how much will the ecu try to adjust the fuel while in closed loop

leonhsieh · 07-22-2005

After reading all the info on honda tech about how obd2 will adjust fuel in closed loop, I just want to know, for all you ppl who have turbo, how do u guys get around it? (I personally reset my ecu every 4 days). Is there any other options beside split second esc1 or getting standalong?? or, just leave it as it is and assume the a/f that we tune at by using piggy back is beyond stock ecu's control??

thx

To remove this ad, register today for free or log in if already registered!

turboengnr · 07-22-2005

it will compensate +- 20%

It only compensates at part throttle. When you got WOT, it takes the last known correction, and locks it in. So if you are cruising, and the correction is -15%, then you punch it, that value is locked in. So you are losing fuel and running leaner.

But the opposite is also possible. It can run very rich by adding up to 20% at times as well.

This is why people's dyno graphs are always different.

You have to tune each individual car for fuel trims, keeping them as low as possible at all times. Once you do that, you will have more consistent fuel curves.

SODJAZERO · 07-22-2005

^^words from one of the greats

turboengnr · 07-22-2005

02fpcivic · 07-22-2005

I hated the piggy backed stock ecu. I never could get it to stay consistent. Every day it was a surprise. CELs running rich, lean, not at all. hehe I got an ex ecu if anyone wants it.. Maybe Ill torture it to death like it did to me.

leonhsieh · 07-22-2005

thx for the input. Then, how can we tune partial throttle? I am worried that if ecu try to compensate fuel to desired a/f ratio(maybe 14.7) at partial throttle while boosting, won't it be too lean during boosting?
thx again

turboengnr · 07-22-2005

you have to use a scanner to look at the long term and short term fuel trims, and spend hours screwing with fuel settings to try to get the fuel trims as close to zero as possible. While screwing with the fuel trims, do not tune using the wideband. While at part throttle, give the computer the a/f it wants. It is normally safe to run it a little leaner while you are only under partial load. When you go WOT, that is when you need the fuel. And thats why you have to get the fuel trims right.

tfnaaf · 07-22-2005

Quote:

Originally Posted by turboengnr

you have to use a scanner to look at the long term and short term fuel trims, and spend hours screwing with fuel settings to try to get the fuel trims as close to zero as possible. While screwing with the fuel trims, do not tune using the wideband. While at part throttle, give the computer the a/f it wants. It is normally safe to run it a little leaner while you are only under partial load. When you go WOT, that is when you need the fuel. And thats why you have to get the fuel trims right.

I'm confused,..... Why not tune with a wideband ?

turboengnr · 07-22-2005

you tune with a wideband at WOT. If you use a wideband to tune at part throttle, the computer will compensate and adjust the fuel to where it wants it. Then when you actually do to full throttle, the value that the computer has locked in will transfer over to the WOT setting, and it will mess with your tune. The computer has a "fuel trim" feature that can add or remove 20% of the injector pulsewidth. That means that if you are running an a/f ratio of 11.3 on one pass (lets say the fuel trim was at +12% this pass), then the next pass could be in the mid to high 13's with a fuel trim of -20%.

You have to tune the car under ALL LOAD AND ALL RPM VALUES! If you do not do this, then you will most likely have fuel trim issues.

djmota · 07-22-2005

Quote:

Originally Posted by turboengnr

you tune with a wideband at WOT. If you use a wideband to tune at part throttle, the computer will compensate and adjust the fuel to where it wants it. Then when you actually do to full throttle, the value that the computer has locked in will transfer over to the WOT setting, and it will mess with your tune. The computer has a "fuel trim" feature that can add or remove 20% of the injector pulsewidth. That means that if you are running an a/f ratio of 11.3 on one pass (lets say the fuel trim was at +12% this pass), then the next pass could be in the mid to high 13's with a fuel trim of -20%.

You have to tune the car under ALL LOAD AND ALL RPM VALUES! If you do not do this, then you will most likely have fuel trim issues.

