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Old 06-03-2022, 09:10 AM
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Default Factory PCM vs. Aftermarket

So, I've been trying to learn late model tuning with HPTuner. It's more complicated that I thought it would be. I removed the torque management, changed PE, etc. on my '04 GMC 2500HD. I still haven't messed with fuel VE map, MAF, and timing tuning. Watched a lot of videos and read a lot. Partly being lazy I guess. So how much easier is tuning with systems like Holley Terminator X and similar?

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Old 06-03-2022, 09:47 AM
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I've never tried to use a stock ecu, but I think probably the main difference is the freedom to choose how you want to tune the engine. You mentioned MAF, and with the aftermarket standalone stuff you can eliminate that if you choose and use speed density instead(or alpha n, blended alpha n and speed density or ITB for that matter). Traction control can be tailored to suit, or turned off, easily. There's nothing that's "locked", except the limits of hard coding on some units. My MS3 has open source code, so those with the computer skills (not me) can even change that.

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Old 06-03-2022, 11:06 AM
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I've never tried to use a stock ecu, but I think probably the main difference is the freedom to choose how you want to tune the engine. You mentioned MAF, and with the aftermarket standalone stuff you can eliminate that if you choose and use speed density instead(or alpha n, blended alpha n and speed density or ITB for that matter). Traction control can be tailored to suit, or turned off, easily. There's nothing that's "locked", except the limits of hard coding on some units. My MS3 has open source code, so those with the computer skills (not me) can even change that.
I think you can run the factory ECU on speed density too. I drive my car year around in extremes of weather conditions. I want to run on a MAF. MAF is another thing I need to figure out. I'm starting up on the truck MAF. But I have a 4" intake pipe with a port for LS3 card MAF. I know I have to change frequency table for that. Ugh. Another reason why I'm looking at aftermarket ECU. Self-learning and built in wide band is also attractive. Still picking up knowledge pieces obviously. Thanks

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Old 06-03-2022, 11:50 AM
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The only guy I personally know that makes really good, but street able horsepower (620 @ the crank N/A) says they moved away from MAF for easier tuning and made better power to boot. Just fyi, maybe don't get too hung up on keeping the MAF, especially if it makes your life more difficult...

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Last edited by Scott65; 06-03-2022 at 11:50 AM. Reason: Addition
  #5  
Old 06-03-2022, 12:01 PM
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Originally Posted by Scott65 View Post
The only guy I personally know that makes really good, but street able horsepower (620 @ the crank N/A) says they moved away from MAF for easier tuning and made better power to boot. Just fyi, maybe don't get too hung up on keeping the MAF, especially if it makes your life more difficult...
I have read up on the two. Forgot most of the details by now. At the time it sounded like MAF was the way for me. For high horsepower applications it makes sense. Cars that run only during the summer, etc. MAF can compensate for temperature extremes much better IIRC. I will keep an open mind though. I don't know enough yet to have a strong opinion. lol I'm super excited to learn this stuff though. It has reinvigorated me to work on it. A $400 engine with aluminum heads, multiport sequential fuel injection, ignition coil packs, roller cam, reverse coolant, side bolted mains...

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Old 06-03-2022, 12:19 PM
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Bang for the buck the LS platform wins hands down. The corrections for driving conditions with regards to changing temps (MAT correction)and even elevation (barometric correction) is easily handled in speed density. When I have a minute I'll take some screenshots of my tuning software showing how adjustments are handled even without MAF.

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Old 06-03-2022, 12:37 PM
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Bang for the buck the LS platform wins hands down. The corrections for driving conditions with regards to changing temps (MAT correction)and even elevation (barometric correction) is easily handled in speed density. When I have a minute I'll take some screenshots of my tuning software showing how adjustments are handled even without MAF.
Agreed.

Ok. Cool!

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Old 06-03-2022, 03:01 PM
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So, I'll attempt to keep this explanation in order of the screenshots. I don't have the ability to put the photos inline( or the skills anyway) There will be two of the air density correction, and the reason requires a little detail, that may be relevant to you no matter whether you decide to tune the stock ecu or go stand alone.
The factory engineers put a lot of thought into the sensor arrangement and the location to take intake air from. Then they calibrate for that and it works well. We the hot rodders take either a factory engine and stick it in a different car(your case) or add efi to a car that never had it(my case). In either case, we've changed the factory engineering, or never had any in the first place and the air intake temps ( or MAT if you prefer) can be inconsistent, or inaccurate, or both. One of the air density tables I'm showing is the default table, and it's based on the Ideal Gas Law which covers the effects of changing air temps on air density(and other things, if you solve for different variables) Makes me once again wish I'd taken science more seriously... Anyway, if you have a well engineered system with accurate temps, and adequate airflow, you probably can run very close to the default curve. In my case( and many others doing retrofit stuff) the default curve doesn't play well, and you get lean conditions where it "should" be ok to have the curve leaning things out. And thus the reason for my curve having a slight "bell" shape as opposed to the default.
Also availe is MAT/CLT correction which corrects for low airflow high temps. I haven't messed with that much...

