Transition AFR's
#1
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Scikotics
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Location: West Des Moines, IA
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I am looking to do some more tuning on my F/IC tonight and have a question about the AFR's. I know that when not in boost, they should be around 14.7 and at peak power, they should be at 12.5 to 12.3 depending on your boost levels. My question is about where they should be at partial boost.
I am running 7psi, so at around 3 or 4 pounds, where do I want my AFR's? Is it linear when I get into boost or should it get a lot richer as soon as the engine sees increased pressure?
Also, does it depend on the RPM's of the engine? At 3psi, should it be slightly leaner at low RPM's and richer at high RPM's or doesn't that matter?
There isn't a lot of info out there on partial boost tuning. I know that the best way to find out these answers is testing it on a dyno, but I'd like to get a halfway close street tune before buying dyno time.
I am running 7psi, so at around 3 or 4 pounds, where do I want my AFR's? Is it linear when I get into boost or should it get a lot richer as soon as the engine sees increased pressure?
Also, does it depend on the RPM's of the engine? At 3psi, should it be slightly leaner at low RPM's and richer at high RPM's or doesn't that matter?
There isn't a lot of info out there on partial boost tuning. I know that the best way to find out these answers is testing it on a dyno, but I'd like to get a halfway close street tune before buying dyno time.
#3
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Scikotics
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Care to elaborate a little more? ![Icon Tongue](https://www.scionlife.com/forums/images/smilies/icon_tongue.gif)
Is it dependant on RPM's at all or just boost pressure?
Is it a linear transition?
assuming the following:
@0psi - 14.7
@7psi - 11.7
does that mean 3.5psi should be exactly in the middle?
ie. (14.7+11.5)/2 = 13.1 @ 3.5psi?
![Icon Tongue](https://www.scionlife.com/forums/images/smilies/icon_tongue.gif)
Is it dependant on RPM's at all or just boost pressure?
Is it a linear transition?
assuming the following:
@0psi - 14.7
@7psi - 11.7
does that mean 3.5psi should be exactly in the middle?
ie. (14.7+11.5)/2 = 13.1 @ 3.5psi?
#4
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I tune mostly on manifold pressure more than throttle position.. i could be in partial throttle but reach full boost or part throttle and not hit boost at all.
Cruise
0-5inHg 13.0-13.4
5-10inHg 13.4-14
10-14inHg 14.4-14.6
14-22inHg 14.4-14.8
Boost
1-3 psi 12.6-12 afr
4-6 psi 12-11.8
7-9 psi 11.7 afr
10-11psi 11.5
Cruise
0-5inHg 13.0-13.4
5-10inHg 13.4-14
10-14inHg 14.4-14.6
14-22inHg 14.4-14.8
Boost
1-3 psi 12.6-12 afr
4-6 psi 12-11.8
7-9 psi 11.7 afr
10-11psi 11.5
#5
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wot 11.8-12.2 E85
coming up on 0-5 hg i tune to 13.5
and normal idle and cruise at 14.7
for a conserve tune
on mine
up to 0-4 psi 13.5-14
4-8 12.8-13.2
8-14 12-12.4
and idle 14.7 and anything in vacuum
coming up on 0-5 hg i tune to 13.5
and normal idle and cruise at 14.7
for a conserve tune
on mine
up to 0-4 psi 13.5-14
4-8 12.8-13.2
8-14 12-12.4
and idle 14.7 and anything in vacuum
#8
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Scikotics
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Thanks guys. That helps me out a lot. :up: Hopefully, I'll get a decent tune on the car and take it to the dyno soon. Then, it will be ready for even more boost hopefully.
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