lzylst

iTrader: (1)

How about a simple drop in replacement filter? EX: K&N

Isn't fuel added based on both TPS and MAP?

gadawg31

lxylst, I have thought of that as well and I mentioned it earlier in one of my previous post. I do see what shipo is saying... more air, more fuel, bad gas mileage... however a proper tune and maybe an air filter could possibly get me a little mpg increase. I don't get what shipo meant about the ECU readjusting after a few weeks. I spoke with a friend of mine that works at the dealership and he stated that once an ECU is programmed it remains programmed. Anyway, at least with this thread I have been able to scratch off certain items and add new ones to research, regarding my accord. I never turn down info, whether I like the answer or not, it is always welcome.

JD

shipo

The throttle position sensor really only comes into play when sensing either idle or at or near wide open throttle; in both of those cases, the engine computer reverts to a preprogrammed air/fuel ratio map. Other than that, the TPS is pretty much along for the ride. I know a lot of folks think otherwise, but consider the following scenarios:

• On a cold winter -20°F day up here in New Hampshire, the density-altitude can equate to as low as 6,000' below sea level, and that in turn means the air weighs about .090 lb/ft3.
• On a "standard day" (a valuation typically used by aviators) at sea level where the OAT is 59°F and there is no humidity the air will weigh .0765 lb/ft3.
• On a warm day crossing the Rocky Mountains (like I did just this summer) where the OAT was 75°F at 10,000' above sea level, the air will weigh only .050 lb/ft3.

If you took a hypothetical car designed to run using the TPS for calculating the air to fuel ratio for the engine, and where the TPS/Computer were optimized to run the engine on a "standard day", and then drove it here in New Hampshire when the OAT is -20°F; the engine would be run so lean it would either A) not operate at all, or B) induce detonation so severe the engine would be destroyed in relatively short order.

The flip side is if that same hypothetical car was then driven over the Rocky Mountains on a warm(ish) summer day, the air to fuel ratio would be so rich you'd have raw gasoline pouring out of the tail pipe.

In reality, the engine computer relies primarily on the MAP (or MAF depending on manufacturer) sensor to weight the intake charge before determining the air to fuel ratio. I said primarily, and by that I mean in the closed loop world of OBD-II, the computer is capable of doing a certain amount of learning based upon feedback from other sensors (primarily the O2 sensors). Here's where we get to the "readjusting" aspect of my previous post; if a change is made in how the engine obtains air and fuel which effectively changes the parameters for the air to fuel ratio, then the computer will be able to sense via the O2 sensors that something is out of whack and it "learns" how to bring the ratios back into alignment.

A few parting comments:

• When you paraphrased me as saying "more air, more fuel, bad gas mileage", that is technically incorrect. Why? Because if (and that is a very big "IF") a CAI was able to provide an appreciably lower intake restriction at say a steady state freeway speed than when compared to a factory intake, then any given throttle setting would simply make the car go faster and you'd back off the throttle to maintain both speed and fuel economy.
• So, why did I say that CAIs often reduce fuel economy? Because the intake resonance (the natural vibrations of the intake charge up stream of the intake valves), a characteristic which is carefully tuned for good mid-range torque and fuel economy by most manufacturers, can be altered to the point where the intake charge doesn't fully mix at low and mid range engine speed.
• Another thing to consider is the "cold air" itself. While cold air is more dense which can then, at the extreme, allow an engine to develop more power; cold air is actually the enemy of fuel economy below a certain point (typically about 40°F for most engines). Many vehicle manufacturers use some form of warming for the intake charge to aid in fuel atomization when the engine is operated in cold weather. Add a CAI and that warming effect is typically lost as well.
• A final note: I don't think I've seen a single car made in the last fifteen or more years that didn't come from the factory with an intake snorkel which sourced intake air from a "cold zone" up near the nose of the car. While not flashy, sexy, and noisy like aftermarket CAIs, they do in fact qualify as a CAI.

gstrudler

Efficiency is the name of the game. When the engine is more efficient, it wastes less fuel and generally makes more power. In the Honda world, yes, the ECU is primarily concerned with the MAP sensor, and then makes small adjustments based on intake temp, coolant temp, speed, primary o2 (when in closed loop), and a couple other factors. The TPS is mainly used for throttle enrichment in the case of sudden throttle opening, and to trigger open-loop mode when in WOT. Note that there are TPS-based PGM-FI systems, but Honda is not one of them.

The "learning" aspect of OBD2 comes in the case of closed-loop mode in which the ECU compensates for running rich or lean based on the o2 sensor during cruise, idle, or light acceleration. The compensation happens in two ways: short-term and long-term fuel trim. The long-term fuel trim is stored in the ECU and is referenced by the ECU from that point forward, irregardless of open or closed loop mode. This is meant to allow the ECU to "learn" the engine and environment, compensating for engine wear over time and environmental factors (altitude, general humidity, etc). Short term is what most people think of when talking closed-loop mode, in which the ECU will add or subtract fuel instantaneously from its' base map based on feedback from the primary o2 sensor.

