Results 1 to 15 of 37

Thread: TPS vs MAP AE 7427 $0E

Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. #1
    Fuel Injected!
    Join Date
    Feb 2013
    Location
    Euless, TX
    Posts
    2,331
    Quote Originally Posted by CDeeZ View Post
    I never had to mess with those settings in my 3 bar SD '411 running my 75MM LQ4... 8 PSI boost. I decapped the stock truck injectors and slapped 75 in the entire IFR table. The only other thing I really had to change was the Min Injector Pulse and Short Pulse Adder. Ended up dropping these considerably in order to allow the decapped injectors to idle without being stupid rich. Throttle response has always been good on this one. The farther you press the skinny pedal, the more likely you are to break loose and start drifting towards the ditch. It's always the ditch on the RIGHT hand side. Maybe with decapped injectors and a compressor the LS AE isn't as sensitive as compared to a wet manifold system like TBI? The decaps turn the finely atomized mist into a stream like a faucet... People warned me that because of this, idle and low speed drive ability would not be good. Of course, this turned out to be bullshit.

    Yes, that seems to be the same thing my TBI is experiencing. It seems to like more MAP AE like you said. Climbing hills is when this is most noticeable on this TBI truck.

    No, when it was 10:1 is when you just lightly tip into the throttle pulling away from a stop sign. When it was lean popping I could see on the WB gauge itself that it was in fact a lean spike. Two different issues. Confirmed the lean spike by looking at logs. I remember Dewey posting on TGO about having the same issue here, he added TPS and MAP AE incrementally in order to cure a lean pop when jamming the throttle open. Only to find that he ended up with too much TPS AE which caused a similar issue to mine where it would go way rich on light throttle.

    Do you think the heads linked above would respond well to more timing? I was thinking if anything it would be the other way around since I would assume these Trick Flow aluminum heads would be more efficient than the old swirlports? Either way, you got me thinkin'. Maybe some more timing is in order here.
    My Assault racing heads have a nice fast burn style chamber and like timing. The Vortecs I have tuned like about 12° at the minimum.

    You are thinking wrong. The old swirl ports like less timing than Vortecs. About 26-28° is all they need.

    Also you likely need to change the shape of your AE tables. Progressively higher values with bigger TPS/MAP delta's. Ease off on the lower values if it is getting rich at slight throttle changes.

    Must have gotten really lucky on the LS. I had the Express van with the 0411 run 5.7 dialed in very well. I went from the factory converter to a looser converter. All of a sudden it started lean popping if you smacked it to the floor. I ended up adding both timing and AE to fix it. After it rapped up much quicker.

    Even port fuel setups can lean pop. Its not a TBI or Carb only thing.

    https://youtu.be/gNyr_Z6Q_ck
    Last edited by Fast355; 03-07-2019 at 04:40 AM.

  2. #2
    Fuel Injected! brian617's Avatar
    Join Date
    Apr 2013
    Location
    Arkansas
    Age
    45
    Posts
    711
    When you change your AE tables both MAP and TPS, are you moving the whole table up and down or are you playing with the curve?
    89 K1500 Scottsdale 5.7L 5spd 3:42 RamJet cam Dart iron TBI heads 427 PCM swap
    95 C2500 Cheyenne 6.5L turbo diesel 4L80e 4:10 DB2-4911 Manual pump conversion 0411 PCM trans control 2Bar COS
    05 Outback XT 2.5L turbo gas auto

  3. #3
    Fuel Injected! CDeeZ's Avatar
    Join Date
    May 2012
    Location
    Jokelahoma
    Posts
    422
    Quote Originally Posted by Fast355 View Post
    My Assault racing heads have a nice fast burn style chamber and like timing. The Vortecs I have tuned like about 12° at the minimum.

    You are thinking wrong. The old swirl ports like less timing than Vortecs. About 26-28° is all they need.

    Also you likely need to change the shape of your AE tables. Progressively higher values with bigger TPS/MAP delta's. Ease off on the lower values if it is getting rich at slight throttle changes.

    Must have gotten really lucky on the LS. I had the Express van with the 0411 run 5.7 dialed in very well. I went from the factory converter to a looser converter. All of a sudden it started lean popping if you smacked it to the floor. I ended up adding both timing and AE to fix it. After it rapped up much quicker.

    Even port fuel setups can lean pop. Its not a TBI or Carb only thing.

    https://youtu.be/gNyr_Z6Q_ck
    Well, more efficient heads require less timing. Or so I've read anyways. That's what got me to thinking that. But, I believe you. It really seems like based upon what you're saying, that with these Trick Flow aluminum heads, that this setup can really benefit from some more timing. I will sprinkle some in today or tomorrow and see what happens. I built this 355 with forged pistons. Since it has forged pistons, I might just slug the entire spark table up 5 degrees and see what happens in the knock retard.

    What exactly would be a good proportion for "progressively" higher values in the Delta MAP and TPS AE tables? Thinking maybe something like bump the first 1/3 of the tables up 25%, the middle 1/3 of the tables up 50% and the last 1/3 of the tables up 75% or something similar?

