Tuning Question
Thread Starter
Intermediate
Joined: Aug 2017
Posts: 47
Likes: 6
From: Jacksonville Fl
Tuning Question
Good Morning everyone
I have a very simple question about tuned
Pcm. I had my 97 A4 coupe dyno'd a couple of months ago and now getting ready to start head cam and exhaust. My question is will the tune I have now be lost due to the battery being unhooked for a couple of days
I have a very simple question about tuned
Pcm. I had my 97 A4 coupe dyno'd a couple of months ago and now getting ready to start head cam and exhaust. My question is will the tune I have now be lost due to the battery being unhooked for a couple of days
Le Mans Master
Joined: Nov 2003
Posts: 8,004
Likes: 250
From: Tampa Fl
St. Jude Donor '12-'13-'14
No it wont be lost if the battery dies because the tune is burned to the computer the same way GM does it, but it probably isnt set up to maintain stability for your aftermarket cam.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
After a battery dis connect you can never loose your tune
However---The ECM has to relearn all the fuel trim data concerning altitde--air density and temperature-- as this is lost-- This is called "learning" Normally on a stockish bolt on engine the ECM will re learn the fuel trims after about 50-75 miles of normal driving--The more modded your engine is beyond bolt ons the longer it will take in miles
As mentioned if you do h s cam or LT headers you will need a retune
However---The ECM has to relearn all the fuel trim data concerning altitde--air density and temperature-- as this is lost-- This is called "learning" Normally on a stockish bolt on engine the ECM will re learn the fuel trims after about 50-75 miles of normal driving--The more modded your engine is beyond bolt ons the longer it will take in miles
As mentioned if you do h s cam or LT headers you will need a retune
Racer
Joined: Oct 2003
Posts: 274
Likes: 42
From: Venice, Florida
Once it's tuned you won't have to worry about a dead battery as the fuel trims should be close to 0. The point is that what tblu92 stated will be a non issue as the whole point of tuning is to get the fuel trims as close to 0 as possible.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
Not al tuners will tune the LTFT fuel trims as the car needs to be driven on the street to get acccurate fuel trim readings Especially on a DYNO tune !! Most all dyno tuners run the engine in the gear ratio closets to 1:1 up to WOT and then only tune the timing and fuel only there---Unless they drove the car on the street thru all the gears at P/T they have not checked the LTFT's correctly-----
Tyocally a bolt on modded eng will have poaitive fuel trims due to the added airflow as the ECM during P/T is trying to correct the AFR back to STOIH 14.68:1
Any positive fuel trim at P/T "just before going to WOT" will be ADDED to your PE or WOR fueling as a lean safety----A negative fuel trim will always lock on "0" and never subtract fuel at WOT--again as a lean safety
PS Even a smal positive P/T fuel trim can make your WOT fuel pig rich say you have a +10% positive fuel trim JBWOT and you have commanded a WOT/PE fueling of 12.5-1 Then your ECM will add 10% to that Now making your WOT/PE fueling a pig rich 11.25 !!!!!
Tyocally a bolt on modded eng will have poaitive fuel trims due to the added airflow as the ECM during P/T is trying to correct the AFR back to STOIH 14.68:1
Any positive fuel trim at P/T "just before going to WOT" will be ADDED to your PE or WOR fueling as a lean safety----A negative fuel trim will always lock on "0" and never subtract fuel at WOT--again as a lean safety
PS Even a smal positive P/T fuel trim can make your WOT fuel pig rich say you have a +10% positive fuel trim JBWOT and you have commanded a WOT/PE fueling of 12.5-1 Then your ECM will add 10% to that Now making your WOT/PE fueling a pig rich 11.25 !!!!!
Racer
Joined: Oct 2003
Posts: 274
Likes: 42
From: Venice, Florida
Yea, a dyno tune is nothing more than a "drag race" tune in my book unless the dyno has a brake to lock into all the different loads and rpm's necessary to get the p/t trims in line. (Most don't and it will cost significantly more) If the OP had a drag race only dedicated car maybe you could call it "tuned for it's purpose" but If it's a street driven car that was just "dyno tuned" then the OP never had a correct tune in the first place. (For it's intended purpose). I'm pretty much in agreement with what tblu92 stated above; although I wouldn't call a +10 part throttle fuel trim a "small positive fuel trim". I think he was just trying to make a point and I'm not trying to bust ***** here but wanted to clarify that for future readers. Ideally you don't want any positive fuel trim and as close to 0 as you can get on the negative fuel trims.
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