There are certain ways to "trick" the ECU when using a piggyback controller to allow you to tune the engine without it constantly fighting you back. Basically you have to force the engine into open loop mode, which is most easily done by sending a false signal for the TPS that makes it look like it's at WOT (at least that's what I've done anyway and have read elsewhere). OP, I installed and street tuned an eManage Ultimate myself and have seen about a 3mpg increase overall in fuel economy. This is not for everyone and you have to install a wideband AFR and do your research as well; my cost for the wideband and eManage was probably $600 or more, and I installed it all myself (which included welding a bung on the exhaust for the wideband o2 sensor and all the wiring of the sensor and piggyback controller). If you can't/don't want to tune it yourself, you're looking at another $150 minimum to do a 1-hour dyno tune, plus any labor for work you can't do yourself. So in the end you're probably out close to $1k for this setup, which may not be worth it to you if all you are looking for is a small increase in MPG. It pays dividends down the road if you end up modding your car, however, such as adding a CAI or a free-flowing exhaust, etc as then you can tune and compensate for them.

shipo

Three miles per gallon? To say that I'm skeptical is a gross understatement. I'd like to see the BSFC results of back to back dyno runs before I even remotely begin to believe that number.

gstrudler

Drive a Prelude that notoriously runs rich, along with a CAI and full custom 3" exhaust and you'll know how I can gain 3mpg after tuning. There are Preludes running around making high 20's to low 30's mpg and 220+ whp. Be skeptical all you want, but once you actually do some tuning you'll understand how it can happen.

speedjunkie_g35

That's funny because every vehicle I have put a intake on has helped with fuel economy. Was it much? No. My 07 QX56 gained almost 2 mpg, my 2000 lexus gs300 only gained .75mpg. My g35 gained 3 mpg. In all cases, they were hwy mileage. More air can make a engine burn fuel more efficiently therefore reducing fuel consumption and improving MPG!!!! Now if you have a heavy foot then yes you will get worse MPG.

shipo

What folks who make this type of statement don't understand is that there is no more air. As I wrote before, IF a CAI was able to allow more air through to the throttle body while in closed loop operation (i.e. tooling down the freeway at a steady speed), which given that your engine is only running at fifteen to twenty percent of its rated power is a ridiculous notion in and of itself, then ECU would simply detect the weight of the intake charge and add more fuel to the mixture. This in turn would make the car accelerate which would in turn make you back off the throttle and presto-chango, you're right back to where you started.

Once folks start to understand that the air to fuel ratio of an engine is based upon the weight of both the fuel and the air, and once they understand that the weight of the intake charge is measured downstream of the throttle body (meaning the presence of a factory intake, a CAI, or no intake at all becomes utterly irrelevant), then maybe, just maybe, they'll stop furthering the silly notion that a CAI can improve fuel economy.

One other point…
Folks who believe a CAI will improve fuel economy also (as a rule) believe that a dirty air filter will reduce fuel economy, and believe it or not, like it or don’t, nothing could be further from the truth in a modern OBD-II controlled engine. Don’t believe me? Cool, please take some time and read the following study produced by the Oak Ridge National Laboratory (the folks who brought America the refined nuclear material for our first atomic bombs) for the Department of Energy.

http://www.fueleconomy.gov/feg/pdfs/...02_26_2009.pdf

So, if a clogged air intake doesn't negatively affect fuel economy, then how in the world will a low restriction intake improve it? Answer, it cannot.

gadawg31

shipo, that article is a really good read; however not saying a agree or disagree, but being in gov't for as long as I have, I would love to see a few more reports that validate their same results. If I had to argue a point right now, this study would be spot on. I just know how agencies are able to skew data and this one could be spot on, but I am always somewhat skeptical. Either way, you can't argue the facts presented, I myself am just a conspiracy theorist at heart. Great article though. I think it rattled several big businesses cages and made them realize that their marketing departments needed t start working overtime.

shipo

There is a huge repository of data over in the SAE.org archives (most of which you'll need to pay for); you don't need to be an engineer to sign up for an account if you're really interested. If you don't feel like paying for the articles, there are any number of forum threads (for all makes and models) which speak to the same issue, and even a few third party sites which speak to the issue as well.

Here is a link to a thread I started a few weeks ago on the issue:

• http://www.hondaaccordforum.com/foru...l-truth-49964/

At the bottom of the first post is this link to a very well versed automotive technician:

• http://www.ricksfreeautorepairadvice...%80%99s-pocket

Regarding the conspiracy theory aspect; for years I've felt like the lone voice in the wind arguing that a low restriction intake (or even no intake at all) will be physically unable to improve fuel economy, and when that study was first published (and before I'd had a chance to read it), I felt my cynical side saying, "Oh here we go, another whitewash from the EPA saying frequent filter changes will improve fuel economy, blah-blah-blah..." Imagine my surprise when they actually got it right!

gadawg31

Yeah, I actually came across your post on "Honda Accord Forums" the other day, but had found the rick's article right before I made my first post. I guess I just needed that extra push to actually trust my brain, since all these years everyone is all about Pavlov's dog theory and basically barked everytime we heard a fuel saving commercial. I started reading the articles under "Stirred Reactor" and it all started to click. I knew then that I would have to succomb to the inevitable. We were actually being proven wrong after all these years, but to a certain degree of defense, I was still dealing with a carbed engine. So it was easy for me to jump on the "your an idiot" band wagon and ride. Something that is very funny to me now actually comes from the Men in Black movie, and Tommy Lee Jones says... we knew that to be true then, imagine what we will know tomorrow... Something along those lines, but you get the point. We have always known these things to produce good gas mileage, just imagine what we will know tomorrow. Any who, good articles and good thread. Not saying everyone is a believer, but I am not here for everyone, only myself. Selfish, maybe, but I'm the one paying the car payment. LOL

JD