Intake, Header, HFC, CBE = Too Lean?

Vegitto-kun

damnit so if I get HFC + exhaust I would have to find somebody that can tune the ECU up.

horray for more money to spend

F.I. Inc.

No you do not. If you run the HFC's and CBE your car will not become too lean. The ECU will correct and do it's job. Here is why the intakes change the A/F ratio's so much more than the exhaust system.

Inside your stock intake tube is a MAF (Mass Air Meter) As the air rushes by it, it samples that air. It works directly with the ECU and is calibrated specifically for the car. If you change altitude your cars A/F ratio will change. Meaning being at sea level opposed to driving in the mountains. In the higher altitude your car will actually be richer. Here is why, the air is thinner up there, your car naturally will take in less air. It naturally wants to lean out due to this and in most cases the ECU will compensate by dumping too much fuel and make the car rich. The MAF and ECU are designed from the factory to do this. However, they only work to a certain extent being that the elements from one place to the next are too different. If it worked perfectly your A/F would be optimum wherever you drove.

Now if you put an aftermarket CAI on the car that changes the location of the MAF or the tubing diameter it will change everything. The car is not calibrated for it. In the case of the Stillen Gen III intakes with exhaust & headers the intakes are causing the car to run way too lean. This is why you need a re tune so at the least amount you can bring the A/F ratios back to where they need to be. I know this how you may ask, over the past two days I dynoed a car that had Stillen Gen III intakes with our exhaust components and the car was borderline unsafe in terms of A/F. We re tuned the car, picked up alot of mid range power and low end torque just be getting the A/F back in the 12's. To be continued I am sure...

Thanks, Tony

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chris410

Well said Tony, everyone needs to keep in mind that most dyno graphs of the G3 intake show a "peak" gain which means next to nothing for overall performance. The K&N drop-ins are your best route to go with the stock intakes along with a CBE and HFC.

However, like Tony said...if you change the location and process of how the car reads the air ratios, you are at risk of running lean because the car may not be adjusting the fuel ECU map correctly. You have two ways of determining this, either pull your plugs and read them (basically if you are running lean you will see a whiteish plug) or get to a dyno and get an a/f reading. If you are running lean, the car "should" pull timing which means you are losing power. Don't make your mods work against you!

You will not be able to put more power using an intake, HFC, and CBE IF the car can adjust air/fuel correctly. If you go the supercharger/turbo route of course the game changes quite a bit. So, for those of you going with the G3, you should at least get your air/fuel readings to make sure you're not going lean. Better safe than sorry!

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Chris
Current: 2014 WRX Stage I + SPT / 2013 Hayabusa 202HP
Former:09 370Z 7-AT PW/Ark Type 2 exhaust/Evo R lip/TSW Nurburgring carbon

semtex

I disagree.

I started off with a CBE and HFC. I never dyno'd before this, only after, so my baseline is with the CBE and HFC.

Baseline: Max = 291.7whp. My only mods were the Stillen cat-back exhaust and the Berk HFCs.



Then I went and added the G3 intakes.
After: Max = 306.4whp.



Net gain = 14.7whp.

Then I added headers.

This first graph shows HP and A/F:


This one shows torque:


So I should be running really lean now, right? And when I get a tune and get my AFR adjusted, my HP should go back down as a result of the AFR correction, right? But it doesn't. And keep in mind that AFR correction is pretty much the only thing a tune is good for right now, because timing adjustments just get bounced back, so it's not like we're offsetting HP loss via AFR correction with HP gain via timing advancement.

Sharif at Forged Performance did my tune, and he made sure the AFR is where it ought to be.



Final number: 318.1

Unless I'm missing something, it does not appear that my gains from the G3 intake were at any point negated by AFR correction, which leads me to conclude that the gain I got from the G3 was legit, and not simply because it caused my engine to run lean.

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316.8whp & 248 ft/lbs (Dyno Dynamics) | 319whp & 256 ft/lbs (DynoJet) (04/23/10)
Stillen G3 CAI, CBE, Pulley / F.I. LTH / GTSpec Ladder Brace / Setrab Oil Cooler / UpRev-tuned by Forged Perf.

chris410

No, what I meant is that IF your air meter is working properly that even with all the bolt on mods, the car should be able to adjust the fuel so that you do not run lean. In other words, the stock fuel system can keep up with the amount of power you will make with all of those mods. If you relocate or your air meter is NOT reading accurately, you could end up with a lean condition.

I wasn't really talking about the "power" itself rather the power compared to what the ECU can adjust to.

Basically, if you have a G3, you're better off getting the car on the dyno and obtaining your a/f ratios. OR...if you have the software, watch the timing during a pull. If you see timing start to decrease through the run, that means your car is going lean and the ECU is pulling timing to compensate...NOT good!

Nice numbers btw!

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Chris
Current: 2014 WRX Stage I + SPT / 2013 Hayabusa 202HP
Former:09 370Z 7-AT PW/Ark Type 2 exhaust/Evo R lip/TSW Nurburgring carbon