Air to Fuel Ratio - CAI before and after
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This is a discussion on Air to Fuel Ratio - CAI before and after within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; So I finally got around to getting my air to fuel ratio gauge installed this past weekend. As I had ...

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    MAINEiac 11blackSTi's Avatar
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    Air to Fuel Ratio - CAI before and after

    So I finally got around to getting my air to fuel ratio gauge installed this past weekend. As I had previously had a Perrin intake on my car, but subsequently took it off due to fears of running extremely lean, I wanted to do a little real life experimenting.

    After getting the air to fuel gauge up and running I did some stock readings. The car was running at 14.5-14.7 at idle. I did a few wide open throttle pulls and the ratio dipped down to 11.0 - 11.2. After this I re-installed the cold air intake and found that the car was again running at 14.5-14.7 AFR at idle. Low and behold, at WOT, it was also running at 11.0-11.2 AFR. Flashed to stage 1 and the readings are about the same.

    I think my next upgrade might be a manual or elecontrol boost control to see if I can get the AFR leaned out a little (high 11's maybe?) to get a little more power, as 11 seems a bit rich.

    Any thoughts?

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    Air to Fuel Ratio - CAI before and after

    Are your data accurate?

    My question involves the value of an intake that does not alter A/F. I'm mostly thinking aloud though.
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    Registered User Heide264's Avatar
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    Quote Originally Posted by 11blackSTi View Post
    So I finally got around to getting my air to fuel ratio gauge installed this past weekend. As I had previously had a Perrin intake on my car, but subsequently took it off due to fears of running extremely lean, I wanted to do a little real life experimenting.

    After getting the air to fuel gauge up and running I did some stock readings. The car was running at 14.5-14.7 at idle. I did a few wide open throttle pulls and the ratio dipped down to 11.0 - 11.2. After this I re-installed the cold air intake and found that the car was again running at 14.5-14.7 AFR at idle. Low and behold, at WOT, it was also running at 11.0-11.2 AFR. Flashed to stage 1 and the readings are about the same.

    I think my next upgrade might be a manual or elecontrol boost control to see if I can get the AFR leaned out a little (high 11's maybe?) to get a little more power, as 11 seems a bit rich.

    Any thoughts?
    Considering you are suggesting using a boost controller to change your AFRs (to dangerously lean levels) makes me question the data honestly. In a semi-high compression highly boosted engine, I wouldn't run above 11.2 on pump gas without meth.

    While I'm not discrediting that the Perrin intake is "MAF matched" or a quality piece, I also doubt that it is a close match. You never mentioned if you let the car learn any fuel trims, and you never posted how the car did through out various loads. A WOT log normally only goes from 2V to 4V on the MAF scaling on a 2.5L. Idling is at the very low end of the scale.

    How long did you wait after installing the intake to do the logs?
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    Which WBO2 sensor did you purchase and where is it installed?

    Since you have installed the WBO2, provided it is installed in the proper location, it wouldn't hurt to rescale your MAFv. Turbulence can occur at specific flow intervals. You will want to reference your map for target AFR first, then compare the actual AFR to the target AFR. The correction % (theoretical to actual) should be applied to your MAFv scaling per MAF. It is important that you do this only while in OL. As such, datalogging OL/CL parameters is also important. PM me for more details. This is very important! Even the stock airbox does not scale the MAFv ideally much less an aftermarket intake.

    FYR, high 11s is much too lean for a boosted motor on the stock TMIC. You will want to go E85, meth injection, or FMIC before ever considering running the car that lean at WOT. Also, of course the car is idling at 14.7:1 at idle! This is the purpose of CL fueling!
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    Master Baiter EJ257's Avatar
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    You mention a AFR gauge. You talking a WBO2 like the AEM UEGO? Without it being a custom tune, it hitting 11.0 sound to me like it's just reading the stock sensor, because base maps are usually into the 10s.

    Quote Originally Posted by Heide264
    Considering you are suggesting using a boost controller to change your AFRs (to dangerously lean levels) makes me question the data honestly. In a semi-high compression highly boosted engine, I wouldn't run above 11.2 on pump gas without meth.
    With a quality TMIC, I'd have no issues running 11.3-11.5 AFRs
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    Quote Originally Posted by EJ257 View Post
    With a quality TMIC, I'd have no issues running 11.3-11.5 AFRs
    Which the OP doesn't have.
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    Quote Originally Posted by zax
    Which the OP doesn't have.
    I'm aware of that. I'm just disagreeing with Brandons hesitation to run above 11.2 on pump gas.
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    Air to Fuel Ratio - CAI before and after

    I don't know all the parts fitted but I can't help but suspect the data are not accurate. For one they did not change in max/min range when they possibly should have changed.

