IAT effect on afr
It is nice to see u post redhardsupra. At low airflows most air flow is down the middle of the pipe not at the edge. I have found that if I relocated the sensor so it did not heat soak things work alot better. I moved it below the radiator but still in the airflow. My friend who runs 12 LBS of boost moved his to on top of his fast intake. That works ok but will still heat soak.
TECH Enthusiast
Joined: Aug 2006
Posts: 542
Likes: 0
From: Memphis, TN
I see better results with the IAT outside of the engine compartment as well. When I use the IAT inside the MAF sensor or in the stock location, I end up just keeping the bias stock. The 1.0 across the board method works well if the IAT is outside of the engine compartment or in a position where it sees a lot of flow, like put where the EGR used to be. But really though, any bias will work (within reason) you will just end up tuning around it, you will bring the VEs to the bias.
TECH Enthusiast
iTrader: (1)
Joined: Dec 2005
Posts: 549
Likes: 0
From: Denver International Airport, Colorado USA
Eagle:
The issue of IAT affect on air density becomes more of an issue running Open-Loop SD. You will notice it when just sitting at idle. The greater the ambient temperature, the more your ECT & IAT will climb. So for the same idle RPM & MAP, as the air density becomes less and less..you get leaner and leaner.
You are correct that running closed-loop, Trims will attempt to bring the AFR to ~14.63. The question is whether the Trim function is valid. Are the narrowband O2's switching in a manner that accurately reflects the true airmass.
Tune a VE Table on the 'street' with a wideband. Get your values. Then return to closed-loop. Are the Trims that you now have accurately reflecting your wideband values?
It can be an endless chase. Perhaps you live in a perfectly flat area , with constant ECT and IAT values, and it works out perfectly. It appears that for many of us, only a dyno would present an ideal solution. Multiple variables could be held constant, saving yourself a lot of frustration.
To the OP, that AFR down the strip would be a little lean for me. Did you get any knock? I get nervous getting leaner than 13.0 AFR at WOT.
..WeathermanShawn..
The issue of IAT affect on air density becomes more of an issue running Open-Loop SD. You will notice it when just sitting at idle. The greater the ambient temperature, the more your ECT & IAT will climb. So for the same idle RPM & MAP, as the air density becomes less and less..you get leaner and leaner.
You are correct that running closed-loop, Trims will attempt to bring the AFR to ~14.63. The question is whether the Trim function is valid. Are the narrowband O2's switching in a manner that accurately reflects the true airmass.
Tune a VE Table on the 'street' with a wideband. Get your values. Then return to closed-loop. Are the Trims that you now have accurately reflecting your wideband values?
It can be an endless chase. Perhaps you live in a perfectly flat area , with constant ECT and IAT values, and it works out perfectly. It appears that for many of us, only a dyno would present an ideal solution. Multiple variables could be held constant, saving yourself a lot of frustration.
To the OP, that AFR down the strip would be a little lean for me. Did you get any knock? I get nervous getting leaner than 13.0 AFR at WOT.
..WeathermanShawn..
No Knock, but my knock tables are massaged a little. Here is a log of my last nitrous run, I don't have my wideband running with hptuners yet. Like I said this stuff is very new to me and I am trying to read and learn as much as possible, to be honest I think its my fuel pump taking a dump as my fuel pressure on a motor run was down to 51 psi at wot. I did hit the rev limiter on this run but does anything look out of whack!
Well, put a hotwire kit on today and fuel pressure is is dropping to 51 psi at wot. Must be the pump. I am still running lean, I wired in my wideband tonight and made a short pass with it being very lean, no changes have been made other than the iat seeing outside air. Either its my pump or the new cold air that is causing this. What do you think?
On The Tree
Joined: Sep 2007
Posts: 151
Likes: 0
From: Horn Lake Ms
man... I did contradict myself. I knew what i wanted to say but it just didn't come out like I planned. I was just trying to say that it has been my experience that when the car should go leaner, it gets fat and vice versa. In OLSD or OLMAF I always see it behave unnaturally, and the best way i have found to remedy the problem is to use a bias of 1.0 across the board. I have been meaning to do some more testing though. I'm trying to get a good setup for bracket racing and I need a consistent car, or at least a predictable car.
I probably did have too much
I probably did have too much
On The Tree
Joined: Sep 2007
Posts: 151
Likes: 0
From: Horn Lake Ms
I moved my bais to 1.0 and retuned the ve table and it helped alot i ran at our local 1/8 mile track bracket racing. My times where within .02 hundreds and really one hundred the passes i was 2 off my 60 was 1 off so it is alot more consistant. my afr stayed real consistant through out the night instead of spiking one way or the other like before.
