car feels slow and im getting 220 mpg to the tank. am i running rich?
 

will buming up the timing help me out?

I get to about 180 before I feel the need to refuel

I seriously doubt you're running rich.. but if you're running a little too lean you might not be getting the umph you're looking for. Is the engine completely stock? Is there a chance your vacuum secondaries have come disconnected?

see here:
https://www.rx7club.com/1st-generation-specific-1979-1985-18/common-cause-power-loss-nikki-carbureted-models-632007/

umm lean makes the motor run better usually just not as safe. I get 300 to the tankon my 83 and i could prolly go farther (i get between 22-26 MPG) before i fill. What mods do you have?

Car is stock. Just had complete tune up done including carb rebuild.

Did you check for vacuum leaks? A vacuum leak can have a big effect on fuel economy and power.

Do you still have the rat's nest? The emissions stuff (the rat's nest) also helps increase fuel economy. A lot of folks rip it out without fully understanding why it's there and what needs to be done to get it running decently without the rats.

I experimented with removing the rats nest one summer and immediately lost 5 mpg, which I never could get back no matter how I tweaked the Nikki. When I reinstalled the rats I got my 5 mpg back.

A video of a cold start up and another with the engine idling at running temp followed by a couple revs might help folks see the problem.

Yeah I too can get 300+ miles to a tank on a basically stock 12a. You're positive you can only get 220miles to a tank? Are you resetting the trip meter on each fillup and calculating your exact mpg on each tank?

Ray i respect ur knowledge on these cars but i stil have to disagree on the rats nest debacle. Touring ur guage could be reading incorrectly as well and u think ur needing to fill at 220 when u really dont lol. My guage is at half by 100 miles and then at like 1/4 at 300. Lol since its bone stock you need to check make sure your cats arent clogged. Also get a timinig light and check timing. I wouldent go bumping the timing w/o a light and knowing exactly what your doing.

only if its wrong. how many gallons is 220miles?

well i filled up today with 14 gallons im pretty sure it was the same last time.

how can i tell if the cats are clogged

and also how can i tell if i have a vacum leak?

220/14 = 15.71 which is low, but not horrible

If you're warming the car up, idling it a lot and not driving on any highways then that number isn't tooooo far off really... My milage is usually about 22mpg in the warm weather and drops to the high teens (18/19) in the colder weather because I warm the car up before going anywhere.

Does your car idle smoothly? Does it miss? If you hold the throttle steady does the engine stay steady or does it hunt around and miss then? If its smooth than chances are you don't have a vaccum leak, or not much of one anyway... You can always go old school and get some carb cleaner and start spraying it around all the vaccum lines (with the engine idling) if the engine speed changes at all then you've got a leak.

i did some testing on my FC, and i found if i filled up and set the cruise control @60, i can approach 30mpg. i also found out that around town it gets 12mpg... how and where you drive is important.

if you use the choke, mileage goes down (in FL you shouldn't need it IMO, i dont use it in CA). idle mixture makes a big difference on these. tire pressure, alignment

I have no rats nest, i also have no cat, and I get 300+ to a tank. My milage is 22-25

so you guys arent using the choke?

When i use the choke its usally idling for 10 min. before i take off. i guess if i cut that out i would be saving some gas.

Its wierd but already it seams like im going to be getting 260-280 on this tank and i really dont know why. oh well lets see when it goes dry

This time of year I use the choke for a few minutes, but I never leave it on long enough for it to automatically kick off. In the hotter weather I can usually start mine without it, but then turn it on for a minute or so to keep it running till it will idle on its own.

If you are letting it run for 10 mins with the choke on everytime you start it then that explains your gas mileage.

aww man..... explains alot

quick update- replaced the cats and am now getting 285 miles on the tank. this was my first fill up after the strait pipe install. mostly city driving.

^^ About 100 more per tank than I get. I get 180-200 with mine but I have a yaw carb and do a fair amount of city. I have the rat's nest installed too, these cars aren't known for fuel mileage.

Is your exhaust stock other than strait piping the cat?

LOL... drop a t2 in it and tell me about fuel economy :-p
I'm at about 160miles on this tank and below 1/4 tank... of course this is a new engine and maybe "sipping" a bit much

yes just the strait pipe. was thinking about doing the headers but i think it will waste more gas. anyone know?

a header will increase mpg not decrease it anything to improve the efficiency of the engine will improve the milage

air,fuel,spark

I dont know if that is necessarily true. At low RPMs you need more back-pressure to get more torque. That makes sense at higher RPMs (the efficiency argument), but the little I remember from auto shop twenty years ago tells me not the case at low RPMs in "city" driving.

If you want performance/mileage then you should go with the headers. Locopr1 brings up a good point, but overall you should be able to tell what the deal is. How fast do you usually drive? Highway? Streets? All of that is unrelated to your car specifically. Me personally, rebuilt carb and tuned correctly with cats probably clogged who knows: 23 mpg 85% highway driving. So if I got the rb headers, even the nice set: dual all the way back to the end....probably get better mileage and more power too.