I need to get this out of my system since it has been bugging me for a while now.

The 1.8ltr 2014 Honda Civic uses the same maf sensor as the 2015 Honda Fit. Same part number according to Hondapartsnetwork. The diameter housing of both vehicles may be slightly different in size. I'm expecting the Civic's maf sensor housing to be slightly larger (Looking at piping diameters between the maf sensor and throttle body).

So, let's say the Civic's maf sensor is larger. What's to say that this larger maf sensor housing will not work on the Honda Fit? Isn't the maf sensor itself designed to work within a certain voltage range? I know the ECU is sending voltage signals to the maf to determine air flow within a specific maf sensor housing diameter but how exact is it supposed to be? Will it work if the maf sensor housing is +/- a said diameter range (be it however small)?

I'm just curious! The maf sensor's are exactly the same. If the housing is slightly larger, I'm game at trying it out. Just want to see/read some thoughts around this. I'm --><-- close to ordering the 2014 1.8ltr Civic's maf sensor housing to cut it up for testing. I'm already looking to bore out the throttle body, larger intake piping, etc and know about air/fuel ratios, tuning etc. I'm specifically asking about sensor swap between the stock 2015 Fit maf sensor housing to the 2014 Civic housing (If the Civic's housing is in fact slightly larger).

 

There doesn't seem to be a general interest in this so I'm posting this information for documentation purposes only. Do not attempt this modification.

I purchased a 2014 1.8ltr Honda Civic LX CVT air cleaner housing to do this mod here --> 2014 Civic Air Box Housing



I used a hacksaw to cut out the maf sensor housing and took measurements of it vs the stock 2015 Honda Fit maf sensor housing. Here is what I came up with.

Stock 2015 Honda Fit Maf Sensor Housing:
Inlet diameter: 2.04" (51.82mm)
Outlet diameter: 2.17" (55.12mm)

Stock 2014 Honda Civic Maf Sensor Housing:
Inlet diameter: 2.24" (56.90mm)
Outlet diameter: 2.63" (66.80mm)


Here are a couple of pictures of the maf sensor housings side-by-side.



I don't even need to tell you which is which because the difference in size is obvious. But if you can't tell, the 1.8ltr Civic maf housing is on the right side and the top of the pictures.

I removed the maf sensor from my stock housing and inserted it into the 1.8ltr Civic maf sensor housing. The I started the car up. No check engine light and it revs just fine. No engine stutter!

I found a bullshit generic filter I could use for testing thankfully so I'll be driving around tonight to see if everything is ok. I'll toss this filter out for an S&B filter tomorrow if all goes well.

Gawd, I hope this works. I'll be keeping my other maf sensor housing with me in case I need to change them out on the side of the road.

Again, I'm not recommending this to anyone. Just sharing my experience! If this works, next up is getting my stock maf sensor bored out by Maxbore. I'll send it out tomorrow if this is successful tonight. **Fingers crossed**

Short Video clip ->
Had to cut it short since the Misses was calling me for dinner. :-)



Please disregard the information below. It's for personal use. Trying to figure something out.
Stock 2015 Honda Fit Maf Sensor Housing:
Inlet diameter: 2.04" (51.82mm) = WOT 12.0:1 Air/Fuel Ratio (Per Android)

Stock 2014 Honda Civic Maf Sensor Housing:
Inlet diameter: 2.24" (56.90mm) = WOT 17.0:1 Air/Fuel Ratio (Per Android)

Inlet diameter scaling for WOT -->
12.0:1 - 2.04" {51.8mm}
13.0:1 - 2.08" {52.8mm} (Perfect)
13.5:1 - 2.12" {53.8mm} (Possible Perfect)
14.0:1 - 2.16" {54.9mm}
16.0:1 - 2.20" {55.9mm}
17.0:1 - 2.24" {56.9mm}

 

a quarter of an inch is a big difference. Id say perhaps you should remove the MAF sensor and coat the inside with a layer of bedliner to bring the flow diameter down to around 2.10 or so. Slightly bigger is fine, a quarter of an inch may cause issues at certain rpms and engine loads.

Plug in a scanner and keep an eye on the O2 sensor, look for spikes.

 

Yes sir! I'm currently in the middle of testing now. Drove the car for several miles and no check engine light, no drivability issues.

