okay, I'm not interested in getting 30mpg or anything like that-- I got my 87 fc na 13b for a track purpose car, not a dd. The previous owner said he had a pineapple street port, which I asked which one he said it was only supposed to add 5-10hp (which makes me question why someone would even port at that point).

On the 3hr drive home from buying it I got 15mpg, which is what I expected from such a rich running engine. I drove it every now and then cleaning it up and correcting some stupid stuff the previous owner did.

I never really "pushed" it until I did the following.

> decarbed internals via distilled water through the air intake.
> followed by seafoam in oil and seafoam in the fuel.
> Removed the cats (its a track car).

I drove it like I stole it to burn out remaining water (prior to turning it off after cleaning). Let it sit overnight and began seafoam treatment, continued to keep it over 4,000rpm as much as possible to circulate oil and clean everything. Changed oil after 100 miles. Burned through rest of fuel driving "spirited" (hey, car feels AWESOME!).

Tonight, when my fuel light came on (yeah, it works... I'm shocked too). I stopped in to get real gas (there is a station that is e0 gasoline) and filled up. 153 miles, 15.2 gallons. To be honest, I topped it off... it clicked off at 14.7-- still it is more or less 10mpg! Holy crap, I knew it was low... but that's crazy imo. Anyone that usually drives spirited that can confirm approx 10mpg as "normal"?

As I said, I have it for track use-- but at this rate I could only drive on a track for about an hour before needing to refuel, a 16 gallon tank!

 

You should be able to get close to 30mpg in highway driving. It shouldn't be running rich.

I get 23-27mpg highway depending on air temps (hotter = better) with my *bridge ported* FB. About 5mpg city. City fuel economy is the bane of rotaries.

 

I have an FD . and I get 23 mpg's on highway driving . is the car chipped/tuned? or is it on stock ECU ? that seems very bad.. honestly LOL BUT then again .. when I WANT to have fun I see the fuel needle actually go down as I drive .

if allowed in your state you could get an ECU to tune and lean out where possible .

 

+1 on the track you can expect around 6 mpg on the stock ECU, on the freeway it should do like 20-24.

if its not doing more than 20mpg on the freeway, i'd look at the O2 sensor

 

I don't see any piggyback mgt, not sure how I could check for a flashed ECU.

I'm fairly certain the O2 sensor is there for show, it's attached to a tube removed from the exhaust flow by some 3 feet.

It's clear form the smell of the exhaust that the car runs rich, but the answer I need to know is "how rich?" From what I understand of OEM O2 sensors on most cars is they are basically on/off switches that tell the ECU if the mix is lean/right/rich but will not say how far the mix is off from the target.

anybody know how I can verify the mix is rich without investing in tools or shop time? Before the suggestion is made, it backfires while upshifting about 8-10% of the time but only if I am shifting past 4k rpm. If I keep it under 3500rpm I never hear it backfire.

 

Not really a scientific way to find that out .unless you get a wideband gauge , borrow a wideband from a friend screw it into the 02 bung (hopefully its in the way of the exhaust ) and read waht it says .