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Thread: 383 tuning help

  1. #1
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    383 tuning help

    First thank for all the earlier posts I have asked question about!! I have a 383 that was built and Iím thinking its not the power I was expecting. Hereís the build info..
    9.5 compression..The shop that built it is a well known shop in this area and builds a lot of race motors from drag to dirt motors and built may motors for me also..Engine was plate honed,block squared,heads milled flat and rings file fit..
    447/471 213/219 @ 50 112 hyd roller
    083 heads that are pocket ported and runners cleaned up
    3074 eddy intake stock(I noticed that I should have had it bored as there is a lip thatís in the flow path)
    Bored 46mm TBI unit
    stock 61ppm injectors
    14 psi regulator spring (fuel pressure checked with gauge and at 13.5)
    Fast chips piggy back chip from Ed Wright

    Truck runs good but I think it should run better..I was asking about the intake, boring it to 2Ē and put on a BB TBI that I have.. Iím thinking that its running on a 2bbl with that TBI and just up to a BB one should help it..timing is set at 0* with plug unplugged..Any thoughts that you have will be great..
    I removed the Y pipe and put another bung in it to see what the AFR is using a wide band with an LM1..
    Thanks again!!!!

  2. #2
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    So, what issues are you having exactly? Sounds like you need to do some real tuning and data-logging along with a wide-band before throwing more money at it. It could be fueling, timing, Power enrichment, or Acceleration enrichment giving you issues. Adding more air with a bigger throttle body may make it run even worse if it's lean now.

  3. #3
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    If you aren't already you need to be data logging your current setup so you can check out whats going on e.g. spark, VE tables.

    A seperate wide band O2 sensor will allow you to get an idea of your W.O.T Air fuel ratio is.
    13.5 PSI with stock 61 lb/hr injectors sounds a bit on the light side to supply enough fuel for a 383 at W.O.T. (a healthy stock TBI 350 would push that)
    Assuming you have everything like spark and VE table close to where they need to be have a look at your Injector DC% in tunerPro, if it get's to 50% then you will be running out of fuel because the injectors will be working too hard.
    Have a read of this: http://www.gearhead-efi.com/Fuel-Inj...ighlight=Kitch
    I use an Innovate LM1 and I mounted the gauge so I can see it while I drive and I eventually managed to get it connected to my Moates APU1 which allows it to stream the wideband O2 data into TunerPro so I can log the data rather than just look at the dash mounted gauge.

    The factory air cleaner is very restrictive above 3500RPM and if your still using that it will be holding you back. If you are using it at the very least look at flipping the lid on it but only once you've checked the Injector DC% and wideband AFR as more airflow may only make your problem worse. Assuming everything else is okay you should see a change in the W.O.T MAP values at high RPM with the lid flip on a stock air cleaner.

    Are you still running EGR with the 3074?

  4. #4
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    Kitch, I had Ed at fast chips do a chip for me that’s piggybacks the original. I sent it back 2 times already as it was rich at cold start and hot restart and cleaned up when it went into closed loop..
    Yes egr is active on the 3704 eddy intake..
    So I guess I need to get turner pro..
    I’m really green on this so I need as much advise as you guys can give me..
    I read threw that post you listed and it really looks complicated to understand.
    I have a snap on scanner so I have some data on there but I’m sure I may need more..
    Thanks

  5. #5
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    What do I need as far as cable to use tuner pro..and I would guess get the RT version?

    Also it has a red/blue 6395 ecm as its got a 4l60E trans
    Last edited by C2500; 01-05-2018 at 06:08 PM.

  6. #6
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    Even the most basic setup which would be a laptop with TunerPro installed and connected to your trucks ALDL port with an ALDL to USB cable would allow you to at least see whats going on in real time with things like spark, throttle position, RPM, MPH, BLM's and what the INT is trying to do during closed loop.

    You won't be able to make any changes with that basic setup but it would be a good start as far as gathering information on how things are running.

