How does the ECU/PCM remapping/reset work?
Discussion
I know absolutely nothing about ECU tuning so apologies if some of these questions appear dumb.
Q1) I've read information where people write "ECU/PCM". Is the ECU & PCM one of the same thing or are they two completely seperate systems?
ECU - Electronic Control Module
PCM - Powertrain Control Module
Q2) When mapping, do you map the ECU, the PCM, or both?
AFAIK the ECU/PCM's in the cars have the ability to 'adapt' to new components and the way that they are driven. A good example of this is uk_hsv's magnificent thread on modifying the air box to have a second 76/84mm hole. Although results would have been seen in a couple of days, immediate results were achieved by doing a PCM reset. How are those results possible (See Q3)?
Q3) How & why does the PCM/ECU reset actually work? Are there 2 areas to the ECU chip (upper & lower) where by the upper (for example) holds the original unmodified map and the lower holds the adapted/modified map? When doing the reset where does the original data come from, if indeed it exists in the first place? The reason I ask is that people on the LS1 forums have achieved results from "I see no difference" through to "Oh my God, it's like my car's been remapped". How is this possible if there isn't an original map to fall back to?
We all know that the remapping of the ECU aims to get the best possible performance from the engine by modifying the original GM Maps. (To those that haven't had it done.....you're missing out)
Q4) Has anyone who's had their ECU remapped ever noticed a deterioration in performance over a long period of 'normal' day-to-day driving followed by a day of vigerous driving (e.g. track day)? In other words, does the ECU's ability to adapt during day-to-day driving affect the performance on the vigerous driving day?
Q5) Hypothetical Q: I've just had my ECU remapped. If I did nothing with the car other than pootle around to & from work or along the motorways for 6months and then take it back to the original remapper would I expect to see a performance degredation between the original and then current dyno results? If so would a PCM reset get me the original performance back? If 'yes', then in your opinion what would be your recommended time period between PCM resets?
Q6) If one has the engine remapped & then performs a PCM reset on the system would I go back to the original GM Maps or would I default back to the map installed by the tuner?
Q7) What's the Manufacturer/Model of the ECU chip? This might help answer some of my Q's
Q8) If anyone has any websites or documents that would aid my learning I'd be most appreciative. I'm not about to get into tuning or steal anybody's work. I'm just highly curious on this subject matter. If anyone would be willing to provide a bogus/traning .DAT file for free, you'd be my hero.
As always your replies are greatfully received & I apologise for the large initial post. It really warrants somebody who knows this stuff drawing it out on a piece of paper.
Q1) I've read information where people write "ECU/PCM". Is the ECU & PCM one of the same thing or are they two completely seperate systems?
ECU - Electronic Control Module
PCM - Powertrain Control Module
Q2) When mapping, do you map the ECU, the PCM, or both?
AFAIK the ECU/PCM's in the cars have the ability to 'adapt' to new components and the way that they are driven. A good example of this is uk_hsv's magnificent thread on modifying the air box to have a second 76/84mm hole. Although results would have been seen in a couple of days, immediate results were achieved by doing a PCM reset. How are those results possible (See Q3)?
Q3) How & why does the PCM/ECU reset actually work? Are there 2 areas to the ECU chip (upper & lower) where by the upper (for example) holds the original unmodified map and the lower holds the adapted/modified map? When doing the reset where does the original data come from, if indeed it exists in the first place? The reason I ask is that people on the LS1 forums have achieved results from "I see no difference" through to "Oh my God, it's like my car's been remapped". How is this possible if there isn't an original map to fall back to?
We all know that the remapping of the ECU aims to get the best possible performance from the engine by modifying the original GM Maps. (To those that haven't had it done.....you're missing out)
Q4) Has anyone who's had their ECU remapped ever noticed a deterioration in performance over a long period of 'normal' day-to-day driving followed by a day of vigerous driving (e.g. track day)? In other words, does the ECU's ability to adapt during day-to-day driving affect the performance on the vigerous driving day?
Q5) Hypothetical Q: I've just had my ECU remapped. If I did nothing with the car other than pootle around to & from work or along the motorways for 6months and then take it back to the original remapper would I expect to see a performance degredation between the original and then current dyno results? If so would a PCM reset get me the original performance back? If 'yes', then in your opinion what would be your recommended time period between PCM resets?
Q6) If one has the engine remapped & then performs a PCM reset on the system would I go back to the original GM Maps or would I default back to the map installed by the tuner?
Q7) What's the Manufacturer/Model of the ECU chip? This might help answer some of my Q's
Q8) If anyone has any websites or documents that would aid my learning I'd be most appreciative. I'm not about to get into tuning or steal anybody's work. I'm just highly curious on this subject matter. If anyone would be willing to provide a bogus/traning .DAT file for free, you'd be my hero.
As always your replies are greatfully received & I apologise for the large initial post. It really warrants somebody who knows this stuff drawing it out on a piece of paper.
[quote]PS. Most tuners use aftermaket software to access the PCM which you need to pay a license for BUT if you want to use a Hex Editor you can pull the whole OS and reconstruct it if you like[/quote]
Thanks for answering this one Paul. I appreciate it.
Pay? If it costs more than £1 it's far too expensive.
Using pre-written software takes the fun out of the exercise. I was planning on using UNIX+HEX Editor to look around. Now I've got this info I'll see what I can do about trying to take a copy of the OS/Tune to play with (unless someone can offer one for training purposes).
Thanks again
Thanks for answering this one Paul. I appreciate it.
Pay? If it costs more than £1 it's far too expensive.
Using pre-written software takes the fun out of the exercise. I was planning on using UNIX+HEX Editor to look around. Now I've got this info I'll see what I can do about trying to take a copy of the OS/Tune to play with (unless someone can offer one for training purposes).
Thanks again
Hi stevemac,
The PCM reset procedure can be found here:
www.mytired.com/cars/index.htm?page=car_rset.htm
According to what I've learned from this thread by performing the reset procedure you should recover the original maps. Whether it improves things or not could only be known by trying it. I've not heard/read of any bad results from doing the procedure. Just make sure you have read it thoroughly first.
I'd recommend that you have a spare 10A fuse on hand just in case. They can be fragile.
The PCM reset procedure can be found here:
www.mytired.com/cars/index.htm?page=car_rset.htm
According to what I've learned from this thread by performing the reset procedure you should recover the original maps. Whether it improves things or not could only be known by trying it. I've not heard/read of any bad results from doing the procedure. Just make sure you have read it thoroughly first.
I'd recommend that you have a spare 10A fuse on hand just in case. They can be fragile.
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