IW STi Forum banner
1 - 5 of 5 Posts

·
Registered
Joined
·
601 Posts
Discussion Starter · #1 ·
Hi all..

Something is bothering me again.. here is the deal...
  • My IDC's seem to be much lower than anyone else (max I see is 95% running 11.2/1 AFR... all of my MI friends run 100+ with the same mods as I have).
  • The values in my primary fuel seem to be way out of wack. I remember reading that there is some discrepancy but mine seem out of line. Here is a typical example: I see 11.2/1 actual AFR (LM-1 wide band) when the primary fuel map value is 12.22
I did just change the stock intake out for a Typhoon but I had the exact same problem with the stock intake. I thought maybe my intake calibration was wacked out but just confirmed that the values I am using are the same as used for stock (which my understanding is OK for the Typhoon).

I can't do any datalogging of learned fuel trim's till later this week but I want to know if anyone else has run into such a discrepancy between the actual AFR and the map values.

Thanks for the input

jb
 

·
Registered
Joined
·
323 Posts
wonder if you got a boost leak now
 

·
Registered
Joined
·
342 Posts
I had the same issue before I installed new injectors. The map would primary fuel table would call for 10.x and wideband would show 11.x.

I've seen a formula used to correct this somewhere. I think it was posted by christian from Cobb.

TurboQueef said:
Hi all..

Something is bothering me again.. here is the deal...
  • My IDC's seem to be much lower than anyone else (max I see is 95% running 11.2/1 AFR... all of my MI friends run 100+ with the same mods as I have).
  • The values in my primary fuel seem to be way out of wack. I remember reading that there is some discrepancy but mine seem out of line. Here is a typical example: I see 11.2/1 actual AFR (LM-1 wide band) when the primary fuel map value is 12.22
I did just change the stock intake out for a Typhoon but I had the exact same problem with the stock intake. I thought maybe my intake calibration was wacked out but just confirmed that the values I am using are the same as used for stock (which my understanding is OK for the Typhoon).

I can't do any datalogging of learned fuel trim's till later this week but I want to know if anyone else has run into such a discrepancy between the actual AFR and the map values.

Thanks for the input

jb
 

·
Registered
Joined
·
1,930 Posts
It is pretty typical, and really isnt worth the effort to tune out because it will always fluctuate depending on gas, elevation, blah, blah, blah. I attempted to get the values really close once and it just drives you crazy trying to do so. IMO for the typhoon, it flows a little bit better than the stocker so I would do some tuning on the intake which should get you closer to your targets. I tried messing around with the scaler/latency before as well and that just through my trims off like crazy but some tuners do change those values to compensate. The Cobb guide has a formula basically just saying if you take your target and actual and find the % difference and then take that difference to you intake calibration at that specific MAF voltage and either increase or decrease my the multiple depending on if you running on the rich or lean side. From my experience it will just leave you going back and forth from tank to tank and etc. and is just better to leave alone. As for the IDC's that could depend of a variety of things such as fuel pump/injectors that come from the factory.
 

·
Premium Member
Joined
·
4,416 Posts
Mine was the same way. I had portions of the map that were calling for 11.4 and I would get 9.8-10.0. There are quite a few posts out there about this. Even the type of fuel can change the AFR difference. Long story short, if your injectors are calibrated correctly then you must tune the Intake Calibration Map in order to bring things into line. For example, if you are showing 300g/s on the MAF, you may actually only be pulling 260g/s. This is because you are commanding 12.2 AFRs but running 11.0. You need to lean out your intake calibration map and then richen up your AFR map to bring things within line. So - long story short, MAF Airflow in g/s means nothing unless the target AFR and actual AFR are the same.

There should even be a post on this subforum about this. I think it was an in depth discussion too.

As to why you are pulling less IDC then friends in the same area ... here is what I would tell you to do (you too overdose ;)):

You and your buddy decide on what to log via StreetTUNER. Set things up identically. If ST is not available then use ECUExplorer. Configure the logging the same. Get out on the highway. Put her in 4th gear at 2000rpms. Both of you start logging. Both nail the accelerator at the same time. Both do a pull to redline. Now compare the results of the race to the results of the logs. Only problem is - I would like to see wideband information inside both logs too :) ... and AVCS.

t
 
1 - 5 of 5 Posts
Top