFR at WOT
Using VCM Scanner to check AFR at WOT I have had a good tune on my truck for quite some time now, and I know the AFR is right where it should be. However, this week, I decided to install a set of long tube headers, ORY pipe, and exhaust. I've noticed a good bit of additional power, and would like to check my afr at wot.
I'd rather not buy a wideband just to check my afr one time...
Obviously without a wideband, I know I cant get an accurate reading. However, I heard I could use VCM Scanner as a narrow band to see what the fuel trims are doing...
I setup a scanner to monitor stft, ltft, AFR commanded lo/hi, rpm, tps, but I dont know what the hell im doing.
I was hoping someone here would understand what I am trying to do, and tell me how to do it. Hahaah.
Thanks
I've attached my tune. Disregard the name, its after the header install. (note the rear o2s removed from dtc).
I'd rather not buy a wideband just to check my afr one time...
Obviously without a wideband, I know I cant get an accurate reading. However, I heard I could use VCM Scanner as a narrow band to see what the fuel trims are doing...
I setup a scanner to monitor stft, ltft, AFR commanded lo/hi, rpm, tps, but I dont know what the hell im doing.
I was hoping someone here would understand what I am trying to do, and tell me how to do it. Hahaah.
Thanks
I've attached my tune. Disregard the name, its after the header install. (note the rear o2s removed from dtc).
Last edited by Justhereforinfo; Dec 18, 2015 at 12:21 PM. Reason: grammar
As you found out you need a W/B for WOT tuning. However you can use the narrow band and LTFT to tune idle and part throttle tuning.
One of the great things about HPT is the histograms. You can create a histogram to log LTFT against the VE table and/or MAF table(depending on what PCM you are using)
There are some reasonably priced W/B controllers out there. If you are using HPT to log it you actually don't have to buy a gauge.
I am assuming you have the Pro version w/ the inputs in the side of the VCM.
Personally I stopped using AFR and went to Lambda. IMO it's muuuch easier.
All widebands are Lambda sensors, all factory PCM's are Lambda based. The manufacturer then converts it to AFR in regards to the fuel type to determine stoich
100% gasoline is 14.68
E10 is 14.2x
E85 is 9.85
Lambda for gasoline, E10, E85 and whatever other fuel is 1.0
Using Lambda when scaling the VE and MAF IMO is much easier. For example is you are commanding 1.0 and your wideband is showing .90 you need to take 10% of fuel out so your actual matches your commanded.
Also logging Lambda in HPT you can set up user defined PIDs such as Commanded Lamda and Lamda Error. Plug those into a histogram and it will show you how much your fueling is off at any given cell.
I know a lot of people use AFR and are very very good at it. For me it was easier to learn and stick with Lambda.
Just my .02
One of the great things about HPT is the histograms. You can create a histogram to log LTFT against the VE table and/or MAF table(depending on what PCM you are using)
There are some reasonably priced W/B controllers out there. If you are using HPT to log it you actually don't have to buy a gauge.
I am assuming you have the Pro version w/ the inputs in the side of the VCM.
Personally I stopped using AFR and went to Lambda. IMO it's muuuch easier.
All widebands are Lambda sensors, all factory PCM's are Lambda based. The manufacturer then converts it to AFR in regards to the fuel type to determine stoich
100% gasoline is 14.68
E10 is 14.2x
E85 is 9.85
Lambda for gasoline, E10, E85 and whatever other fuel is 1.0
Using Lambda when scaling the VE and MAF IMO is much easier. For example is you are commanding 1.0 and your wideband is showing .90 you need to take 10% of fuel out so your actual matches your commanded.
Also logging Lambda in HPT you can set up user defined PIDs such as Commanded Lamda and Lamda Error. Plug those into a histogram and it will show you how much your fueling is off at any given cell.
I know a lot of people use AFR and are very very good at it. For me it was easier to learn and stick with Lambda.
Just my .02
Thanks, I appreciate the responses. I found the AEM EUGO for like $150 new on ebay with the newer style bosch sensor. So I'll probably pick that up for WOT tuning.
Lets see if I follow your theory on part throttle. First, I assume you think I will need to retune part throttle since Ive added a higher flowing exhaust. While the truck runs fine, i do smell gas (thought it was the deletion of the cats), but it wouldn't kill me to verify my fuel trims, since I do have HPT Pro. Might as well use it.
So you are saying to setup a histogram to log LTFT vs MAF or VE. I don't know if my tune is maf or ve or both. How can I tell?
So once I have collected this data in the histogram, I can use it to modify another table to better tune part throttle?
I should mention. The truck is an 03 that had a 4.8. I swapped in a 5.7 243 heads and custom cam/springs. Everything else is from the 4.8. I had it tuned by a good shop, then bought HPT to fine tune the idle, since it wasn't good enough for me. I'm currently happy with the way it runs, but I'd like to check WOT AFR since the tune is commanding 12.35 and my dyno chart shows 12.86. Worried the exhaust may put me into the higher 13:1 range, or worse...
Lets see if I follow your theory on part throttle. First, I assume you think I will need to retune part throttle since Ive added a higher flowing exhaust. While the truck runs fine, i do smell gas (thought it was the deletion of the cats), but it wouldn't kill me to verify my fuel trims, since I do have HPT Pro. Might as well use it.
So you are saying to setup a histogram to log LTFT vs MAF or VE. I don't know if my tune is maf or ve or both. How can I tell?
So once I have collected this data in the histogram, I can use it to modify another table to better tune part throttle?