    The S475 LS has a frankensteined 32 spline T56 built by yours truly. Might have been an issue if it was an auto with a loose converter.

    Oh yeah I'm sure. TBI or carbs seem most susceptible to it, to me anyways. LS has the injectors nearly right behind the intake valves. TBI or carb being all the way upstream of the incoming air, seems like either system would be more prone to lean popping as the fuel would be more likely to fall out of suspension and wet the intake walls....

    Quote Originally Posted by brian617 View Post
    When you change your AE tables both MAP and TPS, are you moving the whole table up and down or are you playing with the curve?
    Well so far, I have usually been slamming the entire tables up by a percentage. RBob and several others on TGO have posted about multiplying the entire tables by 10% to 30%... I can now see the potential benefit from adjusting the curve rather than moving the whole table up..

  4. #4
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    54
    Posts
    3,870
    Well, more efficient heads require less timing. Or so I've read anyways.
    They do. Max timing on the older Bowtie race heads was around 36-38 degrees. Vortec are generally run with 32 degrees.

    Trick Flow aluminum heads
    Aluminum is the key. Aluminum heads transfer heat out of the combustion chamber more quickly and it takes longer for the reaction to occur. So you have to start spark sooner.

    I can now see the potential benefit from adjusting the curve rather than moving the whole table up..
    Correct. The shape of the curves needs to be adjusted to match the engine's needs.

  5. #5
    Fuel Injected! PlayingWithTBI's Avatar
    Join Date
    Dec 2018
    Location
    Tonopah, AZ
    Age
    70
    Posts
    344
    Chamber design has come a long way since the days of the first smallblock. The size, shape, depth of the chamber all play a part in efficiency. Today engineers are looking for faster and more complete combustion and heads with a well designed chamber need less spark advance. Look at some of the old and new designs in this link: https://www.chevydiy.com/chevy-small...-fundamentals/ If the Summit heads are a copy of an old design head, you may need to add a bunch of spark timing. If they are a newer fast burn type chamber the increased efficiency may work to balance the heat loss through the head in a way that lets the stock L05 timing work. My comment wasn't necessarily about curing popping with timing changes, but more of a comment on how close the stock L05 tables will be to correct.
    Here's a picture of the chambers in the Summit 162108 heads CDeeZ and I are using. From what I can tell, based on your link these are the newer "fast burn" style?

    Trick Flow Chamber.JPG

  6. #6
    Fuel Injected!
    Join Date
    Feb 2013
    Location
    Euless, TX
    Posts
    2,331
    Here is the design I run.


    9.6:1 350
    271/284 @ .006
    215/224 @ .050
    .578/.578" w/1.7 rocker
    110 LSA
    106 ICL

    Idle = 24* BTDC @ 750 rpm

    WOT
    12* @ 800
    16* @ 1,200
    20* @ 2,000
    24* @ 2,400
    28* @ 3,000
    32* @ 3,600-6,500

    Cruise timing is up to 48* BTDC @ 3,000 rpm and 40 KPA MAP.

    WOT air/fuel ratio is 12.5:1 near peak torque and leans out to 13.2:1 at higher rpm

    Cruise air/fuel ratio is stoichiometric or up to 16.5:1 in highway lean cruise.

  7. #7
    Fuel Injected! PlayingWithTBI's Avatar
    Join Date
    Dec 2018
    Location
    Tonopah, AZ
    Age
    70
    Posts
    344
    Nice, are you going to put your new marine intake on this setup?

  8. #8
    Administrator
    Join Date
    May 2011
    Location
    Lakes Region, NH
    Age
    54
    Posts
    3,870
    Quote Originally Posted by PlayingWithTBI View Post
    Here's a picture of the chambers in the Summit 162108 heads CDeeZ and I are using. From what I can tell, based on your link these are the newer "fast burn" style?

    Trick Flow Chamber.JPG
    They're a much better chamber design than many of the earlier heads. The spark plug is angled toward the exhaust port to reduce intake shrouding, the chamber walls appear to be slightly tapered at the intake valve to improve flow, and the shape of the chamber appears to encourage swirl during combustion. I would expect these heads to require less spark advance than most of the pre-80's heads.

Similar Threads

  1. 7427 PCM with
    By sfara002 in forum GM EFI Systems
    Replies: 3
    Last Post: 02-24-2018, 04:58 AM
  2. 7427 ECM
    By C2500 in forum GM EFI Systems
    Replies: 1
    Last Post: 01-04-2018, 07:40 PM
  3. '80 Corvette 350 4 spd M/T, '93 TBI, '94 454 TB, 7427 PCM
    By rdicarlo in forum GM EFI Systems
    Replies: 16
    Last Post: 01-12-2017, 12:53 AM
  4. Pin out for 7427
    By myburb in forum GM EFI Systems
    Replies: 11
    Last Post: 08-05-2015, 07:55 PM
  5. 305 tpi with 7427 pcm Possible?
    By Aholt91ss in forum GM EFI Systems
    Replies: 67
    Last Post: 08-25-2013, 02:12 AM

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
  •