Power/Fuel Economy Issue

[90supraturbo]

Okay, so I just did a complete build on a motor and have almost finished with the upgrades, but I have to use the car as is till I have a little more time/money.
Current issue is that I have a Spearco intercooler with 2.5" pipes, boost controller, 60-1 CT-26 and intake, however I am still running the stock AFM and injectors. The car has very little power, uses a ton of fuel (12-13 mpg), and hits fuel cut at 11 psi (ran 13.5 before the build and intercooler upgrade). Am I right in my thoughts that this is because she's taking in a lot more air to fill the intercooler and pipes, and this is running the car VERY rich (thus the lack of power and poor gas mileage and even the early fuel cut)?
I was having some issues with the CPS before the build, but it seemed to be related to a bad wire which I replaced during the build... seems to have fixed the problem but I'm also worried that the CPS could be causing the issue if it's not timing true?
Any thoughts or suggestions would be greatly appreciated.
Thanks!

 

[dbsupra90]

how old is the 02 sensor? no reason it should have that bad of mpg unless you driving it really hard non stop.

in closed loop the ecu will correct for 14.7:1. i have a ton of mods on my car and still get 25mpg+. and thats with a big dog aeromotive pump, 680cc injectors, and a built auto with a high stall converter. if the 02 sensor is fresh, it will compensate. other things you could look at is the temp sensor wiring going to the ecu. if that isnt working the car will stay in "warm up" mode.

lastly, do a good check of the ic pipes and couplers. if that is leaking, it will run super rich. even to the point that the 02 sensor/ecu cannot compensate.

good luck

 

[87mgte]

how old is the 02 sensor? no reason it should have that bad of mpg unless you driving it really hard non stop.

in closed loop the ecu will correct for 14.7:1. i have a ton of mods on my car and still get 25mpg+.

i get 16mpg according to my stock supermonitor... apparently that's bad for a 7m? i drive it hard occasionally just like everyone else, but i'm not pinging it off 8 grand or anything. any vague idea of what would cause the horrendous economy?

 

[Poodles]

I get 18... but it's a whole lot of mixed driving with a spool happy CT26...

sounds like you have a boost leak IMHO...

no boost = great gas milage

that's why going to a turbo with some lag isn't always a bad thing...

 

[AaronsSupraMKIII]

I am getting 12 to 13 mpg too! I drive 50 miles to work every day, and it is fuckin killing me on gas money! I had a crap load of boost leaks, and fixed them, but still gets bad milage. I am still running 440cc injectors, and stock FPR and AFM. Do I need to replace my O2 sensor? If I could even get to to 20mpg It would be wonderful. If I can't get better milage soon, I am going to have to get a 4 cylinder something or other. I have stock CT26 also..

 

[gilberjj]

that's why going to a turbo with some lag isn't always a bad thing...

however, with my 720's feeding the 61mm i had, the gas goes real fast if you do ANY "spirited" driving. The great thing about the map ecu is, i can set it to 15:1 a/f going down the freeway. That is great gas mileage!

 

[dbsupra90]

16mpg is about right if you do a lot of city driving.

i replace my o2 sensor every 15k or so. its a little excessive i know, but i run a lot of leaded gas.

before i had the high stall converter i used to get near 30mpg highway driving.

 

[Nalleywhacker]

i only get about 13 my self and iam stock. i thought thats just what supra got my n/a i had got 12mpg but it had cams...

 

[james_9876]

Super Monitor says.... 18.7mpg

That's stock everything, just K&N, gutted cats, and ported intake and a MK4 fuel pump, stock injectors.

 

[hellraiser456]

i usually sit around the low 20's. however when my knock sensors were out i would get numbers like you guys are talking about...maybe 150miles to a tank. it was brutal.

 

[NewWestSupras]

18 - 23 mpg city/hwy. here. 550's, Aeromotive fpr, MK IV fuel pump, 60-1 turbo, foot in it most of the time. I think my n/a was worse. Not sure about air/fuel ratios till I get my LC-1 hooked up.

 

[sneakypete]

make sure you idle is around 650-700 rpm at idle. for almost a year my idle was around 1100rpm. turn out my isc was clogged up. when i finally straighted it out my fuel economy went up around 3-4 mpg.