I should mention. The truck is an 03 that had a 4.8. I swapped in a 5.7 243 heads and custom cam/springs. Everything else is from the 4.8. I had it tuned by a good shop, then bought HPT to fine tune the idle, since it wasn't good enough for me. I'm currently happy with the way it runs, but I'd like to check WOT AFR since the tune is commanding 12.35 and my dyno chart shows 12.86. Worried the exhaust may put me into the higher 13:1 range, or worse...
I didn't necessarily feel that you will need to retune part throttle. I thought since you were wanting to check WOT you would want to check idle/part throttle also.
Unless the MAF has been removed from the truck, or the MAF has been turned off in the tune, you have both MAF and VE(from the MAP sensor) Below 4500rpm the PCM uses both the VE and MAF. Above 4500 it uses the MAF.
Reason being is the MAF is accurate as long as it has a constant smooth flow of air across it(WOT or hard part throttle driving)However in stop and go driving(city) where you are constantly on and off the throttle the MAP is much more accurate because it monitors the engine vacuum that changes very quickly.
GM uses both MAF and MAP
Ford uses MAF only but it also uses the TPS(alpha-n)to determine engine load. The PCM has a "virtual" MAP reading that it is displays after doing some crazy math.
Chrysler uses just MAP(not sure if that's the case w/ the Hellcats)
To tune the VE table you will need to fail the MAF so it's running off the VE only. Turn off DFCO and COT protection to ensure the PCM isn't adding/subtracting fueling that you don't know about. DO NOT GO MORE THAN 50% throttle and don't go above 4k rpm.
Use the histogram VE - LTFT. Change the cell hit count to 5.
After you dial the VE in then enable it where the MAF takes over at a very low RPM. I normally put 400. That way it's running soley off the MAF and not the VE.
You will have to make a custom histrogram to do the MAF - LTFT which isn't too hard to do.
Unless the MAF has been removed from the truck, or the MAF has been turned off in the tune, you have both MAF and VE(from the MAP sensor) Below 4500rpm the PCM uses both the VE and MAF. Above 4500 it uses the MAF.
Reason being is the MAF is accurate as long as it has a constant smooth flow of air across it(WOT or hard part throttle driving)However in stop and go driving(city) where you are constantly on and off the throttle the MAP is much more accurate because it monitors the engine vacuum that changes very quickly.
GM uses both MAF and MAP
Ford uses MAF only but it also uses the TPS(alpha-n)to determine engine load. The PCM has a "virtual" MAP reading that it is displays after doing some crazy math.
Chrysler uses just MAP(not sure if that's the case w/ the Hellcats)
To tune the VE table you will need to fail the MAF so it's running off the VE only. Turn off DFCO and COT protection to ensure the PCM isn't adding/subtracting fueling that you don't know about. DO NOT GO MORE THAN 50% throttle and don't go above 4k rpm.
Use the histogram VE - LTFT. Change the cell hit count to 5.
After you dial the VE in then enable it where the MAF takes over at a very low RPM. I normally put 400. That way it's running soley off the MAF and not the VE.
You will have to make a custom histrogram to do the MAF - LTFT which isn't too hard to do.
To make changes to your tune using a histogram you want to click in the top left empty box of the histogram. This will turn the entire histogram blue. Select "Copy" Then go into your VE table, some vehicles have a primary and secondary VE table. Click in the top left empty box, it will turn the entire VE table blue, then select paste special %.
What this does is the information from your histogram, +/- fuel trims and then makes changes in your VE table.
If you have a secondary VE table, after you "paste special %" and the changes are made, click in the top left empty box and "copy w/ labels" open up your secondary VE table and paste.
What this does is the information from your histogram, +/- fuel trims and then makes changes in your VE table.
If you have a secondary VE table, after you "paste special %" and the changes are made, click in the top left empty box and "copy w/ labels" open up your secondary VE table and paste.
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Verdad Gallardo The reason there is an extra step IF you have a secondary VE table is this.
The primary table has more resolution. On the left side of the screen where the MAP is listed, it will list 15-20-25-30 kPa and so on. In the secondary it will list 20-30-40-50 and so on. Since the primary table is more detailed you can't just copy/paste into the secondary because the secondary table doesn't have as many cells. Copy w/ labels will only copy/paste the cells that match.
I've never tuned a 03' so I don't know if it has a secondary table or not. I just wanted to throw it out there in case you do or anyone else reading this has a secondary table.
The strange thing is even though the primary table has more resolution, the PCM uses the secondary table for VE fueling(if you have a secondary)
The primary table has more resolution. On the left side of the screen where the MAP is listed, it will list 15-20-25-30 kPa and so on. In the secondary it will list 20-30-40-50 and so on. Since the primary table is more detailed you can't just copy/paste into the secondary because the secondary table doesn't have as many cells. Copy w/ labels will only copy/paste the cells that match.
I've never tuned a 03' so I don't know if it has a secondary table or not. I just wanted to throw it out there in case you do or anyone else reading this has a secondary table.
The strange thing is even though the primary table has more resolution, the PCM uses the secondary table for VE fueling(if you have a secondary)
Damn, already bought the EUGO. the price was right... I had an NGK AFX a while back on my fox body, but i think they have been superceded by something more expensive.
I attached my tune to my first post, but I guess it didn't show up.
I really appreciate the explanations. It invaluable, and pretty hard to come by. I actually think I understand the majority of it too.
Thanks again. I'll get crackin as soon as the wideband gets in.
I attached my tune to my first post, but I guess it didn't show up.
I really appreciate the explanations. It invaluable, and pretty hard to come by. I actually think I understand the majority of it too.
Thanks again. I'll get crackin as soon as the wideband gets in.