Spectrum24x

I went through the same thing when i first got my NA.. its called denial =D max i've ever gotten is 18 including some highway commutes. These are sports cars not hybrids.

FC_fan

iTrader: (2)

haha, civic hybrid and then going to an FC? you must have been sad. I just did regular maintenence on mine including cleaning the crud off the spark plugs every month. I guess just good condition makes it more fuel efficient? lol. FC+fuel efficient, no such thing. get a cheap 2nd car like a civic for normal driving and keep the 7 for "special" times.

RotaryEvolution

iTrader: (30)

sticky injectors, faulty fuel pressure regulator or timing is off. those would be the major contributors to poor fuel mileage.

HOZZMANRX7

iTrader: (43)

I've been driving RX7's since 1979. Over that time period I've owned and passed on maybe 15 RX7's. So I've have lots of different looks as what kind of gas mileage that can be expected tank full to tank full. I regularly check my mileage at each fill up.

With that as background, anyone that says they're getting more than 22 mpg combined I can only guess they simply aren't doing their math correctly. Either that or the circumstances they are measuring are line they're filling up at the top of a long hill, then coast down to the bottom of the hill and fill up again for calculations.

15-18 mpg is the realistic range to be expected with the majority of the time at the lower end of that range. 14 mpg really isn't all that out of line. My best was driving non-stop from LA to Vegas, fresh tune, oil change, new o2 sensor, air pressure at 35psi, and I kept the speed at or below 65 mph (which drove me nuts for that long a haul and occasional people flipping me off as they passed me) all the way just to see where the best mpg might be. It calculated at about 23 mpg.

RotaryEvolution

iTrader: (30)

not always, i do get 23.5 MPG on long trips doing ~80 MPH with some spirited driving in my T2 but also doesn't have all the crap weighing down the power and restricting it, a standalone also helps but it isn't a pipe dream. it is common knowledge that n/a's don't get as good of gas mileage as T2's do though, sad but true.

i do agree that 14-15 isn't horrible but it does seem to be on the low end for highway driving. checking timing and an SAFC might be a worthy investment vs banging your head against the wall for weeks trying to figure out where your gas is going. people claiming 25+ i think have been hitting the pipe a bit too much, especially in an n/a.

i drive many FCs and none of them get near as good of gas mileage as some people here claim, i figured i would at least come across some but nope.

ifryrice

I've gone through somewhere in the ballpark of 15 FC's over the years that I've personally driven for any serious amount of time, 25mpg would be about ball park average for the majority of them on highway. Most of my measuring was on delivery of the vehicle (I bought/resold a LOT) so I'd confirm odometer between the vehicle I was in, my follow vehicle (my ride home), and usually the GPS for giggles. Ideal speed was around 68-70mph in the GTUs and it'd bring home ~28 every time. Highest ever was 32 coming from Upper Michigan -> Syracuse, NY which matched the GPS & odometer.

Yes, i know, there are flucuations in fuel level using different filling stations, but the change usually wouldn't account for a difference that large. A lot of people have that 'one' tank that they pulled some magic number from and like to use that when they hit these threads, but averages tend to be more realistic

RotaryEvolution

iTrader: (30)

maybe you live in the bermuda triangle.

falling out of airplane doesn't count as mileage either..

just sayin'

ifryrice

I'd volunteer to pull the twins off the GTUs and do some datalogging, but I've grown rather fond of boost. No more good mpg for me, ever.

RotaryEvolution

iTrader: (30)

i suppose, then again a turbo shouldn't decrease your fuel mileage unless you are heavy in boost full time.

heard from 2 people with the same amount of 7's having opposing stories, just speaking from personal experience having been driving customer's cars for years and having to put gas in them and noting mileage i still haven't seen one break my own car's mileage(since i do fine tune it after all with all the time i spend driving it..)

FC_fan

iTrader: (2)

I threw my friends SAFC in my all stock car just because he was taking it out to put into another car he got. I literally put that in my car to see what kind of mpg I was getting. highway ranged a lot, between 65 and 80 mph, there were discrepencies of up to 6 mpg. so I guess I might be getting anywhere from 26 mpg highway. in town, I was getting 19-24 mpg depending on how I drove. the biggest diference came from how much throttle you give from a dead stop and how smooth you handle the clutch. I don't do spirited driving through town so thats not an issue. I was also taking the calculations from the "full" of the tank (pump auto shut off) to exactly 3/4 of a tank. I do notice that below half tank goes a little faster.lol. but hey, you don't have to believe me. the guy with the years of rx7 driving has more experience so listen to him. does seem to be the norm.

RotaryEvolution

iTrader: (30)

pull the stick out of your asses, it may be possible but it certainly isn't common. the n/a's were tuned rich or the cats would die so if you were getting that much gas mileage you either had uncorked exhaust or were blowing through a cat every 6 months with glowing hot exhaust. yes, pulling the cat off does in fact increase mileage(if you drive conservatively) but i'm not advocating bypassing your local emissions laws.

jackhild59

iTrader: (7)

You are making an outrageous claim to high gas mileage.

