I think the rotary engine in the FD defies logic. First off I check my gas mileage every week and no matter what I do I get 15.x MPG. I mean literally last time I drove like a granny always shifting under 4000 rpm, never using A/C for this experiment I got 15.3 MPG.

This time I drove like a madman, boosting up and down in short spurts, using the a/c on full, etc. I got 15.8 MPG. Both were my normal driving locations only difference was how I drove. It makes no sense.

When I drive highway on trips I get from 20 to 23.4 with my ac running.


Anyone else finding similar things?

 

There has to be other factors involved? There should only be one variable for any experiment..... I don't think i get more then 10 mpg when im playing. I definately notice a difference in the dip of my tank. Did you do this test running from full tank to empty tank? If you are just using the stock fuel gauge I think this could play a large part........ I don't know ??? I'd like to see pics of someof your interior peices... I'm workin on my stereo and need some inspiration!

 

Hello there, I too am not amused about the rotary's MPG. The primary reason for it's poor fuel economy is the fact that the rotary has poor thermodynamic effiency. Thats the reason that a "1.3 liter" motor needs a radaitor that could cool a 350. That being said keep in mind that you will never get honda fuel MPG, but you aren't driving a honda either. I see you are using a Power FC, I am also, and I noticed that the part throttle tables are stinking rich. I have been playing with my tables only on the vacuum side of things. What I have done is turn off my O2 sensor feedback , then I started watching the O2 voltage while crusing, and idling. I have been puling fuel out of all of my tables less than P10. Many of my tables are in the 94 range now, and my O2 voltage is down considerably. The car stinks much less now, and believe it or not the engine is more responsive when you blip the throttle, which it should be, most engines get unresponsive once they get rich. There does not seem to be a downside to the pulling of fuel out. I know that Rice Racing says that one of the primary differences between good engine management systems, and tuners, and poor ones is the ability to get the light load, and drivibility parts of the engine's operation right. Rice Racing, can you disclose to us how lean is too lean under PART THROTTLE. I think we all understand that the full throttle range must be around 12.0:1 or richer, but is there a lean limit for the motor, and where is it? I am still pulling out fuel from my cruise tables, but I am getting wary of going leaner. You will never get honda fuel economy, but you can get 50 or more miles on a tank if your maps are optomized.
J

 

a while back I was toying iwth the same thing. I have a WB o2 and pfc but no datalogit. I turned off the o2 Feed back. Watched teh cells I use when crusing. I had it narrowed to about 9 cells. then I removed about 5%The indicated AF was still 11.8:1. real rich for crusing. seems to me the engine should run real nice crusing at stoich 1(14.7) I figured I would continue to play with it and get it at loeast in the low 13s.
one thing I know from tuning another turbo car. under light load if you go too lean, the power will surge a bit. you'll be crusing, and it'll feel like you your A/C compressor keeps turning on about ever 1-2 min or more. I notice you can feel the power fall off. but I could never feel the power come back too gradual I suppose.

I learned when you hit that point richen about 5% and it'll run great

 

I don't use the stock fuel gauge, I fill it up, check the mileage vs the gallons I put in. I put about about 15 gallons in each time. I have a bad O2 sensor too, lol.

 

i seem to be getting from 14 to 17 mpg heh not to good but better than my truck (11-13)

 

Oh man please tell us what kinda truck this is so I can stay far far away from it . I get roughly 15 on the highway and about 13 on the street. But then again I'm running a single turbo.

Would a bad 02 sensor lower mpg?

 

Absolutely it would.

Matt
93 SSM

 

I agree, the MPG just doesn't seem to vary that much for the way I drive.

Pure town driving (work commute): about 13.5 to 14 mpg with most shifts happening between 3k and 4k at light to med throttle

Fun driving: several miles of town and highway with lots of med throttle to 4k+ and a few WOT to redline bursts = 15.5 to 16 mpg

Overall, I pretty much get 15 mpg.

 

the trick to fuel economy in the fd is you have to keep it out of boost and in the closed loop part of the map. its only in closed loop from 1500 rpm to 3200rpm, and it will go out of closed loop at about 1 psi. i was getting 16-18mpg normally and 23 mpg all freeway

mike

 

Yeah, but that's NOT the way to drive an RX-7, especially an FD. I don't really care about the mileage anyway. I mean it sucks, but you deal with it owning a car like this.

 

Considering gas is 4 dollars a gallon in this communist country, I definitely have been experimenting with gas mileage. No matter what I do, in city I get like 15mpg and on the highway I get like 23mpg. On the highway I stay at like 65 or 70 mph (under 3k rpm when the second turbo starts to spin). In the city, it actually helps a lot to have my stock BOV disconnected from the air box for this reason:
under light acceleration the BOV lets out boost. you can hear this. So you know when you are operating not under boost cuz you hear the BOV letting out boosted air.
I never bringing it past 2500 or 3000 doesnt seem to make a difference. The only thing I have yet to figure out is this: When I got 23mpg that was without AC and going 65MPH. I still have to see if I remain under 3k and have AC on I can still accomplish this.

The other thing I have been wanting to know is...when do the secondary injectors come online? In relation to RPM, throttle position, or both?

I cant wait till I get back to a free country where there arent $2.40 of tax on each gallon of gas.