Need tuning help. Burns major fuel
 

I have a 1990 1.6L Miata, turbocharged with a DIY kit. I would say the turbo is a 20-30 trim, and Im running 7psi, AEM wideband, pro sport boost gauge. Now the problem I am running into is the fact that the car gets terrible gas mileage. The device its using for fuel management is a MF2 mappable injector driver, which uses 2 injectors right before the throttle body, and Im not sure how to tune it exactly. So if anyone has any advice it would be helpful

probably just add more fuel as you transtion into boost. May need to use a o2 clamp to stop the stock ecu from trying to do anything funky if you are still in closed loop.

interesting I wonder if I could use one of these fuel controllers as a boost controller

Well, I honestly have no idea how to use this product, and if you could explain what an o2 clamp is that would help. Miata's are an unfamiliar territory to me, seeing as how I came from the DSM world, and turbo's came stock, so sorry for anything noob questions or responses.

o2 clamp is used when you transition into boost under closed loop the stock ecu doesn't try to pull fuel and go lean.

Do you have any of the DSM parts, ecus, etc, I know some of the miata guys here are running their miatas on dsm ecu's because abit of the miata stuff is the same as the dsm stuff, CAS is, etc.

I figure there is probably software to tune the injector driver that you have, map vs rpm?

it will probably have a map that you use to add more fuel, no idea if it has some pre set maps, but just tweak the fuel it adds until you find the right afrs you want under boost.

Main problem I see with this is you don't know you are providing even fueling to all cylinders with just one wideband under load.

http://www.kcsaab.com/aquamist/websi...f2/mf2tec.html

Its probably flooding you with fuel even when your not in boost, that is, if it is rpm-based as of now. Check if your map sensor is proberly connected to the MF2.

o2 clamp could probably help with tip in, but that doesnt seem to be your problem. An o2-clamp is a little circuit with a boost sensor that feeds the ecu an AFR 14.7 signal when in boost, so that the oem ecu doesnt interfer with the extra fuelling.

No, I do not have any DSM parts sadly, but around here a DSM ecu would not be hard to attain.

And you turn a dial for every rpm (1000 increments) either to increase the fuel or lean it out a bit. But I feel that is it using too much fuel because I can go through half a tank in a day driving to town (which is 7 miles away) maybe 3 time, and back to my house.

And when ever I am under a load the afrs is usually between solid 10-11.4, cruising it usually goes anywhere between 10-14.4.

How might I check this?

There should be either a pressure switch or a map sensor (in either case a small box that has a vacuum line running to it) that is connected to the mf2.

10 is a little rich for cruise, dont you think?
On a random note, have you checked for fuel leaks?

I have never heard of anyone using a DSM ECU to control a Miata.

You need to define "horrible" gas mileage - I used to get 16-17mpg around town, ~23-25mpg highway.

And Im supposed to check and see if its hooked up right to it?

And yes, I do think 10 is really rich, that is why Im trying to see if anyone has any suggestions as to what I should do, also car idling wideband says its running at 17.1 but I can see little black specs of unburned fuel on the ground from my exhaust.

I can use about almost half a tank going from my house to town (which is about 7 miles and mostly highway) and back about 2 times.

here's what i would do if i were you.

1. remove the two extra injectors and your stupid fuel controller that you dont know nor care to know how to use.

2. get an fmu.

3. figure out exactly what turbo i actually have.

4. replace the pro sport boost gauge with an amatuer sport boost gauge.

5. learn how to tune.

Its not that I dont know how to completely not use it, but simply the fact that when I turn the dial counter-clockwise to lessen fuel amount it still wants to run 10-11's on the afrs.

Sorry I was asking for assistance. Thought that thats what forums were for, attaining help and information.

its just such a shitty fueling device, it's obviously not working correctly and dumping in fuel all the time.

for 7-8psi you need nothing more than 265cc injectors and a FMU to raise the fuel pressure.

I would agree with that. I just dont have the funds right now to switch to that, so I was trying to make due or find a way to at least compensate with what I have until I did.

what AFR are you idling at?

I almost want to suggest disconnecting the two injectors...

What brain said is reasonable, you dont really need the MF2, a rising rate FMU would probably solve your problems. Hey, for what you save on gas the FMU will be paid for really fast :)

Did you have an pressure switch / MAP sensor?

Ha. There's probably a few FMUs for sale here in the classified. Simple, mechanical, it works.

Regarding your MF2, if turning the trim knob on it does nothing, maybe it is not wired up properly?

It idles at about 17. Sometimes more.

And Im unsure, Id say most likely, but I'd have to check.

stupid lean idle and stupid rich in boost..

i actually dont think idling at 17:1 is possible...