AFR reading
 

I don't have a wideband AFR to measure this, so I'm curious to know if it's possible to run too lean with just bolt-on mods on an untuned AP2? I/H/E - no ITB's

I would suppose that it's "possible" but I'm not sure how likely it is. I know the DBW S2k's can be twitchy about that stuff.

Either way, I'd think you're ok, but at the same time might be a good idea to get someone to check it out for you and make sure.

I would say it is possible but very unlikely to cause any harm :shrug: people have been doing it for a really long time and Ive never hared anything to worry about...

I wouldnt worry about it, thats one of the great things about being N/A we dont have to worry about all the stuff the boosted guys do :banana:

I know that it doesn't matter for daily driving, but what if you're tracking the car and running high rpm's for an extended period of time? I know the safe thing to do is to watch the AFR and monitor the knock sensor, but I'd rather not spin the wheel and throw down the extra cash if someone's already done this.

Wb's aren't that expensive. If you're worried about it pick one up. These are good and cheap
http://prosportgauges.com/wideband_AFR_Gauge.aspx

Lean? i'd say rich before lean. My 02 with aem v1 and a t1r cat/test pipe runs very rich or so it seems to smell very rich (i've own a 2 rotarys before so i know the smell) With Header and exhaust i could see it running rich but lean.. is another story. i wideband is a good idea in any performance car but imo if all is well no check engine lights and so on i dont see the car running that lean to even cause a scare.

I'm not an expert at this, so correct me if I'm wrong, but wouldn't the increased airflow cause the engine to run more lean? And if so, does the ECU compensate this by adding more fuel or is a piggyback EMU necessary to correct?

It's been proven SO many times...

Any type of "flow" mod added to the S, will lean it out. It was never an issue with older years, especially 00-01 S2000s due to the ECUs running so lean from the factory. As the years progressed, Honda seemed to lean the AFRs out more and more.

Someone else expressed concern about running lean with TP/E on the "S2000 Modifications and Parts" section so I got a bit worried. In any case, I think I answered my own question. I wasn't able to find the answer on this forum, so I'll repost it for other fellow newbs, but this was taken off the Integra forum.

http://www.team-integra.net/forum/display_...ng+Common+Topic

SOME BASIC ECU INFO THAT YOU SHOULD KNOW:[B]

The ECU has 2 modes of operation:

1. closed loop
2. open loop

closed loop uses the front O2 sensor before the cat (on both OBD1 and OBD2 called the PRIMARY O2 sensor ) to control the injector opening time (called duty cycle).

In closed loop, there's 2 adjustment modes:

1. short term trim
2. long term averaging trim

your primary O2 sensor is a NARROWBAND type of sensor (see the dyno tuning section of the articles and look under Air Fuel Ratio Tuning BASICS to see the relevance of this).

Because the primary O2 sensor is too slow to react to the rapid changes in the exhaust's O2 content as the rpms rise, we need to use open loop control, once the throttle is pressed past 1/2 or when you go past 4000-4500 rpm usually.

In open loop, the ECU's programs control the injector opening time instead of the primary O2 sensor. These programs are laid out in the form of a table (see the ECU Basics article for an example of what a fuel table looks like) .

The commands for the injector are called "fuel values". The table has manifold absolute pressure (or MAP, a measure of air flow) as the indicator of how hard your engine is working . rpm is used as the other indicator. Another way of saying "how hard the engine is working" is "engine load".

The programmers enter the actual time the injector should be open for each manifold pressure (MAP) and rpm combination.

So once you press the throttle past 1/2 or go past 4500 rpm, you change from closed loop ECU control to open loop ECU control.

--------------------------------------

The stock ECU program usually runs fine in "closed loop" operation (not too rich or too lean), as long as the O2 sensor and it's connectors and the longterm trim averaging are fine .

However, the stock ECU program has 2 problems:

1. it runs too rich in open loop

and

2. the ignition timing tables are retarded too much in the lower rpms for both closed and open loop (you usually need more advance in the lower rpms and this is why your engine feels like it's lagging or bogging).

The common false idea is that you run leaner because your engine breathes better after adding i/h/e (+/- IM) and the fuel delivery stays the same as before.

The fuel doesn't stay constant though.

The reality is, in closed loop, the longterm averaging responds and changes with the extra air flow to keep the air fuel ratio near the optimum range based on the primary O2 sensor readings and so you should not run too rich or too lean.

The other reality is that the stock ECU's fuel tables for open loop operation kick you into running too rich (not too lean). The stock ECU programs for fuel delivery usually over compensates for the new mods in open loop after i/h/e is added.

Resetting the ECU doesn't change the open loop commands. It only resets the baseline primary sensor voltage after the engine has warmed up for closed loop operation and clears any CEL warning codes.

So when you have added i/h/e or i/h/c/e, the ECU isn't a nonresponsive unchanging program.

In closed loop, it reads the amount of O2 that is coming out of your header and based on this amount, it changes the injector opening using short term correction and then averages these over time for longterm averaging correction.

In open loop, the program is set. With more air flow, the ECU goes to a different MAP-rpm-injector opening combination command to deliver a set amount of fuel.

eg. using hypothetical numbers to show you the idea:

let's say at 6000 rpm in bone stock trim, your closed loop has a MAP of 2 psi and an injector opening of 55% duty cycle.

With the intake and header scavenging, your MAP (air flow) becomes higher to say 3 psi.

In open loop, the ECU reads a new MAP of 3 and reads down the fuel table commands and looks up MAP = 3, rpm = 6000, and then chooses the injector opening command for these 2 inputs. Usually, the injector opening time or duty cycle is longer or larger with a higher MAP...say 65%.

