I'm not a combustion engineer but how is it possible to run lean if you only modify the exhaust side of things under NA circumstance?

 

intake as well...

 

Do a search on the AJ-Racing thread, they talk about the car running too lean when you add a test pipe to the I/H/E setup


EDIT:
Here you go, bask in my epic seaching ability
https://www.fitfreak.net/forums/aj-r...questions.html

Actually you were involved in this post... the second post basically is what i was going off of.

 

With the CAI vs Chamber vs SRI I was careful to put in "I think" and "I have no concrete evidence"... just my own obervations when you reduce the backpressure on this engine it seems like the amount of initial resistance to overcome with a CAI seems to impact things a bit.

Take it or leave it, would love for somebody to prove it.

 

I'm looking for technical answers as to why with addition of a test pipe will increase lambda.

 

I see your point, unfortonately I don't have an answer. What I do know is that they seem to keep running into this issue whenever they use testpipes.

I can only theorize that significantly reduced backpressure is maybe letting more air pass through the entire system than the ECU is compensating for?

Anyway, just something to be aware of for our OP when considering a test pipe.

 

So reading through the whole thread (thanks for posting the link, btw) it seems like yes the fit will lean out, but not to the point of potential catastrophic damages.
I'm running Fujita CAI, A-Spec test pipe, and skunk2 50mm b-pipe/axle back. (So this would be assuming my mods would behave similar to the T1R parts)
I feel less power than before from idle to 2500. By 3000, there is a much more drastic change in feel between VTEC/no VTEC, more than before the test pipe (but with the other mods) and definitely night and day from bone stock.
I'm considering removing the axle-back portion and seeing how it sounds/or if any performance change in the lower RPMs.
If it does, I'll run a stainless pipe from the b-pipe to the rear to look "normal". If not, I'll just deal with it I suppose - boost should be in the future anyway, just not sure when.

Oh, and some non-scientific anecdotal evidence: I run scan gauge - Running on stock parts, using the "Instant Horsepower" gauge, I never got a reading higher then 74.X up through to redline in 2nd gear. With the skunk2 cat back and a couple different intake setups, I got to 84, redlining 2nd. With the test pipe, doing the exact same thing, redline 2nd, I got to 104.
I know the numbers are probably bogus because it's just a scangauge, but the take home message is that to me it seems there is enough of a power increase with the mods (especially the test pipe) to warrant an increased reading from the little SGII. For all I know though I could be making 3 more ponies with all these parts though in reality. But hey, at least it's something.

Uh, Where's the OP in all this anyway? He sort of disappeared after page 1?

 

i didnt yet add this in here...but currently the only performance mod to my car is a test pipe. my wideband a/f gauges reads over 18:1 when partial throttle sometimes. it sometimes goes higher and reads "---"

 

Where is your wideband sensor tied into?

 

That can't be right? I'm assuming your car runs fine? I'm no pro with the who AFR thing but it seems like 18:1 is VERY lean?

What wideband are you using?

I'm thinking of starting off by picking up a regular A/F gauge for the time being, then whenever kraftwerks graces the presence of my engine bay upgrade to a wideband... but is it even worth it to get a narrowband - I keep reading online it's not accurate or really valid because the ratio computed is so broad.

And an off topic question - with JUST the testpipe, is there a performance gain to be felt at all? I'm tempted to play with my exhaust setup until I get the "best" feeling.

 

Lol.
This thread delivers.

 

i dont see how it can be wrong. its a AEM UEGO wideband. brand new. and there are no other mods to the engine. it idles at 14.9 and for teh most part is 15.5-16.5 when crusing. but once and a while it flashes to 18 and 2 times ive seen it go "---". im not that worried since the car is mostly stock...its probly supposed to be that way to get good MPG.

 

Just confirming, what sort of throttle position are you seeing this enormously lean condition? Also, where is the wideband mounted?

 

its partial throttle...just enough to maintain a 60mph cruise on the highway in 5th gear. at WOT is is much richer...more lieka 15.5-16.0

wideband is mounted a couple inches before the secondary o2 sensor.

 

Is anyone running I/H/E with test pipe? I'm interested in trying out the cat-delete but all this talk about leaning out too much makes me wonder if anyone's had the whole setup for a while w/o any problems.

 

i say dont do it. my test pipe is has caused me nothing but trouble ever since i got it. ill be selling it soon. its a t1r. PM me if interested.

 

what kind of problems? mechanical or law enforcement?

btw i'm selling my t1r test pipe. don't need anymore i have the j's test pipe

 

As a preamble, I am not an engineer nor do I claim to be one. The following is based on my personal experience, study of the subject and logic. So take this with a grain of salt.

The reason the test pipe causes the Fit to go lean, is because the engine runs on a speed density fuel injection system.

Let me explain.

Speed density systems rely on two primary sensors, the Manifold Absolute Pressure sensor (MAP) and an Intake Air Temperature sensor (IAT). These two sensors work in conjunction with the ECU to precisely and accurately "predict" the amount of air passing through the engine.

Notice I said "predict", not measure. That is because the speed density system doesn't actually measure the amount of air passing through the engine. It calculates this value using the amount of manifold pressure and air temperature, and then based on a set of values already entered into the ECU that represent the Volumetric Efficiency (VE) of the engine, it "infers" or extrapolates how much air should be entering the engine.

The formula is expressed thusly: (Engine Mass Airflow Rate) ≈ RPM × MAP / (absolute temperature)

This is based on the presumption that the fuel tables that are set in stone in the ECU concerning VE (volumetric efficiency), stay the same.

When you increase the size of the intake/exhaust tract, you are changing the VE of the engine, without changing the preset values in the ECU.

The MAP and IAT are still reading the same values. What the ECU doesn't know is that even though pressure and temp have stayed the same, the amount of air has increased, sometimes dramatically.

Most of the time, but not all of the time, most of the time, since factory engine ECUs tend to run on the rich side, leaning the mixture down some will increase horsepower. But at a certain point, it begins to lose power. Especially in the higher RPM range.

The only way to compensate, is to increase fuel delivery. And that can be done by increasing base fuel pressure, or changing the ECU fuel map parameters to reflect the new VE value.


Ref:
MAP sensor - Wikipedia, the free encyclopedia
Speed Density to Mass Air Flow Conversion

 

and a high five to sid regardless what'ss 100% true. makes me wanna go on n learn to tune