I also have carbon fiber infused nylon filament and PET-CF filament both of which can easily withstand under-hood temps. (ETA: Scroll down to post #8 if you want to get to the crude CAD models screen shots)









So, first question, how hard would it be to relocate the ECU? (I really hate that it seems to be more and more common to have the ECU under the hood of cars, what the hell are they thinking? I / we don't need it to go to far, just not THERE directly in the way... See I'm thinking of either modifying the bottom of the air box, closing off the OEM intake tube, and making a printed one to draw air from down lower around the foglight area. OR and this I think would be easier and less likely to suck in water if you hit a deep puddle, from the drivers side fender area. A 1" or so tube with a dip in the main intake extension I would think would also help allow any water that ever did get sucked up, to drain out easy enough if you're just going fown the highway in a rain storm, just run a hose off that 1" extension coming off the intake ugh extension downward so it can drain in a way that also helps prevent it from sucking in hotter engine bay air. These engines aren't sucking in a ton of air even at WOT and high up in the rev range, I just want the air that they are pulling it, to be cooler... And everything I have seen is either really a hot air intake... or screws with the OEM I'm guessing hot wire sensor?

I'm thinking this summer I'd also like to do something with the exhaust... I hate that this version of the engine doesn't use a "header" of any type whatsoever but has the passages cast into the head with a single outlet...but it is what it is. but depending on the OEM exhaust inside diameter and if and where it's using crushed bends...maybe make some some changes there for efficiency sake of both sound and flow, and potentially wrap it. But anyway back to the intake.

If I come up with something nice that uses the OEM air box, would anyone be interested? If so which would you rather have, an adaptation that draws from the fog light area, or from the fender? And how difficult to move the ECU? Is there enough slack to move it far or would everything have to be extended to move more than an inch or so? (the wiring)

P.S. The box to the right, where the intake inlet is actually at, I see a few screws there, will the top half come off? Could be as easy as drawing up something in CAD and printing it out that attaches like the OEM top if that is what it is, that basically lines right up with the OEM air duct from the grill area to then drump around the ECU and intake area. Between the brake fluid resoviour and the ECU... I'm trying to think of how to extend out the OEM inlet but without moving the ECU, I don't see it.. BUT if that top half just comes off... that could be easy.

 

The air box "assembly" (not sure what else to call it) comes out pretty easily if you want to take a better look.
The service manual gives all the removal details, and I can look that up for you later if you want, but it's pretty self-explanatory once you remove the 12v battery to make some space.

 

I'll try to get that done this weekend so I can also take measurements of everything and start modeling the OEM unit in Fusion 360.

 

I'd probably say depending on cost I'd be interested. I'm not interested in most aftermarket intakes for the reasons you stated, as well as the cost. Not worth it for basically no significant performance gain.
At the end of the day, this car is designed for great economy. Most of the time you change intake and exhaust you're going to likely improve either "performance" or economy, but rarely both. At least not without changing driving habits significantly.
I wouldn't want an intake that's going to decrease what little power a Fit already has and pay to do it. And I wouldn't want an intake that's going to insignificantly increase economy that costs $300 so I'd have to drive 30K miles to make up the cost of the intake in fuel savings.

 

Denser air charge means more fuel is needed to keep the targeted air to fuel ratio, which does net more power for the same amount of throttle, IF mechanical and ignition timing are correct. On an ecomodders forum I'm a member of people intentionally do hot intakes drawing air from right next to the exhaust manifolds to thin out the O2 in the air charge on purpose to help increase fuel mileage...

As I'll eventually be looking for another one of these things but with a manual transmission and trying to convince my brother to try to get into 24hr of Lemons with a couple of our friends.. which means focusing on reliability more than anything and increasing efficiency, which is why I'm starting to investigate things like this as well as thinking about what can be done to the exhaust... partly for sound but also flow and thermal considerations. (when a loud clanky V8 is around it would be very hard to hear the Fit's stock exhaust, and you wouldn't want to take your eyes off the track, when there's a car next to you, to look at the tachometer.... So you do need to hear the exhaust. anyway.... so yeah starting to look and study things on this automatic Fit that i'm fixing up and probably going to give one of my kids after I find a manual one for the right price in decent shape.

