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Should LTFT be this high with Cobb SRI?
- Thread starter Lee456
- Start date
It looks like a number of people are getting LTFT's very similar to what I got. The high positive numbers seem to make sense because if you let in more air the ECU must adjust the fuel to compensate, but I was worried because I read a lot of stuff saying that anything over 4 or 5 was BAD. On the other hand, when I put an intake on my last car, a Jeep Wrangler Rubicon, it came with a module that was wired in to adjust the mixture. When I put an intake on my prior car, a BMW Z3, I got a device that hooked up to the diagnostic port and reprogramed it, sort of like a primative Cobb AP. On the Speed 3 I did nothing except let the air in and the car is compensating for it.
I posted a similar question on the other forum in a section devoted to the Cobb AP, which I was thinking of buying to correct the LTFT's, and got a number of replies that said pretty much this same thing. One said "Im presuming you are currently on the stock ECU tune. If that assumption is correct, those LTFT's are normal with your mods. So long as it is running right I wouldnt worry about it. You have increased the ability of the engine to pump air, the ECU has detected that and is compensating with the LTFT. If you WANT to correct the LTFT's, the AP with the correct tune will do it for you, but there is no NEED to."
For what it's worth, I checked the Air/Fuel ratio with the Cobb and the with the factory airbox with holes in it and they looked the same. 14's most of the time dropping to 10's at WOT. That's what really matters to the engine. I understand the ECU can only correct up to 25% and if you hit that you've got a problem. That worried me a bit when mine got up to +14.9 accelerating with the Cobb.
I had pretty much resolved myself to ignore the number's, but ended up giving up on the Cobb out of concern for the battery box breaking. Although there isn't a lot of talk about it here, quite a lot of them have broken. I have a Nano coming that should be here Wednesday. I'll see what the LTFT's are with it and post them here after I run it a couple days. I bet they will be similar to the Cobb.
I posted a similar question on the other forum in a section devoted to the Cobb AP, which I was thinking of buying to correct the LTFT's, and got a number of replies that said pretty much this same thing. One said "Im presuming you are currently on the stock ECU tune. If that assumption is correct, those LTFT's are normal with your mods. So long as it is running right I wouldnt worry about it. You have increased the ability of the engine to pump air, the ECU has detected that and is compensating with the LTFT. If you WANT to correct the LTFT's, the AP with the correct tune will do it for you, but there is no NEED to."
For what it's worth, I checked the Air/Fuel ratio with the Cobb and the with the factory airbox with holes in it and they looked the same. 14's most of the time dropping to 10's at WOT. That's what really matters to the engine. I understand the ECU can only correct up to 25% and if you hit that you've got a problem. That worried me a bit when mine got up to +14.9 accelerating with the Cobb.
I had pretty much resolved myself to ignore the number's, but ended up giving up on the Cobb out of concern for the battery box breaking. Although there isn't a lot of talk about it here, quite a lot of them have broken. I have a Nano coming that should be here Wednesday. I'll see what the LTFT's are with it and post them here after I run it a couple days. I bet they will be similar to the Cobb.
From what I've heard LTFT's between +/-10 are normal and anything between +/-20 is safe, correct me if I'm wrong. Same as Lee my A/F numbers are right around +14.7 at idle and dip as low as +10 WOT, so the car dumps in lots of fuel and runs rich, thats normal for a turbo car.
Yep, the A/F is fine with the Cobb as it was with the stock box and my old HKS intake. The only concern here is with LTFT readings.
Lee's post makes me feel better though. It makes sense that the ECU is compensating for more air coming into the engine, and it makes sense that the Cobb is showing me higher readings than the HKS did (from a performance standpoint).
Lee's post makes me feel better though. It makes sense that the ECU is compensating for more air coming into the engine, and it makes sense that the Cobb is showing me higher readings than the HKS did (from a performance standpoint).
Speed3Rookie
Member
My ltft are 0-0.8 at idle, 0-1.6 part throttle, 0 WOT and 7.8 on decel.
