I did a lot of reading about 15-17% pulleys and how they run on stock tunes. everyone says they are fine, and safe. but the injectors are whats limiting them.

Here is my dyno tune to prove that is 100% FALSE
13+ afr is SOOO lean, and extremely bad for the car.

Sure throwing jcw injectors on it will help make it safer, but u lose the performance.

Go get a proper tune with mods people. safety and performance.

Why waste over a 1000$ in mods if you only get 50% of the possible gains, and you put your car at risk?

Mod list for my car: 17% alta pulley, Alta intake w/ box and hose. MSD ignition, NGK 1 step colder plugs, JCW catback. DT bypass valve.

-B

 

13+ AFR is bad, but you are at 11+ after the tune... isn't that pretty lean too? Suggests something else is going on?

 

just above 11.0 is ideal and much richer than 13+. look what is ideal for tunes with other supercharger/turbod cars....

-B

http://rusubaru.com/afrs-101/

that may help explain better

 

AH ok - thanks for the link. Hadn't seen that one before. Didn't realize the trims should be around 11.

 

its a common misconception about what AFR numbers mean rich and lean, most people think higher means more fuel, its actually backwards. Even jcw tunes are bad for cooper s's because of how the stock S head flows in comparison. i sat down and spoke with a tuner for a long time about whats the best option. I couldnt be happier.

-B

 

The "ideal" AFR is 14.7:1. Numbers lower than that are rich, numbers higher than that are lean. Some cars will intentionally run slightly lean at cruise with light throttle for fuel economy. The "lean-burn" cars will run AFRs in the 20s for light load conditions.

12:1 is, in many sources, considered a "good" ratio for forced-induction cars. The extra fuel helps to cool the intake charge and the combustion chamber somewhat. Running 13:1 would likely indicate some risk of higher temps, but I wouldn't think it would be a huge risk. Technically, 13:1 is still rich--just not as rich as 12:1.

Running 11:1 gives you even more excess fuel. It gives you extra margin for any unanticipated circumstances that come up (e.g., a hot day makes your charge cooler less effective, you get heat soak, etc.).

I'm not sure that 13:1 is "instant motor death", as is being implied here. I do think you are cutting into your safety margins, though, so temps should be watched (intake temps, exhaust temps if you have them, oil temps, etc.) if you run it.

 

Dang now I want a tune.

 

Remember....it has been known for years the car is a bit lean wot...(full throttle when the o2 sensor is out of the loop, with no fuel trims applied)...remember this is how a car is dyno'd...worst case.
But for a daily driven nontracked car....most are fine...if you have 92-93 octane it helps.
I decided to get jcw380's and a tune...car ran better after each mod...and I have kept the car since new...no issues...I considered the injectors and tune to be cheap insurance....and both added power so it was a nice gain also.

 

14.7:1 is the target/ideal AFR for CAT efficiency in closed loop, in open loop WOT you should be aiming for 11.5:1 (+/- 2) for "safe" performance from about 5500 rpm+ with our cars, w/ @ least 91 octane, (look @ the graph, this is why the dip starts @ 5500, it's the ECU's way of bringing the ratio down to safe levels) and of course the higher the octane, the higher your AFR limits are. (this is the basis as to why W/M allows you to make more power, lean = mean, the leaner you can run "SAFELY" the more power you'll make, the more octane you have, the higher the threshold for detonation, and W/M besides it's cooling benefits is basiclly an octane booster)

As far as the before #'s, while not optimal, not motor grenading either, although you probably wouldn't want to push it that hard in high heat (this is one of the reasons a GPIC is a "MUST" for a track car w/ a 17% pulley) and yes a set of 380 should put you right in range w/o a tune, since the injector pulses are controlled on a % basis as far as fuel demand is concerned.

And, from what is on the graph, the result is a good/safe tune that will be good for all different conditions, remember when it comes to tuning, if you push the limits too much, you had better hope the external conditions don't change for the worse, whats good for a 70* day isn't good for a 90* day if you're right on the edge.