(These cars I think would be perfect for a race like that, as they wont shred tires, guzzle gas, have over heating issues etc. things like silicon coolant and vacum lines, blah blah you get it and just being able to stay out on the track for long stints means you're making laps while others are coming into the pits.

 

Well, I didn't "feel like" taking the air box inside and taking hundreds of measurements with calipers as I'm just trying to get a better look at the air box, and figure out a rough plan, but I did take it out... darn ECU is really in the way, which is annoying to remove... like seriously WTF stop putting ECU's under the hood of cars...anyway... took a good many tape measure measurements just for a rough model. I think, I'm going to try to get a stock air box out of a junk yard and look into modifying the resonance chamber since it has that nice lid you can just take off and gain access into it, to adapt it for an actual cold air intake.

The rough idea I had after looking at it, was to cap off the OEM entrance after in the resonance chamber cutting out the pathway the intake air flows though (the molded channel, just cutting the top of up off in a large oval, preferably if there's room to get to it with a rotary tool, in the corner to have a much larger pathway into the lower portion of the filter element area. With the OEM entrance capped off, the lid to the resonance chamber could the modeled to be printed in PA12CF (nylon) or PET-CF to have an attachment for a silicon hose.... if it will fit and clear the hood, then with some aluminum elbows, or just short sections to connect other silicon elbows which honestly.. silicon would conduct less heat and probably be cheaper than manderal aluminum bends could be routed to either draw air from the fender well, or down near the mouth of the front bumper.

Just for anyone else who may ever like to reference some rough measurements should they come across this..

 

Side comment, WHAT THE CRAP IS EVEN THAT!


Sourced this from TRQ... yes Honda thought it was a great idea to have the incorporated manifold into head design.. then have the exhaust slam into that abomination.....

 

Here's the crude model, keep in mind CRUDE model, took me a couple hours, measurements are not perfect, it's not a high resolution model, it doesn't need to be. When I get a OEM air box off of a junkyard car I'll make a much more detailed model of the parts that matter. The point of the crude model, is to now then add in things like the battery, ECU, remote brake fluid reservoir etc. in relation to the crude air box to figure out routing for the printed part and such.

 

Hey that looks really good!

 

Thank you. It really is just a quick crude thing, I'm an amateur at CAD and Fusion 360 while very powerful is not the most intuitive software. Takes me a long time to make a highly detailed model as I just don't have the methodology or experience of some that or taught it vs self taught.

Anyway, so here's a quick hollowing out and mock up of the internal structure of the bottom half, that illustrates what I was talking about doing earlier if anyone read all that lol. Again, the idea being to seal off the OEM air entrance into the box, draw air though the cut away in the tube in the resonance chamber area, and modify or print a whole new top for that chamber to accept air, that way it still goes through the OEM filter and what not.

This raises where the air would come it at vs the OEM location, which gives more freedom I think to "aim" the tubing which ever direction I want to without running into an obstruction or having to relocate other items, though I imagine some relocate the battery just to get it out from under the hood, and for those people, maybe a different modification could be made to the factory air box that's lower just on the front bottom of the box.





At this point, I need to model the battery and whatnot around the air box in relationship to the air box, so that's the next step before adding anymore detail, though adding more detail than needed is sort of a waste of time... but I do like pretty models.

 

Most of the stock air box is about muffling noise without restricting air flow too much. All a replacement intake needs is a tube for the MAF sensor with the same internal dimensions as the original, and an air filter. Add an elbow for clearance, and you have an ebay "performance" intake.

