Carb. vs TBI vs. MPFI

[tiger9297]

Here's a scenario:

carb, TBI and MPFI. Say all flow 700 CFM and are installed on the exact same long block.

I'm not talking efficiency, all I want to know is will they make relatively equal power (hp/tq)?

 

[blazinzuk]

I pulled out an old car craft article I had for this, they did this exact same test on a dyno. The TBI and carb made within 3 hp of each other and 5 lb ft of torque. The multi port made about 5 more than the TBI. They dyno author of the test said with some tuning they could get the carb to run better than the TBI, and almost equal with the multi port. They also said in real world conditions ( i.e. your car acutally moving down the road and air swirling and temp changes humidity changes etc) the MPFI would always make more power because it delivers the fuel in a more efficiant manner. I have read other things in car mags that concur with this. So what I am saying is I think in a real car, driving, the MPFI will always make more power

 

[tiger9297]

Basically from that article they are still saying that the difference would be roughly 3-5 hp/lb ft. tq. so all in all there is very little difference. I don't think driving down the road in the "real world" 5 hp would be very noticeable. Seems the main difference would be only in the area of efficiency.

 

[ryoken]

MPFI freakin rocks... It'll be the route I go....

 

[blazinzuk]

Basically from that article they are still saying that the difference would be roughly 3-5 hp/lb ft. tq. so all in all there is very little difference. I don't think driving down the road in the "real world" 5 hp would be very noticeable. Seems the main difference would be only in the area of efficiency.

Kind of, in a dyno cell the enviorment is controlled air is flowing straight into the engine humidity is controlled and temp of the room. In a truck air coming into the motor is more chaotic, the temp can change rapidly, humidity can also change rapidly. MPFI can keep up with these changes better.
Since it is hard to do an equal test in the real world no mag will do so to show results, but MPFI is a more efficiant way of delivering fuel, not efficiency as MPG but more fuel is atomized and delivered to the combustion chamber in atomized form. So while on the dyno the differences are small, in the real world the differences would be greater. As a side note the MPFI did not consume as much fuel as the other two. They did not give the specific numbers.

 

[Wingnutt]

Overall, either FI system will outperform a carb in real world driving. The carb only has so much adaptability and is limited to its fixed mechanical limits. TBI, or TPI (multiport FI) either one can adapt or react more quickly, and precisely along with having an infinite amount of adjustibility within its physical limitations thanks to a myriad of sensors and the computer.

As far as TBI or TPI, the multiport will be a tad better because the intake of a TBI still has to keep the fuel atomized AND still deliver an even mixture to all the cylinders; whereas a multiport system has it’s injectors located just upstream from the intake valve. Another reason for the multiport’s superiority is that the algorithms buried within the computer’s programming are much further advanced than that of the TBI.

All three produce power amounts within 1% of each other, but the carb will require the most work to get there and to maintain it’s efficiency. The TBI is a good system, but requires more knowledge of how it interacts with everything else to tune initially, but then aside from normal maintenance is worry free. The multiport system is the most advanced and will require the most knowledge to get right, and like the TBI, once it’s right, you can basically forget about it.

 

[hawkeye649]

Overall, either FI system will outperform a carb in real world driving. The carb only has so much adaptability and is limited to its fixed mechanical limits. TBI, or TPI (multiport FI) either one can adapt or react more quickly, and precisely along with having an infinite amount of adjustibility within its physical limitations thanks to a myriad of sensors and the computer.

As far as TBI or TPI, the multiport will be a tad better because the intake of a TBI still has to keep the fuel atomized AND still deliver an even mixture to all the cylinders; whereas a multiport system has it’s injectors located just upstream from the intake valve. Another reason for the multiport’s superiority is that the algorithms buried within the computer’s programming are much further advanced than that of the TBI.

All three produce power amounts within 1% of each other, but the carb will require the most work to get there and to maintain it’s efficiency. The TBI is a good system, but requires more knowledge of how it interacts with everything else to tune initially, but then aside from normal maintenance is worry free. The multiport system is the most advanced and will require the most knowledge to get right, and like the TBI, once it’s right, you can basically forget about it.

I'd like to say that TBI is a very good choice if your planning on swapping from carb. Simpler than TPI, and IMHO it's simpler than carb, and it's rather cheap equipment. Also works at all sorts of angles unlike carb. It's a nice median between carb & TPI that can be easily adapted to different engine configurations within reason.