Hi Guys,

I know the FDs spend alot of fuel but im not getting 200 miles on a full fuel tank
(98 octane).
I dont have many mods affecting the fuel system.

rebuilt engine on Banzai Racing with around 6000 miles on it
Apexi induction
Apexi power fc (reseted and did auto learn to see if it wold get better) and needs to be tuned.
Greedy Profec b 2
3" Downpipe and catback
bigger aluminium radiator

I have a AEM wideband to install to see the air/fuel ratio. I should be
running rich as hell to spend this much, right?. maybe the o2 sensor is screwd up?
by the way the wide band replaces de o2 sensor right?

Well any help will be appreciated. thank you in advance

 

There is your issue. A tune make all the difference in economy .

 

yeah your fuel mileage should be about double that after you have it tuned.

FWIW, 100% highway driving at 70mph i get about 20mpg (~400mi/tank), but the AFRs are only in the 13s most of the time. it may go up to 22-23mph after i lean it out more. that's been my experience with my other rotary cars. i got 26mpg (100% highway driving) one time in my life in an FD and it was on the stock ECU with everything functioning properly.

high/city mix mpg is about 17 or 18 for me.

 

i'm not looking for economy. i just don't want to be too rich on fuel and damage anything.
Just trying to find out if its around the "normal average" for an FD

 

I can pull 25 mpg in my single turbo FD cruising on the freeway, 80 mph light load burning 91 octane.

 

The gas tank is just over 20 gallons. It sounds like you are not getting even 10 mpg. If its all city driving, with some "spirited driving", 10 mpg isnt that unusual.

 

I'm getting about 300 miles a tank on E85.

 

its ussualy on a freeway arround 70/80 mph. i usually don't get traffic. just regular driving with a bit of spirited driving from time to time but not that much.

 

Gas milage also depends greatly if you're a lead foot on not
.

 

i tried once just cruising and got about the same average.

 

If you are using the base map on the PFC you should be getting at least 15 or even 16 hwy and city combo.

Check your o2 sensor

A good safe tune with out a lot of cruising alterations should net you 14 hwy and city.

I typically get about 300 on a tank with just touch of lead foot. If you drive aggressively most of the time the mileage isn't going to be good, likely about where you are now at 10mpg.

 

There are no tuners where i live for the fd or power fc. yes, its on the base map with the auto learn after i reset it. i also have the datalogic so i can extract the map if anyone wants to take a look at it.
i will try to get a new o2 sensor to swap.

 

Oh wow. 250-255 is about all I get. I thought it was normal. haha

 

What's your boost and AFR?

 

Think it was 11.3 @ 7lbs up and 205 rwhp. Ignition was breaking up a bit too.

 

Might be breaking up because it's a bit rich especially for that boost level

A colder plug may help

Possibly plug, wiring or coil issue

I'm no tuner but if it was my car I'd have it re tuned at 11.7 or even leaner

My track car is tuned very conservative at 11.4

 

my old FD at that speed would go 380+ miles on a tank

 

I usually refill at the 1/4 tank line. In the city I can get 200 miles and on the highway I can get 300. I got the exact same mileage with the stock ecu and the PFC base map. That's with light premix as I'm still running the OMP.

 

Oh that was at wide open throttle. As for everyday stuff I'm not quite sure (no wideband). I'm losing coolant (even with the car off) just filling it up is disappears w/o any sign of where it's going. No smoking coming out of the back, but still it has to be going somewhere. I have another motor I'm putting in just to be sure. Tracking down all the parts for a single turbo conversion seems to be more complicated than I anticipated.

 

When I bought my car and drove it 660 miles back from where I bought it, I got 24 MPG. After putting a ceramic downpipe on, a 180 degree thermostat, 185 degree fan switch, and blocking off my EGR ('94 model), I seem to only get about 22 now.

 

as you can see in the picture at 133km wich is around 83 miles i'm already at almost half a tank


Gyazo - 08094ce07852e397ad91aef21e1a1bc3.png

 

Your fuel gauge cannot be used to calculate gas mileage. Check your mpg when you fill the tank.

 

i know. i was just showing how fast it has gone down. when i fill it up again i will do the latest estimate.

 

As a (somewhat rough) average, 20 litres of 98 octane fuel will last me about one week of normal driving.

I found my stock FD is actually more efficient than the 5.0L V8 I used to drive, and is more efficient than the current 4.0L straight six I'm driving daily at the moment.

The key seems to be the boost gauge. If you drive it based on the idea that 'boost causes fuel enrichment' and you stay out of boost and watch your foot, they are not too bad at all.

Having said that, OP you sound like you need a tune.
10-16mpg is on the low end of spirited or city driving. 20-26 would only be achievable on highway I would think.

 

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