TBI or Carb???

[rampant racing]

my friend mark has an 88 ford t bird.302 injected,3.73 gears and an overdrive.he gets 28MPG! he is a fuel efficiency nut(read that cheap) and knows the mpg of all his vehicles .he has an aod trans in the car.if a motor is lugging at low rpm it can take more fuel to run than an engine at a higher rpm and running efficiently/smoothly.your best bet is an aod trans and a taller tire if you can.the lower first gear in the trans will get you out of the hole quickly and highway cruising will be very EASY on the wallet.my 2008 mustang is at 2000 rpm highway speeds and gets 30 mpg canadian gallon.now stock they have a 3.31 gear and get 35mpg but i put a gt rearend in it with 3.55 gears.keep in mind it is also supercharged and makes 350rwhp ,that's well over 400hp at the motor without the nitrous.get yourself an air/fuel gauge and wideband o2 sensor to keep an eye on things.you should be getting more mpg but your cam may be hurting you. what are the cam specs (all of them) and what is the vacuum at idle and cruising?if you go sequential you tb can go just about anywhere and the injectors won't interfere at all with hood clearence.hear is a pic of an intake i made for my stang ,notice the tb is lower down at the front.you could make a bonnet or plenum on top of the manifold and mount the tb forward or off to the side.because the sequential efi system only passes air and not fuel through the tb it can be just about anywhere.tb injectors with the injectors in the tb still must deal with fuel distribution problems to all cylinders such as fuel suspension dropout and fuel perculation on hot days especially if you race it or are a spirited driver.mutiport efi is the ONLY way to go in my opinion if you are going to switch to injection.just my 2 cents.good luck.notice the box between the runners on the manifold.it is filled with dry ice and chills the manifold to -38degrees.cold air=hp.it was worth 2 tenths of a second in back to back testing in the 1/4 mile.yes that is frost on the manifold.i just sit a six pack on it for a few minutes if i get beat out and drown my sorrows.lol

[roverman]

IMHO, NOT being an expert, I feel tbi's do just about everything better than carbs, especially for street use. Things like a correct air-fuel ratio, regardless of atmospheric conditions, are a big. Used/rebuilt oem systems are real cheap and adaptable to our motors. Fuel distribution ? Say (2) 2bbl/tbi's on an Offy/ 2bbl manifold, should have very good distribution.I feel tbi's also "atomize" better. Why not use Rover injection ? Good Luck, roverman.

[302GT]

A carburetor, if properly set up will do at least as well as most TBI set-ups, and not much worse than a port injection set up once the engine is warmed up. Cold starts are a different matter.  

High mileage is not really that dependent on a perfect air-fuel ratio; the real key is ignition timing. Any carburetor (if properly set up) can provide 16:1 A/F ratio at cruise. The limit to using a lean ratio is burning it. All modern fuel injected cars have an integrated engine management system of which the fuel injection is just a part. Computer control of ignition allows the use of 10:1 compression and regular gas, impossible with "old school" technology. It also allows ignition advance levels of 50 degrees or more at cruise conditions. High compression and high ignition advance contribute greatly to fuel economy, but need computerized ignition control to be practical.  

A lean mixture burns slowly, a nearly closed throttle lowers actual compression to as low as 4:1; a very advanced ignition timing is needed to get the most from these conditions. With a knock sensor, timing will be advanced just short of detonation on the most sensitive cylinder (impossible with a conventional system). When the throttle is snapped open from cruise conditions, compression may go right up to 10:1 and the A/F ratio may go to 12:1. If the timing stays at 55 degrees there will be severe detonation. Computerized ignition systems can handle this easily, conventional systems cannot. Note that most of the carbureted conversion V8s run just a mechanical advance distributor, not even a vacuum advance. This gives, at most a 20 degree range to vary ignition timing, and has no provision for advancing timing at cruise conditions. No wonder carburetors give much worse economy than fuel injection...

To get the best economy, add an integrated engine management system, not just fuel injection.

[BlownMGB-V8]

Thanks Larry, that's some pretty advanced thinking. :-)

There are a few of our cars capable of this, and our numbers are growing.

JB