Here is my question. So everyone agrees that adding an intake or exhaust "is a waste of money". How is it that my car feels like it has 20 more HP when I am in California at sea level then? I live at 2100 ft, you would think that adding an intake would help by allowing for more air (oxygen) to enter the engine but so many say the ECU calibrates back. If the ECU calibrates back then why do I have so much power at sea level? Does the ECU calibrate back only the amount of air and not measure the oxygen level in the air? For those who understand the Honda ECU, would adding a intake at elevation help?

 

At sea level, air is denser. When it gets cold, air is denser. An intake doesn't force more air or condense air into the engine. An intake just increases the "hole" to allow more air in OR brings in colder air OR creates less bends to help with the air velocity into the intake.

At least that's my understanding of it all.

 

Are you spending tons of time at sea level or just a few days at a time? IIRC the Intakes work for a period of time but the computer learns the new level of oxygen over time. if you are only there for a few days, it may be that the computer hasn't had enough time to adjust accordingly. now if you are spending weeks at that elevation, it could be that the slow "de-tuning" over time isn't noticed and in turn becomes a placebo effect.

~SB

 

The other issue is, how long have you had the new intake?

 

I am talking about a bone stock car here. Someone with Honda ECU knowledge please.

For those who are trying to educate me on the basics, feel free to advance it a bit. 20 years background in modifying and racing. My specific question is the Honda ECU (which I am not familiar with). I know Nissan used to limit the throttle plate to less than 100% if it sensed airflow at a predetermined max rate. I'm curious to know if Honda does the same thing.

 

If I remember correctly in the pre ECU fuel injection days the lesser amount of air density at high altitudes required that the fuel jets in carburetors to be changed on cars from lower altitudes when passing through and back to the larger ones when returning to lower altitude.... Possibly due to the lesser density of the air and reduction of flow velocity when using the intake your MAF sensor isn't signalling the ECU the correct information and the A/F ratio is too rich at high altitude... My car never has been in the mountains but with an aftermarket intake it did great as far as having power to accelerate and deliver great fuel mileage once I was cruising above 4,000 RPM. That was at no more than 650 or so above sea level... High IATs and the A/C being in use killed the performance then and now with 10 PSI boost, intercooler and a reflashed ECU...

 

MAF stands for Mass Air Flow, so the MAF Sensor is sensing the amount (mass) of air flow, not the elements contained within.

 

Exactly. Same question I have. This works on just about every other car. The only way this would work on this car is by regulating drive by wire. I am not convinced on this one until I hear that the ecu is actually programmed to do this.

How would this work for a dirty air filter? How about a performance filter such as K&N? One should be able to determine this with the scan tool by watching throttle position and MAF/mass air flow.

I could look at my scangage and see if it reads throttle position.

 

Intake systems incorporating low restriction air filters will pass greater amounts of air at the same atmospheric pressure but the difference is very small unless you're cranking over 5500 rpm. When you at sea level as opposed to 2100 ft the atmospheric pressure is higher and therefore pushing more air intio the intake system than at 2100 ft. Again the difference is not huge but it is noticeable; I don't have my charts here but I want to say the difference is .2" of Hg per thousand ft so if thats right the pressure at sea level is 29.92" hg and at 2100 ft its 29.52. Thats a 7% power loss which is like cutting your Fits max power to 110 from 119 hp. That is noticeable so its not the air filter thats most of the gain but the change in elevation. At 6500 rpm the lower restriction air filter would probably gain 2 of the lost 9 hp, maybe 3 but at 3500 rpm not much.
K&N's are great for racing but not for the street, especially the opportunity for the re-oil fouling the MAF wire.

 

OP What you are talking about has little to nothing to do with the ECU. Its about oxygen mass flow and charge face velocity.

What you are experiencing with the change in altitude is exactly what you should be.

Greater altitude means less oxygen mass per unit volume.

A larger "less restrictive" intake pipe or manifold will shift your power band to the right because charge face velocity has dropped, and thus port velocity has dropped.. This hurts cylinder filling and torque where you spend most of your time in the rev range.

Horsepower is derived from torque, which is directly related to cylinder filling/evacuation (VE) Less torque at any given point means less horsepower.

You results are exactly what you should expect in this case.

 

I am with the OP and I can speak on this topic in greater detail than most (6 times published author for an online auto magazine, 20+ years experience with autos, etc...). I posed the question about the air filters to point out that we can use them with a scantool to test a hypothesis, considering we lack information about the Honda ECU programming, we don't have anything else.

 

Roger, if you can't understand the relationship between altitude, charge density and power output.. you have no business postulating about engine performance.

That is elementary stuff.

 

Thanks for the smart ass remark... but read the OP's post closely, he understands power drops off at higher altitude, we all agree. I was commenting on the statement about "So everyone agrees that adding an intake or exhaust "is a waste of money""

Does the ECU recalibrate to limit mass air flow?

I question the logic in the sentiment about an intake or exhaust being a waste of money

I am aware of its effects on the power band, and understand it being due to the scavenging effect, although i have never heard the term charge face velocity. I am sure your knowledge is beyond mine, i don't question that.

 

It limits torque through timing, fueling and TPS voltage in the event he were moving enough air to warrant that.

This is not what is occuring to the OP.

His intake shifts the power band to the right, but nothing else in the system is complimentary.

So he has basically shot himself in the foot. The stock airbox is not super restrictive on an otherwise stock Fit.

Were he moving greater oxygen mass, then there might be some ECU interfering..

 

So, this ECU effectively limits power. What was their point in doing this, to limit the movability? Protect the drivetrain?

 

I live at 4500 ft and I actually get WORSE gas mileage when I'm in LA each month, than when I'm in SLC.

I'll pay closer attention to the power when I'm in LA next time. I hadn't noticed much difference, but you may be right.

 

The ECU cares naught whether you have a low restriction filter; it only takes the measured amount of air flowing in the intake and calculates with the temperature, atmospheric pressure, and required injection amount for the load on the engine, among other things, to signal the injectors how long to open the injector valve.
The advantage of low restriction air filters is the reduction in the pressure drop across the filter which theoretically means less hp is lost sucvking the air thru the filter. It is work and work per unit time is power. Low restriction filters, or none at all for racers, is an advantage when the rpm exceeds 5500 rpm because thats the rpm requiring enough air sucked in begins to show a reduction in thed power loss from the air flowing thru the filter. Its also why engines for public consumption are 'converted to sea level so everyone has a commoin reference. Of course, those in the dyno trade know that no two dynos are the same so differences between must be at least 5% before anyone notices.
Its also what makes forced induction matter, higher intake inlet pressure = higher air flow = higher hp.
As far as Nissan,I need more info; our Nissans had the same situation as Honda so I don't understand the 'throttle plate"
The ECU does not re-calibrate in the usual sense but it does change its output signal to the injectors and ignition timing based on the MAF sensor signal, the atmospheric pressure signal, the throttle opening, and the knock sensor signal. All those are in a 'map' of conditions that the computer selects what matches what. Unless you add forced air, camshaft, valve size, rpm limit, or somethoing else outside its existing working range you don't need to worry about it unless you're tuning for non-emissions controlled operation..

 

What? I don't have a clue what is said.

 

We class it as a waste of money because the gain in power below 5500 rpm is virutally negligible and therefore cost has lirttle gain. Youll get far better reward from better tires, better gasoline.

 

The engine breathes well enough for regular folks... got it.

Glad i never mod'd it. I'll save that cash for the mid life sports car the wife said was ok to buy. Kids are going to get the Fit in a few years anyway, and they don't need any extra power.