I was wondering if a quadrajet could get gas mileage that is comparable to fuel injection, namely TPI? I just did an engine swap and the fuel economy is taking my lunch money..

 

Depends gear ratio... If you are turning about 2300rpm or more on highway, stay w/carb. If less than 2300rpm w/standard or lockup auto, may benefit from EFI under load with it's spark control capability. The farther you are below 2300rpm, the better the EFI mileage. 2000rpm ish at 70mph is where most vehicles are OEM

 

Consider this. My E4ME is doing perfectly well behind my well-modified 305. I get 21 MPG on the highway with 3.73 gearing. I recently turned in nearly 100 MPH in the quarter mile, have a rather big lopey cam, and haven't seen a single trouble code yet!

One shortfall is startup: The engine runs rich until the computer goes closed loop. After that, it tames right down & runs great!


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Daniel Burk
http://www.isthq.com/~dan/fcar.html
'84 Trans Am WS6/L69
KB SFC, Moser axles, Torsen Diff. PST suspension, Braided stainless brake lines,
5-point racing harness, Koni struts, 11-inch rear disks,Spohn Adj. torque arm,
Ported 305 heads w/1.94"intake valves, Comp Cams XE262H, Griffen alum. radiator,
Speed-sensitive steering conversion, underdrive pulleys, Crane Hi-6 & more. 1.05g skidpad verified.
New best E/T! 14.400 at 98.6 MPH in 88 degree air at Stanton, Michigan.

 

The money and headache of TPI (not to mention if you actually want to make it fast and run well) will far outweigh any potential gas mileage increase.
I remember the last time someone did a post your gas mileage thing. there were 3 or so CCCS cars (mine included) that were turning in 26+ highway mpg and running 13s or quicker. The only TPI cars that came close to that number were a couple bone stock 2.73 geared cars (read: 15s rides)
And just cuz i only metioned highway as good, around town isn't bad either. I could usually get around 18 in my Z in moderate stop-go.
Properly tuned CCCS rules. The only limitation i see with CCCS is it is a PITA to tune on a low powered car. My grand prix does OK, but still has a slight dead spot to it. I think it's a combination of a too low TPS (lost my tool though, grrr) and just a hair quick too opening of an AV (i have it completely free swinging like it was on my Z, but my Z had the airflow to get the fuel flow to not bog when cool...the GP doesn't until it is fully warmed up.
...ed

 

Friday I drove from Denver to the middle of Nebraska: no wind, 75 mph for about 70 miles, 65 mph for 100 miles, the rest of the 355 total at 55-60 with construction delays at two points along the way. I stuffed the tank full this morning.

Mileage? 30.6 mpg. This with a non-functional TCC.

We'll see what I get on the way back, but even I was surprised that the 14 gallon tank made it here without replenishment.

I just put the 2.73 gears in last weekend, and averaged over 20 commuting for the week. I'll take those numbers, but I'll still do the TPI when I can get it done. Not for mileage, of course.

Oh, RPM's were ~ 2100 @ 75, 1850 @ 65, 1725 @ 60. Gee, what will the mileage be with TPI at those engine speeds?

Sorry, carb guys. Another one about to bite the dust. But, not for the mileage, of course.

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82 Berlinetta, orig V-6 car. Rescued w/86 LG4/TH700R with all harnesses, sensors, ECM, etc. 2.73 open. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, ported heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. Currently 396 .030 over, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.