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Different TPI intake and sensor compatibility question

Discussion in 'The Garage' started by sled_dog, Jul 26, 2005.

  1. sled_dog

    sled_dog 1 ton status

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    Thinking about my plans for the LT1 intake. Yeah it will gain me some RPMs and hp up there, but the loss of torque is looking too great.

    Here are Dyno numbers from the Popular Hotrodding article:
    [​IMG]

    If I had similar results, I think I would be angry. I'm not sure why I thought the LT1 intake was a good idea, looking at these results.

    So here is my thought, what about a "custom" intake? Say taking a low rise single plane and drilling it for injectors, slap a 454 Throttle body(minus the injectors of course) on top of it and call it good. Now that is where the sensor question comes in. Do you guys think the TPS and IAC(bigger of the two hurdles I bet) would be compatible? TPS sensor, as long as the wiring is the same, I can't see an issue(and even then repinning a connector so it is the same, not difficult).

    Also, would this be enough airflow for a TPI motor? I think 454 is something like 650 with the injectors, so figure like 680 maybe... I think stock TPI is what, 700? A Holley 4bbl throttle body would be nice, but $$$

    Mainly my goal is to make RPMs with a TPI setup and still have torque. I'm not saying, the exact same torque as the stock TPI setup, but not 50ft-lbs less.
     
  2. sled_dog

    sled_dog 1 ton status

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    oh and before anyone says "Check Thirdgen.org" I haven't yet but will be spending the evening tonight going through stuff over there.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Well, one thing to consider is what does the graph look like under 2000RPM, and where do you NEED the torque?

    (I had written up a bit on the stock vs. LT1 intake, then deleted it, but your last sentence brings it back: I don't have the article, but "SR" on that dyno graph leads me to believe thats an LT1 intake vs. a stealth ram or whatever, not a stock TPI setup. Am I wrong?)

    In my case, "high" gears with larger tires, manual trans, strong low end torque is much more important than the range that the stealth ram(?) shown is making power.

    Looking at the (typical) stock lack of any meaningful torque curve, that LT1 dyno graph may be flat even at 2000RPM, which means it is probably quite a bit stronger on the low end than whatever it was compared against. HP at most looks like about 25 less, but that's for sure going to be a tradeoff.

    IIRC, the TPI throttle body stock is right around 550CFM. There are enough variables though (intake tract, MAF or not, runner design, base, plenum) that increasing just one isn't going to solve all the problems. Depending on low end torque, going from a long runner setup to a single plane intake (for example) is almost certain to hurt low end. May help up high, but where do you really want it?

    If you look around on the web enough, I have seen people that have fabricated "boxes" that bolt to a carb intake, that mount the TPI TB. Looks goofy to me, but I think that is one way people are going FI on engines like Pontiac and Olds.

    TPS and IAC on the BBC throttle body should be compatible, at least with the TPI parts. I believe some TPS' had the wiring on the connector pinned differently, but that's easily changed.
     
  4. uglyangelracing

    uglyangelracing 1/2 ton status

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    In that chart what are they useing as the baseline?
     
  5. sled_dog

    sled_dog 1 ton status

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    IT is a Stealth Ram equiped stroked 350.
    http://www.popularhotrodding.com/enginemasters/articles/hardcore/0803phr_beast/

    See, I'm gonig to be running 5.13 gears with about 40s(undecided yet, last thing to buy anyway). My 383 is fully balanced, now I don't want to be reving 7K with it but I'm thinking limit it at 5500-6K and expect to hit it. Its hard to say whats the best way to go dangit. You are right, the torque curve is very flat on the LT1, I think that and the fact that I have a 383 were what was going through my head when deciding to go with an LT1 intake. But I didn't realize those test numbers were also a 383(well a 379).
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Well I have to say from experience, if you aren't building it solely for low end, you will probably be disappointed by not having additional power up high.

    I know on my motor the low end torque is good, but I certainly notice when the engine starts to run out of power. It doesn't stop running or anything, but you can just feel that turning more RPM's is pointless, you've reached a point of diminishing returns.

    I'd do some calculations on where the RPM's are going to be based on tire size and gear selection. If you like to go fast, I suspect that the 5.13's may actually be detrimental to speed even with 40" tires, but you'll have to compare the RPM's at whatever MPH to other combinations. If that makes sense. I know that with my setup, my truck would still be accelerating strongly with 3.08's at the point that it now starts to fall off with 3.42's. If I had 3.73's or 4.11's, it would accelerate quick, but I'd run out of gearing before I'd picked up much speed.

    I really think this is one of those things you HAVE to run to find out what you like. No one thinks the same amount of power is right, no one thinks the same engine RPM's are right, and no one can tell exactly how a vehicle will perform with certain modifications. You can take some educated guesses, but in the end the results and how those make you feel are the answer. 50 ft/lbs for instance is quite a bit, but until you run the LT1 intake (for example) how are you going to know you will even use that often? You might feel a big surge of power halfway through a run, then have it run out when you want more.

    You've also already got the LT1 intake though, so assuming you can't return it, what's to say you don't install it, then if disappointed, swap to something else? From when I was looking, most of the aftermarket plenums required different fuel rails, and I thought that cost alone was insane.
     

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