    It is a steep part of the learning curve you're on at the moment but given time and help from the guys here it gets easier.

  7. #7
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    Where to purchase that ALDL to usb cable?? Don’t see it on tuner pro web sight.

  8. #8
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    Try a google search but Moates has what you need if you can't find it else where.
    http://www.moates.net/gm-19851995-c-64.html

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    If no one has pointed it out to you yet, until your motor is up to a certain temperature it will only operate in open loop and when in open loop the engine basically runs of the preset values in your PCM's VE table.

    If the values are set on the high side it will generally run rich, if they are on the low side it will run lean.

    That's one of the things we change when we tune, to try get the values in the VE tables close to what the engine likes best so to speak.
    In theory once you get the VE table set up correctly you could effectively drive around in open loop all the time but I certainly wouldn't recommend that.
    During W.O.T. the PCM defaults to open loop and ignores the O2 sensor, thats why it's important to get the values in the VE table correct.

    When the engine eventually goes into closed loop the narrow band O2 sensor takes over and tries to trim the fuel to near stoichiometric.
    So if your truck seems to be rich when in open loop but better when warmed up and in closed loop, that's just the O2 sensor doing it's job.

    Tuner Pro can actually be set to display the point that it changes from open loop to closed loop.

    Any time you change your fuel pressure you will need to potentially redo your VE tables.
    More fuel pressure = richer across the board
    Less fuel pressure = leaner across the board
    You need to make sure you have enough fuel pressure with your stock injectors so that are not maxing out their duty cycle at the top end. Then you tune from there.

    A bit of a crude description but hopefully it gives you a bit of an idea.

    Some of the more knowledgeable guys here might ask you to upload a TunerPro log from your truck and they can then comment on what they see is going on in your log.
    Last edited by Kitch; 01-06-2018 at 04:39 AM.

  10. #10
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    Thanks for that last post.. Ill go over to moats and order a cable and get tuner pro.
    I’m not sure what chip ed at fast chips uses but can I with the proper equipment reprogram that chip?

  11. #11
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    I think I should get the aup1 auto prom package??

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    The apu has always worked well for me. Moates has always been helpfull when needed. Might be an idea to have them ship a few extra chips. If you are going to seriously get into tuning it yourself a zif socket comes in handy and the ( off memory ) g1 adapter
    6395, BHDF, 7.4 BBC lightly modded now 6395 BMHM back to BHDF

  13. #13
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    I'm not sure what Ed at fast chips uses, did the piggy back chip he sent you look anything like the Moates G1 memory adaptor?

    I use an APU1 and have been happy with it, I've used it with my 94 Chevy van and my 95 GMC Yukon.
    I did buy a GP1 package so I could fit the programable chip to my PCM but if you don't need the quick change ZIF socket and a spare chip then you could just buy the G1 memory adaptor.
    I also later bought the HDR1 memecal header only because with the APU1 it allows you to read the contents of the stock chip.

  14. #14
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    Kitch, myburb, So if I get the apu and a GP1 package I should be set to tune this then? Do I also need the ZIF ? What does that do for me? I want to order what I need to do this..
    Here’s a pic of Ed’s piggy back adapter. 9D2DEA51-D0A3-4859-96F7-F95841CFF9BB.jpg

  15. #15
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    The prongs on the chips are very thin and I tended to get one bent trying to put it in. The zif allowes you to just drop the chip in and flip the lever and you are done. If you want to get the tune really good you will tweak and data log a LOTA LOTA times. The only problem with the zif is it makes the chip sit up higher. Moates does have a low profile zif. What some do is use the zif while you are tuning and when you get the tune done then you can carefully insert the chip without the zif and then the cover on the case will fit ok. That adapter you have looks like it does a similar job to the g1. With the g1 you retain your limp. Not sure if yours does.
    6395, BHDF, 7.4 BBC lightly modded now 6395 BMHM back to BHDF

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