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Thread: 2007 Trailblazer SS - Procharged Tuning Assistance needed....maxing out MAF hz....

  1. #1

    2007 Trailblazer SS - Procharged Tuning Assistance needed....maxing out MAF hz....

    As the title says, I'm helping a buddy try and get this thing dialed in a bit before heading to the dyno. At 1/2 throttle and 3/4 throttle, all is good. However, at WOT, the MAF hz starts to go in the 13xxx where I can't add or take out fuel. At the moment, it is extremely lean. I have upped his boost-a-pump voltage as he is running more boost than we thought (looking at a gauge) but is there something else I am missing that would help solve this upper rpm fueling issue.

    Thanks!
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  2. #2
    Senior Tuner DSteck's Avatar
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    Tune it in speed density.

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  3. #3
    Quote Originally Posted by DSteck View Post
    Tune it in speed density.
    Yeah, I had a feeling that's where we were going as I was reading last night that 12,200 hz is 512 g/sec which would be maxing out the MAF.

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  4. #4
    Senior Tuner DSteck's Avatar
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    I think there's a custom OS that would extend the MAF and the airflow limit. Might be worth checking.

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  5. #5
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    Quote Originally Posted by DSteck View Post
    I think there's a custom OS that would extend the MAF and the airflow limit. Might be worth checking.
    2Bar COS does exactly that Dave, 1024G-sec/15400Hz, I had the same issue maxing out both in mine scaling everything sort of helped but then the Trans started misbehaving.

    Side benefit of the COS is no need to use the Bluecat tool for coefficients as you get a normal VE table again.

  6. #6
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    Just tried it, the COS for the 07 TBSS does extend the MAF hZ to 15400 with a 1024g/s limit.

    You have a few options:
    1. Run the COS for +2 credits and get the extended limits and "normal" VE table.
    2. Tune SD coeff's using BlueCat's tool
    3. Scale the entire tune to get around the 512 g/s limit.

    1 or 2 are preferred, #3 isnt as easy or quick to do and you lose some resolution when scaling.
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  7. #7
    Quote Originally Posted by IJ. View Post
    I had the same issue maxing out both in mine scaling everything sort of helped but then the Trans started misbehaving.
    Any tranny table that has pressure needs to be scaled by the same factor as the rest of the car - I had issues as well the first go around.
    2006 CGM A4

  8. #8
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    Quote Originally Posted by 0352goat View Post
    Any tranny table that has pressure needs to be scaled by the same factor as the rest of the car - I had issues as well the first go around.
    Scaled the Trans as well Goat, lost quite a bit of resolution in the process so it never quite drove the same as unscaled..

  9. #9
    Senior Tuner DSteck's Avatar
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    Yea, there's say easier ways to scale that don't screw up the torque model...

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  10. #10
    Ok, options 1 and 2 sound the best.

    Now, for the dumbie questions:
    - After a lot of research I've done....it gets confusing and I want to run it the best way possible. However, some say to run the 2 bar MAP, re-scale the values, and tune away. Some people say, keep the 1 bar and run a LS3/7 MAF and rescale the values and tune away. Others say to use the open loop gains to add fuel which that sounds like a bad way to going around it.

    I looked at the BlueCat Virtual VE stuff and seems to be nice system for tuning but would definitely need a base VE and spend a lot of time tuning it to get it right.

  11. #11
    Quote Originally Posted by ScarabEpic22 View Post
    Just tried it, the COS for the 07 TBSS does extend the MAF hZ to 15400 with a 1024g/s limit.

    You have a few options:
    1. Run the COS for +2 credits and get the extended limits and "normal" VE table.
    2. Tune SD coeff's using BlueCat's tool
    3. Scale the entire tune to get around the 512 g/s limit.

    1 or 2 are preferred, #3 isnt as easy or quick to do and you lose some resolution when scaling.
    Ok, can someone explain #1 because I see that you can convert the OS to a 2 Bar MAP - Speed Density but don't know how that will extend the MAF tables? If I do and it does extend the tables, then I would need to run a 2 Bar correct and do I need to change the VE or will stock VE be sufficient.

  12. #12
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    You get 1024 G/sec and 15400Hz in the MAF High table, yes you need to build a VE Table.

  13. #13

  14. #14
    Ok, I did the COS and gained some great MAF tables which is where I need to be to fine tune it. Now, I pulled a VE table from a 2006 GTO LS2 with the 63 lb/hr injectors and running 8 psi boost off the tune repository. I did all the things in the video and pulled the MAF tune that I had on the Original OS for the High MAF tables and then interpolated them so the MAF should be close to spot on as it was and the VE tables I would assume would be close if then tune I pulled from was good and its and stock LS2 as the TB SS and has the same injectors.

    What are y'alls thoughts before I start loading this file up?

  15. #15
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    Is this specific to the e38 (or 67). In other words, not the E40?

  16. #16
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    Sure it isn't droppng a good amount of fuel pressure causing the MAF to max?
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  17. #17
    Hey Shane.....we logged the fuel pressure, lb/hr on the injectors, etc and it all stayed good. He has a Kenne Bell boost a pump on it as well. The problem becomes that he can hit 12,200 hz about 70% throttle and at full throttle it wants to be closer to 13,400-14,000 hz which on the old OS I couldn't tune with. I'm going to try the COS in a few weeks and report back. We are going to stay with the 1 Bar MAP for right now and upgrade to the 2 Bar at a later date if needed.

  18. #18
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    How much did fuel pressure drop?

    I had the same issue before i changed the pump in my old G8 where i was going from 58-60 PSI to mid 30's and it cause the MAF to max and go lean of course.
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  19. #19
    Fuel pressure never dropped. It was consistently 55-60 from idle to WOT. Mostly 58-60 at WOT. I upped the voltage of the boost a pump as it's adjustable when we were tuning and fuel pressure stayed pretty consistent so we returned it to the previous setting. I've looked at the Trailblazer SS forum, everyone that runs over 8 psi runs into this problem with the 2007 and 2008 TB SS as it's the new OS. The 2006's don't seem to have this problem as most are at 10 psi and below due to the TB SS 11:1 compression.

  20. #20
    Well, I have it running. It took a few passes for the new OS to start working properly but once it did, the A/F ratio and spark knock disappeared and the fine tuning began. The truck seems to run smoother and part throttle response is much improved! Still got some work to do with the decel going to rich and cold start being lean but so far so good.