Multi point vs. Tbi - Team Camaro Tech
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post #1 of 13 (permalink) Old Mar 2nd, 13, 10:50 PM Thread Starter
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Multi point vs. Tbi

Edelbrocks Pro-Flo Injection is a multi-point injection. I've always been told that the multi point injection is better than the Throttle Body Injection(TBI), yet I see more post or ads for the TBI injections ie. Fast or Msd. I'm looking to convert but I'm getting confused as to what's better, either the multi-point or the TBI.
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post #2 of 13 (permalink) Old Mar 3rd, 13, 07:22 AM
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Re: Multi point vs. Tbi

My understanding is as follows:

TBI is easier to install - generally as a replacement for a carb - but, like a carb, puts the fuel into the air stream that flows through the intake manifold. That allows the fuel potentially to drop out of the airstream. MPFI injects the fuel (generally a pretty fine mist under 3+ atmospheres)directly above the intake valve, so you know that each cylinder is getting all the fuel it's supposed to get.

The MPFI should be capable of greater fuel economy. In practice, I doubt you'd see a huge difference between a TBI and a MPFI AFTERMARKET system.

If we're talking OE systems, MPFI is better than TBI.

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post #3 of 13 (permalink) Old Mar 3rd, 13, 07:41 AM
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Re: Multi point vs. Tbi

Like Mike suggests, if you're building one, then TBI is the simplest.
However, if buying ready-made, then a MPFI is the way to go, but, TBI's would be cheaper.

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post #4 of 13 (permalink) Old Mar 3rd, 13, 12:18 PM
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Re: Multi point vs. Tbi

To me it depends on what your end goals are?

i mean, and i could be wrong, with mpfi each injector does not squirt individually---instead i think they "batch fire" one bank, then the other, then the other side etc. etc. etc.... So what's the real advantage(s) over TBI? Or am i wrong again?

For me, if i was running anything except a tunnel ram, independent runner manifold or a roots supercharger i would prefer TBI.
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post #5 of 13 (permalink) Old Mar 4th, 13, 04:49 AM
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Re: Multi point vs. Tbi

MPFI = multi port fuel injection. I have the f.a.s.t computer on a proflo intake. The computer can be run as bank to bank or mpfi, which is what i am using

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post #6 of 13 (permalink) Old Mar 4th, 13, 01:24 PM
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Re: Multi point vs. Tbi

MPFI uses the batch system while SPFI (sequential port fuel injection) fires a single injector per cylinder.
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post #7 of 13 (permalink) Old Mar 4th, 13, 02:55 PM
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Re: Multi point vs. Tbi

With MPFI one can adjust fuel individually to each cylinder which varies dependent upon airflow differences and heat of the block/combustion chamber varies depending upon location in the block. If you ever get a infrared heat gun you'd be suprised at how different each cylinder runs. I've adjusted some inidvidual injectors up to 25% more or less due to the differences.
Quote:
Originally Posted by puff puff View Post
To me it depends on what your end goals are?

i mean, and i could be wrong, with mpfi each injector does not squirt individually---instead i think they "batch fire" one bank, then the other, then the other side etc. etc. etc.... So what's the real advantage(s) over TBI? Or am i wrong again?

For me, if i was running anything except a tunnel ram, independent runner manifold or a roots supercharger i would prefer TBI.

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post #8 of 13 (permalink) Old Mar 5th, 13, 03:38 AM
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Re: Multi point vs. Tbi

Quote:
Originally Posted by mahunt View Post
MPFI uses the batch system while SPFI (sequential port fuel injection) fires a single injector per cylinder.

Opps thanks for the correction

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post #9 of 13 (permalink) Old Mar 5th, 13, 08:26 AM
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Re: Multi point vs. Tbi

Quote:
Originally Posted by Camaro67_rcl View Post
Quote:
Originally Posted by mahunt View Post
MPFI uses the batch system while SPFI (sequential port fuel injection) fires a single injector per cylinder.
Opps thanks for the correction
So far as I can tell, SPFI is a subset of MPFI, which can be either batch fired or sequential.

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post #10 of 13 (permalink) Old Apr 3rd, 13, 07:15 AM
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Re: Multi point vs. Tbi

If the MPFI is firing in batch, I don't see an advantage over TBI. It needs to be sequential to offer an advantage IMO.
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post #11 of 13 (permalink) Old Apr 3rd, 13, 02:14 PM
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Re: Multi point vs. Tbi

Fuel doesnt have to make a turn inside of the intake. In some cases, if you are not pulling enough air to atomize ALL the fuel (this is a simple terms explaination) then you can have fuel "fall out" of the air and not be evenly distributed to each cylinder (or even pool at the bottom of the intake). The advantage to MPFI is that each cylinder sees the exact same amount of fuel given that the fuel is sprayed into each individual runner. This equates to a more even burn on each cylinder and overall more power with the possibility of better gas mileage. dont know that you will see the later, but I can tell a difference. This is just how I see it.

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post #12 of 13 (permalink) Old Apr 3rd, 13, 02:59 PM
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Re: Multi point vs. Tbi

Quote:
Originally Posted by Bangin' gears View Post
If the MPFI is firing in batch, I don't see an advantage over TBI. It needs to be sequential to offer an advantage IMO.
Even batch fired is superior. How superior is up for debate. But it unquestionably makes it possible to deliver the exact same amount of fuel to each cyl. TBI does not.

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post #13 of 13 (permalink) Old Apr 6th, 13, 08:16 AM
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Re: Multi point vs. Tbi

I get that but, Carbs face the same challenge and their performance is universally considered fine.

All I'm saying is if I were to consider going from one of the nice new TBI setups from MSD, Edelbrock, FAST, to a multi point EFI, It had better be sequential. The in the middle batch firing efi solution is more expensive and does not provide all the benefits.
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