Speed Density Approach
Speed Density Approach Is there any advantage to switching the computer to a 1 bar OS with HPTuners versus just eliminating the MAF and turning off the SIS light? Are there additional tables offered when you go to a SDOS? Thanks
FormerVendor
Joined: Nov 2012
Posts: 390
Likes: 0
From: Dyno Tuning in KY
You'll also gain access to RTT if your OS is supported. There are a few small other things it does too. For the earlier OS's 99-00 the custom OS eliminates the secondary VE table and replaces it with a TPS vs RPM VE multiplier table that comes in very handy for large cam cars or ITB cars at low engine speeds to help increase airflow model resolution.
You just dont have very good resolution of the fuel table since 98's have fewer cells already. EFI Live doesnt offer any custom os for 98's but HPT does offer one.
You'll also gain access to RTT if your OS is supported. There are a few small other things it does too. For the earlier OS's 99-00 the custom OS eliminates the secondary VE table and replaces it with a TPS vs RPM VE multiplier table that comes in very handy for large cam cars or ITB cars at low engine speeds to help increase airflow model resolution.
Thank you for the replies. Excuse my ignorance, what does RTT mean? Thank you. I am on a stock LS1 longblock with some bolt ons (LS6 manifold, PP TB, intake, headers, exhaust) in my s10, so I will just leave the 85mm MAF in it probably. Thing I noticed is that in open loop (STFT and LTFT turned off), Speed Density (well MAF turned off), I get consistant power under WOT and seems to run a little better. And my VE table is still not even tuned all that great. I am ~5-10% off (ratio of wideband to commanded lambda) all over the place. What gives?
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oh duh...Thats where its at! Every control system interface I have ever had access to has had RTT support and feedback, besides HPTuners.
Why does the 99-00 PCM only support RTT? What about 01-02 PCM's? I have a 2002 Camaro PCM that I have unlocked as well. The AC does not work when plugged into the harness. But my 99 Camaro PCM controls the AC just fine.
Maybe I missed it, but it would be nice to see the different types of ECU # reference to the year and model, to the available support for the different OS changes. That would be a big spreadsheet but very beneficial.
I also would like to get a 04 GTO PCM to run lean cruise. I read that the AC wont work with that PCM though....still figuring out the protocols between ECU's and their related subsystems they control.
Why does the 99-00 PCM only support RTT? What about 01-02 PCM's? I have a 2002 Camaro PCM that I have unlocked as well. The AC does not work when plugged into the harness. But my 99 Camaro PCM controls the AC just fine.
Maybe I missed it, but it would be nice to see the different types of ECU # reference to the year and model, to the available support for the different OS changes. That would be a big spreadsheet but very beneficial.
I also would like to get a 04 GTO PCM to run lean cruise. I read that the AC wont work with that PCM though....still figuring out the protocols between ECU's and their related subsystems they control.
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Verdad Gallardo Ebay has PCM's for a "2004 Pontiac GTO with the 5.7 liter" it says. Can anyone verify that the number: 12586243 is correct? And this is the only known PCM in the states that has a functional lean cruise mode correct? Thanks
You can use RTT on a 99-02 (896 or 411 pcm) You dont have to have a GTO pcm to run lean cruise it can be done other ways its just not easy. I messed with lean cruise with EFI alot because its very easy to set up with a cos. Lean cruise however isnt very easy to do, each vehicle is different and it takes a lot of driving with a wideband to make any gains. Its not practical for a shop or a tuner to try to do while tuning someones vehicle since its so time consuming.
FormerVendor
Joined: Nov 2012
Posts: 390
Likes: 0
From: Dyno Tuning in KY
Also with the HPT 2bar custom OS you can use it NA as well. You'll just never use the boost portion of the new 2bar VE table. You just need to rescale the map sensor settings so that it is still setup for the stock 1bar sensor. Also you keep the same 5KPA resolution in the vacuum region of the VE table and it does away with the small secondary VE. So it's a nice option for the 98's.
Me personally, I would spend the $100 credit money on a new 0411 PCM. There are a lot more options with the newer PCM's!
I'm not gonna say RTT is junk... because it serves a purpose...
but its slow as hell when working on the VE table ...especially when you are making broad changes to start with or when you have a lot of cells to change...
most of the time its way faster to turn off the car and write the calibration and then start it back up...
still use the OS for the other benefits of eliminating a secondary VE and retaining use of both the High and low spark tables..
but its slow as hell when working on the VE table ...especially when you are making broad changes to start with or when you have a lot of cells to change...
most of the time its way faster to turn off the car and write the calibration and then start it back up...
still use the OS for the other benefits of eliminating a secondary VE and retaining use of both the High and low spark tables..
Thanks. Why is it advantageous to eliminate the secondary VE? What purpose does it even serve and if you copy the Primary VE with labels and paste to the secondary VE, would this be the equivalent of not having it?
normal car operation the ECU does a Blend of the MAF and the Primary VE table
Early years, for whatever reason, GM felt that if the MAF should ever fail, it should go to a new subroutine that excluded the MAF calcs...resulting in using the Low octane table and Secondary VE...which were both tuned for a little safety/fudge factor from the factory..
low octane table had less timing, secondary VE had more fuel
GM's thinking was to go slightly rich and have less timing would be safer when/if the MAF failed.
getting rid of the secondary VE is good because the secondary VE is half the resolution of the primary table
Primary table is in 5kpa steps, secondary ve is only in 10kpa steps
either unplug/remove the MAF or simple Fail it in the tune by setting the fail frequency to 0 hz
after that... you will be in SD
depending on what software you are using for tuning
I suggest going over to the HP Tuners Forum, or the EFI live forum and strat reading.....lots of good posts, lots of people willing to help you learn how to tune on your own car...