That is not to say that everything went well. Been keeping an eye on ignition timing, maf sensor g/s and air/fuel ratios. Recorded a large portion of cruising this way and will compare it with cruising on the same streets/highways tonight for comparison. Been using cruise control at various mph's on the highway too and will compare.

I did do one wide open throttle (W.O.T.) run and tested for knock detection. Knock was detected. Air/fuel ratio was 15.0:1 during this run as compared to 11.8:1 stock or 12.2:1 with the same setup with the stock maf sensor. I need to be sure if this is due to a misreading by the maf, if extra air is coming, a combination of the two or something else. More testing is needed.

I really need to get rid this cheasy air filter but it is helping me know that the car can drive like this. Need to test with a filter of the same brand. Will pick one up tomorrow. This filter could be contributing to the high air/fuel ratio. I don't know how exactly. I experienced this phenomena with a Weapon R air filter, which made my RAV4 run way lean. Here...I uploaded a picture so you can see exactly what I'm talking about, as far as the filter goes.


Note the differences with the air/fuel ratios. This was all tested on the same day, same dyno. Just changed the air filter.

 

filter versus no filter will not really effect AFRs. Just sound for the most part. So I tend to not think the WR filter did that.

EDIT what I think happened is you caught the ecu doing emissions sensor testing or some sort of drive cycle test.

 

*Update 10/2/14*

I have to change up my current intake setup to accommodate this larger maf sensor. Since the inlet and outlet is larger, some of my current piping will not fit. I'll think of something and will be working to build it tomorrow sometime.

In the meantime, I've let my fuel tank pretty much go completely empty. It read '0' miles on my range and I must've driven it another 8-10 miles after it hit '0'. Since I was experiencing knock while testing this maf and leaner air/fuel ratios, I've switched octane from 87 to 92. After I modify my current intake setup to work with this maf sensor, I'll do some more testing.

Hopefully, all goes well. I'm ~~><~~ close to sending my throttle body out to Maxbore for boring out. Either way, I'll be sending it out the week of 10/13 (Or even 10/10). Really excited about that as well.

 

Just finished looking at some videos I did comparing the stock maf sensor to the Civic maf sensor that I did the other day. Two videos, same route I took on the highway, same on/off ramps, etc. Same temps..same night.

All I wanted to do is see if the maf sensor would run ok while in the Civic maf housing without throwing any codes. It ran well! No weird drivability issues, nothing.

I had my Android Torque pro software going and was looking at the maf sensor g/s (Grams Per Second) at various mphs, using cruise control. I was testing 65mph, 70mph and 75mph. I'm going to share what I saw at just one of these mph'ers but it was the same overal.

Stock Maf Sensor @ 70mph = 15.3 g/s Average

Civic Maf Sensor @ 70mph = 18.5 g/s Average

So it appears to flow some more air, even while cruising. I tried to look for general calculators on the net to convert g/s to horsepower. It isn't an exact science but there were a few places I read that you have to multiply your g/s X .8. Doing this shows a 3-4hp difference. This is cruising though and I'm NOT saying that this is the case. I need to do some full throttle tests.

I'm heading out now to try to redesign my PRM intake to support the Civic Maf sensor for testing on 92 octane. Then I'll test both at the strip, provided the Civic maf sensor does not knock while testing it before hitting the track. Just realize too that with the larger maf sensor housing means larger intake piping. So if there are any hp gains/loses, I can not fully conclude that it is from the maf sensor itself. I can test this by connecting the maf sensors just to an air filter but I'll save that for another time. I hope all this comes out well!

 

That does not make sense. with the same sensor in a bigger tube, the ecu would actually be seeing LESS flow. That is why a bigger pipe makes the car run leaner.

Perhaps you have your numbers reversed.

 

No, I do not have my numbers reversed. These are the numbers that I got so I'm reporting it. This is what I got while cruising on the highway. Also, during testing I just done, part throttle is showing more flow going through the maf at part throttle, steady state conditions. Not much but very little. I don't try to make sense of these things. I've found over the years that I don't have too any more. I leave that to the experts. I just report what I'm coming up with. HOWEVER....

My wide open throttle runs I've done moments ago support exactly what you stated. The Civic maf sensor g/s is only showing a max of 77 g/s with the PRM intake. Previous runs I've done (Some 24+ runs) using the stock Fit maf sensor housing are showing a max of 96 g/s. And they are pretty consistently around here.