Bullshit.



You can't do it that way without introducing huge errors. You are sincere, but you are inept. Again, you are not measuring gas mileage correctly. You have to fill the tank, zero odometer (or record the mileage), drive enough miles to obtain a reasonable measurement (say 100+ miles) then refill the tank. Divide the miles driven by the gallons used to refill. The result is the miles per gallon. The larger the distance, the more accurate that calculation will be. Errors are introduced by the slight inconsistency in nozzle shut-off at the pump.

To be really accurate, do the math combined for several tanks. Sum the gallons used, then sum the miles. Divide. Now, the sampling error will only be for the one last fill up.

ifryrice

As I said, my 28-30's were done on catless cars. On stock cars, 25-26 was still pretty normal. The largest problem with comparison is the vast number of variables. Speed is probably the largest contributor. I'm sure if most of us cruised along at 60 instead of 80 we'd see some rather different numbers.

davidxp6

so after the new fuel filter, o2 sensor, new intake, full racing beat exhaust with header and presilencer and sparkplugs. my driving conditions stayed the same.



highway to work, about 15 miles one way. i stay at about 70 miles give or take traffic and the improvement is marginal. but there is improvement

thanks again for everyone input so far, now another question pops into my head.


servicing fuel injectors :

for cold starts, sometimes its a bit rough for the initial cranking of the rotors. not always but sometimes. it idles fine and pulls strong but i just dont know why with conversative driving i am getting such poor MPG.

someone did tell me that my injectors could be leaking and flooding. which could also be ******* me on my gas mileage also. so that brings me to my first question..

after searching the FC and FD posts, some people serviced their injectors as early as 40,000 miles and some havnt aand are still going strong at like 80k. my car is at 126,000 miles and the old man who owned it probably never really cared much to service them at all so its safe to assume they are a bit old. if not broken by nature of age.

is it hard to do in terms of DIY? and what exactly is required to perform the service? is it just a take it out, replace the o rings and soak it in some cleaning solution? or should i just buy new ones? i have access at my shop on some 550cc hks injectors/ various sizes but i cant find a post or manual to tell me what size is the FC non turbo injectors. primary and secondary.

if getting it serviced by a professional is more feasible, where can you guys recommend sending them to in the LA/ San bernodino county area?

lastly, if anyone in the area can help me with an inspection as a weekend project? i will gladly buy you lunch or dinner and supply enough beer to get us buzzing but not enough for us to break anything in my car.



again i want to thank you guys for your inputs, good or bad. and cheers to a new year already

ifryrice

Have you verified the car goes into closed-loop @ cruise? Usually a cheap AF/R gauge is a good indicator for this, but even using a multimeter hooked up to the O2 sensor could give you an idea (you'll see it start hopping back and forth between rich/lean constantly as you maintain cruise). Checking o2 feedback, your various sensors (@ the ECU), cleaning up ignition are things i'd start with before shipping the injectors off (due to downtime). You'll have to remove your intakes, endure some downtime as you have them shipped off, have to replace a few gaskets/orings and such, but it's pretty straightforward and easy to do. Compression also has a sneaky way of playing with economy (And cold starts)

HOZZMANRX7

iTrader: (43)

Man, there must be a huge difference between Wisconsin gasoline and what we get anywhere from Seattle to San Diego where I've roamed over the years. I'm sorry my friend, but there has to be something you're doing wrong in the way your measuring your mpg cat or no cat.

The deal is, leaning out a NA increases HP which is where the value of a SAFC comes in. Leaner means less gas obviously. Reason I'm pointing that out is I'm running a professionally dyno tuned SAFC II in the auto vert, so it is running the leanest that should be expected. Further, it was serviced to the nth degree before I drove it Vegas taking care to get the best gas mileage otherwise. K&N drop in, RB downpipe and presilencer. Even in those best of circumstances, 20-24 mpg in the best of circumstances. I measure by filling the tank until the over flow clicks are almost immediate to insure fair measure.

In that same Vert I average between 16-18 mpg around town. I will give that an automatic will typically get lower around town mileage than a manual in the best of circumstances. But not more than a 1-3 mpg difference.

Side comment, I would expect a TII might get better gas milease since it's stronger engine doesn't have to work as hard to maintain the same speed. However, TII's tend to run more rich than an NA, so probably a wash ultimately.

ifryrice

Possibly, but given that the car's been in 7 different states with similar results, i'd have to disagree on fuel quality. Though the cheese gas is good stuff. As I've mentioned, my measurement's are typically calculated using more than one method. The GTUs has been my best performer yet, and it just naturally ran lean(in comparison to my S4) at cruise. Hell, even my FD gets 26 on the interstate @ 70. (Averaged over my 1400 mile trip from Baton Rouge to the frozen tundra). What speed are you averaging?