Stock ECU, OBD2, A/F Controller, Aftermarket ECU...
04-18-2001, 04:43 AM
#1
Registered User
Thread Starter
Hi all, did some digging and didn't find too much on the topic. So...
I'm curious as to what opinions are regarding the ECU's handling of power breathing mods (or others) and how a/f controllers or an "upgraded" (Spoon, Mugen) ECU will yield more power. My experience with other Honda engines has been that OBD2 is smart enough to alter ignition & a/f mapping to "compensate" for breathing & cam timing mods to effectively reduce or eliminate them in the interest of emissions. I'm sure this wasn't Honda's intent, but a byproduct of their emissions engineering.
I've had good success in the past with Honda's MAP-based airflow detection using an a/f controller to lean it out. What I'm really interested in is if it's worthwhile to do this with a stock ECU or to ditch it altogether (Spoon, Mugen, maybe even a standalone). Can anyone comment on successive dyno runs over time (if mods "dissappear") and as to the effectiveness of an a/f controller?
Sorry for the dissertation, thanks in advance for replies.
I'm curious as to what opinions are regarding the ECU's handling of power breathing mods (or others) and how a/f controllers or an "upgraded" (Spoon, Mugen) ECU will yield more power. My experience with other Honda engines has been that OBD2 is smart enough to alter ignition & a/f mapping to "compensate" for breathing & cam timing mods to effectively reduce or eliminate them in the interest of emissions. I'm sure this wasn't Honda's intent, but a byproduct of their emissions engineering.
I've had good success in the past with Honda's MAP-based airflow detection using an a/f controller to lean it out. What I'm really interested in is if it's worthwhile to do this with a stock ECU or to ditch it altogether (Spoon, Mugen, maybe even a standalone). Can anyone comment on successive dyno runs over time (if mods "dissappear") and as to the effectiveness of an a/f controller?
Sorry for the dissertation, thanks in advance for replies.
04-18-2001, 08:24 AM
#2
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I just gotta warn you now, if you're not a serious tuner, don't try and go with a full aftermarket tunable computer like MoTeC, SpeedPro, or any of those. You will spend a large fortune trying to tune it and I still haven't met anyone that really knows how to do it right. My friend's turbo prelude has been running pretty badly for the past 6+ months because no one knows how to setup and tuen his SpeedPro computer to work right. We've rewired damn near the whole car just to get it to run. But it still runs like poop.
04-18-2001, 08:41 AM
#4
Registered User
Thread Starter
Thanks for the input. I wouldn't consider myself a "serious" tuner but more capable than most. I wouldn't think that an NA S2k would have as many problems as a turbo 'lude (that has a world of problems inherently), though I know full and well what a complete aftermarket unit would entail.
I really have no plans for a standalone- what I want to find out, though, is if that's what it would take to get lasting results from an a/f controller. I know in Preludes specifically that Honda's implementation of OBD2 will "undo" mods in an attempt to wrangle emissions back under control. So much so that OBD1 conversions are now commonplace (you can get an adapter harness for crying out loud).
Has anyone dynoed & tuned an a/f controller, then returned later to find that additional power "missing" or otherwise reduced?
I really have no plans for a standalone- what I want to find out, though, is if that's what it would take to get lasting results from an a/f controller. I know in Preludes specifically that Honda's implementation of OBD2 will "undo" mods in an attempt to wrangle emissions back under control. So much so that OBD1 conversions are now commonplace (you can get an adapter harness for crying out loud).
Has anyone dynoed & tuned an a/f controller, then returned later to find that additional power "missing" or otherwise reduced?
04-18-2001, 10:26 AM
#5
Registered User
marcucci,
Even the OBD1 systems will take out fuel changes if they are what I call "full time" changes. What I mean is, the stock ECU systems (OBD1 and 2) look for a specific A/F ratio range while at part throttle, closed loop operation. The injector pulsewidth is initially taken from the ECU map. But then the system looks at O2 sensor readings to determine if that pulsewidth is correct. If it is not, the ECU applies a short term fuel trim correction of up to 20% in either direction. If the correction is required for more than a certain period of time, the ECU begins to alter the long term fuel trim (also capable of +/- 20%).
The real kicker here is that what the ECU learns at part throttle, it also applies to full throttle, which is why Hondas can make a lot of power from bolt on mods without any additional ECU tweaking. Now, if Honda's full throttle ECU maps were set for maximum power, this wouldn't be a problem, but unfortunately, they are not. They are set overly rich to play it safe and provide Honda reliability. Furthermore, if you have a VTEC engine, the corrections needed on the small cam may be different than those on the big cam lobes. And how often do you spend at part throttle while in VTEC?
So, if you simply change fuel pressure or increase fuel delivery through the standard aftermarket controllers, the ECU will take it out eventually if it doesn't match its fueling criteria. I had a friend with a heavily modified Integra GS-R. His tuner put in too much fuel pressure and too much injector timing on his reprogrammed ECU (OBD2). The car was running a long term trim of -19% and a short term of -9% - because the long term couldn't go any higher, he kept throwing a code.
