What can we benefit from multi-port fuel-injection systems? Oposed to a single... Is there a large performance and power gain?

Short answer is no. A multiport fuel injection system should give a little quicker starting and slightly better throttle response (you may not even notice).

The gains are in the intake design. For example, TPI is well known for it's low end torque.

Peter

Thanks Peter. I figured about the same thing I just wasnt sure. Especially when you read what things do from the companies selling it, they always make it sound like it's going to turn your ride into gold bars graemlins/beers.gif Whats TPI?

Its definitely not going to make your ride into gold bars. I have the Holley C950 system on my GTO. I works very well. The main benefits are precise fuel and spark control at all conditions. The cold starts are just like a new car. Turn the key and go. Throttle responce is very crisp. However, you need to learn to tune it in order to get all the benefits. Just like you would a carburator.

Andrew

I think another way to view it is it will tame a wild engine quite well.

I would expect throttle response to increase significantly...as would fuel mileage.

For example: my 96 LT4 is engine rated at 415 HP with 219 cc intake ports yet will idle along at 1400 rpm in 6th and get 28 mpg.

I expect similar results from my soon to be finished 407 with 210 heads and Holley 950 Commander.

smile.gif

It simply comes down to tuning... if you can really nail the tune down with the EFI you will probably gain alot of part throttle divability and a bit of low end torque depending on your setup. My buddy who recently switched to a FAST system on his race car found that over a standard carb the EFI was about the same hp wise, but he lost abit of upper end hp with the EFI over his custom race carb. This makes sense as those are ment for full throttle fuel atomitazation (sp?) and to take advantage of the Joule Thompson effect.

Personally I'll never run a carb on anything ever again.

Other benefits to EFI (at least mine which is a Holley Commander 950)
- Programmable Ignition Timing (This REALLY helps a car run better)
- Data logger - I can datalog passes at the track and see converter performance, spin, shift points, engine temp, air temp and other items.
- I can run the ECU on any new engine combination and don't need a new one (might need larger injectors)
- I run a wide band oxygen sensor. I can tell it to run at ANY air/fuel ratio at idle, cruise, WOT (basically and load and RPM)
- To me it has been 100% reliable
- Idles at any RPM in gear and in neutral. I don't have to have it idle at 1400 in neutral and 600 in gear. It's 800 all the time or whatever I want.
- Programmable inputs and outputs and timing retards I use with the nitrous
- If I ever want to run a turbo or blower it will be simple to tune.

I can turn the key with my big solid roller at 30 degrees and it fires right up. To change for different air at the track it is a couple of minutes with the laptop and I can have it dialed in perfect for that air.

I couldn't stand to go back to a carb, on anything.

TPI is the GM tuned port injection. The long runner injection system of the 80's and early 90's. Those long runners worked wonders for low rpm performance. Still, comparing port injection vs throttle body injection the big gains are in the intake design.

Peter