jmmorriso

Would it be possible to use a wideband controller with adjustable analog outputs to lie to our ECMs by using its signal instead of the stockO2?

NismoPick

Why would you want to do that? If you want wideband, leave your stock O2 sensor and ecu alone & weld in a new O2 sensor bung for your wideband... then hook up your wide band unit.

IMO... it's overkill to use wideband on any NA 280zx. A $35 regular a/f gauge is plenty. A wideband is needed for FINE tuning on higher hp cars, especially turbo/supercharged cars when propper a/f ratio is SUPER important.

jmmorriso

Im just asking if it can be used to tune A/F to make up for other mods, seems like it would be easier than doing the z31 ecu swap and using an SAFC. with a wideband you should be able to lie to the ECU and richen it up, right?

NismoPick

The O2 sensor doesn't do the "enriching." Adjusting the AFM cog, ohms from the head temp sensor (using a potentiometer), and adjusting the fuel pressure are the ways to adjust a/f ratio on the 280zx. On the Z31, a SAFC is used to make a/f adjustments w/ the MAF, along w/ the other adjustments I've just mentioned.

jmmorriso

So what is the O2 supposed to do?

NismoPick

Monitor the a/f ratio for the ecu...

Here's a wonderful explanation: http://www.volksparts.com/o2sensors.htm

jmmorriso

Iknow adjust ing the AFM will fatten her up, ive seen that on the smog machine, but I thought fooling any of the sensors too much would keep the ECU from going into closed loop. It seemed like telling the ECU it was lean wouldnt be so much of an endaround, and it would be more consistent throughout the rev range and wouldnt fluctuate with engine load.

NismoPick

You deffinately need to learn more about the efi system & how it uses each sensor. Do you have a Haynes Manual?

jmmorriso

I KNOW how the ECU works, there is a minimum and maximum value that each sensor must be within or the ECU to go into closed loop. Thats why those $12 performance modules on Ebay dont work, and why an AFC wont work either. If you mess witht the CHT to make the car think its running hotter than 205 or so, it wont go into closed loop. If you mess with the AFM any signifigant amount, the car wont idle cold, or wont idle warmed up, or can still lean out at the top end, because the flapper goes wide open at such a low rpm. Plus, CO and NOx go crazy with the AFM set rich which tells me that Opening the flapper too much causes the ECU to throw that reading out too, because high NOx almost invariably means that the engine is lean.

NismoPick

Actually...

Some of those $12 ebay ecu upgrades have potential for benefit. Those ecu "dials" are just potentiometers that can be installed on the chts & increase the signal to enrich the a/f mixture.

The AFC's work quite well when set up properly. It adjusts for throttle position & rpm so it runs the desired a/f ratio through the powerband.

But a separate wide-band O2 sensor won't enrich the a/f mixture. And to get it to work w/ the stock ecu, it would have to put out the same signal as the stock O2... making no difference in the a/f ratio.

jfairladyz

I've actually tossed an idea similar to this around in my head a while back. The difference being that I wasnt considering using a wide band controller to alter the signal but rather trying to alter the signal of the stock O2 itself. The problem I was having is that I couldn't figure out what to use to alter the signal of the stock O2. The voltage is so low, and it's signal so sensitive to the ECU that I couldn't find what I needed. I know there is such a device...I just dont know what it is or where to find it. A voltage regulator is basically what I was looking for, but one that can handle 0-1 Volt. In the end its just easier to convince the ECU that the engine is still cold and from there you can manipulate it any way you'd like. But at the expense of losing any feedback to the ECU. I built one with a built in A/F gauge (never got the LED driver and so the gauge was never completed) and used it succesfully in both my turbo and non-turbo Z's without any notable side effects. Of course I didnt drive the Z enough to gauge the affect on fuel economy but I can only imagine it got worse as the car was forced to run rich. I was also working on setting up a throttle activated switch so the device wouldn't have to be manually turned on and off. No need to dump fuel while cruising down the highway right

And yet another idea I wanted to mess with that would ultimately be an even better solution is to alter the actual resistance readings coming from the AFM. My problem there was locating the type of resistors used by the AFM. If you've ever cracked one open you'll notice they are just these really thin flat resistors that are bonded to a plate with a carbon track. As the swiper moves along the carbon track it sends a signal to the corresponding resistor in its path. I again had no idea where to find these resistors so I could tinker with resistors of different values. If I could change the resistance of the lower positions of the AFM I could successfully install larger injectors by tricking the ECU into injecting less fuel at idle and low rpms. Then resistors in the more open positions to dump more fuel for higher RPM performance.

