The most likely reason for your bad mileage is the type of driving you are doing. While driving only around town, an FD will get lousy mileage. You don't get very good mileage while sitting at a stop light.

There isn't anything wrong with your car.

 

i'm not sitting at the stop light. its pretty much combined driving. I guess 7mpg is not normal

 

First you said single digit mpg in city driving. Now you say 7 mpg combined. Which is it?

 

THe city where i drive it combines both types of driving. One day i spend most of time in 5th gear 50mhp but gas milage was still bad

 

You're confusing the hell out of some of the people here.

Anyways, I'll elaborate on my "city-only" driving. At one point in my life, I used to only drive the FD to and from campus. At that point, I was netting 9mpg. This was on a car with fresh O2 sensors, clean injectors, etc.

The drive was approx 2mi. If you only drive it incredibly short distances, having single digit MPGs is no unheard of.

 

This would be fully expected

It takes about 50% more gas while its warming up then it does when fully warm.

 

I see. I Got my car about a week ago. I was warming it up in the morning and driving it for about 10-12miles. The car idles well and holds 0.6bar of vacuum at idle when fully warm. but it stumbles when revs fall down at about 1500. I was told on this board that this happens because its runing ritch. i will hook up O2 gauge and examine my A/F.

 

You say you are not sitting at a stop light idling. Then you say you let it sit idling, to fully warm up before driving it???? I don't see the difference as far as gas mileage is concerned. Maybe it would be smarter for you to not say anything at all

 

IMO, unless there is something significantly amiss with your car, the most important factor in gas mileage is the type of driving you do (obviously, freeway best, short stop and go worst). And, if the car idles for a significant % of the time it is running, that is going to severely reduce the MPG.

Even under the best of conditions (warm weather, no traffic jams, minimal idling), local non-freeway driving will give, at best, 15 mpg, and at worst 10-12 mpg.

Dave

 

man what do you want from me
you never look at your idle before you shut it off for example? i'm warming it up for about 3-4 minutes

 

Why??

 

Under-inflated tires create more rolling resistance.

 

yeah..but BIG difference? I mean i sure you dont mean some1 rolling around on flat tires

 

It's not going to raise you 10 mpg, maybe 1-2 mph difference if that. Now, "over-inflating" will not show a benefit. So anything 'over' the proper inflation is not going to help. However, under-inflating does shows a decrease in mpg (as well as unwelcome wear characteristics).

 

I used to get about 20mpg combined (mostly highway) ~80mph @ 3k in 5th. about ~15in-Hg. Don't recall what my injector duties were.

PFC, 3" exhaust w/ HF cat.

 

I get 18-22 MPG on avg in my 13b-rew swapped car with a haltech.

 

All JDM FD's come without a pre-cat? Am I to assume that there are downpipes on all of the JDM FD's? When I bought my car it had a downpipe on it already, i'm replacing it with something else but i'd like to know if the JDM cars come with downpipes.

 

Would like to put my input here about my gas mileage. I had all bolt ons... Full exhaust, intake, pfc, pettit ic, wires, and plugs. I was getting between 20-30mpg no boost city/highway. I was amazed always heard about bad gas mileage with these cars, even after my single install I believe I was getting better gas mileage! Once got 375 to a tank. This was with a reman motor, now I just dropped in a heavily ported motor and a R85 turbo with a 3row FMIC interested on how my mileage will be now

 

Sure they have downpipes but people here told me that there are no precats in those downpipes

 

There is no way you ever got 30 mpg (or even close to it) on a tank of gas with combined city/highway driving. Getting 30 mpg on strictly highway mileage is just about impossible.

If your gas tank was nearly empty, you didn't even get 20 mpg on that tank. I'm not sure you should be bragging. An FD gas tank is just over 20 gallons.

 

i believe its every 10 psi under is a drop of 1 mpg.

I was seeing 25 MPG on the highway, i made it to Buffalo on a single tank of gas, 395 miles i believe the total trip was.

as for the FD gas tank, you lose about 10% to evaporative space, so call it 18 gallons.

 

Sure you don't have a Hummer engine installed? My car's millage on the highway is in the 20s. If I get on it, I can drain a tank in a very short distance but I never actually did the math.

You are right to always let it warm up. I would go back and check the spark plugs. Do they smell like gas? How fowled up are they? White? Black? Are they OEM (NGK)? Change them =$30

Next, you should be changing out the fuel filter every 30k miles, if you are not sure if it was done--it wasn't. The filters are $25, but they are a major pain in the *** to change out. Check to see how dirty the fuel in it is.

Third, pull out the injectors and send them to a cleaning/balancing shop. This will cost you a little over $100 and give you piece of mind.

Basic maintenance that will cost you less than $200.

 

Please explain how "evaporative space" accounts for a 10% loss of fuel, when I fill my tank, and it has 20+ gallons in it.

 

An FD is perfectly capable of warming up properly while driving it. There is no reason that a good running FD needs to sit and idle while not moving. That is a complete waste of time and fuel ($).

 

How much can you put in your tank from empty? The most I can ever recall putting in mine was just over 16 gallons.

Dave