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TBI vs Port Injection


zane9000

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I was just curious about peoples opinion on which is better. This is meant for a street driven car that I am building for performance. Emissions is not an issue, I am asking stricktly from a performance stand point. I am running a megasquirt so I will have full control over how the fuel is injected.

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From a performance standpoint, Port injection would give you a more accurate fuel delivery to each cylinder. There were a lot of factory cars equipped with TBI, but not too many of them were performance oriented that I can think of (except the starion/conquest). If you've already got an L28et, and megasquirt, I'd think you would be ahead of the game instead of trying to retrofit some kind of TBI getup on there.

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As someone who is currently moving from TBI to MPFI, I can tell you that, in terms of performance, everything else being the same (and here I'm thinking airflow), they're - different. Tuning a "wet manifold", per TBI, causes the system to behave much like a carburetor, in that there's a fuel charge present even after you've shut off the injectors. This is most evident in transitions on/off throttle. "Dry" manifolds, per MPFI, have no such behavior, making them (perhaps) more controllable under those conditions. That said, there's a lot to be thankful for with fewer components. For my swap, I installed a Holley StealthRam and a new computer, a GM '7730, so I'm having to learn a new (and much more complex but complete) environment. BTW, the car is no faster (at this point) than it was with the TBI, but I have a *lot* of tuning to do.

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that's true. specifically i am asking because now I'm am wondering where I should put the injectors on the SU manifold that I am converting to EFI. I had originally planed to do port injection but after olderthanme's thread I got to thinking about the possible benefits of TBI.

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Well, there were some good ideas being kicked around on the thread you are referencing (most of which were mine, eat your heart out, OTM! j/k). I think if you are shooting for ultimate performance, putting them in the same location they came on the fuel injected cars would be worthwhile. You might as well switch to o-ring style, to open up your options with aftermarket injectors.

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well, I AM going to have to go with the dual throttle body SU set up to get my supercharger to work (long story) so since I have to do some customizing anyway, I was just wondering which way would be better in the long run. But I think I will just drill 6 holes at the base of the runners so I can still use my fuel rail that has the stock positions on it.

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