Hey guys, I finally got my Roush tvs installed on my 5.0 and have been running around on the roush tune. Needless to say, I purchased a better tune and began some datalogging. My question is in regards to AFR and fuel trims. My logs during WOT show STFT on both banks around .84 in the mid rpm range. Measured AFR drops to as low as .73 % lambda (10.2) on both banks. I did request a conservative tune, but this doesn't seem right, does it? I am in contact with the tuner, but I figured I'd get a quicker idea on here. Thanks.
TVS Tuning - Short term fuel trims / AFR
- Thread starter BrianH87
- Start date
Wow! Roush tvs here. Stft around 1-0.98, afr 0.80 -0.79 lambda
Your stft is adding way too much fuel. Who is your tuner? Mine is tuned by Justin @ vmp.
Your stft is adding way too much fuel. Who is your tuner? Mine is tuned by Justin @ vmp.
As far as the tuners name goes, lets just say it's one of the well known TVS tuners. I'm not saying anything bad, I'll wait for my response from him. For comparison's sake, I put the Roush tune back on. I did a few logs with that tune and the short terms fuel trims never deviate much from 1 on both banks. Measured AFR on both banks around .78 - .80. I would think that this rules out a problem with my vehicle. No CEL's or anything. Even though the Roush tune is weak from 1-3000 rpm's, it seems to pull pretty good from 3000 to redline. I may end up just sticking with the Roush tune.
Where about in pitt are you? Did you go to Wolfpack?
Rodeheaver's in Uniontown uses AED, he is pretty good. I tuned remotely with James Gordon of tuning by james and I will tune with him for life...I would not accept what you have.
I'm in Forest Hills, just east of town. I have heard of Wolfpack, but I really didn't want a Lund tune. I may give the other place a shot. Something just doesn't add up here. I'm wondering if the tune wasn't set up correctly. I only have the base Roush TVS 575 complete kit.
Oh that's cool...Yeah Wolfpack is good to work on my car but I'm not fond of the Lund tunes anymore since my first one that since has been retuned by james. Lund is ok but I was just looking for more detail than what I thought 500$ was going to get me with him.
Tim at Rodeheaver's is great to work with. For me it's worth the drive. He does the work for me that I can't do.
James Gordon has tuned my last 2 cars and he will not avoid addressing any of your concerns.
It's really scary to me that people only find out they have tuning problems after doing their own data logging....I don't know how some of these people sleep at night after sending out some of these mail order tunes with out checking a log to confirm a good running car.
I've never actually heard of James Gordon. Is he local? If he can handle your setup, I'm sure he's quite capable of mine. I've actually been in contact with Shaun from AED and he's been very helpful thus far. And I didn't even pay him a dime yet.
If I hadn't of stumbled upon James I would definitely work with AED.
James is in Florida. He used to work for SCT. I saw him in a couple 5.0 magazines and started talking to him when I was having problems with my Lund tune in my old Kenne bell car. He really opened my eyes and is a perfectionist almost to a fault.
Once he fixed my Lund tune he had my vote....I don't know if Lund was banking on the fact that I might not notice somethings or he just said good enough for my 500$ but either way it was less than stellar and it had everything to do with drivability not power. I did not expect that from him. And my car was dyno tuned by Lund. My car never saw a dyno with James and I couldn't be happier. I dynode it at the end just for reference to see where I was at.
This is not possible, Lund tunes the fastest coyotes on the planet and has actually been touched by the hand of god to tune these cars.
Just wondering. If you see stft hovering above 1.00 does that mean you are running out of fuel? I.e either pump or injectors
No. It could mean a lot of things. The maf transfer curve might be a little off, or the weather changed, or the fuel is a little different..etc etc
Fuel trims are just that--trims. They're supposed to trim the fueling to get to the exact commanded lambda. The computer can see +/- 25% change (.75-1.25) before it even throws a trouble code.
I wouldn't worry about it.
Fuel trims are just that--trims. They're supposed to trim the fueling to get to the exact commanded lambda. The computer can see +/- 25% change (.75-1.25) before it even throws a trouble code.
I wouldn't worry about it.
So let me get this straight... I understand how LTFT and STFT work. But theses trims are just reacting to programmed values for afr, right? And those programmed values can be logged as "lambse" ? Or am I off on this?
Before the car warms up and reads the various inputs going to the ecu, the car is running based on the estimate from the tune. After a while the ecu changes the tunes "guess" to what it believes is lamba. The more accurate your tune is, the closer to 1.0 it will be. .84 is pretty far off. Datalog a cold start and you will see it go from 1.0 and creep down to the .8x you saw before.
The PCM does everything in Lambda once it knows the stoich value of the fuel (pump gas ~ 14.08)
The PCM will always try and target lambda 1.0 aka 14.08 a/f (but lets forget air to fuel ratios...they suck) unless certain conditions are met to go into WOT tables usauly RPM and Throttle %
The Desired Lambda at WOT tables are even in Lambda
So when it is using your maf table that is tuned for your application
And the end result is not what is in the WOT tables, the pcm being a closed loop system uses Short Term Fuel Trims to Trim the fuel to the correct Lambda that is commanded (WOT or light load). There will always be some sort of STFT going on as long as the PCM is in closed loop mode (monitoring the wideband 02 sensors).
With that being said... .85 is pretty far out to lunch....by my standards...and most all other reputable tuners. Try to data log Long Term Fuel Trims, they will show things such as vacuum leaks, and if you have LTFT issues AND STFT you have some issues at hand.
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