Bringing TBI and Multi Port Fuel Injection to a New Level.     EFI Conversions and Tuning! Seattle to Portland! E-mail Tuning Consultant!
Page 2 of 2 FirstFirst 12
Results 16 to 20 of 20

Thread: How to extend AE duration?

  1. #16
    Fuel Injected!
    Join Date
    Feb 2015
    Location
    New Zealand
    Age
    50
    Posts
    241
    Hi guys,
    This is just wanted to say thanks for your replies.
    I'll need to take some time to go through what you've posted, I'm sure once I've got my head around things I'll have some questions.
    Thanks again for the help.

  2. #17
    Fuel Injected!
    Join Date
    Feb 2015
    Location
    New Zealand
    Age
    50
    Posts
    241
    Hi Dud,
    Just trying to understand your statement "The smaller the number, the longer the pulse time".
    If I'm understanding you correctly then reducing the uSec values as a trend should potential increase the AE duration?
    I had previously assumed that the larger uSec value meant longer pulse time at the injectors.
    I made up and AE vs TPS difference graph to for you to comment on as a visual example of what I think you meant, please let me know if that looks correct?
    Attached Images Attached Images

  3. #18
    Fuel Injected! dud's Avatar
    Join Date
    Jan 2016
    Age
    51
    Posts
    30
    Yes. Lower values = longer AE duration.

  4. #19
    Fuel Injected!
    Join Date
    Feb 2015
    Location
    New Zealand
    Age
    50
    Posts
    241
    Thanks for confirming that.

    Looks like I've been going the wrong way, increasing AE vs TPS values when I should have been reducing them to increase the AE's duration time.

    It potentially makes sense now, about a year ago I went back to a near stock bin which would have had stock AE vs TPS values and I remember thinking the van felt like it accelerated a little bit better.
    Unfortunately the next day I increased the fuel pressure and tuned for that, at the time I probably thought I'd better increase the AE vs TPS values because stock values must be too low.
    I've put my van away in storage ready for the winter but once I've gone through 84Elky's last post I might need to get the van out of storage and try some things.

    Thanks again.

  5. #20
    Fuel Injected! 84Elky's Avatar
    Join Date
    Jul 2012
    Location
    Montgomery, AL
    Posts
    130
    Quote Originally Posted by dud View Post
    TPS Difference AE Coefficient vs. Temperature will stretch out the AE pulse time. I had a lean spot that occurred before the engine got heat soaked that I couldn't get rid of until I worked with this. I think it's because of the volume difference between the new vs. old intake manifolds. For me this also made the engine feel more responsive and smoother.

    The smaller the number, the longer the pulse time.

    Beware that you may have to adjust AE vs. TPS Difference accordingly.
    Thought I'd weigh in here. Apologies for the long post.

    First, the table Dud referenced (0x4B5A=TPS Difference AE Coefficient vs. Temperature), applies to AE-TPS only.
    Let's look at exactly how it's used:
    -A coefficient (% change factor), is extracted from the referenced table based on coolant temp
    -That coefficient is later used to lag filter the Current TPS%. Lag Filtering is a technique used to smooth-out values to avoid rapid changes.
    Formula: NewFilteredTPS% = PriorFilteredTPS% + [(CurrentTPS% PriorFilteredTPS%) * LagFilterCoeff]
    The smaller the coefficient, the closer the new filtered value (NewFilteredTPS%) is to the old value (PriorFilteredTPS%). Plugging values into the formula will prove this.
    -After the NewFilteredTPS% is computed, it's subtracted from CurrentTPS% to obtain a Delta TPS%, and to determine if TPS% is rising
    -If Delta TPS% is not rising, AE-TPS is NOT invoked; or if currently invoked, it's exited
    -If Delta TPS% is rising --AND-- NOT currently in AE-TPS --AND-- the Delta TPS% is > (0x48B9=TPS Difference to Enable AE [Factory = 1.17% .vs. the posted BIN here = 0.78%], AE-TPS will be invoked.
    -Once invoked, an AE-TPS PW is extracted from the table (0x4B45=AE vs. TPS Difference) based on the Delta TPS%

    So why this detail? On-balance, the Delta TPS% will generally (note "generally") be larger with lower lag filter coefficients because TPS% - [lower]NewFliteredTPS% = [larger]Delta TPS%. This means the AE-TPS PW extracted from the 0x4B45=AE vs. TPS Difference Table will be larger (larger Delta TPS% = larger AE-TPS PW). But remember "generally". Delta TPS% is calculated 160 times a second. Due to varying engine conditions (TPS position), it's impossible to know at any point in time exactly what a given Delta TPS% will be.

    IMO, it would be far better to change the PW provided at any given Delta TPS% by changing values in the 0x4B45=AE vs. TPS Difference Table. Now one knows exactly the AE-TPS PW that will be provided at any given Delta TPS%. Don't have to wonder what the Delta TPS% will be. Can't control it anyway. Other than for the coefficient, it's calculated with values we can't control.

    Granted changing the table coefficients "may" work, but here's something that is supported by a multitude of tests over many years: Mildly changing lag filter coefficients (and there are many) rarely results in consistent output. Exact results are indeterminate. And radically changing coefficients can have unexpected results.

    Bottom line, it's best not mess with them. The GM Engineers had significant data to support what they used. As above, there is generally a more concrete way to achieve a desired result than changing filter coefficients.

    FWIW, Elky

Similar Threads

  1. Replies: 3
    Last Post: 05-19-2017, 11:13 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •