rcjone Posted June 7, 2009 Report Share Posted June 7, 2009 Am getting only 18.3 mpg on my new engine and su's. BAD news, what with gas going back over $3 per gallon Very Soon so... Does any one have any input on how to get more miles out of a gallon of gas with this setup?: L20B with 2500 miles on it. 38mm SU's with a SSS manifold. ZTherapy rebuilds. Have K/N filters. A87 head (closed) ported to match the manifold. A B/W trans ( only 1 arm so a manual is not an option ). Don't know what compression but am using regular without any problems. Suggestions, ideas, an unused miracle perhaps? Quote Link to comment
HRH Posted June 7, 2009 Report Share Posted June 7, 2009 My SUs get pretty decent mileage in my 510, but I would say swap to a higher geared rear end. Stock is 3.90, the stock clutch Subi diff is 3.70. That would help a little bit. Or, if you already have the 3.7 subi diff, have you calculated the amount of gear correction you need? Like when you switch to big tires on a 4x4, your mileage will be slower than you're actually going. Same effect for raising gear ratios (numerically lowering). If that's the case, you may be getting 20 or so but measuring incorrect speedo mileage, not actual mileage. Of course, the auto trans is going to suck some power too, but not much you can do about that. Quote Link to comment
datzenmike Posted June 7, 2009 Report Share Posted June 7, 2009 A basic 620 will give over 25MPG and it weighs 2,750 and has 4.375 rear end. I would think the 510 would be in the high 20s at least. Is the choke linkage set properly to fully shut off in the off position? Are they jetted properly for the L20B... could the jet size go smaller? Do all wheels turn freely, no brake dragging? Is the vacuum advance working on your distributor, could it be leaking? Could the mechanical advance be stuck, no advance? Could the cam be improperly timed, advanced/retarded... chain stretched? Do you have a stock cam??? Are you running a heavier oil than necessary, could you run 10W30? Are your tires inflated to the manufactures rated pressure? Are you carrying unnecessary junk in the trunk? Quote Link to comment
rcjone Posted June 8, 2009 Author Report Share Posted June 8, 2009 A basic 620 will give over 25MPG and it weighs 2,750 and has 4.375 rear end. I would think the 510 would be in the high 20s at least. Is the choke linkage set properly to fully shut off in the off position? Are they jetted properly for the L20B... could the jet size go smaller? Do all wheels turn freely, no brake dragging? Is the vacuum advance working on your distributor, could it be leaking? Could the mechanical advance be stuck, no advance? Could the cam be improperly timed, advanced/retarded... chain stretched? Do you have a stock cam??? Are you running a heavier oil than necessary, could you run 10W30? Are your tires inflated to the manufactures rated pressure? Are you carrying unnecessary junk in the trunk? Stock cam. Runnibg 20-50 like the book says, will go to Amzoil 20-5 when I ge 5k on the engine. Tires are @ 32/36. The rebild etc was done by a Datsun Master Mechanic ( I saw the certificates! ) so will have to assume all is right under the hood. I advanced the timing 1 degree to see if that would help a bit, no data yet. Quote Link to comment
Z-train Posted June 8, 2009 Report Share Posted June 8, 2009 I'm getting 18 MPG with my 810 Wagon with an auto in the city.SOmething is amiss in your set-up. Quote Link to comment
Phlebmaster Posted June 8, 2009 Report Share Posted June 8, 2009 :P I get 9-12 mpg. :lol: Quit yer whinnin. :D Quote Link to comment
fastdadd Posted June 9, 2009 Report Share Posted June 9, 2009 :P I get 9-12 mpg. :lol:Quit yer whinnin. :D YOU LIE!!!....you mean you used to get 9-12 Quote Link to comment
Phlebmaster Posted June 9, 2009 Report Share Posted June 9, 2009 YOU LIE!!!....you mean you used to get 9-12 Shhh!! :D Soon to get 20-24mpg in my Z!! :lol: Quote Link to comment
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