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Thread: Mile Per Gallon !!!!

  1. #1
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    Lightbulb Mile Per Gallon !!!!

    Hi all! My Z is a 280z '75 and its getting about 15 to 18 mpg right now... ARGGG!! I have not done any serious upgrades to it... It is an L28 with FI 4 spd tranny. I dont drive it to hard... Just the occasional 0-60 run getting on the freeway =) I have been doing all the work myself on the car, and this Z is my 1st car I bought about a year ago. It was running on 4 cylinders due to timing and I had allitle help with a friend and we got that problem fixed and that was a huge boooooossssttttt in the cars performance. But the things that I have upgraded/changed in the car are: New coil, new spark plugs, new wires, new oil filters/oil every 3000, new air cleaner every 5000, new rotor cap. I havent touched anything inside of the engine yet... And wanted to see if anyone knows what I could do to get the MPG up around 25 or so... The FI were leaky allitle while ago and I changed all the fuel line plumbing, so no leaks now... Dont know if it could be fixed by changing new FI themselves and wiring... Electric Ignition or whatever.

    My second question is that I wanted to upgrade the engine componets to get some more HP out of it... And was curious if anyone knows what upgrades I should consider and if there possable to do myself. I purchased the HAYNES manual when I first bought the car and have self taught myself everything I know so far. The upgrades I am considering, are: Air intake, Performance Distributor, Performance Camshaft, Limited Slip differential, 5 spd manual, headers w/dual exhaust... I guess everything costs money, just want to know which ones I would see the biggest difference in...
    Thanks for your time! Im from Olympia, Washington.
    Dean

  2. #2
    Master of Weaponry Dtsnlvrs's Avatar
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    Well I not being there to help diagnose it myself, I will refer you to a local shop in the area. www.fairladymotors.com doug has been working on Z's for close to 20yrs....he really has his stuff together. He can help you figure out exactly what is causing the poor fuel mileage....could be a sticking cold start injector, temp sensor, faulty AFM...really tough to say. Give Doug a shot...he should be able to you out.
    Russell A. Buckwalter
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  3. #3
    No where near a pro mushupork5's Avatar
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    what you can do to increase the mpg will also decrease your acceleration, on the driver side of the engine there is a little black box off the FI block a few inches from the front of the motor, pop of the cap and you will see 3 metal strips \|| kind of like that, the middle one moves as you press the accelerator and it rests on the metal strip on the right, the closer the left strip is to the moving one (make sure they don't touch) the faster you will accelerate. The further (make sure the moving piece can still get there) the better mpg you will get. Set it where ever you like. Play around with it and then test your results.
    76 280z, or what used to be until 11-17-2003 oh it was back, dead again on 1-22-2004, hole in the engine

  4. #4
    mmm Z cars.. ohhh bbabyy PrOxLaMuS©'s Avatar
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    check your tire pressure?

    LoL.. simple but big factor.

    BTW Dual exhuast.. is an Iffy with a straight 6 engine... kinda useless and there is no performance gain compared to single exhuast.

    1978 280Z Boring Mods :
    F54/P90a, Holset HY35W turbo, 3.75" downpipe, 3" exhuast, NPR intercooler, 440cc injectors, Innovate Wideband, Arizona Zcar springs, Tokico 5 ways, MSA sway bars
    www.putfile.com/proxlamus
    SEE my 280Z in ACTION! VIDEO!

  5. #5
    Instant Human, ADD Coffee Z Kid's Avatar
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    Proxlamus, thats not totally true for the L series engines in mild tune its probably correct, but for high performance L series and definitely the bigger bore straight 6's ie jag XKE motors its quite a benefit to have the twin pipes from the donk back.
    I can only please one person per day,
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