Can someone do me a favor and post what your short and long term fuel trims are. At idle and @ 2500 rpm with no load. I have a CAI and am having a CEL issue. I have the old P0171 lean condition bank 1 and have checked for vacuum leaks with no luck. I want to rule out a bad MAF but would like to know where the baseline is before I go any further.
Thanks in advance.

 

I broke down and threw in the old box to rule out the new intake and all is back to normal. Is it possible that the ecu/maf can't adjust for too much air? If so is there a way around this for our cars (09 Fit sport).

 

For those of us that did not already know, I figured out what my issues were.

After installing the Cosmo Intake (cheap ebay model) and chasing a P0171 code (Lean condition) I swapped back to the stock air box and everything fell back in line. This did not make me happy so I looked deeper and after seeing a thread on the forum about making a CAI with the MAF section from the stock air box it made me look closer at my setup. I mic'ed the stock box and my intake and found a couple of issues. For one the MAF sensor sat .177 higher in the Cosmo intake tube then the stock intake and the ID of the tubes differed by .300 with the Cosmo being larger. First thing I did was Mill down the MAF sensor seat to center the sensor. I reinstalled it to see if it cured it but with no success. I then turned a piece of Delrin matching the profile of the stock intake tube and press fit it in to the Cosmo tube. Reinstalled it and the numbers fell within spec not throwing a light now for over a 100 miles.

I'm assuming that the MAF sensor and trims are calibrated, locked down within these dimensions. The larger area the Cosmo had threw the MAF sensor out of spec and the ECU could not adjust for it. I hope once it is unlocked I can go to a larger pipe and get more out of it with adjustments. As of now I'm happy I was able to install the CAI for the $100 I spent. I wonder what the $250+ CAI's have inside that they have no issues. I would like to know what they did to make it work if they have larger ID's.

 

With the larger pipe, the MAF told the ECU X amount of air passed but in reality, Y amount passed... The ECU saw that via the Oxigen Sensor and Got crazy about it!! You effectively eliminated the problem when you reduces the diameter of the pipe...

As for the fuel trims question, mines are varying between -5.4 and 5.4 Short term and -1.5 Long term! I have a GD3 with Denso IK22 Plugs and a Fujita SRI!!

Marko!!

 

For the record, since I was searching for fuel trim values to compare and happened on this thread:

Stock GE8 MT, sampled @5s on commute route but with almost no traffic, unlike usual

@2513 RPM:@822 RPM:

 

Good info all. Thanks for the thread; it's good to see stuff like this in the GE8 section.

I second what DOHCtor said. The mass air flow sensor calculates incoming air volume by measuring its velocity (with the sensor) and multiplying it by the area of the pipe/tube opening.

I'm not sure going to a larger tube will increase potential gains (even with an unlocked ECU). I think it depends on the size of the tube relative to the size of the throttle body opening.

 

im confused at what you had to do to remove the code?

i finally got this code after months of having the intake in my car

 

Disconnect the negative cable for about a minute. This should reset it. If you have already done so and the code returns you may have a leak some where in your system. Check your connections from the MAF sensor area to Throttle body. The MAF sensor could be dirty also. You could attempt to clean with electric cleaner or compressed air BUT be careful. Very fine wires and damage could accure. What intake do you have?

 

I thought the fit used a hot film maf like most other hondas