Baro correction is there, but needs to be tuned in actual conditions. I rarely go 100 miles away from sea level, so I don't mess with it. I use the feature that allows the sensor to compare pre start up MAP sensor reading and handle it internally. You can also add a second map sensor(1 bar) and constantly compare the two. Over my head, and unnecessary in my case...
I also have the ability to run a MAF sensor, but choose speed density instead. Hopefully this is helpful.
ETA: screenshot of menu where these options are
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  #9  
Old 06-05-2022, 07:28 PM
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Stock LS1B or E40 ECU = Use EFI Live to get control of air temp modifiers through custom OS tweaks. Can run speed density no issues.
Stock E38 ECU = Use HP Tuners for the same air temp. Can run speed density no issues.

Stock ECU's are pretty complicated to understand for the beginners, but they're also the easiest to get the car started and running.

Aftermarket ECU's are much easier to understand for the beginners, but they're harder to get the car started and running.

The cost of aftermarket ECU's and support from vendors, community, base map availability is much better than using the stock stuff IMO and the cost difference isn't that horrendous between the 2.

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Old 06-06-2022, 08:25 AM
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Quote:
Originally Posted by Scott65 View Post
So, I'll attempt to keep this explanation in order of the screenshots. I don't have the ability to put the photos inline( or the skills anyway) There will be two of the air density correction, and the reason requires a little detail, that may be relevant to you no matter whether you decide to tune the stock ecu or go stand alone.
The factory engineers put a lot of thought into the sensor arrangement and the location to take intake air from. Then they calibrate for that and it works well. We the hot rodders take either a factory engine and stick it in a different car(your case) or add efi to a car that never had it(my case). In either case, we've changed the factory engineering, or never had any in the first place and the air intake temps ( or MAT if you prefer) can be inconsistent, or inaccurate, or both. One of the air density tables I'm showing is the default table, and it's based on the Ideal Gas Law which covers the effects of changing air temps on air density(and other things, if you solve for different variables) Makes me once again wish I'd taken science more seriously... Anyway, if you have a well engineered system with accurate temps, and adequate airflow, you probably can run very close to the default curve. In my case( and many others doing retrofit stuff) the default curve doesn't play well, and you get lean conditions where it "should" be ok to have the curve leaning things out. And thus the reason for my curve having a slight "bell" shape as opposed to the default.
Also availe is MAT/CLT correction which corrects for low airflow high temps. I haven't messed with that much...

Baro correction is there, but needs to be tuned in actual conditions. I rarely go 100 miles away from sea level, so I don't mess with it. I use the feature that allows the sensor to compare pre start up MAP sensor reading and handle it internally. You can also add a second map sensor(1 bar) and constantly compare the two. Over my head, and unnecessary in my case...
I also have the ability to run a MAF sensor, but choose speed density instead. Hopefully this is helpful.
ETA: screenshot of menu where these options are
Interesting. I'm still trying to digest all of this stuff. I guess all of the throttle body setups are speed density?

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Old 06-06-2022, 08:29 AM
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Quote:
Originally Posted by krisr View Post
Stock LS1B or E40 ECU = Use EFI Live to get control of air temp modifiers through custom OS tweaks. Can run speed density no issues.
Stock E38 ECU = Use HP Tuners for the same air temp. Can run speed density no issues.

Stock ECU's are pretty complicated to understand for the beginners, but they're also the easiest to get the car started and running.

Aftermarket ECU's are much easier to understand for the beginners, but they're harder to get the car started and running.

The cost of aftermarket ECU's and support from vendors, community, base map availability is much better than using the stock stuff IMO and the cost difference isn't that horrendous between the 2.
That exactly sums up my assumptions. There are so many settings in the factory ECU. Then tuning the VE table and timing map is a chore. Still trying to completely understand tuning VE table and MAF. You have to disable the MAF, PE, zero fuel trims, etc. Then data log as much of the table as possible. Self learning doesn't seem like it should be very difficult. How well does the aftermarket self learning actually work?

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Old 06-06-2022, 08:44 AM
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Interesting. I'm still trying to digest all of this stuff. I guess all of the throttle body setups are speed density?
Yes, that I know of anyway.

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