Very expensive on gas...
 

I recently purchased a miata with the following mods:

-greddy turbo kit (no intercooler)
-MSD
-1.8 injectors
-high pressure fuel pump

The car runs very very rich and is costing more than a v8 on gas.
Just wondering if anyone can help me fix this problem.

What kind of gas mileage are you getting? I think the 2 obvious choices would be to put the 1.6 injectors back in or buy something that can control how much fuel is going in the motor. I'm probably gonna be shot for suggesting it, but an SAFC would be a cheap, easy way to lean the car out off boost and gain mileage.

Im getting about 160miles a tank.

That's terrible. With very spirited driving on my turboed 1.6 I'm getting 26. Being conscious of my driving it goes to 30 and this is in town.

Have you checked your timing?

O2 sensor?

what fuel pump? If you can't adjust the pulse width of the injectors, then I would think a high pressure fuel pump could be a bad thing. More pressure would equal more fuel for a given pulse width.

Megasquirt

I average 20 on my setup. If it's all Highway I can get ~25 mpg.

Go standalone.

Chris

that's around 17mpg, that's about what i was getting on my band-aid setup, megasquirt is the best answer

I do all city, and I get worse mileage then that. But I do drive the piss out of it. As others have said, engine management and leaning it out will get you power and better mileage.

I get better mpg now (with turbo and MS) then i did pre-turbo.

Alright so il get the megasquirt. Is there anything else i need to make it work? While im at it i think im gonna get an intercooler. Are the kits on ebay any good? Or should i get it custom done localy? Thanks for your help guys.

Talk to "Stripes" about piecing together your intercooler. he is known for his piping.

Heres what she looks like

http://img107.imageshack.us/img107/1579/dsc0318bs4.jpg

Nice looks!

If you're getting 13mpg (160miles/12 gal tank), something is definitely up. Do you have a wideband? I would expect low 20mpg from what you said assuming casual driving. Is there an FMU in there as well? A high pressure pump shouldn't mess with rail pressure inless it's overwhelming the stock FPR (right?). The only time I got that low of gas mileage was when I was tuning/screwing around for about an hour boosting most of the time.

I know everyone says get Megasquirt because it is the end all be all solution to tuning, but I'm sure you can figure this out without going full replacement ECU right away. That way you can plan out a bit more what you want to do as far as upgrades and enjoy the car in the meantime. Unless you are good at tuning/know a good tuner in which case I'll shut right up.

answer: drive better.

Somehow going from stock ECU/injectors to turbo plus 550s my gas mileage has gotten atleast a 3rd better. I used to squeeze one week out of a tank of gas and now I go atleast 2 without filling up. I haven't crunched any real numbers yet but i'm pretty sure i'm at 30 MPG highway.

The megasquirt really is the best way to nail your fueling.

1.6's have 10 gallon tanks and i usually put 9 and change in when i fill up, that's where i came up with 17mpg

Car looks good, but there's no way without an intercooler you're running enough boost to need an aftermarket fuel pump. My highly educated guess is that it's a Walbro 255lph and is overpowering the stock fuel pressure regulator at idle, and giving you about 100psi of fuel pressure at a Greddy-stock 5psi of boost... which means you're AFR's are probably down in the 8:1 range in boost.

!!!LISTEN CAREFULLY!!!

YOU NEED A WIDEBAND 02 SENSOR! THE INNOVATE MOTORSPORTS LC1 IS A FAVORITE AROUND HERE. YOU'LL NEED A LAPTOP OR TO BUY A GAUGE... $300 total! THE OTHER FAVORITE CHOICE IS THE AEM WIDEBAND THAT USES A BUILT-IN GAUGE... $250!

I'd fix your current problem on the cheap before spending $1000 on other parts. You'd be surprised at how much power you'll pick up with just a little tuning.

You could also consider installing a fuel pressure gauge and going to a dyno with integrated wideband hookup. A gauge will cost about $20 to install and a short dyno session will be about $75.

:facepalm:

Gotcha, just felt like showing my ignorance.

1.6s have 11.9 IIRC. Generally is on E and can put just over 9 gallons, past E, up to 10.2 ish

Auto Performance Engineering - Walbro fuel pumps specs
make sure your fuel pressure is all good like Sam said if it is not pull the pump and use the site i linked you here to verify its identity 99.99% of the swapped fuel pumps are walboros so this will help. If some mis informed ricer has put a 255 in there then you can chuck it to someone with an eclipese mustang etc and get a 190 wich will work much better for you. How ever if it is not a 255 or other uber pump then check the routing of the fuel line by the filter and look for a inline aux pump aka. peiburg fuel pump that Fm was using for its FM1's for a good while. If there is one there simply take it out of the system and repeat your tests to see if that helped.

If none of this helped then you probably need a new stock fuel pressure regulator. If your fuel pressure is all hunky dory then you need to still check for the Aux pump i mentioned above and from there i would check plugs, air filter etc looking for obvius and worn peices. If this is all good verify your timming isnt fucked up.
And from here the only culprits that could be fucking you over are a stuck fuel injector, or bad coils. So check the coils first since that is easy and only needs a multimeter, and then if it checks out get some known good 1.8 or 1.6 injectors and drop em in there to verify. (or if you wanna be spendy send them out to be cleaned at 25 $ apeice)
I hope this helps you man GL Also where the hell are you put a local on your sig. Maybe one of our expereinced board memebers is in the area and could help you.

you might be right, lol. then i could have gone a lot further on a tank than i thought when i though i was about to run out of gas!:bowrofl: either way when i'm dead on E it's like 9.5 gallons to fill

i have filled 11 gallons before on my 92 we have a 12 gallon tank same as everone else.

17mpg around town sounds about right. I never got better than 18 when I was DDing my car.

16 around town, 28 on the highway...

For comparisons sake, I am still N/A and I'm getting about 21 or 22 in town. I just drive like a bat out of hell.

Guessing and replacing parts costs a fortune.

Take it to a tuner and for a quick couple hundred, they will sort it out.

Listen to them and then start replacing parts they recommend or just pay them for their services and have them install what's necessary. Then have them dyno it for a clean setup and drive it like a bat out of hell for years to come!

I'm getting about 19-20 mpg on backroads and around town with my foot always in it....not much time spent on highways

I have ran my '90 completely empty twice now. It took 11.5 gallons both times. I really need to get a gas gauge...

In the last 3 days taking tuning runs I have about 80mi on it turboed and I have used up half the tank per the gauge. A lot of WOT pulls peaking at 18psi. No knock FTW!

It sounds like its too rich. Get a wideband and make sure its always at 14.7.

Dump the SportFag wheels and your problems will go away :giggle:


I managed to put 13.1 gallons in my NB :D (no, the pump was not reading wrong)
BTW, running that rich will dilute your oil and will help cause the motor to pop if you don't keep changing the oil...like ever 1500-2000 miles.

Guys, the OP hasn't logged on in a month.