Thats a very good thought you bring up. While the fan was more than likely not running, could the wind/airspeed be having an effect at 75mph? I do not have the front undertray on the car (%$^& previous owners) so I'm wondering if air is getting blown around up onto the filter and causing the sporadic readings? Below is just an underhood picture so you can see what the intake looks like. I do feel like i see the gauge being more sporadic at highway speeds vs say at 60mph

 

Your air filter is no where near the radiator fan and its positioned perfectly to not be affected by incoming air flow negatively imho. Have you checked your maf scaling and compensation tables like I suggested and compared them to a stock version of your Rom yet?? I see the large metal pipe, which again if not scaled properly will cause all the issues you're having. Most tuners that I've talked to recommend the rubber/silicone style intake upgrade instead of a metal pipe because they cause less issues with scaling the maf.

 

I think there's a how-to catch can thread for that car on here somewhere btw.

 

yeah the MAF scaling tables are all stock. I'm not exactly sure how the MAF scaling would change this though as the O2 feedback is centered around zero. It certainly seems like the MAF is picking up fluctuations in the incoming air even though the throttle etc are all constant. It fluctuates the same as if I were to be blipping the throttle a little (like cruising with a TPS of 25% and then blipping it to 30%).

Yea the catch cans are a little different internally, but I got the basic idea from that DIY catch can thread.

 

Change your Closed Loop - LT Trim Control Ranges to the following to keep LTFT from effecting open loop.

75.48

62.9

522.0700000000001

496.91

 

Well they look nice man, I like it.

 

Could you explain the end of this post a little better plz? I've been tuning cars for a couple years now and I understand open/closed loop but what does
75.48
62.9
522.0700000000001
496.91
mean?

 

+1 on not understanding that post

 

I assume he is telling us to leave the car in closed loop at higher load levels but random numbers don't really help us out. Nor am I interested in altering the vehicles natural open/closed loop load and rpm parameters either. I get the idea, but proper maf scaling would fix the issue without messing with when the car goes into open loop.

 

Read the advanced fuel thread linked below. They found that LTFT affected WOT fueling, and a fix was to lower the LT Closed Loop trim to 500hz.

https://www.evolutionm.net/forums/ec...l-options.html

 

The issue isn't happening at wot though. The whole thread is about the car swinging rich during low load cruise speeds on a non stock intake tube.

 

As Mychailo mentioned, AFR should be swinging back and forth around 14.7:1. That is how closed-loop AFR control works with factory narrow band oxygen sensor.

Zeitronix seems to filter some of that swinging and shows rather "steady" 14.7:1 at the gauge, but AEM seems to show "unfiltered" numbers.

I think MAF signal becomes more "unstable" after putting hard intake pipes, and especially if it is too close to the MAF output, if possible, try to maintain enough straight silicon coupler section between the hard pipe and MAF housing.

I also got random rpm dipping and lean idle condition sometimes (especially when trying to move forward from dead stop then suddenly stops again with clutches in) after putting Cusco hard intake pipe, and playing with ECU settings help, but not fixed completely. (Thanks for your input about this jrainwater at another thread)

 

I have heard that the "silicone" intakes that are molded for the Evo are way easier to tune, have the same positive effect the metal ones do, and are all around easier to work with. Can anyone confirm this with personal experience please??

 

I've used one for both my BBK Full, BBK-3B, and HTA Green. Both intakes (one for standard compressor inlet and one for the FP anti-surge cover) worked fine.

 

What brand did you go with for the silicone intake?