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MPFI or TBI?

Discussion in 'The Injection Section' started by onlychevy6, Mar 16, 2007.

  1. onlychevy6

    onlychevy6 1/2 ton status

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    Which systen is better for our blazers. Mine is a daily driver. Currently running a 350 with a carb. most of the offroading out here is rocks and trails. Not too much in the means of mud. However when i am in Texas there most likely will be.

    So please inform me on which is better and why?

    Thanks

    Jeff
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    To be honest, unless you are running a huge motor, I don't think you can lose either way. (MPFI seems to be a bit easier, if costlier, getting to work on larger, high RPM motors)

    The advantage you'll see from EFI in one of these trucks is more about overall driveability and running at angles than it is anything else.

    Some great features if you like to tinker (like programming your own PROM's) but other than that, it's simply things like not having to deal with a picky choke, "losing" tune, cold starts, hot starts, etc.

    As common and fairly cheap as the TBI trucks are, I don't think it's a wild stretch to say that installing a TBI system and seeing what you think before making the jump to MPFI is unrealistic. Neither system is more complex than the other (much, lol) so if you install TBI and like it, stay with it. Cheap, and it does what you ask. If you need more after that, consider selling it off to partially finance MPFI. If you do it right, you'll already have all the fuel and power issues figured out from TBI, so it would be pretty simple after you understand TBI.

    I run TPI because I got it fairly cheap, and I knew the people I was getting it from. Aftermarket MPFI (to me) is crazy expensive, but I understand that is because the components are expensive, and the volume of sales isn't there to bring the cost way down.

    What are your current beefs with a carb? If you want to go injection because it's "cool" (no arguments there :)) then I'd say just go TBI. If you NEED MPFI for whatever your driving demands are, then go that way. If you are unsure if you need MPFI, start with TBI, see if it works for you.

    Either way it's not a 4 hour project for someone that has never done it before (even if you've done it 10 times it's not a 4 hour project) but it's doable as long as you are willing to spend the time to do it right, so it's reliable in the long run, especially as a DD. Are you able to put it up for a week or two while doing an install and working out any bugs?

    My opinions anyway.
     
  3. onlychevy6

    onlychevy6 1/2 ton status

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    I have wanted to switch over to fuel injection for a couple reasons. More realiable i think. I am not injection smart. I found two systems available through affordable fuel injection on ebay. they are complete systems and the MPFI is about a grand more than TBI. The other reason i want fuel injection is due to the stall factor when you are at various angles.

    As far as the motor it is pretty much stock except for the cam. which i would imagine would need to be changed if i switch over to fuel injection. Also don't you get a few more miles per gallon using fuel injection compared to carb.?
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    Easy answer is, if you want mileage, go with a 6.2 diesel. Plain and simple, that's the ONLY way you are going to get "good" mileage in one of these trucks.

    Perhaps some people do pick up a couple/few MPG's when they swap to EFI. But that's ridiculous. You see/hear people on this board (no offense lol) getting 10-12MPG freeway. If you are getting 10MPG, and increase it by *1* MPG, you are doing amazing things...that's 10%. OEM's would KILL to get 10% better efficiency on any vehicle, because it's almost impossible.

    The only way your MPG can possibly increase a large margin (say 2MPG) by swapping to EFI, is that the carb simply isn't setup right. The problem with the trucks is aerodynamics and weight. Carb or EFI, they still fight that. You've gotta dump gas to get and keep them moving, doesn't matter carb or EFI. EFI can still waste fuel, it need to be tuned as well.

    As a for instance, I got 17MPG highway best in my '83. K5/305/Q-jet/700/208/3.08's/31" tires. With my current injected setup, I expect to get about the same. 20MPG if something miraculous happens. :)

    Mileage is not a reason to swap...the cost of injection STILL buys much gas, you'd have to run a lot of miles to recoup the purchase price of EFI with a 1 or 2 MPG increase.

    If it were me, I'd be shopping around for a 1987-89 donor truck and get the TBI setup (complete) for maybe $300. Preferably hear it run first.
     
    Last edited: Mar 16, 2007
  5. onlychevy6

    onlychevy6 1/2 ton status

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    Yeah i see that as well. I currently am pulling between 11 - 12 mpg in my 75.

    my set up is 350/350/205 on 37" tires. I am not heavy on the skinny pedal. i cruise about 65-70 on the freeway while driving approx 125 mile a day to and from work. I also run 89 octane gas. when i run 87 i get about 10-11. I was not expecting much as far as milage. maybe 1 more mile if that. But mostly wanted it for consistancy. I though about going with the diesel but i don't feel like going through that headache right now. LOL...
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    Diesel can't be much more headache than injection can it? I mean it's essentially a drop in with a 6.2L donor.

    The temptation to buy a "bolt on" solution is great, but if you can't diagnose or understand it, you will be frustrated to no end when it doesn't work right, which will happen at some point. Read all the TBI posts in the garage that people have thrown parts at problems and not solved them. *That's* what not understanding the system will do, along with a lack of wanting to learn proper diagnosis. A lot of wasted money and increased frustration.

    Even with knowledge of the system, problems will make you think, or lead people down the wrong road. Plenty of "professionals" can't properly diagnose problems, they are as bad as the 5 minute pill pushing doctors. Throw things at the problem until the problem goes away, if it doesn't, give up. :)

    Slowing down to 60MPH will probably net you another 5-10% fuel economy increase right now. May not be feasible (speed limits being what they are) but it's certainly one free way to increase economy.
     
  7. onlychevy6

    onlychevy6 1/2 ton status

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    thank you for all your input so far. Also your website it pretty informative. If there is one thing i have always wanted to do is understand how fuel injection really works for the better.
     
  8. Thunder

    Thunder 3/4 ton status

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    I would go with TBI on a stock or mild mod 350. Cheaper, easyer, maby small increase in milage. The real MPG increase comes with a 700r4 OD.
    Diesel.... Only a matter of time untill the new ULSD fuels take their toll on the old diesel engines. Injection pumps , injectors, seals, are all made for fuel that have sulpher and other additives no longer in diesel. Sulpher is a lubericant just like lead was in old gas. Sure you can pour in additive$.. but that just adds to the price of a fuel that is already 50+ cents more a gallon than gas. The government does not want all those old rattlers on the road anymore. Unles you go with a new ULSD diesel engine i think older 6.2s and 5s are a loosing battle.
     

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