bradleyss14

Setup:
GM/Bosch 36lb injectors from Supercharged 3800
Cam: 231/242, 113+3 LSA .600 total lift
243 heads, LS1 bottom end
LS6 Intake Manifold
1-3/4" long-tube headers. Front O2 sensors used with extensions mounted in the collector of each header
**NOTE: Long Term Fuel Trim tables are disabled by tuner at the moment** We had a bad fuel injector dumping a bunch of extra fuel and causing the LTFT tables to become "corrupted" with bad data, so he disabled them for now so we could find the bad injector. The injector has been replaced and all 8 have been flow-tested again. New spark plugs and new O2 sensors were installed out of caution as the O2's were 20 year old original to the car. The bad injector was causing differences of 20% or more between the two banks, so the tuner wouldn't go any further until we got this issue resolved. Now I think we're nit-picking, but I don't want to schedule an appointment and end up wasting their time.

Symptom:
The Short Term Fuel Trim numbers are, on average, adding fuel to Bank 1 and pulling fuel from Bank 2

In a stationary, sustained 2000rpm test in closed-loop, the STFT delta between the two banks never exceeded 7% while the average delta was 3.93% difference with bank 1 being richer than bank 2. I have even swapped the injectors from one side to the other again and the numbers stay consistent. Unfortunately, my OBD2 reader only pulls data once every 1.5 seconds. I may end up having to get an HPTuners OBD2 interface to get better data, but this is what I have right now.

• Are these numbers close enough to take the car back for the final street and dyno tune session or are the two banks too far apart still?
  • If they are still too far apart, what else should we be looking for to bring them closer?

bradleyss14

HP Tuners log file attached now. (Yeah, I went and got one...)

RonSSNova

This looks perfectly normal to me. I've seen many.

Ron

bradleyss14

Thanks Ron. I got the same message from the tuner as well. The standard OBD2 reader that I had with an iPhone app was only pulling once every 1.5 seconds, so a lot of the story was missing in the gaps. Thanks again for taking a look!

brownrd

Is it normal to leave LTFT off in the "final" tune? I was monitoring my STFT and LTFT and noted that the LTFT never changed, so I assume they are disabled. Very similar set up (cam, intake, headers, etc as the OP). Not sure why the tuner would have left them disabled....

bradleyss14

I've been reading a bit on the HP Tuners forums and it doesn't seem unusual for people to leave the LTFT turned off even after they have their final tunes completed. There's a TON of information over on that forum if you want to go get lost in "information overload".

When he disabled my LTFT's, the value read "0" all the time and never changed.

tblu92

I use EFILIVE and often with LT headers and cams we were taught to turn OFF the LTFT's as with those mods the LTFT's often go crazy But we were also taught 1st to see what the LTFT's read before turning them off--- if they are +/- 10% make that correction 1st to the MAF table then turn them OFF
Also again we were taught to NOT be concerned with any of the STFT data