I'm guessing something they fluid-modeled? Is that an O2 bung on top? It makes a little more sense if you try to see it as a mandrel bend, flattened at the inlet, then a lobe got added to house the sensor head. Otherwise I'm with ya - integrated manifolds and close-coupled cats are lame.

 

IMHO… if you have a 3D printer … just print out an adapter to install the MAF ( my recommendation is to be 60mm ID ) measuring the distance between the TB and the MAF location ( you can measure it from the OEM air box… ) and make it so it gets to the point where the ram air assembly on the hood directs the air …. And slap a quality filter on it….

 

I was starting to think about this, so you're saying the reason almost all the aftermarket intakes throw codes, is the tube the sensor mounts in, isn't the OEM inner diameter, which I'm guessing mess's with it's calibration or ability to accurately measure the air flow though the tube, probably due to air velocity being slower for the given throttle % the ECU see's and the increase in demand of fuel for that amount of throttle over the expected value range?

Q: Can the ECU and or that sensor, as it's calibrated/mapped be adjusted though things like the Ktuner? I'd think they'd have to be able to be, otherwise I don't know how someone would turbocharge an L15A and the ECU not freak out entirely from the massive increase in air passing the sensor. Heck I'd expect at least of older cars, often a MAF had to be swapped out for a unit that could measure significantly more airflow.

Got to remember, I'm not traditionally a Honda guy, grew up deeply steeped in the Mitsubishi world. I am really starting to like Honda's for aspects I never gave much thought in the past though....it's almost like raw power and going fast, especially on the street, isn't all there is to a car being fun to drive LOL.

P.S. For now at least, if all that's really needed to keep the ECU from throwing a CEL, is the portion of the tube the MAF/MAS sensor sits in being the same... that's to easy to print. I can absolutely just get another air box (I really don't enjoy taking the air box out and don't want to do it again just for much more detailed measurements of that tube) and break out the calipers and make a high resolution model, and use brass threaded inserts etc. for the sensor to bolt down, and then I guess the easy answer is molded silicon hose from there.

One of the reasons I was trying to keep the OEM box is also the filter it's self, in my OPINION often the flat pleated boxy filters likely flow more air than at least the smaller cone style filters, that's my speculation anyway due to them likely having more surface area for the air to pass through. I could absolutely be wrong there though. I should probably figure out the surface area of the OEM filter and roughly the equivalent as a cone style. With turbo cars we always used as massive of a "cone" style filter as possible to try to reduce the air pressure drop in front of the compressor (turbo's compressor) but there's not a ton of room in the engine bay of the Fit, again which is why I was trying to use the OEM filter and feed it air that at highway speeds anyway would be from a higher pressure area like the drivers side tire well.

 

That's the gist of it. A larger tube bore around the MAF slows down the air flow for a given total mass-air-flow rate (more or less the point of making the tube bigger). The sensor has no idea what the tube bore size is - it's only measuring air speed and temperature. I haven't seen an explanation as to how the ECM/PCM/ECU diagnoses a bad MAF, though I can guess: Classic Hondas don't have a MAF sensor. They use a "speed-density system" to measure air flow, versus a "mass air flow" system. Speed-density relies on knowing the engine's displacement (liters of stuff moved per engine revolution - 1.5 liters in the Fit), the speed of the engine (revolutions per minute, or second, or whatever convenient unit of time), and how dense the air is that the engine is pumping (as measured with the Manifold Absolute Pressure sensor, and Intake Air Temperature sensor). The ECU programming has a spreadsheet-like table that it uses to skip all the math of calculating mass air flow and target air-fuel ratio. The table has engine speeds on one axis and MAP values on the other axis, where each cell has a value of how much fuel to inject for those engine conditions. The value gets tweaked a bit by the air temperature value, and a few other processes like the oxygen sensor cycle (called closed-loop operation) or the cold engine warm-up routine. As you're probably aware, "tuning" an engine involves changing the values on that table (actually tables as VTEC operation has its own separate table), as well as a similar table(s) for ignition advance.