Although I tested for knock several times and got none, my wide open throttle air/fuel ratios were around 17.1:1 (Not Good!). WOT ignition timing advance was around 11.5 so that seemed normal. Also, my hp was maxed out at only 92hp temporarily. I could get ticks of 116-119hp on some really good runs on previous testing with the stock Fit maf sensor housing so I'm losing a significant amount of hp. Mind you, some of this may be attributed to me running 92 octane. I will be testing the result of running higher octane tonight vs my other runs on 87 octane.

So, I won't be testing the Civic maf at the dragstrip tonight. I'll hold on to the civic maf sensor housing and await some tuning to compensate for the wider diameter (I hate waiting. Maybe I'll think of something). In the meantime, this is all the testing I'm doing on this for now.

 

ECU is calibrated to the voltage the MAF sends back. Changing MAF piping size on stock tune is a dice roll. You're best to leave that alone. It may use the same sensor but all the sensor is doing is sensing, it's the ECU that interprets the data.

Again, it's good to see the effort

 

WOT has that much change in sensor reading? I would return to factory for now.


Take that civic maf tube, anduse a plastic welding kit and close the diamter a bit. aim for perhaps 1/16 or 1/8 inch bigger then factory. If it ran well at part throttle with that big of a difference, I bet you would have some good results from being only a hair bigger.


You have successfully proved a bigger maf is not enough to challenge the intelligent honda ecu at part throttle, but it does lose control at WOT.

I thought Honda had programmed to use MAP at WOT, not MAF. that is teh case on GD and GE, I see no reason for honda to have changed it, unless some new programming tricks have giving them some balls recently!


EDIT do some runs with the MAF sensor unplugged. I am interested in what the bigger tube could do. The ecu will know the MAF and IAT are unplugged, so will be forced to utilize the coolant temps and MAP sensor readings to determine fuel mix.

 

I would've had no idea what you were talking about but think I have a general understanding from reading up on this a couple of days before trying this. I know what you mean by closing the gap slightly underneath the sensor itself, to close off the diameter a tad bit to help with the readings. I still may do that but it seems counter to using a wider diameter for more air in the first place. Similar to what the the inside of the HPS piping looks like inside that I took a picture of -->



And yes, I thought the maf sensor didn't take a reading during wide open throttle (WOT). I thought the ECU goes into a pre-programmed map to add fuel. And maybe it does. Perhaps it goes to the pre-programmed fuel settings but with the extra air coming through (That it can't detect because it's going around/beneath the sensor), it's not adding enough fuel. So it simply reads 17.0:1 air/fuel ratio but can't compensate because it's just taking a maf reading rather than trying to add extra fuel.

And Apexi SAFC Neo or other fuel addition source would help here. I only use it to add fuel during WOT on my Subaru and leave it to stock settings during regular driving. You'd still have to be careful under non-WOT runs, under a heavy load but you can set this in the Apexi SAFC somewhat by telling it to add more fuel at specific throttle openings. The shop I talked too (First State Motorsports) couldn't get an ECU diagram to know how to add this unit though. This could work though I believe. Only testing would show though..

I like your thinking around this 13Fit!

 

Well....I thought I was done for now. Was laying in bed thinking on what 13fit was saying about putting something inside the maf sensor to simulate a smaller diameter. Then got to staring at the HPS intake over and over again. Yeah, I got problems. Just when I was going to line up layers of duct tape into half of the maf to reduce the diameter......an idea hit me.

Looked it up online and voila....it exists.




The insert portion is all I need so the maf reads correctly. The back half of the civic maf is signifcantly larger than stock and should compliment the throttle body being bored. Everything will be open right up to the back of the maf sensor itself and everything in front of the maf sensor (The intake itself) is opened up. Splendid!

I ordered the part and am expecting it to arrive next week before heading back to the track. Awesome! This just might work! Don't see why it won't.

 

De36 runs a SAFC on his GE to control WOT fuel/air trim and has had success with it.

You guys just need to figure out the ECU pinout.

 

Thank you Wanderer for the heads-up.

 

**Update**

The Spectre maf airflow sensor kit came in. Had a nice cool Spectre bag with it, with all the reducer pieces inside as well as maf sensor connectors for a 3" pipe they provided. The kit is very nice and I'm sure if could be really useful for someone using a 3" intake. However, this is where I made my mistake.

