• Tuning 85 and setting up TPI with new motor
  • Tuning 85 and setting up TPI with new motor
  • Tuning 85 and setting up TPI with new motor
  • Tuning 85 and setting up TPI with new motor

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  1. #1
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    Default Tuning 85 and setting up TPI with new motor

    Hi Guys,

    I am working on an 85 car. I bought it with a hurt motor and and put another motor in. I used parts that came on the car (intake, exhaust, chip(azzato), etc).

    I got it running and it runs ok. But its my first corvette and my first tpi.
    Do I have to set idle w/idle motor interrupted on the throttle body? What about TPS? I need to get a book that explains TPIs, any recommendations?

    I tried timing at 6 deg w/o computer and then at 10 deg. 10 deg. seems to run a bit better but idles high. Not sure what to set it with Azzato chip.

    Fuel Pressure set at 42psi.

    Motor
    .040 400 with 2 valve relief flat tops, forged, -5.4cc, molly rings
    As Cast TFS 195 heads
    Comp XFI 268 Hydro FLAT tappet cam with 1.6 (224/231 at .050, .520/.515 and 113 lsa)
    Edelbrock base, Superram intake, 52mm tb, 24# injectors

    1 5/8LTs with X pipe and magnaflow mufflers, 2.5" dual, no cats.

    It has 1 5/8LTs on it with no cats and off road exhaust. It still has the stock 1 wire 02. Do I need to convert to an aftermarket 3 wire 02? If so why? What brand do you guys recommend for 1985.

    MAF- its stock with no screen. Should I try to re-screen it, look for a new one? No idea what the limit of stock MAFs is.
    Looks like airintake is stock with lid mod and KandN filter (dry, very little oil).

    Thanks guys I Just need advice on how to set this up and get tpi running right before tune. I suspect I am running lean.

    I need a dyno tune on this car pronto. I just want to setup tpi the way it needs to be setup with a new motor before a tune.

    Right now car runs but can get "confused" at traffic lights sometimes of extended idle.

    Lack of 9th injector (and possibly incorrect setup sensors) seems to make it run rough until it warms up.

    Plugs look ultra clean/lean. Maybe need different heat range too.

    But first I must setup all baselines (timing, tps, idle, look at 02 sensor and MAF).

  2. #2
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    Default

    Quote Originally Posted by Igor View Post
    Do I have to set idle w/idle motor interrupted on the throttle body? What about TPS?
    I tried timing at 6 deg w/o computer and then at 10 deg. 10 deg. seems to run a bit better but idles high.
    Corvette Action Center Knowledgebase :: 1985 - 1991: Technical Article: How to Adjust your Early C4 TPS and Idle Speed
    That is a biggish cam ; is not going to want to idle nice at 500 rpm.Run as much initial advance as you can without out getting knock counts WOT.(will show on scan )

    Quote Originally Posted by Igor View Post
    It has 1 5/8LTs on it with no cats and off road exhaust. It still has the stock 1 wire 02. Do I need to convert to an aftermarket 3 wire 02? If so why?
    Need to scan to see if it goes closed loop at warm idle. If O2 sensor too far back it will cool off and drop ECM out of closed loop @idle. Big overlap cams also upset the O2 at idle making it go troppo .Some tune so idle is open loop only
    MAF I would not worry about so long as it works.
    9th injector is cold start only; no affect after engine running.
    Was the chip done for this cam?
    You have a"hot" setup ; big cam , big exh , big heads , big intake. It is not going to idle like a stocker

    Bottom line you need a scan to check that all the sensors are working right and to check that the fueling and spark advance settings are correct

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    Thank you for your reply.. I will follow those steps in the next day or two and see how the car runs.

    No the chip was not tuned for this application. I didnt think the cam was that "hot", says 2000-6000 with 350, so with 408" I am assuming 1600-5600 which would work ok with the super ram and the 3.08 gears.

    The car is automatic with 9" converter with 11" lockup disk, so plenty of stall.

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    Quote Originally Posted by Igor View Post
    I didnt think the cam was that "hot", says 2000-6000 with 350, so with 408" I am assuming 1600-5600 which would work ok with the super ram and the 3.08 gears.
    Sorry missed the "400"
    Looks to be a good combo; just need some fine tuning.You are still dealing with cam overlap at idle which throws the O2 off.
    Still think you will have to raise the idle;I have 226/520 in my 383 and it has a lumpy idle @ 850

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