I have always been one to make my own renditions of expensive performance parts considering i am a machinist and have access to almost anything i need. However, my fit is sort of confusing me. I recently made my own short ram intake, almost identical to the prm i believe, but not positive considering i dont know their exact specs. MAF position in the intake tube is identical to stock, but about two minutes after running the car the CEL comes on and reads a lean code.

normally the light wouldnt bother me, almost every car ive owned has had it on. The lean code normally wouldnt bother me much either considering most hondas ive had have run better and had more power on a leaner mix. Dyno testing has showed a 3-5 hp drop with the new intake, and is showing it super lean. What am i doing wrong? I want to elaborate on my design in the future and just want to know what needs to change to make this work. any help would be appreciated. thanks

 

Right now cold air is denser and with out knowing how much air is going in I can only guess. Higher octane would help it a little leaner mixtures need higher octane also pure gasoline w/o ethanol would help richen up the fuel trims. Usually the opening to the intake is restricted to slow the air across the MAF. Also the throttle body and MAF need to be re calibrated which requires tuning. You are obviously running more than 30 percent more air which requires more fuel.

 

Get your code(s) pulled it could be a number of things.

Can we see some pics of your MAF tube? That could help.

 

Without a flow meter and balancing the air in and out and making sure the head can flow the extra air, its going to be hard to make it work. They test and test the intake and there is a harmonic balance between all the parts. (head, exhaust, intake manifold and cam) It takes a lot of money and time to do this plus the remapping of the ecu which there is not a system out there for the Fits.

If you have a flow meter you can use clay to restrict the air flow and remake it to that when you find out what works but it cant be that much over stock.

 

Sounds like the tube you used might be a different diameter, where the MAF is mounted, than stock.

 

+1 to this. Inner diameter where the MAFS is has to be exactly 2" or a code will be thrown. I had the same issue and resolved it by lathing an aluminum tube with an outer diameter of 3" and inner of 2" with beveled ends to friction fit inside of the adapter tube I purchased by Spectre. I haven't had a code since.

Post some pics and measure what you have.

 

The intake tube that i used is supposed to be 2", i suppose i didnt measure it to be exact. however, i did measure the depth of the maf in the intake tube as well as distance from the throttle body. i wanted to be as close to stock as humanly possible before i welded it in the first place, because of past experiences with mafs. but i will take some pics tmro morning and post them up as well as some precise measurements.

 

The Mass Air Flow Sensor is critical on any engine that has one. The ECU is monitoring the output voltage of it & making critical air fuel ratio changes constantly.

Today's engines are very complex. The parameters are very tight & any modifications can easily damage the engine if you don't know what you are doing.
You can't just weld up some pipe & bolt your MAF sensor into it & expect everything is ok.
Just try to think of some guy randomly monkeying around with a carburetor, randomly swapping in jets without knowing what he was doing. That's exactly what you are doing...



When the CEL light is on, it SHOULD bother you. It's a visual alert into the ECU that something is wrong. As soon as the CEL came on after your home made intake & it was a lean code causing the CEL, you should have removed your intake immediately. The CEL lean code is extremely dangerous to your engine.
I won't even comment that you actually dyno'ed your car with the CEL on & running so lean. I hope you did not damage your engine.

I'm actually surprised the engine did not go into a limp mode to protect itself from the dangerous lean condition.
This means that the Honda FIT ECU programming is pretty lame.


I recommend that you install the stock intake & leave everything stock while you learn modern engine theory.

The 1st step in modifying anything is a full understanding of the theory of operation. This goes for your toaster, for your laptop, for anything in your car.

I'm not trying to be harsh, just giving some facts along with my opinion...

 

would disconnecting the battery for a bit to reset the ECU help?

 

There are a scant few bits I am inclined to agree with in this diatribe, but it's pretty safe to say that this post is mostly opinion. Bolded the give away for emphasis. This ECU, the GE8's, is a feisty mistress and if it decided there was real trouble it would have let him know.

Trust me. If he's running even 10% leaner than stock up tio he's not doing any damage considering how ridiculously rich these cars run under WOT on most fuels, and it probably pulled a bunch of timing as well hence the drop in power.

We don't know how lean its running nor do we know what code he's actually throwing.

OP Ditch your DIY MAF tube. There's more to it than even matching the ID.