    Until the OP clarifies though we won't know.
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    My suspicion as well. From the sound of it, I don't believe the OP has a WBO2 sensor. Certainly not with the stock DP.
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    Quote Originally Posted by EJ257 View Post
    With a quality TMIC, I'd have no issues running 11.3-11.5 AFRs
    Fair enough. I would it would free up a good bit of power actually as well. Once you pass that 12.0 AFR, the power starts to drop off pretty quickly. If you could add a few more degrees in to get to MBT... Now you are at a worthy tradeoff.

    I've had no issues with a spike at peak torque that hit 11.5. I haven't ever tried to push the envelope with my stock TMIC though.
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    MAINEiac 11blackSTi's Avatar
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    Quote Originally Posted by zax View Post
    My suspicion as well. From the sound of it, I don't believe the OP has a WBO2 sensor. Certainly not with the stock DP.
    Yes I have the AEM Wideband O2 Air/Fuel UEGO installed. It has the 4.2LSU sensor installed about an inch before the catalytic converter on the downpipe.

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    OK, well in that case:

    Quote Originally Posted by zax View Post
    Which WBO2 sensor did you purchase and where is it installed?

    Since you have installed the WBO2, provided it is installed in the proper location, it wouldn't hurt to rescale your MAFv. Turbulence can occur at specific flow intervals. You will want to reference your map for target AFR first, then compare the actual AFR to the target AFR. The correction % (theoretical to actual) should be applied to your MAFv scaling per MAF. It is important that you do this only while in OL. As such, datalogging OL/CL parameters is also important. PM me for more details. This is very important! Even the stock airbox does not scale the MAFv ideally much less an aftermarket intake.

    FYR, high 11s is much too lean for a boosted motor on the stock TMIC. You will want to go E85, meth injection, or FMIC before ever considering running the car that lean at WOT. Also, of course the car is idling at 14.7:1 at idle! This is the purpose of CL fueling!
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    Master Baiter EJ257's Avatar
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    Quote Originally Posted by Heide264
    Fair enough. I would it would free up a good bit of power actually as well. Once you pass that 12.0 AFR, the power starts to drop off pretty quickly. If you could add a few more degrees in to get to MBT... Now you are at a worthy tradeoff.
    AFR has less effect on power than boost and timing. A few points leaner will likely not see the gains an additional 1 of ignition timing or another pound of boost.
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    Registered User Heide264's Avatar
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    Quote Originally Posted by 11blackSTi View Post
    Yes I have the AEM Wideband O2 Air/Fuel UEGO installed. It has the 4.2LSU sensor installed about an inch before the catalytic converter on the downpipe.
    Post up some logs, including long term/short term fuel trims from the ECU then. I'd be curious to see the fuel trims through the power band. I'd be surprised if it actually matched up across most of the MAFV range. I had a lot of issues in between 2-3V when adding my intake.

    The irony of the situation (if I am not off my rocker): If the car didn't use fuel trims to compensate for a fueling error, and the MAF housing is the same diameter, then you didn't gain anything by going with the intake. Same MAFV, same voltage, same fuel, same burn ratio.... Same air flow. This applies to everything - WOT response, low load cruising, and while in transient.
    Quote Originally Posted by Trainrex
    He was throwing balloons filled with sulfuric acid and shrapnel at the swat team. They finally had to take him down with rubber bullets.
    2011 STi Build Log
    -Part 1 - Reading, Data Logging, and Analyzing Data
    -Part 2 - Turbocharger 101 & Basic Boost Control
    -Part 3 - EcuFlash, Experimental Defintions, and a Drive By Wire Intro

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    Registered User Heide264's Avatar
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    Quote Originally Posted by EJ257 View Post
    AFR has less effect on power than boost and timing. A few points leaner will likely not see the gains an additional 1 of ignition timing or another pound of boost.
    Especially with our cars being so far from MBT while on pump gas =(.

    With the AFR leaning out, and timing already overly retarded (as to deter detonation)... I bet EGTs would be sky high.
    Quote Originally Posted by Trainrex
    He was throwing balloons filled with sulfuric acid and shrapnel at the swat team. They finally had to take him down with rubber bullets.
    2011 STi Build Log
    -Part 1 - Reading, Data Logging, and Analyzing Data
    -Part 2 - Turbocharger 101 & Basic Boost Control
    -Part 3 - EcuFlash, Experimental Defintions, and a Drive By Wire Intro

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