Running rich

[Jeo]

Not sure if this should live here or in the electrical section, but its here now so lets run with it.

Have been meaning do something about this for a while now, just never got around to it. But now that my bike has finally sold (only 12 months of trying), I've got a decent chunk of cash that wants to be sunk back in to something with wheels.

Between the great clumps of carbon, using way to much fuel and my AF metre spending way to much time on rich, I believe my car is running rich. What can I do about it? Is there enough flexibility in the stock ecu for a shop to re-tune it for me, or am I better off buying a piggyback/afc and again letting the shop re-tune it?

And if I'm going to all this effort of getting a shop to re-tune things, is it worth getting the intake and exhaust done first? Since I always planned to get them done eventually anyway, and with excess cash, now seems as good a time as any.

Car is a 91 NA, running the engine from what I believe was an NA8. Now the conversion was done many years ago, well before I bought it, but from the pictures I've seen of other ECU's I believe I'm still running the stock ECU. Did they change between the NA6 and the NA8? Can I tell what I've got just by looking at it? Could this be causing my problems?

Cheers,
Joe

[Keith]

I dunno the answer but Ive got much the same problem. Ive got a CAI and big exhaust but still only a standard exhaust manifold, but I think freeing up the breathing will not affect the rich running. Funny thing is my car was only just tuned up and had the major 100,000 k overhaul.

[Steampunk]

Is your AFR gauge/meter accurate? Best bet is first take it to a place that can measure the AFR.
Running rich is not a bad thing, but if it's constantly below 12.5:1 AFR through the entire rev range, then that is way too rich.
The cheapest option is the Digital Fuel Adjuster from Jaycar. It doesn't look as pretty as the Apexi S-AFC, but it has alot more adjustment points. Quite a few people on the forum uses, or have used, these.

In answer to ECU question, yes, they are different between NA6 and NA8, in fact after a little bit of research, there are probably a dozen or more ECU model-numbers for all NA's

If you have always wanted to do up the intake and zorst, then yes, do it before you go to tuning shop.

[corners]

Hmmm I have the same issue..

ask 1red5

I think it may be the O2 sensor thats going to my next port of call....

[zoomzoom]

Just a note, don't trust a narow band oxygen sensor to give you a usable reading for a guage. All it will tell you is if you are north or south of 14.7, and is therefore useless, since even on an na engine you should be targeting much richer than 14.7.

Tim

[Mr Morlock]

Alphabet soup for me but Sasso seems to me to ask the right questions-the first step is actually to define the problem in a quantifiable way- ie how do you know it is running rich- evidence etc. One of the annoying things about older cars is that they were always going out of tune - points, plugs carburettors etc- I thought new technology fixed all that.Impressed at the level of knowledge shown by forumites on engine diagnostics- anyway back to my AM now ( radio that is)

[Mr Morlock]

Sasso - whew.. glad that was sorted out - maybe I will feel confident enough to try FM
Thanks for info- I will cut and paste that for reference.

[Jeo]

Thanks all

It shouldn't run rich or need tuning, something is broken. You need to make sure you have then NA8 ECU otherwise its going to give the wrong fuel, you also need the right injectors and AFM, if they just plonked a 1.8 in place of a 1.6 then obviously its not going to fueled right. Next thing is replace your narrowband O2 sensor because the ecu uses feedback from that, if it doesn't have it it goes into limp mode and dumps fuel in. Also check you have the right TPS.

What AFR meter do you have? is it wideband?

Does your car blow black smoke out when you accelerate (even a little) or does it smell realy rich or use a lot of petrol?

Like I said, I belive it's still the 1.6 ECU but how would I know for sure? Anyone got a model number floating around?
No idea about the injectors. Almost certain its the 1.6 AFM when compared to others, but here's a picture anyway


What O2 sensor do I need/want?
How would I check my TPS?


Not a wideband AFR, just the simple little Jaycar one. I was more worried about the smoke + poor fuel consumption. AFR was more of an "ohh, that all adds up now" moment.
Yes, she blows a little smoke on acceleration, no idea what it smells like, fuel consumption is almost always in the 12s per 100k.

Thanks again guys

[Fatty]

the voltages of the afm vs maf- they both work on a 5v scale, but work in opposite directions. so it would be impossible to just plug the afm into an na8 ecu and get it to work. you could use a voltage inverter circuit tho, but even then the fule map will not be correct.. but yeah i'm guessing the engine is running of the na6 ecu somehow, probably still with it's original 1.8 injectors. that would be my guess anyway.

as an aside, i've read a few people on here dismiss the narrowband gauge as totally useless for any sort of tuning, saying it can only be used as a rough guide at best. my real world experience says completely the opposite as i was able to upgrade to 460cc injectors and tune the fuel map (piggyback dfa) using nothing but the cheap jaycar gauge as a reference. the car's driveability and fuel economy (yes, i measured it several times) was identical to stock.

anyway i agree with others, you need to find out what sensors , ecu etc you actually do have fitted to the car. a new o2 sensor probably isn't a bad idea...

if it turns out that all you need to do is get the fuel map sorted , i'd just chuck a dfa on it and be done with it. and yeah it's probably a good time to do some breathing mods too .

[Jeo]

Legends, thanks for all of this guys

Do I just want a a new O2 sensor from Mazda or should I be looking somewhere else?

I'll get on the TPS stuff and check the injectors once it stops raining. And I'm thinking shortly after that it may well be 'take it the the shop and say fix' time.

[Fatty]

you tuned your turbo fuel map with a narrowband ? Its hard enough tuning it on the street with a wideband, you really need a dyno.

no, i fitted the injectors in preparation for the turbo install... so i drove the car for a few months naturally aspirated, on the big injectors. then the first thing i did when the turbo was on, was to get it dyno tuned. obviously the 2 fuel maps were VERY different... i certainly wasn't gonna try to tune the turbo fuel amp on my own (i figured i'd prefer to keep the pistons on the INSIDE of the block)

[StanTheMan]

but is bad if you just cruise around like grandmar.

Not sure I entirely agree with that

This car is not a turbo. On a spirited run I get around 8 or 9 L/100km I'd expect most n/a NA's to get around that or fairly similar . When driving to the shop or up the road. the car hardly warms up when it gets switched off again. And I'am driving like a grandmar.....Thats when I get 12l/100km.

on the racetrack though......well my guess would be somewhere around 25-30/100km or worse but that's to be expected.


However I'd love to get my hands on one of those instruments you guys talk about. & check my own. since I've just mucked around with the crystal & afm spring for my tune.

[Jeo]

Ok, so I went and saw two differnt shops earlier today, one the I know through the turning work they do for my uni race team and the other is a sponsor of the local mx5 club. Both suggested that a piggyback would end up causing more truble than it was worth and I should just rewire it with a 1.8 ecu. I am getting the breathing mods done at the same time and it should all be in soon enough