The maf adapters are all for a 3" pipe. They are supposed to reduce the piping size as follows:
3" to 2.75"
3" to 2.5"
3" to 2.25"

What I needed to do is reduce my maf sensor inlet from 2.25" to 2". Specter doesn't sell a 2.25" adapter reducer (Or even a 2.5" one that I could find). So I was stuck in a dilemma.

So out came the knife and hacksaw. I cut up the 2.5" and 2.25" several ways. I took a fair amount of pics but I'm too tired (lazy) to put them up now. Very ghetto looking.


What I ended up doing is sliding the cut up 2.25" into the 2.5". Then sliding both of those into the Civic Maf sensor to reduce the inside diameter down. Both pieces were slid into the inlet side of the maf sensor, with both pieces allowing the maf sensor to be inserted through the top. Here is what is looks like inside.

I need to work on making the inlet air transition into the maf sensor smooth. Right now, it's an abrupt/harsh transition. Any suggestion on what I can apply to make this transition from the silicone hose to maf smooth? Some type of liquid/paste that hardens that wont' get sucked into the intake. I'll be stopping by Home Depot tomorrow to find something to smooth this out inside.

The stock maf sensor Inlet diameter is 2.04" (51.82mm).
Now the Civic maf sensor with the two Specter pieces inside has an inlet diameter of 2.07" (52.99mm). Close enough! Not exact but I'm gonna test it out anyways.

The piece is all ready for me to swap out with the stock piece while testing at the track. Don't worry, I won't be installing them the way you see them. The stock maf is on the left side and the Civic maf housing is on the right (It's upside down though but you get the point).


I am waiting for my throttle body to be bored out by Maxbore and sent back to me. I'll be testing that throttle body with the stock piece on the left with a few drag runs. Swap to the Civic maf housing, do some more dragstrip runs. Then may swap again back and forth a couple of times just to remove any beliefs that cooler air temps are making one setup seem favorable to the other.

How will it turn out? Who knows! Who cares! It's all good fun and I like testing things like this out. This is all for now.

 

very slightly bigger is perfect. Its allowing you to trim a bit of the richness away in favor of performance, and as a bonus, may add MPG's, though minor.


In for results. I like the idea of bigger tubing behind the MAF and a bored TB.

Perhaps a future step is to include very mildly ported runners that are somehow bell-mouthed to the plenum/TB tube

 

In for fun.

 

Been thinking about what you said around this. Took some measurements again just before leaving for work and this is what came up. First I had to convert your fractions to decimals though. Grrrrr!

1/16 = 0.0625" = 1.5875mm
1/8 = 0.1250" = 3.1750mm

Stock maf sensor inlet diameter is 2.04" (51.82mm).
Add 1/6 = 2.10" (53.41mm)
Add 1/8 = 2.17" (55mm)

With the two Spectre pieces inserted inside the Civic maf sensor, the diameter measures 2.153" (54.68") **Measuring top to bottom of maf sensor** Perfect!

Measuring from side to side is 1.97" (50.05mm). It's slightly wider top to bottom due to the piece that is cut out to make room for the maf but the side to side measurements are slightly smaller than stock.

Overall it may all equal out to break even or be slightly wider than the stock maf diameter. Just had to see what was going on here. If I'm seeing this right, I'm thinking WOT should show somewhere around 14.0:1 air/fuel ratio. Thanks for the suggestions 13fit and Wanderer. And I'm keeping that future step on port matching the manifold in mind. Just taking baby steps. Something has got to be done about the exhaust soon. VERY Soon!

 

*Update 10/8/14*

Stopped by Home Depot to try to find something to smooth out the transition of air on the inside of the Civic maf sensor piping. This is the where the air just enters the maf sensor, going through the two Spectre piping inserts. It's really rough and can cause problems with the maf sensor reading (From what I read) and so it should be as smooth as possible.




^^So I found this material called 'Water weld' that once applied it hardens up (cures) within 20 minutes to fully cured in an hour. That is the white material you see inside the inlet of the silicone hose, where it meets the maf sensor piping. It's not perfect but it is what I was looking for. I did not apply this on the discharge side of the maf sensor (Where the Spectre piping ends an the internal maf diameter continues). It's rough there but the air will not hit it directly as it would going into the maf sensor. The HPS piping is like this on the discharge side as well. No need to smooth it out there.

Again, I have no idea what to expect. This is all experimentation but fun. I'll be testing it out on the road, than the track tomorrow night if my Maxbored out throttle body arrives.