That in my opinion would be the ideal way to do it. I was thinking about hitting up junkyards and finding similar AFMs from other cars and testing the resistance values within the AFM to see if I could find what I was looking for that way. I never got around to it and now I'm living in the middle of no where without a junkyard, that I know of, for quite some distance. And still no idea where to get such resistors. Plus I'd have to get my Z back first

jmmorriso

Look at the Innovate Motorsports LM1 and LC1 they have tuneable 0-1v analog outputs, you can make the outputs read more lean or rich than they really are. Simple, done. This is what I have been trying to get at the whole time, but only J seems to be paying attention

NismoPick

What you're not understanding is tuning isn't just "adjusting" the a/f signal. Like I said before, the benefit of a wideband is MINIMAL w/ the stock ecu.

If you are wanting a more tunable setup, the stock 280ZXT efi isn't a great platform. Upgrade to a Z31T ecu, MegaSquirt, or SDS. The latter two have the option for wide-band O2 from the get go.

But what do I know anyway...

jmmorriso

what the difference between richening it up by making the ECU think its running lean or richening it up by making the ECU think its hot? With the wideband you at least get a reliable A/F ratio reading, no one I have talked to has been impressed with the accuracy of simple A/F gauges.

jfairladyz

If you make the ECU think its hot its going to lean the mixture out. Hot air is less dense and so requires less fuel to burn. The idea behind the CHTS adjustment is that you can trick the ECU into thinking the engine is still cold. By doing this you can then mess with the signals of other sensors, like the ATS and the ECU wont use the O2 signal to correct. This is at the cost of losing feedback from the O2. But then again the O2 is really an emissions peice and isnt meant as a fail safe. Altering the signal from the O2 sensor can accomplish much while retaining feedback. If the sensor reads a specific voltage at 14.7, then using a voltage regulator to attain that same voltage reading but at a slightly richer mixture would fool the ECU into achieving the ideal performance ratio.

a narrow band wont tell you what your a/f ratio is. That is the drawback. Sure the lights can tell you if you're running rich or lean (they are accurate in this respect), but thats it. They cant tell you by how much.

jmmorriso

I thought if you told the ECU the engine was hot, it would richen it up, to prevent detonation. Same with ATS, made sense to me, but i guess not the engineers.

jfairladyz

I see where you're coming from with the CHTS. But with the ATS it doesnt make sense to richen the mixture. Hotter is less dense then cold air. So it has less mass. Less air means less fuel is needed to keep the ideal a/f mixture.

EatmyDust

wait why would you dump more fuel in when hot to prevent detonation? fuel is more volitle when hot, meaning more prone to detnation. secound of all once you are runing hot, it dosn't take as much fuel to power the engine do to volitility. the fuel atamizes beter, and you have less of that cold resistance of the oil, and oil clearance.
some people like to dump more fuel in when they are hot to produce more power, but to tell you the truth it isn't really that much more, and you end up leaving a cloud of partialy burned fuel behind when you romp on it.

jmmorriso

More fuel will cool the combustion chambers and sparkplugs off to prevent detonation, plus the ignition of a rich mixture doesnt burn as hot as a lean one, but since there is more fuel, same BTU, but running rich to cool the motor is why you have to run EXTRA rich on the bottle and goofy turbo guys have methanol injection, because the atomized fuel tranfers heat away from the metal parts.

jfairladyz

^ That makes sense. But still, tricking the ECU into thinking the engine is hot will not get it to richen the mixture. It will lean it out. That why you want to manipulate the ECU into thinking it's actually colder then it is: so it does dump more fuel in with the warmer air thats actually going into the engine. And that is where what EatmyDust said comes into play. The ECU by default will lean the mixture with warmer air. All's it cares about is hitting 14.7:1. So less air mass means less fuel is required to hit that target. The ECU isn't concerned with performance, only emissions. Sure the engineers tried to program in as much performance as was practical while still being able to deliver excpetional emissions output, but thats no where near the full performance potential of the engine.