Got my car tuned on E85 a while back. Fuel temp sensor and upstream O2 sensor went bad at the same time about 2 months after. Replaced them and the car runs a lot better but now the AFRs are different. Idle bounces from like 15-17 but usually on the higher side, WOT is around 12.3, and cruising is pretty normal around 14.7-15. Is the idle and WOT too lean? I talked to the tuner and he said on 91 it’s too lean but on E85 it’s acceptable. Should I be worried? I’m trying to schedule another tune.

 

If the 02 sensor is in the test pipe you may want to check the gasket between the test pipe and DP. If it leaks it can show a leaner AFR.

We have old engines, low or mid 11's are where it will live for a long time. The guys chasing power at 12 afr get their prize.

If the file isn't locked, just add some fuel to it.

 

I would shoot for 11.8-12.0 on a street car.

If you do long hwy pulls or track use, 11.6-11.7

 

I respect your opinion but will explain my point on things for the group. We both may have different results with the same car or dyno's so this is just for sake of discussion.

I've run my cars at 11.2 and 11.8 and the power was very close to the same. Smoothing zero and really looking close.
Two back to back dyno passes on each setting. Really give it a chance to build some heat up.

The added fuel will keep things cooler and parts will live longer. Is a leaner mixture worth chasing 20hp when the reading is average of 4 cylinders? What about some no name injectors that are 5+% off hole to hole? Intake or exhaust manifold design and flow differences?

Now, a richer mixture is harder to ignite so your ignition system needs to be strong enough. The car may feel more crisp on a leaner setting but that may come at a cost later.
I've also encountered a difference in wideband readings from x ecu to y wideband on the same car with the same sensor . I prefer the richer mixture and will look at the plugs.

Lastly, I may have the longest (13-14 years and 20K+) running high Hp evo in the world and its definitely not targeting 11.6-12.0

 

I've got just about 100k miles with E85 and bolt ons. I shoot for 12 during spool then taper to low 11s out the top. I think of this stuff as liquid cooling with a little bonus oxygen. Also with the way E85 likes to gunk up I don't mind having a little safety margin built in there.

 

Our logic and findings are the same, we are just targeting different mixtures.

I personally run 11.3-11.5 on track on E79 and religiously read my plugs and swap them out before every track day.

Nobody should be using no name injectors. If they are, they get what they get.

 

So moral of the story is you’re telling me my car is running too lean lol

 

So what is the interval for tuned up Evos and spark plugs (400awhp+)?
I didn't think to change them before track days, but one broken plug = death !

 

I do mine every oil change. I use inexpensive copper plugs though, I don't know if there is an equivalent for the 4B.

 

There isn't. It's a $45 change for 4B11. Still cheaper than an engine.

 

my e85 typically test at 90%

i like almost 11 at full torque... ramping up to mid 11's up top.
14.5 at cruise
low 13's at idle... makes it lope a little more...

 

As mentioned before the richness cools things, and correct me if I am wrong the excess fuel also slows down the flame front of the combustion event further reducing the onset of KNOCK.....
I won't do my old man KNOCK KNOCK joke....

ok yes I will.

KNOCK KNOCK
who's there?
YOUR PISTONS

 

Agreed. I like keeping an eye on the plugs....the original data logs .

 

Just adding fuel to the fire here.

501whp, 175k stock bottom end, stock head bolts, stock head minus springs and cams.

I ran 13+ AFR after 5k on E for 3 years, didn't have the pump to keep up and was broke and wanted to race.

That same car now makes 535 whp and has 190k on it now, although she runs 12.0 up top now.

These cars are rather tough.