I am getting about 8 mpg and it is driving me crazy. I know this is not normal and it has to stop. I just filled up last week, and after 66 miles, my tank is almost at half.

I am non-sequential, and have removed the airpump, along with the ACV and all that other stuff. My AFR's at idle and cruising are about 10:1, which is way too rich. Has anyone measured their AFR at idle and cruising with a wideband with the airpump and acv hooked up still. I suppose it should be arount 13:1 at idle and 15:1 while cruising.

My air intake thermosensor was dead, which makes the ECU thing the air is always the coldest, making it super rich, so I thought that was the problem. Well, I replaced it and the mileage didn't change at all.

I don't drive like a maniac and probably only boost only once when I drive the car somewhere. I am not sequential any more so I really have to get on the gas to produce any boost, which I barely ever do.

Mods in sig.

 

thats really bad. i filled up yesterday, full tank. I drove it for 170 miles and am a little over the middle mark and I boost A LOT. I'm surprised I get that much mpg driving so hard but I am all stock, not even a downpipe. clean your injectors and replace the o2 sensor, those made the biggest difference on my past rx7s

 

Yeah I bought the new oxygen sensor, but I'm wayyy too lazy to install it now. I think maybe I will some time I guess... It's just that my stupid pettit downpipe has the sensor bung facing right towards the secondary turbo compressor housing so I have to take off the whole downpipe to take out the sensor, such a pain! Maybe if I find some time tomorrow I'll replace it

 

It's probably toast. on my fc it was original and i had over 100k on the car. i had it replaced by a mechanic for $15, took 10 minutes. after i replaced my o2 sensor and had my injectors cleaned i went from 10mpg to about 23 on the freeway. better to do it now than burn all that money literally from higher fuel costs. i really hated spending $35 on a tankfull and be on empty after only 200miles, gets very frustarting especially with the prices for gas here in cali.

 

I usually get about 15mpg avg city/hwy driving.

 

Ive been getting 12 mpg on a STOCK FD lately and its been pissing me off, what happen to the 15 in the city bs?

 

I get about 15-16 mpg mixed driving.
I replace plugs, fuel filter, vacuum lines, had my injectors cleaned and balanced and added a crane ignition system. I noticed when I ran with the M3 ECU the mileage was much worse (richer fuel maps). I switched to stock to pass emmissions. I may just leave it in.

 

I've decided I'm going to change the fuel filter and o2 sensor today, since I have both sitting in my garage but was too lazy to ever install them.

 

Wow, that's really bad. I've gotten 24mpg hwy on trips before (staying off boost)

 

Pettit DP does NOT need to be pulled to remove O2 sensor. Jack the car up, and crawl underneath. PLENTY of room to get at it with a big 'ol wrench.

Don't forget the anti-sieze on the threads only, getting it back out after 30K miles with no anit-sieze sucks!

 

ahha, you are wrong. Believe me, it's not possible to get the o2 sensor out without removing the downpipe. I just did it today, and it hit the secondary compressor housing just like before.

Anyways, I changed the sensor, still bad milage, but I think it may have gotton a little better. I changed it this morning and drove for 64 miles today, all city or freeway in the traffic, and the 64 miles took about a quarter tank, I guess that's much better than before. (i'm assuming the fuel gauge is linear, is it?)

And on the fuel filter, I know this sounds way stupid, but I couldn't find it, haha. I know it's by the rear differential but I looked and couldn't find it. Is it like behind the differential, because that's such a stupid place to put it when there is plenty of room behind or in front of it.

 

I just got 22.4 mpg on my last tank. I had to commute with my FD for a week since my daily driver is down. It's about 70% highway and about 30% stop-n-go traffic. A cleaned up fuel system and an a/f gauge do wonders for mpg. I blow the carbon out at least once a day.

Sonny

 

yeah I also get 9 MPG... on city drive... but on Freeway I get 18 mpg...

 

You have a M2 ecu meaning its a non-tunable re-flashed ECU. You run rich on purpose from the design of the re-flash due to safety purposes. IF you notice some black smoke on the road... go on a dyno and see how black you can get the shop before they turn your car off. I got a friend with almost the same mods as you. He got a used HKS twin power and you dont even see any black smoke when hes on the road. His AFR at idle is around high 11's. So maybe its time for an ignition upgrade.

Jeremy

 

Yeah, rich under boost; it doesn't change the idle and cruising fuel values, if I recall correctly.

My plan is to get all four injectors cleaned and balanced at RC-Engineering, because I am planning to do the fuel recall kit and FPD already.

 

I think it does during cruising due to the ecu being chipped with fuel maps due to RPM. And cruising at 80 for me is around 3500 meaning thats basically about full boost range if at WOT. And you do ALOT more cruising than you do idling... though im stumped with the idle.

Jeremy