Exactly! even at NA I only tune for WOT on my piggy back. partial throtle tuning with a piggy back is just about useless.

tfnaaf · 07-22-2005

Quote:

Originally Posted by turboengnr

you tune with a wideband at WOT. If you use a wideband to tune at part throttle, the computer will compensate and adjust the fuel to where it wants it. Then when you actually do to full throttle, the value that the computer has locked in will transfer over to the WOT setting, and it will mess with your tune. The computer has a "fuel trim" feature that can add or remove 20% of the injector pulsewidth. That means that if you are running an a/f ratio of 11.3 on one pass (lets say the fuel trim was at +12% this pass), then the next pass could be in the mid to high 13's with a fuel trim of -20%.

You have to tune the car under ALL LOAD AND ALL RPM VALUES! If you do not do this, then you will most likely have fuel trim issues.

Well, im deffinately a N00B when it comes to e-manage tunning for sure. But if you have the tiem could you possibly explain How to tune by watching the fuel trim?

turboengnr · 07-22-2005

no prob

it is actually quite simple.

you need some sort of OBDII scanner that has a data streaming capability.

When you have that, set it up to watch the LT_Ftrm and the ST_Ftrm (long and short term fuel trims). When you have that, you need to have your laptop setup to watch your fuel tables in real time.

When you have those set up, you need to start cruising at low RPM (around 2k) and then start accellerating with a specific amount of throttle. You then watch both the fuel trims on the scanner and the fuel map on the laptop. When you see the fuel trims start to add or subtract fuel, you do the same on the fuel map.

so lets say you are at 3250 RPM and the scanner shows a LT_Ftrm of -2% and a ST_Ftrm of -14%. You should gradually take out fuel in the fuel map until the fuel trims come back down to around zero.

The difference between the LT_Ftrm and the ST_Ftrm is simple. The ST_Ftrm's are what the computer is doing at that specific point in time. The LT_Ftrm is the trend that the computer is seeing.

You know how they say your computer "learns"? Well, they are talking about the LT_Ftrm. Over time, the computer averages out the data it recieves and outputs it as a single variable (LT_Ftrm). When this is at or close to 0%, that means that you spend most the time with a 0% fuel trim correction factor.

When you disconnect the battery, this is the value that gets erased and must be "re-learned" in order for the car to run at its potential.

Typically i like to see fuel trims between +5% and -5% on the LT_Ftrm.

02fpcivic · 07-22-2005

Very informative man. I knew it wasnt just me. What you are saying totally clarifies my old problem.

turboengnr · 07-23-2005

glad i could help!

tfnaaf · 07-23-2005

Quote:

Originally Posted by turboengnr

no prob

it is actually quite simple.

you need some sort of OBDII scanner that has a data streaming capability.

When you have that, set it up to watch the LT_Ftrm and the ST_Ftrm (long and short term fuel trims). When you have that, you need to have your laptop setup to watch your fuel tables in real time.

When you have those set up, you need to start cruising at low RPM (around 2k) and then start accellerating with a specific amount of throttle. You then watch both the fuel trims on the scanner and the fuel map on the laptop. When you see the fuel trims start to add or subtract fuel, you do the same on the fuel map.

so lets say you are at 3250 RPM and the scanner shows a LT_Ftrm of -2% and a ST_Ftrm of -14%. You should gradually take out fuel in the fuel map until the fuel trims come back down to around zero.

The difference between the LT_Ftrm and the ST_Ftrm is simple. The ST_Ftrm's are what the computer is doing at that specific point in time. The LT_Ftrm is the trend that the computer is seeing.

You know how they say your computer "learns"? Well, they are talking about the LT_Ftrm. Over time, the computer averages out the data it recieves and outputs it as a single variable (LT_Ftrm). When this is at or close to 0%, that means that you spend most the time with a 0% fuel trim correction factor.

When you disconnect the battery, this is the value that gets erased and must be "re-learned" in order for the car to run at its potential.

Typically i like to see fuel trims between +5% and -5% on the LT_Ftrm.

VERY informative! Thanx