So the ECU in open loop adds a set amount of fuel to compensate for the extra air flow as the rpms rise. Sometimes the fuel value command entered in the table for a given MAP-rpm load is too much or too little. This is why you reprogram/tune and enter a better fuel value depending on what air fuel ratio you get in open loop.


SO PLEASE LOSE THIS IDEA THAT YOU RUN LEAN WITH i/h/c/e (+/- IM).

btw this is also why you need to fuel tune, even with only i/h/c/e.

DO I EVEN NEED TO FUEL TUNE OR REPROGRAM MY ECU WITH JUST I/H/C/E ? :

Another urban myth that's out there that we see every time a person slaps on an intake and then joins ti.net. is this :

i/h/c/e doesn't need fuel tuning.

Well, if you would have actually fuel tuned your engine to the new package, it runs more efficiently than stock, since the stock commands errs on the side of safer (safer = running too rich since you don't detonate).
So yes you run too rich after i/h/e using a stock program and so you should reprogram or fuel tune to get better responsiveness and more power.

Chris S2K

Thanks 1 million time man!

It depends on parts really, the length of the primaries on the header,manifold, length/diameter of exhaust etc etc.

Its certainly not going to run lean all the way through the rev range (it will run too lean in some areas i gaurantee that), I know its a bit different but my AP1 ran too lean and actually too rich in some areas and i have all bolt on's - i tuned it though.

Its WOT you need to be concerned with where the AFR should not exceed 13.2 to be on the safe side.

Narrowband is pretty useless for tuning.

Cheers

The numerous charts i've seen with A/F ratios have shown lean (14, 15, 16) in ap2 with I/H/E

Are you running lean in WOT? I would say so. Am I sure? No, go get a A/F reading on a dyno going WOT.

A/F in WOT changed in 04-05 and even more lean 06+

(See mod list below) I'm running h/tp/e with a drop-in and my afrs *are* leaner than factory trim. I see 12.8s @ WOT on my early ap1 ecu (which is known to run rich.) IIRC an early ap1 can be in the high 11s to low 12s @ WOT? I know later model ecus only got leaner so I'd be even more inclined to worry about afrs on an ap2.

I intend to keep my car for a long time so I'm very concerned about engine health. For that reason I bought the Uego. I highly recommend a wide-band to anyone that intends to put their car through its' paces.

Thanks for all the input guys, obviously, my main concern here is to get a better understanding of how bolt-on mods affect the engine and possibly mitigate the risk of damage on the engine. But I'm still not sure if I fully understand this yet.

I was finally able to find some A/F graphs on a stock engine (AP# unspecified) and this particular engine runs a bit lean at partial throttle, but rich at WOT (which is safe). Is this a graph of an AP1? It makes sense to me that Honda engineers would have made the engine run rich in WOT in order to protect it from detonation, but I'm now hearing conflicting stories on that :shrug:

https://www.s2ki.com/forums/index.php?showt...0&#entry6505186

Drewmob - thanks for posting; looks more and more like I should be getting a wideband.

what you stated means running richer after the mods.

lets say 14.7-1 ratio is stock air-fuel ratio

when u mod it and you see your wideband go to 13-1 or 12-1 that means its getting richer in fuel.

air =14.7
fuel =1

now lets say u get 10-1

air=10
fuel =1

that means less air to the same part fuel means you are getting more fuel at 10-1 than at 14.7-1 which means you running richer than 14.7-1

anyone please correct me if you know for a fact that what i said.. thank you

Your argument is flawed from the beginning. 14.7 is stoich, but not stock. Stock @ WOT is MUCH richer than stoich, especially in an AP1.

In my comments that you quoted, I stated that I went from high 11s-low 12s @ WOT (STOCK) to around 12.8 @ WOT (modded.) This means that I was running significantly leaner after modifications. FWIW, I do run pretty close to stoich @ idle...

Later model ECUs ran progressively leaner from the factory which *can* cause them to run lean after significant airflow mods (i/h/tp/e...) I'm not sure where the danger line is here since my knowledge is relative to my car.

Like I said before, it is best to keep an eye on your afrs as you modify your car...

Hope this helps.

Has anyone heard/read stories of anyone damaging their engine from running too lean from bolt-on mods?

its more of a long-term wear issue as opposed to a retainer cracking and immediately destroying an engine.

[QUOTE=drewmob,Nov 10 2009, 12:19 PM] Your argument is flawed from the beginning.

Yeah, as a generalization cars run rich @ WOT from the factory.

you want to be around the 12.5:1 mark.

Theoretically you could go to 13 or 14 and make more power but you're on a thin line. It's best to keep it in the 12 range to keep the heat down.

I ve read numerous articles on this and the concensus seems to be, don't go past 13.5. any leaner and you could damage your engine. i install a vafc and got tuned to 13.5 @ wot. before the vafc, i've got i\bbtb and was running between 11 and 12 afr factory. stock ecu's will compensate some for bolt-ons, hence forth learning ecu. seen this on the dyno. if your really concerned, have it dynoed. that might ease your mind on this matter.

Yeah, I went a step further and acquired an EMU :)

In WOT anything leaner than 13.2 is bad (ie melt piston bad :D) the best range for power is 12.7 - 13.2.

With my vafc2 it hover around 13.0 to 13.1 in WOT

I cry when i see people tuning and its highier than 13.2 :eek:

very helpful . one question , vafc can only tune for wot right? on a budget, but a greddy ultimate would be better tahn a neo ? cause sometimes they are found for the same price lol