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Old 30-01-2012, 01:52 AM
cewrx7r1 cewrx7r1 is offline
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Default AFR Tuning With Fixed Rate WI

I am only running water injection.
After reading so much my brain melting, I need more info. Did not find any posts about what my logs are showing.

Everyone talks about tuning for for a certain AFR with WI. No problem.
If the WI system flows a variable rate such that the % of WI stays constant across the rpm band, then no problem. My system flows a fixed rate based on boost pressure, and my EBC has perfect boost control such that boost stays very stable from 4000 - 8000 rpm.

I am flowing 375 cc/min at 4000 to 8000 rpm. But air flow and fuel injection rates are constantly changing. The results that after tuning for a fixed AFR across the rpm band, the results end up with varying fuel changes. This results in a calculated air only AFR range that get leaner as revs increase.

Look at the attachment. The question is, should I change my tuning strategy; so that the target AFR WI changes per fuel cell would be different so that the calculated air AFRs are all the same?
Attached Files
File Type: zip AFR INFO.zip (2.6 KB, 8 views)

Last edited by cewrx7r1; 30-01-2012 at 07:13 AM.
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Old 31-01-2012, 08:58 PM
cewrx7r1 cewrx7r1 is offline
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Smile Re: AFR Tuning With Fixed Rate WI

No need for an answer now.
Peter answered all and more of my questions.
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Old 31-01-2012, 10:41 PM
Richard L Richard L is offline
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Default Re: AFR Tuning With Fixed Rate WI

Sorry I am too late. Not enough hours in a day for me.
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Old 02-02-2012, 12:33 AM
Dust Dust is online now
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Default Re: AFR Tuning With Fixed Rate WI

Cewrx7r1, please post what you learned so that others can benefit.
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Old 02-02-2012, 01:31 AM
BMWTurbo BMWTurbo is offline
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Default Re: AFR Tuning With Fixed Rate WI

Please share. I'm trying to work out the exact same thing currently.
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Old 02-02-2012, 02:29 PM
Liborek Liborek is offline
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Default Re: AFR Tuning With Fixed Rate WI

Something along the lines that water to fuel ratio will be higher in midrange and lower in top-end, and its a good thing, as highest knock surpression is needed at torque peak, then it can taper of. To much excess water would cause power drop at to rich AFR, but at correct AFR power loss will be minimal.
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Old 30-06-2012, 11:00 PM
cewrx7r1 cewrx7r1 is offline
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Default Re: AFR Tuning With Fixed Rate WI

The fixed AFR tuning does lean out the fuel above maximum torque more than below resulting in the fuel values being closer to 12.2AFR without WI. This should result in a greater % increase of power at the higher rpms and help flatten out the torque curve. But you do not want to remove so much fuel that the calculated AFR without WI is leaner than 12.2 AFR as you will loose power.

I am now starting to experiment with doing some pre-turbo WI after reading this thread:
http://www.rx7club.com/showthread.php?t=987107

I am comparing normal WI nozzles with a different type of nozzle that only can be used in the filter where the air flow is parallel with the injection flow.
http://www.bete.com/pdfs/BETE_PJ.pdf

For best pre-turbo injection, axial flow is best to prevent water from wetting the sides of the filter or ducts. See pictures of mine in the filter.

I want to thank RiceRacing and Peter94RX7.
Attached Images
File Type: jpg WI Into Filter 2.jpg (46.0 KB, 8 views)
File Type: jpg WI Into Filter 1.jpg (63.1 KB, 7 views)

Last edited by cewrx7r1; 01-07-2012 at 12:41 AM.
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