I don't think citing the EPA fuel economy figures from 1994 is a very convincing argument considering testing has changed to become more strict and representative of real-world conditions. My Evo X was rated at 17/23, you really want to tell me that a rotary from '94 is more fuel efficient than an I4 made 15 years later?

Many people here are not on stock ports which I'd say changes things quite a bit. I'd also say that if you're using any kind of water/meth injection then I wouldn't be surprised if you're able to lean out maps more than most as the traditional tuning method for keeping rotaries running was always to throw fuel at it.

 

This is my experience…on pancake flat interstate with no wind.

Spark plug life is shorter and in my experience, especially while on the stock ECU, depended alot on ambient temp and idle time. I try to avoid as much of the latter as possible but there’s always some idling. I typically check plugs a couple of times a year and don’t hesitate to change them if called for. Plugs aren’t that expensive and easy to do. And for me seem to make the biggest difference in starting, power and fuel consumption.
And I wouldn’t confuse “start the car and GO” with being responsible. I’m not sure what is meant by “extended warm up”, but I still try to stay out of boost until the engine is fully warmed up. Here in the Midwest in the spring and fall that’s probably more “extended” than in Florida, and IMO there IS a need for that.

 

Agreed. Once my FD starts, and is running, I'll start driving it - I don't spend much time sitting in the driveway idling it. Any car will warmup to operating temps and be most efficient when its driven under some load versus just idling. But I will absolutely stay out of higher RPMs (i.e., >4K) and stay off the boost until it's up to full operating temperature. Heck, I programmed the engine protection features in my Link ECU to literally force me to be responsible - if I get stupid and try to rev it too high or get boost happy while the engine is still cold, it will say NOPE and pull the DBW throttle back on me.

 

they actually still use the "gram strategy" today. its partly how the ND Mx5 is 2300lbs and will get 40mpg easily.

so the longest i've ever driven on one tank in the FD was 380 miles, and the light wasn't quite on yet, but had to pee really badly!
best mileage i've ever gotten in an Rx7 was coming back from Sevenstock in 2005, i got 27mpg on one tank, there is a big chunk of that coasting down the grapevine, but still the FD in the group was 23-24, then the T2 and then the P Port 1st gen....

 

Yeah I should have been more clear on the "start the car and go" - definitely drive low/no boost and under 4000 RPM until the car is warmed up. Sitting idling in the driveway for 15-20 minutes is what you don't want to do.

Also, a street port shouldn't make much if any of an impact on fuel economy in theory. If anyone has evidence one way or the other post up!

Dale

 

My S5 FC's current 13BT engine has an aggressive street port (intake + exhaust), and it gets about the same mileage as it did when I had an OEM stock ported 13BT in it. Between 21~24 MPG highway, 14~17 MPG when being flogged on the dragon. So that's one anecdotal data point to say that a street port has minimal impact on fuel economy. BIG caveat though is that I switched to an aftermarket ECU (AEM Infinity), along with fuel system, wiring and sensor upgrades after my engine swap. I found that with the stock Rtek 2.x chipped ECU, I couldn't get the new ported 13BT motor to idle well enough below 900RPMs, and it had a few other minor drive-ability issues that the Rtek simply could not tune out.

 

Things to improve fuel consumption on Stock ECU:

*Good tire pressure

*Minimize idling time

*New plugs

*Stock t-stat

*No pre-cat and properly functioning main cat.

*Aftermarket exhaust system while still avoiding boost creep.

*Improved intake system while avoiding boost spike.

*Adult driving habits.

In my experience bad sensors (IAT, Fuel temp, O2 and Boost) and failing coils cause the car to really run like crap or not at all. In any event for me it’s always been obvious and it’s doesn’t need to be pointed out that something “is broken”.

If on an standalone, I’d add to above:
*Good tune

*Sensor check

*Stock boost unless tracking/racing

*Ignition amp if running higher boost


And I pretty much agree with those suggesting another car if you want Civic mileage out of the FD. It’s just one of the reasons I don’t think it makes a good DD.

My .02

 

When my fd was stock, I would regularly get 25mpg highway. Even with 108k on the og engine. City driving I could never get above 13mpg. Having perfectly operating stock twins at the time made it hard to stay out of boost. I did carbon cleanings once a year, changed the plugs every 12k and NEVER did the extended warmup. I always lets the AWS (accelerated warm-up system) do its thing and when the idle dropped, Id put it in gear and drive the car. Don't understand why so many think idling to warm up is best. All you're doing is producing a ton of carbon deposits because the combustion chamber is taking too long to heat up that way. With rotary's, you wanna heat up the combustion chamber as fast a possible. Doing this helps burn off the excess fuel dumped in during cold start and your plugs foul less. It also reduces the chance of flooding because the plugs stay clean.

 

totally with you, Dale, on the 20 mpg area... a really good guidance.

i would also add that a properly ported BREW should post similar numbers as a good port offers less resistance to the charge air so the throttle doesn't have to be as aggressive. the stock primary port is a curious item. overall it has a reasonably good shape but Mazda constructed a large obstruction to effectively throttle it down a bunch. i assume for MPG or emissions? weird if MPG because i do a ton of work on the primary so it flows a lot better and my ports still do 21 mpg on the highway on just the primary.

the newer EV14 injectors do help v the older (really old nowadays) EV6s. the dynamic item in the EV14 weighs one fifth of the EV6. way better atomisation which does help both power and MPG.

 

23 years of daily driving FDs and I get 16 to 17 with a PFC and 14 to 15 with a stock ECU. This would be 50/50 hwy and city. If I drive it remotely hard or say back roads fun around 12mpg.

YMMV!

 

My bmw M5 with V10 engine making 500whp will not get better than 15mpg driving like a grandma.... Rotaries aren't bad

 

This chart was taken during its original engine, from new until about 3 years ago. Car was a daily driver then, now pretty much a garage queen only driven on in-town, short trips. It has always run pig rich when cold, this in Southern California. I've thought many times about putting a 620-ohm resistor in parallel with the coolant temp sensor, to bring the cold voltage down from 2.2 volts to more like 1.6 volts, because it's never that cold here. But never did it. Current mileage is around 14 mpg on average, but the engine is a new Mazda 13B from Ray Crowe that now has about 3K miles on it, and it's not shown on the Excel chart. On the road, car used to get about 21-22 mpg, but in town more like 12-13 because too much time was (and is) is spent driving it while still warming up. Current tune is by Neptune Speed (Yoshiya) of Huntington Beach, and the car runs beautifully, cold or warm. Engine configuration is as shown below my post, and is up-to-date.

 

I get 30mpg. Drive behind trucks at 55mph on the freeway and put my car in neutral anytime that is a slight decline. Sometimes i push my car in the parking lot to get more distance out of my tank so i don't have to turn it on and move parking spaces.

I kid. I've never measure mpg on my FD as i never cared/tried to get good mileage out of it considering it rarely comes out of the garage now and days. I think it would be time to do some measurements on it next time i drive it.