Whose running TPI?

Discussion in 'The Garage' started by blazd88, Dec 14, 2006.

  1. blazd88

    blazd88 1/2 ton status

    Mar 16, 2004
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    Lubbock, Tx
    Got a hell of a deal on a TPI intake. FREE. Just wondering who was running it on a stock 350. I now theres alot of options as far as chips and so on. Is it enough of a pain to not mess with or go ahead and buy a harness and computer. Just wondering what gains could be expected on a blazer.
  2. Txchevy18

    Txchevy18 1/2 ton status

    Aug 29, 2006
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    Im trying to get all the parts together right now for my swap. I wanted the tunabilty of fuel injection and something a lil out of the ordinary. Being able to tweak every bit of horse power out of it will be nice and as with all efi's u can run severe angles. Tpi seems to fit the bill quite nicely, plus a 2-4mpg gain isnt bad either. It will be a whole lot more work to get it up and running but it should be pretty sweet when im done. Also dianostics should be a lil easier w/ the aid of a laptop.
  3. Russell

    Russell LLY Escalade Status Premium Member GMOTM Winner

    Jun 23, 2000
    Likes Received:
    Edmonton, Alberta
    I'm running TPI :)

    Couple things about this particular injection system:

    Its built for low end torque, even more so than your current TBI system, when you hit 2200 rpm or so, the harmonics in the runners really boost your torque by cramming more air in than you'd normally get.

    Next, don't expect it to increase your horsepower. It was originally designed to give a 305 the torque of a 350, which it did quite well, but that also means that it doesn't flow enough air for a 350, and falls flat on it's face at 4500 - 5000 rpm.

    Third, it isn't a sequential injection system like some people think, it still fires all of it's injectors at once, so some fuel is always wasted.

    That said, it really wouldn't be too terribly challenging for you to swap it in to replace your current TBI system, far easier than trying to swap it into an older truck that has no EFI system at all.

    Here is a rough list of the things you'd need to do to make it happen:

    1) You'd need to replace your in-tank fuel pump(s) with Camaro pumps to supply the 45 PSI that TPI need to operate. Right now your TBI pump only produces about 12 - 15 PSI. The Camaro pump bolts straight in. To go along with the new fuel pump, you'll need to make sure that you don't have any low pressure fuel lines on your truck anymore. The braided steel lines that you have running from your frame to your throttle body right now are high pressure lines, and work great for TPI, but you need to make sure that you don't have regular clamped lines going from your fuel tank to the frame. Finally, you'll either need to have your TPI fuel rail modified to make the fuel hookups appear out back to use the stock TBI fuel lines, or you will need to extend your TBI lines to reach the front of the engine where the stock TPI fuel rail hooks up to the fuel lines.

    2) You'd need to change the ECM out to whichever your TPI uses. 86 - 89 TPI units run a Mass Air 1227165 ECM, while the 90 - 92 units run a Speed Density 1227730 ECM. Mass Air is slightly more complicated, as you need to run a couple relays and a bunch more wiring to control the MAF. MAFs are also far more expensive than a MAP sensor, which is a simple 3 wire hookup. An 86 - 89 ECM will bolt straight into place of your current 1227747 TBI ECM, using the same mounting points, and connectors, while the Speed Density ECMs are far larger, and will not fit in the stock location. Only 86 ECMs do not have VATS to worry about, anything newer than that, Mass Air or Speed Density you'll need a chip to eliminate VATS.

    3) Regardless of which direction you go, Mass Air or Speed Density, you'll need to do a lot of re-pinning of your stock TBI harness, but you can re-use most of the TBI wiring harness with the TPI setup, though you will need to add a number of wires for TPI that don't exist with the TBI setup. There are excellent wiring diagrams of both TBI and TPI at www.chevythunder.com which can help you re-pin your stock wiring harness to work with the TPI setup.

    4) You'll need to change your knock sensor to match the ECM you go with, and if you run Mass Air, you'll need to make sure you run the correct TPI EST module, it looks identical to a TBI unit, but it is vastly different.

    Since the TBI harness and TPI harness are so similar, you will not need to add anything under the dash, and can re-use the park / neutral switch wiring, the SES light, ALDL connector etc from the TBI setup. You can also re-use a lot of the under-hood stuff too, like much of the wiring (IAC, EGR solenoid, TPS etc), and also re-use a lot of the TBI components, such as the distributer, coolant temp sensor (same sensor as the Intake Air Temp sensor under the upper plenum), MAP sensor (if you go Speed Density), etc.

    Also, since you are coming from a TBI engine, you shouldn't have much trouble, if any, running the engine a stock 350 TPI chip.

    Overall, a TBI to TPI swap can be accomplished pretty quickly, easily, and look totally factory when you finish. Again, read over www.chevythunder.com and you'll learn just about everything you need to know.

    I'm sure I've missed a few things here, but if you decide to go ahead with the swap, and run into any snags, feel free to give me, or any of the other TBI / TPI guys in the Injection Forum a shout :)

    By the way, post pics of everything you got with the setup, and I can give you a very rough cost estimate of collecting any missing TPI specific parts.

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