There are ways to trick the ECU, but the best add on solution I've seen to date is the Apex-i AFC-VTEC. This system has a part throttle correction (which I wouldn't bother with), but it also has a different set of full throttle fuel corrections, triggered I believe when the ECU sees a WOT indicator from the throttle position sensor (TPS). This is trick because the ECU doesn't look at the O2 sensor at WOT, so it won't try and correct for your changes.
UL
Even the OBD1 systems will take out fuel changes if they are what I call "full time" changes. What I mean is, the stock ECU systems (OBD1 and 2) look for a specific A/F ratio range while at part throttle, closed loop operation. The injector pulsewidth is initially taken from the ECU map. But then the system looks at O2 sensor readings to determine if that pulsewidth is correct. If it is not, the ECU applies a short term fuel trim correction of up to 20% in either direction. If the correction is required for more than a certain period of time, the ECU begins to alter the long term fuel trim (also capable of +/- 20%).
The real kicker here is that what the ECU learns at part throttle, it also applies to full throttle, which is why Hondas can make a lot of power from bolt on mods without any additional ECU tweaking. Now, if Honda's full throttle ECU maps were set for maximum power, this wouldn't be a problem, but unfortunately, they are not. They are set overly rich to play it safe and provide Honda reliability. Furthermore, if you have a VTEC engine, the corrections needed on the small cam may be different than those on the big cam lobes. And how often do you spend at part throttle while in VTEC?
So, if you simply change fuel pressure or increase fuel delivery through the standard aftermarket controllers, the ECU will take it out eventually if it doesn't match its fueling criteria. I had a friend with a heavily modified Integra GS-R. His tuner put in too much fuel pressure and too much injector timing on his reprogrammed ECU (OBD2). The car was running a long term trim of -19% and a short term of -9% - because the long term couldn't go any higher, he kept throwing a code.
There are ways to trick the ECU, but the best add on solution I've seen to date is the Apex-i AFC-VTEC. This system has a part throttle correction (which I wouldn't bother with), but it also has a different set of full throttle fuel corrections, triggered I believe when the ECU sees a WOT indicator from the throttle position sensor (TPS). This is trick because the ECU doesn't look at the O2 sensor at WOT, so it won't try and correct for your changes.
UL
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04-18-2001, 04:23 PM
#8
Registered User
Mingster, I don't think the WOT correction with the V-AFC should go away. Part throttle certainly should.
Marcucci, I've done some work on OBD2 Preludes and the gains from Iceman intake, Mugen header and Mugen exhaust were stable. In fact, the header picked up more power after the ECU adapted. Provided the gains aren't coming from an unnatural leaning out of the system (rather than increased airflow - although both may occur) then you should be fine. What should happen is the ECU should see a lean condition with the mod thanks to increased airflow through the engine. This should result in the long term fuel trim being bumped up. More air + more fuel = more power. By doing a continual reset, you may be perpetuating a lean condition, and the car will learn pretty quickly anyways. I do know that the gains from adj cam sprockets get taken out quickly though, because they alter ignition timing, which the ECU doesn't like.
Remember, all the ECU really knows is how much fuel it injects, the manifold absolute pressure and the O2 sensor reading. If the O2 reads lean or the MAP goes higher, more fuel should be injected, resulting in more power.
UL
Marcucci, I've done some work on OBD2 Preludes and the gains from Iceman intake, Mugen header and Mugen exhaust were stable. In fact, the header picked up more power after the ECU adapted. Provided the gains aren't coming from an unnatural leaning out of the system (rather than increased airflow - although both may occur) then you should be fine. What should happen is the ECU should see a lean condition with the mod thanks to increased airflow through the engine. This should result in the long term fuel trim being bumped up. More air + more fuel = more power. By doing a continual reset, you may be perpetuating a lean condition, and the car will learn pretty quickly anyways. I do know that the gains from adj cam sprockets get taken out quickly though, because they alter ignition timing, which the ECU doesn't like.
Remember, all the ECU really knows is how much fuel it injects, the manifold absolute pressure and the O2 sensor reading. If the O2 reads lean or the MAP goes higher, more fuel should be injected, resulting in more power.
UL
04-19-2001, 07:46 AM
#10
Registered User
marcucci,
You've hit the nail on the head. The stock top end fueling is way too rich for maximum power (ever see a DOHC VTEC Honda on the dyno? about 500 rpm from the limiter it starts putting out a haze of black smoke from the tail pipe - that's where the soot on your tips comes from).
When you add the header, etc. it should lean things out across a wide range. Because of that, the ECU will richen things up and the trim numbers will apply across the rpm range - so you get even richer up top. Sucks, doesn't it?
UL
You've hit the nail on the head. The stock top end fueling is way too rich for maximum power (ever see a DOHC VTEC Honda on the dyno? about 500 rpm from the limiter it starts putting out a haze of black smoke from the tail pipe - that's where the soot on your tips comes from).
When you add the header, etc. it should lean things out across a wide range. Because of that, the ECU will richen things up and the trim numbers will apply across the rpm range - so you get even richer up top. Sucks, doesn't it?
UL