FFCam1991

Hey, My fuel economy isn't terrible right now but I think it could be better, especially for a stock 305. The only things I have changed that could affect it one way or another is new plugs and wires, new cap and rotor, and rebuilt bosch design III's 22 lbs injectors. Timing is at 8 degrees BTDC. I did mostly highway on my last tank and I got 20 mpg, imperial, so that is like 17 American. I have no error codes anymore, the new injectors took care of my rich O2 sensor code. I know that I have a non-stock chip as well, but that was done by the former owner and I don't know anything about it. All I can think of is maybe changing my PROM. Any ideas to get the maximum fuel mileage out of this car? Thanks!

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afremont

With those injectors and a stock eprom, you'll be running fairly rich when not in closed loop.

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In the land of the blind, he who has one eye is king.

FFCam1991

So besides changing the PROM (not sure if I could burn my own, but I'd like to try), what else is there? I forgot to mention I have new air and fuel filters.

afremont

You could lower your fuel pressure with an adjustable regulator. I didn't notice before that you have a custom eprom. All bets are off now. Your chip may be set to make your car run like a raped ape instead of being miserly. No single setup can give you both. If I ever get my car running right again, I'd like to experiment with some prom tuning. www.moates.net has everything you need including an eprom simulator that lets you make real-time adjustments to the "eprom" settings.

__________________
In the land of the blind, he who has one eye is king.

FFCam1991

Just rechecked my fuel pressure...

Ignition on it is 42 psi, which quickly fell to 40 psi. After 5-10 or so minutes it was down below 20 psi and it kept falling. With the engine on it held steady at 38 psi for the full 5 minutes I had it on. After I turned the engine off and kept the ignition on, it held at 40ish psi for longer than before, but it too eventually fell below 20 psi. Not sure if this could relate to my fuel consumption problems but any thoughts? My understanding was that fuel pressure should hold steady with ignition on.

gurkgurkgurk

i have the same problem, but i have a 305 tpi, with mild upgrades, edelbrock headers, 3 inch y pipe, high flow cat, cat back exhaust, hooker muffler. upgraded ignition. and i still get around 15 to 17 mpg.

im thinking i need to adjust my valve lash, perhaps thats whats holding us up alittle bit in terms of fuel economy, im also thinking of upgrading to K&N filters, but ive heard mixed reviews about them

transam85dudeman

dude, man, you shouldve gotton 19# injectors. and timing should be at 6*BTDC. The TPS should be set around .555 volts with the diagnostic link grounded. thats totally normal that your fuel pressure drops, if it make you feel better, i get an instance drop to 0 in 20 secs, because the hose that connects the fuel pump to the inlet slipped off a little, but she runs faster than any mustang. but i should have never used self-tightening clamps on the the neoprene hose in the tank, i should have used clamps really tight. ive swapped my injectors with stock #19 pound VENOMS. dang those run little rich, but worth it, i believe that maybe perhaps that u got injectors made for 350 but a step below... its chill man. if you want hella good milage.. then following the following. new headers. new high flow cat, new flowmaster, tb spacer, tb coolant bypass, tb airfoil, i dont recommend K&Nfilter unless its speed density, bigger 50,000volt coil with wider gapped plugs, adjustable regulator for fuel, (because you can have #19 injector and just raise the pressure level and bam instance horsepower. try cutting out the a/c compressor from the belts( i cut the belt off the a/c compressor and got good milage)Port and polish the inside of the plenum and make it smooth. repack the front bearing and inflate the tires to spec. i have a book called TPI secrets. MUHAAAAA. its awesome.

FFCam1991

Wow thanks for all the ideas. It's good to know that this isn't a problem with my fuel pump or anything like that, I guess if it's holding steady pressure with engine running that's what matters most.

I'm kind of on a budget here, actually planning on selling the car soon, but I want it to be in great shape for the next guy. If I was keeping the car, I would definitely retool the exhaust and do some intake work, but that just isn't in the works right now.

I guess I should have gotten 19 lbs injectors but I was assured that 22 lbs would be fine.

If I do custom burn a PROM, what kind of gains can I expect (if it gets done right)? This is something I'd like to try out and if it nets me some fuel economy, so much the better.

Thanks again

gurkgurkgurk

i wouldnt recommend messing with your fuel pressure too much without having it tuned properly. also those 22 pound injectors are alittle much for your 305 since 19 pounds were what came from the factory on them.

id say if your trying to get every ounce of MPG out of your camaro do lots of maintanance, valve adjustments, fuel filter, air filters, gear oil, tranny fluid, coolant flush and perhaps and some water wetter to it, new spark plugs, wires, rotor, dist. cap, also free mods are good, like Throttle body coolant bypass, also some weight reduction goes along way, getting rid of stuff that you dont use. like spare tire, jack, any crap you have laying in the trunk, also not to mention making sure your tires are filled to the correct air pressure, also make sure to get an alignment if your tires wear unevenly. ive experienced cars that have really bad toe, and you almost seem to lose power because of the fact the tires are so pidgeon toed.


and transamdudeman, you from the bay? i can spot that "hella" a mile away haha

FFCam1991

Hey,

It's got a pretty solid tune up I think. Plugs, wires, cap, rotor, new fluids everywhere, new filters...if those injectors are wrong for my car I'll be pretty pissed off because those were specifically recommended to me by the company I bought them from. 35 psi in the tires.