Hey everyone. I want to start off by saying that this is day two with my new 2012 Honda Fit. It reminds me a lot of the old '86 CRX Si I used to have when I was a teenager. I love it =]

SO... I put together a custom intake, got it in the engine bay, everything sealed up nice and tight, everything was clean. I go to start my Fit and she starts right up without a problem. It'll run for about 5 seconds, then the idle will drop, and it'll stall out. No CEL, no warning lights. I checked to make sure everything was tight and nothing was missing, started her up again, same end result. Put the stock air box back on, car runs great, No CEL, no warning lights.

My best guesses as to why it's doing this are: Maybe the MAF (IAT whatever you new honda guys call it now) is reading too much air coming in compared to what the stock air box was allowing; or the little port on the side of the sensor is facing the wrong direction.

When installed, that little port was facing towards the throttle body. Looking at its placement in the stock air box, I didn't think it mattered all too much which direction the air flowed across it, but maybe I'm wrong. I didn't try flipping the the sensor around, because if that WASN'T the issue, I didn't want to do any damage.

The "port" I'm talking about is boxed off in red.

The "port" I'm talking about is boxed off in red.

lol the blue painters' tape was just there to hold the sensor in place while the silicone I was using to seal the sensor into the intake tubing dried.

lol the blue painters' tape was just there to hold the sensor in place while the silicone I was using to seal the sensor into the intake tubing dried.

Anybody got any advice or suggestions?

 

Perhaps the general voulme of air in the location the MAF is doesn't relate closely enough to that of the stock air box, and it is causing the sensor to inaccurately calculate the flow?

 

that looks janky as hell. just put the stock intake back on

 

I would stall myself and refuse to start if I was your fit

do yourself a favor... put back your stock intake and read the $50 intake DIY thread.

 

You were told once, and you didn't listen. You have to do your homework BEFORE you put crap under your hood if you expect it to work. No matter how many forums you post this on, you will get variations of the same answer. Eventually, honda-tech will get you the same response. This guy got some gentle guidance on what to look for and where to find it regarding the answer to his "what's wrong" question on one of the other Fit forums, and he got pissed off because no one would design his intake ,correctly, FOR HIM.

To the OP, aside from the insults here (accurate), you just got more guidance on where to look for your answers.

 

 

I will post that the MAF and IAT are completely different. One measures incoming air flow (MAF) the other measure intake air temperatures (IAT).

Also the direction is going to matter. It is measuring incoming air and isn't going to do all that good of a job if it is facing backwards.


Lastly, buy a decent intake. If you are going to be designing your own intake you should at least know the main functions and names of intake metering devices.

 

 

Good attempt but a few things.

Read the DIY thread, there is TONS of info there on what works and what doesnt.

Silicone and sensors dont mix. Using silicone to hold in a sensor is somewhat silly too. I know some RTV or gasket maker silicone is more then hardy enough to hold it in forever but its not right. Plus silicone and sensors dont mix. If you used too much and happened to suck any silicone onto the sensor you coulda kissed it goodbye.

Also the biggest issue I see is sensor mounting location and tubing size.

Is that a 2 inch tube? The MAF runs on a 2" tube and it knows how much air moves through that TWO INCHES. making a larger intake means your moving more air and it doesnt know that....

Also MAF's its reccomended you have straight pipe before it... cant remember how long but its best to help with air turbulence. Fuuu i knew a number that nissan 240's like but that is escaping me now haha.

Anyways, look at redesigning your CAI or just buy one. It'll save you tons of headache.

 

lol youre a moron. suck it.

 

As a side note, this is how grownups talk to eachother.

But, on topic... I made sure to be VERY careful as to not get any of the epoxy on the sensor. I ended up putting the stock box back in place while I wait for the shop to open tomorrow so I can go pick up some narrower piping. I know you said the tube that the MAF is installed in the stock location is 2", but I think it might actually be 2.5? I know the opening coming from the TB is 2.5"... I'm not sure why they'd neck it down; that seems kind of silly. I'll measure it up tomorrow just to be certain, but you very well may be right; my track record doesn't look so hot it seems. I took another look at the direction the MAF faces in the stock position and realized that I did indeed have it installed backwards. I felt like it was wrong as I was doing it... but I honestly didn't think it'd matter. I had that sensor mounted at the angle on the piping, which could be yet another reason for my issue.

I've read three DIY's prior to starting my project, and most of them leave out all this information that I'm getting from you. One DIY didn't even refer to the MAF AT ALL and only refered to the IAT. They lack so much... it's insane.

 

lol at "it looks janky". You cant even see half the damn thing cuz it's covered in masking tape...

Miserable fail? I don't really agree... more like $20 down the drain, and now I have to get another 35mpg on my drive to the shop again. No big deal.

 

Well, it is $20 you could have used towards a proven design and a better aesthetic look, but I do understand the desire to create something yourself.

There is a lot more to intakes than just a pipe length and the sensors. A lot of people seem to overlook this. The amount of angles and sharp turns before the MAF can and will alter correct reading. It creates turbulence which does not allow the MAF sensor to read correctly.

As for the intake tube, I would find it hard to believe the internal width of the piping is 2.5" I think the throttle body opening is only something like 45mm which is less than 2".

 

What he said...lol

 

Im 95% sure the section where the MAF is located/metering is 2 inches.

The air filter housing with the MAF in it has a small velocity stack inside if I remember right when I last took mine apart to try the filter flip mod for a night.

There was also a few inches before the sensor in that housing.

I read a LOT of the DIY thread for info on how to make one if I decided too. And in the end I decided that it was much more worth it for me to buy a Injen or other reputable companys design as it means I wouldnt have to cut up my airbox or buy another lid to modify.

That and other companies have done way more R/D then you or any of us can lol. At least I hope.

Like TBH, the stock airbox from what I see isnt that bad of a design. Honda did a good job making sure air was going to get into the engine and efficiently as well as putting things in place to get cool air to the airbox.

Personally if I were to build my own intake setup I'd look at trying to include a good straight section before the MAF sensor and have it bolt in rather then silicone'd in. And although kiiinda trivial if you design your intake right i would also measure mounting depth of the sensor. But in theory all the air no matter the location of your intake should be moving at the same speed assuming you didnt mount it in a corner which would be silly.

Good luck with your intake today!

 

red plastic piping = janky

 

Ahhh yet again... When I put the 2.5" coupler on there I just got it in my mind that the ID was 2.5". Couldnt have been more wrong. I'm gonna go find the actual ID specs for the stock MAF housing.

 

lol well then my bay will = janky

I think chrome looks like garbage... and I already had red that I liked. Maybe I'll pick up some black for s*its and giggles...

 

I spent a few hours designing a MAF mount that I can bolt the sensor onto. This way I don't have to chop up my stock box. I'll post up some more pics later of round 2. Maybe it'll be less "janky" =P

 

Are you that hard headed? You have been told where to get infos on your concerns... even already given soecific dimensions so you would'nt dig in your toolbox for a measuring tape.