Anyone Ever Touch/Adjust their Variable Resitor out to the LEan Position? Or Does it make Much of a diffrence on fuel economy? i want to lean my car out..How far can i safely Turn This Variable Resistor? i tryed to read up on this ****,Seems to be a Secret or somthing that know one should know about! 86-88 Models seem to have this ****..Im sure its used for Tuning But anyone have anything more on this Subject?

 

What is your warmed up idle? ~750rpm if you lean out too much your system will overheat and you'll start blowing gaskets.

 

^^^

Haha what? That's a bit misinformed. You will not "blow gaskets" if you lean it out at idle. If you lean it out too much it'll just die from lack of fuel. If you richen it too much it'll just chug from excessive fuel. It won't hurt the car either way.

Best way to know exactly where to have it is start the car, have it warm up and idling normally, go over to the variable resistor and slowly turn it in one direction. If the idle speed/sound improves keep going slowly until it starts to sound worse, then go backwards a bit to where it was good again.

The variable resistor is ONLY for idle, it will not lean your car out over the whole range if that's what you think. This will also not effect fuel economy at ALL I can imagine, it might save you 0.01 gallons per tank from idling a tiny bit leaner, but I doubt it will even do that.

 

well i dont want that to happen..My idle is about 800 nutral,500 in drive..but that really dont mean **** if you think about it..the idle can be adjusted from a few diffrent area'

I want to lean her out alittle..Not starve her. she might get PISSED.ya know how bitches can get

 

Ddub that answers alot right there!! i was afraid to touch it thinking that if i ROMP on it and its to lean ill blow it up... So i guess my other question would be WHere is the main adjustment for the Fuel Input to lean it out alittle...?

 

Inside the ECU where you aren't going to be able to change it unless you have a fuel controller or standalone, sorry.

 

a good example of a fuel controller would be the apexi s-afc. For a little over $200 you can get a nice looking unit that allows you to change your fuel 50%. Supposedly running 20% lean is completely possible and for some ppl (w/ ignition amps) has put them well into the 30mpg range.

 

WHAT?!!!?!?

The adjustment screw is only for idle.
You cannot hurt your engine turning it.


-Ted

 

yeah totally my bad there...sorry... some reason thinking it could adjust the fuel/air ratio as well.
but on that note i have another question...
when i start my car warm (but cold outside) it starts goes to about 800 rpm then right after it dies if i dont give it any gas.

 

i leaned my car out to -17% across the board, and it still held together.

 

well since i guess i am the only one here who has screwed with the variable resistor i will give my opinion.

first, adjusting the screw only leans out the primaries at idle and won't affect your economy unless you sit in traffic for hours at a time at idle constantly.

second, the mixture variables from this screw are minute, though everyone sais not to mess with it i couldn't see great difference in full clockwise or full counterclockwise positions, the engine barely changed either way so the difference in fuel couldn't be much.

third, there is a way to tune your engine with the variable resistor at idle, the procedure is in the FSM. you can find a link to an online FSM for your vehicle in the FAQ at the top of the forum.


to really get mileage out of your car you need to tune it with a standalone or a SAFC properly, and keep in mind if you have a turbo then i wouldn't run leaner than stoich under a load or you could have lean detonation and possibly chuck an apex seal.

 

Seconding what Karack said. I got all the gook out of it and played with it, and was underwhelmed. It didn't adjust the idle mixture enough to kill the engine. The procedure for setting it, IIRC, is to jump the idle set connector, set the idle to somewhere in the 700-800 RPM range, tweak the idle adjust screw until the engine is at the highest RPM, then reset the idle to 750 RPM. It really didn't affect much.

-=Russ=-

 

I've played with it, and have since removed it completely. Didn't I say most of what you posted already?

 

Against the above opinion, here is tested fact, as measured via wideband testing on an 86 GT:

The primaries are only being used below 3800 rpm, so no matter what, it only affects the primary injectors. Furthermore, it ONLY affects the idle air/fuel ratios. There is ZERO affect when any kind of throttle is applied, regardless of the AFR screw position.

However, its a little more than minute changes. I tested 13.2:1 AFR's at full lean, and 12.4:1 AFR's at full rich.

Lastly, if you are running stoich under load on a turbocharged engine, with any fuel, you will blow it. Instantly. You must tune rich under load. Regardless, the idle-screw only has an affect on fuelling at idle, not under any boost.

 

Yep, if your TPS isn't adjusted within spec or you have an intake vacuum leak, you will not get the full effect.
If the car is in top tune, I can kill the idle by going to at least one extreme.

The engines like to run rich, so most likely going to the "R" side isn't going to do much, but adjusting towards "L" should kill the idle.


-Ted

 

Intriguing...

Any side effects of doing that? Like engine knock or increased heat?

I'm going to assume they did it with an NA or stock-boost Turbo... In fact I would think knock would keep a turbo from doing that...

 

yea.. at -20% youve got a darn good chance of knocking. it wont affect gas mileage too much, safc is only used during accelaration. at cruise, it just goes into closed loop anyways.

 

there is so much information in this thread it makes me cry.

 

my TPS was set just fine, the idle doesn't change much with the resistor on my FC, not saying it won't with any other though i keep it about 2/3 or richer because it doesn't affect your mileage much.

and yes, i had a brainfart on the stoich comment. turbos have to run richer when boosting to compensate for the compressed denser air.

 

ive always thought about adjusting the fuel map by messing with the afm. if u changed the spring inside or sumthing u get it to run leaner/richer but that would not be a good idea a more feasible idea that is really cheap would be to hook up a variable resistor where the apex-i safc unit would normally read air flow to the ecu. but, this would only allow u to make it richer/leaner by a single linear factor over the entire fuel map. (ie. xx% leaner at every rpm). still, this idea is cheap cheap cheap.

 

It would be cheaper, safer, and easier to simply decrease your fuel pressure at the rails. You would get the same results.

 

All petrol engines have to run rich under load, not just turbos. Stiochiometric mixtures are simply too hot, and the excess fuel is used to lower the combustion temps. Since compressing air heats it up, the higher the compression ratio and/or boost the more fuel must be added to keep the combustion temps safe.

 

Lean = Boom

-Anthony

 

petrole engine make more power betwen 13/1 and12/1 afr because a of incomplete combustion in fact fuel dosent lower combustion temp a lot,water is more efective to do this, more fuel gona slower the combustion ,retard timing gona do the same thing so stik to 12.5/1 afr ,if the engine knok retard timing and/or add water (windshild washer fluid work great)use 10% of your fuel mass. look at : www.msefi.com and :www.innovatemotorsport.com/resources/rich.php for more info

 

How does incomplete combustion make more power? Regardless of how you try to explain it, you're wrong.

Adding more fuel DOES lower combustion temps... so does water. Water is NOT more effective than dumping in more fuel, but adding water doesn't cost power like dumping in fuel does.
LAstly, using a windshield water pump for water injection is a pretty shitty set-up.