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Hi guys,

To aid my turbo build, I have my wideband installed on my 100% stock D17A2 to observe its behavior in open loop. The car is forced open loop by removing the primary O2. I plan to tune it this way for boost using AEM FIC.

The car idles at around 14.7-15.2
Cruising under 3200 rpm, AFRs are around 16
At 3200 rpm, AFRs richen up to 14.7 and stay there
WOT, AFRs sit around 12.8-13.0

I found out VTEC engages at 3200 rpm.

Would you guys say this is normal? If so, why does the engine run leaner out of VTEC?
 

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Are you sure your wideband is calibrated correctly and that you dont have any fueling issues like clogged injectors?

It isnt surprising that it runs lean before vtec, I am sure they are trying to get better gas mileage out of it in the cruising RPMs.
 

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Are you sure your wideband is calibrated correctly and that you dont have any fueling issues like clogged injectors?

It isnt surprising that it runs lean before vtec, I am sure they are trying to get better gas mileage out of it in the cruising RPMs.
I used to have an exhaust leak that messed with the wideband but I fixed it. i also tested the sensor, wiring, and gauge. With the leak, AFRs were all over the place every second. Now, they're stable - so I'd say the leak is fixed. I ask my original question cause I thought it was possible I still had a minor leak that "shifts" my AFRs.
Clogged injectors, I do not know. But car runs fine, doesn't get hot like running lean would make it.

But I thought the same thing about gas mileage. It makes sense. Thank you for the input.


seems pretty normal to me. though im surprised it is that good in open loop...
Thanks! And it surprised me too. I was actually testing to see how consistent it was in open loop. The weather here also doesn't change drastacially, in temp and humidity.
 

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I tune my d16 to about that. High vac is around 15.8 to 16 AFR.
But isnt that d17 vtec e?
Which would mean its a lean burner, till vtec kicks in.
X2.

12 valves pre vtec helps the fuel atomize and mix better due to very light cam lift on one intake valve while the other intake valve is opened like normal, creating a swirl. Better fuel atomization at light loads/ cruise/ low rpms means less fuel required= leaner Afr. If that's a LEV, ULEV, and maybe PZEV, then it would be an economy type of VTEC. Would make sense to have leaner Afr if that motor applies to all the above.

Any vac leaks?

And you meantioned its in open loop? What maps are you using for open loop? Im not sure if your running the emanage or not. Also if the Afr goes learner than 15.8 the combustion temps tend to go decrease along with NOX.
 

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Discussion Starter #7
X2.

12 valves pre vtec helps the fuel atomize and mix better due to very light cam lift on one intake valve while the other intake valve is opened like normal, creating a swirl. Better fuel atomization at light loads/ cruise/ low rpms means less fuel required= leaner Afr. If that's a LEV, ULEV, and maybe PZEV, then it would be an economy type of VTEC. Would make sense to have leaner Afr if that motor applies to all the above.

Any vac leaks?

And you meantioned its in open loop? What maps are you using for open loop? Im not sure if your running the emanage or not. Also if the Afr goes learner than 15.8 the combustion temps tend to go decrease along with NOX.
That makes sense.

There are no vac leaks that I know of. I tested for them with carb cleaner right after doing my HG and none showed.

It's in open loop by removing the primary O2. To my understanding, it's running off it's stock open loop "map". I will be tuning that map with AEM FIC. I actually got the FIC installed yesterday (stock motor) to play with it prior to boost/injectors. It seems to function exactly as I expected. No STFT to fight fuel and no issues with MAP/CAM signals. Drives like stock and I can add fuel as I'd like.
 
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