http://www.teamfc3s.org/forum/showth...1&pagenumber=2

Some people have a hard time believing is possible to get 30+ mpg out of a 13B with a standalone.
So who else here has done?

 

I don't see why you couldn't get 30MPG. My 86GXL gets 26MPG with the mods in my sig and the crappy S4 ECU.

 

I have a standalone, and I get 16mpg on average.

 

I'm getting 28 to 28.25 mpg, stock ECU, which definetly doesn't make the cost of a standalone worthwhile

Even with an SAFC, you're talking mostly highway mileage to hit 30...And during cruise, the standalone can't schedule fuel any better than the stock ECU, which is in closed loop at that point...

 

I think I found your problem as far as gas milage goes Bdoty:
"1988 10th AE

Powertrain: Jspec motor, mild streetport, TO4S 60-1, Spearco FMIC, Fluidyne radiator, Haltech E6K, Tial 46mm wastegate, ACT 6-puck clutch, 720s and 1600s.

Suspension: Tokico adj. shocks, Eibach springs, 17" Konig Imagines.

408rwhp, daily driven "

 

Hehe, ya that might do it. Gas mileage is directly related to how often I am in boost, which is sometimes a lot.

 

Grrrr... threads like this make me angry at my car. 86' GXl RB header, Pres-silence, cat-back, KnN adaptor, S-AFC that's all the engine mods I have I'm even still on stock sized rims and tires and I'm getting 20mpg on all freeway mileage, that's with the S-AFC tuned down in the cruising range.

 

maybe your speedo is off

 

a stock rx7 makes 17/24 MPG. just ask the window sticker (i think thats right...). HOW THE **** do you get 30??? I wanna do that to mine LoL... do you like keep it below 2k rpms or somethin? LoL... thats what my dad does with his jeep...

 

I get 31mpg on my '89 GTUs at 75-80mph on the highway, stock ECU.

 

what mods do you guys have that allows you to do this? in a completely stock GXL i never got even close to that...

 

Free flowing exhaust, cai, upgraded plug wires, platinum plugs, new fuel filter, timings about 10 degrees advanced, and lightened a bit.

 

Freeing up the exhaust helps MPG a lot. My NA used to get 26mpg freeway w/ the only mods being a racepipe and weight reduction (2400lbs).

ScrapFC says he also gets 26mpg. He has header and freeflow cat in his heavier GXL.

Most NAs don't ever get stand alones, but it will help mileage.

 

And people wonder why its called the kiddie forum over there, LOL!

 

I get as high as 32mpg highway.. stock ecu, 55mph, s-afc leaned out 25% at 2000RPM, free exhaust and intake.

I also get as bad as 8MPG town.. due mostly to a heavy foot.

 

Your down 25% at cruise? alright, that's it I'm getting a wideband. I'm gonna take out all the fuel I can on the low-throttle map.

 

Yeah, if you don't have cats to worry about overheating you can lean it WAY OUT at cruise.

You will feel the car surging if you get it too lean- this puts extra wear on the drivetrain so richen it up to eliminate lean surge.

 

I usually average about 24mpg on the freeway, but when I factor in the fact I have large tires it goes up to about 25mpg. I could do some more weight reduction to get that number to go higher, but I don't want to take out that much stuff.

 

what kind of AFR's can you lean out to during cruise? i always figured you could go pretty lean since its at such a low rpm (maye 14.5-16) but how lean can you take it during cruise/

 

I get 16, 17 if I'm lucky.

 

I've noticed during my "mini-hesitation" problems that she'll run so lean the O2 sensor voltage drops to about .1v, so, however that translates into AF ratios, that's a little more leaner than you could run normally. In my case the FPR is screwed...

Surprisingly, I haven't noticed any better gas mileage running with her screwed up like that...This is in cruise, closed loop, BTW...

 

Not necessarily true. Closed-loop is a configurable option on programmable ECU's, so if you can leave it off and tune for mixtures leaner than stoichiometric during cruise. Stoichiometric is good for emissions but not necessarily economy.

 

It is true that the stock ECU is in closed-loop during cruise, but that doesn't mean it's accurate. The S4 ECU is an 8-bit system with the same processing power as a TI-82 scientific calculator. A modern system should easily beat it in both resolution and sampling rate, making it much more accurate and thus more efficient.
Also, by going to a standalone, you should be able to do away with the fairly restrictive stock MAF sensor and switch to a speed-density measurement using a MAP sensor in the dynamic chamber. Removing restriction in the intake is just as useful as removing it in the exhaust, since the engine doesn't need to burn as much fuel to create the energy it uses to move air in and out. Extra HP is just a happy side-effect of being able to move more air more easily.

 

I have a standalone and my mpg suck! I won't do the math though...if I do I might come to my senses

My mpg is better then when I ran the stock ecu and less mods.

 

The AFM is hardly a restriction until you get into much higher than stock power levels. Supposedly the s5 ECU had a more powerful processor, bonus good news for the s5 owners.