Something is really wrong. 11mpg would mean you are in limp mode, or your primary O2 sensor is dead. You should be more specific about "decent amount of mods".

 

whats limp mode and how would one know?

 

*17 inch Giovanni chrome rims with Fusion low profile tires
* AEM V-2 cold air intake
* DC headers
* Greddy EVO 2 cat-back exhaust
* AEM under drive pulley kit
* AEM fuel rail
* AEM fuel pressure regulator
* Skunk 2 intake manifold
* Skunk 2 trottle body
* Nology spark plug wires
* Spoon spark plugs
* short shifter
* APEXI super V-Tec controller
* Momo shift knob and boot
* Pioneer head unit
* DC strut bar
* Eibach lowering springs
* 20% tint all around / all windows.

sorry about all of the non performance mods listed..i just copied and pasted from my other post...but yea..11 mpg..its terrible

 

Giovanni rims??? haha what are you on?? And I guess you have the super duper ultra vtec controller that must be a super rare jdm spec VAFC......yea

 

i'm willing to bet money that u did the math wrong. you're probably really getting 18-21mpg.

*cough*blackiswhack*cough*

 

i dont think i did the math wrong..the first time i calculated it i got 12-13 mpg..the second time..(this time) i got 11.8 mpg..so idk..

 

how did u do the math? what numbers did u use?

 

Ok..i got 185 miles to a full tank of gas..which is about 15.9 gallons..so 185/15.9=11.635~ ...therefore i get around 11-12 mpg..

 

Bad math

1. Fill up car and hit the tripometer reset
2. Re-fill after 100 - 200 miles normal driving
3. Record the mileage on tripometer and the amount of gas it took to fill it up
4. Gallons/Miles

 

next time u fill up your gas.. take the miles used on the take of gas divided by the amt of gallons entering your car..for example when the low gas light comes on.. im usually end up filling my gas tank up with 13.5 gallons

 

yea i might be off by a few gallons..but i know im not off by more than 10..im still getting really low mileage =/

 

how do you drive your car?... what rpms do you shift at?

 

I try to shift at around 4000 rpm...when im merging onto a highway i might get it a little higher..but for the most part 4-4.5k rpms

 

ahha i called it again.

if you drive until your gas light comes on, you usually fill up around 12-14gal. also, u should be getting anywhere from 250+ miles on those 12-14 gallons.

btw, how is your driving style/habit? do u like to redline the car alot, or drive at 80+mph? that also affects your gas mileage

 

When my gas light comes on i have around 185 miles on the tripometer..and i drive about 60 most of the time..70 max...also..what is a standalone EM? and if i got one do you think it would fix my problem?

 

Those mods are very mismatched with his fuel management. If you are running a larger TB and the Skunk2 IM, you really need standalone EM. A simple VTEC controller isn't going to cut it at all (plus you are leaving a lot of gains on the table).

 

I'd say your math is way off. Why would you divide by the actual capacity of the fuel tank? A driving to the fuel station on fumes? Go to Fuel Economy and learn how to accurately track your fuel economy.

Edit.. when my fuel light comes on my car is usually around 375 miles on the trip meter, I refuel when it hits ~410 miles.

 

my prelude can reach 7km/1liter of gasoline (the traffic is so bad) but if in the high way my prelude can reach 10km/1liter... i modified my engine just using a MSD6AL, Dastek Piggyback, remmaping Ecu, RPM limiter by pass, custom headers, but i dont used my air filter... the other is Standart.. i used 92octane gasoline

i think your engine is fine... sorry if my english is bad

 

First, I'm going to join the "bad math" chorus. If you fill when the needle hits the E line (like I do since my low fuel light doesn't work), you're filling 13ish gallons. The bad denominator, however, isn't going to get you 10mpg - more like 2.

My instinct is to take all that fuel stuff off (fuel rail, fuel pressure radiator, throttle body etc), since it doesn't sound like you drive it all that hard anyways. Also, what's your driving pattern? Are you driving to work on lots of surface streets with stoplights, or are you mainly highway cruising to work?

 

* AEM fuel rail
* AEM fuel pressure regulator

Why do you have these items? You have an otherwise stock car with the exception of the skunk manifold and TB, which I'm also unsure of why you have them installed on your almost stock car. These mods are probably cutting down on your mileage ( not the fuel rail) but what psi is the aem fuel pressure regulator set to? The next time you fill up, just divide your trip meter that you reset when you filled the tank and the amount of gallons you put in the car. If you did the math correctly, I'd look at the fuel pressure regulator probably making your car run rich as hell. Then see if the O2 sensor(s) are reading correctly.

 

well his math is wrong initially but something is still off. he's only getting 185mpg when the light turns on. usually you're using about 11-12gallons at that point. so if u do that math he's still only getting 15-16mpg

it's probably what artifex and 98auto said.

 

alright guys thanks for the responses...im going to recalculate my mileage next time i fill up...thanks again

 

Just want to add this: if anyone can actually fit 15.9 gallons of gas in their 5th gen, I'll pay for the tank . . .

On several occasions I've driven the car completely bone dry. Then added exactly 1 gallon, driven roughly 20 miles, then filled up. I've never been able to get more than 14.5 in there.

 

The most I've gotten is 15.4 gallons at a fill up. I thought it was run dry, but nope, looks like I'll have to drive another 15 miles next time I get to that point.

 

ive gotten 15.1...

 

i have a 12gallon tank (pretty sure thats all it will let me ever put in).

i have mine dyno'd for 92 octane pump gas. I get around 19-21 city. Lol call me a liar, i swear thats what i get. check basic things such as the PCV valve for starters. Mine was never changed so i did it, its cheap and a good place to start, honda sells them for $16

 

i have a 12gallon tank (pretty sure thats all it will let me ever put in).

i have mine dyno'd for 92 octane pump gas. I get around 19-21mpg city. Lol call me a liar, i swear thats what i get. check basic things such as the PCV valve for starters. Mine was never changed so i did it, its cheap and a good place to start, honda sells them for $16

your tank is 15.9 gallons but u never drive it long enough to pump that much. i usually put in gas once the light comes on and it's around 12gal maybe 13gal.

i use to get 19-21mpg with bolt ons and conservative driving but i was doing mainly city driving. now i get around 23mpg since i drive on the freeway more. i got 26mpg a couple of time but that's when i drive about 200 miles round trip going to my parents house and back.

i always thought the epa rating was 21/23mpg.

***edit. looking at old articles from road&track and car&driver on The North Texas Prelude Owner's Group, it's says 22/26

 

My gas milage seem really bad, im going to calculate it and report back.

 

i play it so safe that i've never been able to put more than 12.9 gallons. im at 250-260 at that point though... so theoretically the full tank should get you at least 300??

 

Gas Mileage

I have a 1998 Prelude that I bought new. I got the 26 city and 31 highway mileage that was on the the window sticker. As the car is now 10 years old, my mileage is slightly less. I think it's all about how you have the vehicle serviced and how you drive. I hardly ever go over 4000 rpm's. Also, I have a 5 speed manual transmission, and I'm sure that makes a big difference. I have never kept a car this long, but this one is a classic.