Most ppl don't monitor ltft until they get an intake or tuning solution.
I would wager you would be surprised that your ltft are not at zero with a stock vehicle.
I would also wager that you are not getting zero kr with a stock vehicle.
Anyone log these two yet while still stock?
Most ppl don't monitor ltft until they get an intake or tuning solution.
I would wager you would be surprised that your ltft are not at zero with a stock vehicle.
I would also wager that you are not getting zero kr with a stock vehicle.
Anyone log these two yet while still stock?
serialtoon
Member
- :
- 2008 Mazdaspeed 3
<--- NOOB ALERT! But i also have a Cobb SRI, should i be worried? What is the bad part of running a high LTFT? I can only say that i wish i had the money to dump on a car, but alas i do not. So please, feel free to indulge me on this matter. BTW, this is my first boosted car, so treat me like a noob, please.
Most ppl don't monitor ltft until they get an intake or tuning solution.
I would wager you would be surprised that your ltft are not at zero with a stock vehicle.
I would also wager that you are not getting zero kr with a stock vehicle.
Anyone log these two yet while still stock?
Exactly!
Super Unique
Member
- :
- 2008.5 Mazdaspeed 3 Black Mica
LTFT on this car while completely stock was still +5 to 7 on WOT and 2 to 3 or 3 on idle etc...
Also zero KR while stock, and still no KR with cobb SRI running amsoil filter. I have watched intently, and still not a single incident of KR either while watching data live, or long drives that were logged to SD card and retrieved for later analysis.
Also zero KR while stock, and still no KR with cobb SRI running amsoil filter. I have watched intently, and still not a single incident of KR either while watching data live, or long drives that were logged to SD card and retrieved for later analysis.
- :
- 2001 Mazda MP3
what exactly is lift? i know about knock retard... well somewhat, and of course A/F ratio... but never heard of lift... someone care to explain?
From what I've heard LTFT's between +/-10 are normal and anything between +/-20 is safe, correct me if I'm wrong. Same as Lee my A/F numbers are right around +14.7 at idle and dip as low as +10 WOT, so the car dumps in lots of fuel and runs rich, thats normal for a turbo car.
From what I've learned in a short time, anything greater than +/-10% (yes, expressed in percent) is "generally" not good.
what exactly is lift? i know about knock retard... well somewhat, and of course A/F ratio... but never heard of lift... someone care to explain?
Use the FAQ!!!
desperado-c
Member
- :
- Mazdaspeed3
LTFT
Long Term Fuel Trims
Ie., corrections to the amount of fuel that is being delivered to the injectors to compensate for increased/decreased air mass entering the intake. Without these corrections the engine would run too lean/rich. In addition to adding a less restrictive intake lots of things can affect how much air is entering the cylinders, such as warmer/colder temps and high/low humidity. All these factors can lead to corrections to LTFT. As regards an intake specifically, you want it to have LTFT readings at idle that are close to stock. That way you know that the stock ECU can make the necessary corrections to keep the air/fuel mixture within specifications.
- :
- 2001 Mazda MP3
thank you desperado
john blutarski
Member
- :
- 2004 Subaru WRX STI
My KR warning goes off all the time. It's enough to drive a good man insane... I think I'll check all my hose clamps since I've read some guys found this to help and that the stock IC and turbo inlet clamps are loose as heeell
Speed3Rookie
Member
Also zero KR while stock, and still no KR with cobb SRI running amsoil filter. I have watched intently, and still not a single incident of KR either while watching data live, or long drives that were logged to SD card and retrieved for later analysis.
I can almost guarantee you that you are the exception...not the rule.
Anyone else that's still stock that has a dh care to share their experiences?
I'm still not liking these LTFT readings. I get around 7.6 under moderate and 14.6 under heavier acceleration in 6th. I ran a few datalogs tonight... absolutely no KR though.
I guess I'll give this Cobb intake/Amsoil filter combo another gas tank or two before I take the logs really seriously.
I guess I'll give this Cobb intake/Amsoil filter combo another gas tank or two before I take the logs really seriously.
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