ANYWAY. I expect modern ECM/PCMs have none of the processing power limitations of those classic ECUs. So, why choose one air metering system (speed-density or mass air flow) when you can have both? When the two systems disagree, the diagnostic system kicks in to figure out which sensor value is out of whack. If the issue is non-obvious, it just throws some general fuel trim out of range error or whatever.

Almost certainly.

A little history: Most tuning suites get their job done by completely replacing the ECM/PCM programming. In the early days of hacking, people would read the ECU program off a dedicated memory chip on the circuit board, modify it, write it to a new chip (you might have heard of chip burning) and then plug or solder that onto the ECU board. That went on for some time until the people that made (were selling?) the chip editing software got pissy with people selling chip programs made using that software, which blew up even further as the original program on the ECU chip is "owned" by Honda, so making copies and selling them (edited or not) was Software Piracy proper. Honda was looking the other way until the lawyers got involved.

What does a tuning software company do to deal with that situation? Write their own ECU software from scratch. When you go that far, you can make the ECU do whatever you please, within the limitations of its hardware. Write a program that heats the exhaust manifold to just the right temperature for searing steaks, or plays Rick Astley on the fuel injectors. Not good enough? Build your own ECU hardware with a pre-amp output to run a subwoofer for that sick 80's synth bassline. So yes, a tuning suite that replaces the ECU/ECM/PCM software (and probably hardware) should have no trouble modifying the MAF calibration. It can probably be programmed to ignore the MAF all together.

The concern with a "stand-alone" engine management system like that is its street legality. As I understand it, federal regulations require that all the original emissions equipment remain operational, and emissions remain within limits. No shop is going to go through verifying all that - they'll just tell you to get an original ECM, and if that won't run your engine anymore, that's your problem. If you live in an area with no vehicle inspections, well... Nobody's going to check any of that. A cop might give you a fix-it ticket if your car is rolling coal, or shooting flames, or waking up half the town with backfiring. However, a properly tuned, well-behaved vehicle can fly under the radar in those situations.

 

I have to wonder why they went away from speed density, a lot of people go from MAS/MAF's to speed density... because once the VE map of the engine is dialed in, it just works even if there's multiple issues up stream of the intake manifold... Oh well is what it is in this case for these cars. I don't suppose they have a MAP sensor on the intake manifold somewhere do they?

 

Ahh, you're an older fellow like myself I see... yes I remember the Ostrich EPROM programmers. They were a far superior option to lying to the ECU like early off the shelf solutions, especially since that then screwed up the ignition timing map to be way more aggressive there by limiting how far you could take things using that method.

Luckily I live in a "free state" that outside of the capital city which I'm not going to name, no one gives a flying F about emissions equipment, you can literally run around my area with open headers for the most part so long as you're not doing that and driving like an A hole at night, no one cares. So I couldn't give less of a crap about that aspect of it, other than hating CEL's... on ECMLink (DSM/Evo software for editing the OEM ECU) you could just turn off all that crap and or re-purpose stock inputs and outputs easily, so I do miss that as well as selecting a ton of off the shelf sensors had been built into a database for drop downs you could just add to various inputs... didn't know how good I had it LOL. (and that was on a 1990 OBD1 ecu that didn't have the computational power to really keep up with the engine so it had a work around with some sort of algorithm.. I forget how it all worked but it sort of compensated for needing a CPU that was a little more powerful)

 

They do.

 

I'm not about to spend the money on a stand alone for this thing, but it's interesting to know it's setup in such a fashion you could just use speed density with the available sensors, I guess you weren't just talking about a hypothetical earlier between two sets of sensors (ways of determining air mass vs time or rpm)

 

Looks like J's Racing did the same basic thing I'm talking about... except they want $1,000 for theirs.



Though if they're going to duct the air in under the air filter like that, I'm not sure what the compartment off to the right is for?

 

I'd guess a resonance chamber/silencer to illuminate intake noise.