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Old 07-18-2018, 06:42 PM   #1
pcampbell
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Member#: 437670
Join Date: Jan 2016
Vehicle:
2005 2.5 SC OB

Default Knock at same load / Rpm / afr / boost with meth?

Iím doing initial test runs with 50/50 water meth and running to an issue where I had a knock event on near identical circumstances as pre meth. Iím trying to figure out if itís just a fluke or something I need to be concerned about. I havenít changing timing yet. I have only leaned out open loop timing but seeing the same final wideband afr post meth injection. Iíll post an example here.
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Old 07-18-2018, 06:46 PM   #2
pcampbell
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2005 2.5 SC OB

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So the first example is on gas. The second example is on just gas pre-meth. The only thing I changed was I reduced the target AFR from roughly 12.46 to 11.2, but added the meth injection. The only hing I can think of is maybe I need to decrease target AFR up to like 12.2 or 12.0 rather than 12.46. I haven't even increased timing yet so I'm a little concerned that It's knocking. It appeared to be a just 1 event. (I have each knock event set to -3 degrees right now...). Any thoughts?


Quote:
LOAD rpm fbkc basetiming totaltiming iat boost maf mafv target afr
1.81,5095,0,9.77,12.5,77,6.67,151.24,3.88,11.2,11
1.75,4959,-3,10.04,10,75,6.24,140.23,3.74 ,12.46,11.4
My initial thought is to change the target AFRs to 12.0 or 12.25 and continue. I haven't gotten to the fun part... increasing timing...
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Old 07-18-2018, 07:29 PM   #3
pcampbell
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2005 2.5 SC OB

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To reiterate, what I'm seeing is nearly identical conditions.. very similar final AFR, 1 knocks, 1 doesn't (although I don't know if the knock is repeatable...).

One has 12.5 target, 11.4 final including the 50/50 meth mix.
The other has 11.2 target, 11.0 final and is pure E10 93.

So I'm really surprised to see the 11.4 water/meth knocking.

Is there any way to consider that this is a fluke other than to try again? Any amount of knocking at 1.8 load makes me a bit nervous. I was pretty close to getting around to increasing timing by 1 degree, too.
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