ECU reset mod
05-05-2002, 07:42 PM
#12
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I have read some about short and long-term fuel trims as well as open and closed looped scenarios. I am more concerned with timing not fuel. Do you agree that while in open loop the ECU runs off a base map, and in a closed loop fuel is determined by long term and short-term fuel trims? By resetting the ECU you are going back to stock timing which is good as you are going to get in OBDII. The long term and short term trims will be erased and will start over and begin re-learning while the car is a partial throttle (closed loop). I am not saying you are going to gain any power by resetting an OBDII, only keep what you already have.
Many of the Prelude guys dump the OBDII and go to older OBDI computers. In the earlier version it did not control the timing so with this conversion and an old adjustable distributor you can gain a good 10hp.
Many of the Prelude guys dump the OBDII and go to older OBDI computers. In the earlier version it did not control the timing so with this conversion and an old adjustable distributor you can gain a good 10hp.
05-07-2002, 02:39 PM
#15
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LTFT is applied under all operating conditions.
Under certain conditions an ECU reset could increase power, but you're not guaranteed of that. For example, let's say after a learning cycle your ECU finds optimum mixture requires a 9% leaner fuel trim (on LTFT), but also retards the ignition timing by 2 degrees due to heat/gasoline/whatever.
Now you reset. You get your timing back (for a while), but your A/F ratio will be to rich now, possibly negating your power gains from ignition advance. Or, you might even be making less power.
The software that Utah recommends is a cheap and effective way of really understanding what happens with your ECU. I also suggest regularly visiting the Hondata website and reading their tech articles. Short of the factory, no one knows Honda ECUs better.
BTW, OBDII isn't a bad thing, but as you pointed out there was no easy way to adjust ignition advance on 5th gen Ludes, so OBDI ecus/distributors were nice ways to gain power. In any other application, I find OBDII sensors/datalogging useful for tuning without buying an expensive sensor/data acq suite.
UL
[QUOTE]Originally posted by TypeSH
[B]I have read some about short and long-term fuel trims as well as open and closed looped scenarios. I am more concerned with timing not fuel. Do you agree that while in open loop the ECU runs off a base map, and in a closed loop fuel is determined by long term and short-term fuel trims? By resetting the ECU you are going back to stock timing which is good as you are going to get in OBDII. The long term and short term trims will be erased and will start over and begin re-learning while the car is a partial throttle (closed loop).
Under certain conditions an ECU reset could increase power, but you're not guaranteed of that. For example, let's say after a learning cycle your ECU finds optimum mixture requires a 9% leaner fuel trim (on LTFT), but also retards the ignition timing by 2 degrees due to heat/gasoline/whatever.
Now you reset. You get your timing back (for a while), but your A/F ratio will be to rich now, possibly negating your power gains from ignition advance. Or, you might even be making less power.
The software that Utah recommends is a cheap and effective way of really understanding what happens with your ECU. I also suggest regularly visiting the Hondata website and reading their tech articles. Short of the factory, no one knows Honda ECUs better.
BTW, OBDII isn't a bad thing, but as you pointed out there was no easy way to adjust ignition advance on 5th gen Ludes, so OBDI ecus/distributors were nice ways to gain power. In any other application, I find OBDII sensors/datalogging useful for tuning without buying an expensive sensor/data acq suite.
UL
[QUOTE]Originally posted by TypeSH
[B]I have read some about short and long-term fuel trims as well as open and closed looped scenarios. I am more concerned with timing not fuel. Do you agree that while in open loop the ECU runs off a base map, and in a closed loop fuel is determined by long term and short-term fuel trims? By resetting the ECU you are going back to stock timing which is good as you are going to get in OBDII. The long term and short term trims will be erased and will start over and begin re-learning while the car is a partial throttle (closed loop).
05-07-2002, 02:53 PM
#16
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One major drawback of this mod will be that the ECU will NEVER be able to perform diagnostic tests that are based on readings from multiple trips. This will include most EVAP/EGR tests and some others I don't remember right now. As an example, if there's a leak in the EVAP system there's a good chance it will never be detected.
05-08-2002, 05:38 AM
#17
I noticed last night that the headlight warning bell does not operate with the backup fuse removed. This might just be another small price to pay (until I run my battery dead for the first time).
With regards to performance, the car has been running great. Although there may have been many good points against resetting the ECU, I haven't noticed nearly as much loss of power due to heat.
With regards to performance, the car has been running great. Although there may have been many good points against resetting the ECU, I haven't noticed nearly as much loss of power due to heat.
05-13-2002, 09:21 AM
#19
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I understand what UL and Utah are saying, but...
Have either of you actually seen an OBD2 system MAKE power? This would seem to me to be a fairly simple issue of removing the fuse making power. We've been doing it for quite a while in Prelude circles with no ill side-effects. I understand the F20C has a higher CR and is more well-tuned, but so far it seems to follow the same pattern.
By the way, what exactly is "short term" and "long term" in the time domain? How many RPMs are we talking about here? Minutes? Hours? Days? I would think anything "dangerous" that would lead to detonation would be handled pretty quickly.
Have either of you actually seen an OBD2 system MAKE power? This would seem to me to be a fairly simple issue of removing the fuse making power. We've been doing it for quite a while in Prelude circles with no ill side-effects. I understand the F20C has a higher CR and is more well-tuned, but so far it seems to follow the same pattern.
By the way, what exactly is "short term" and "long term" in the time domain? How many RPMs are we talking about here? Minutes? Hours? Days? I would think anything "dangerous" that would lead to detonation would be handled pretty quickly.
05-13-2002, 05:08 PM
#20
Interesting enough I have seen someone reset for a power gain. Not quite a buttometer but gauged by the ability of the car to overcome the grip of the tire (i.e. peel out) after an ECU rteset. I know the driver well and he is consistent in his launch technique. The car was run at the LA fairgrounds and I remember the night very well. I think the key is knowing what adjustments the STFT and LTFT are seeing before you start. You may reset and have a decrease if the car has changed location (i.e elevation). The unit of measure is number of cycles (not time). A cycle is defined as a start and the temperature reaching a certain temperature.
Utah
Utah