Power FC how to tune to better gas mileage
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BDC Motorsports
Joined: Jun 2002
Posts: 3,667
Likes: 6
From: Grand Prairie, TX
The VE of the motor (alterations to the stock port, be them street or bridge ports) will have a fairly dramatic effect on this as well as the spark advance curves used in the map. I personally don't see it feasible to get into the 15's and 16's:1 except on a stock port motor. High 14's is more realistic for any Closed O2 loop operation when on the highway. If you aim for higher ratios, you run the risk of stumbling.
B
B
BDC,
Lean AFR cruising works just fine for a street port if you kill the closed loop, give it a try. I was able to run upwards mid to high 16's and even some 17:1 at cruise with no issues on my street port motor, no cats tho. You just have to tune the tip in right to prevent a lean stumble upon throttle tip-in, I've documented this many times on this forum over the years. We documented it well in Chuck's notes I believe, they would help anyone by providing more of a "how to".
Closed loop around stoich is more to keep the old tech cats alive, closed loop cools the cat as it cycles rich every few seconds. You'll get better mileage by turning it off and tuning cruise to a lean afr. Worse thing about closed loop on the PFC is that it can start coming on at idle and low speeds.
Lean AFR cruising works just fine for a street port if you kill the closed loop, give it a try. I was able to run upwards mid to high 16's and even some 17:1 at cruise with no issues on my street port motor, no cats tho. You just have to tune the tip in right to prevent a lean stumble upon throttle tip-in, I've documented this many times on this forum over the years. We documented it well in Chuck's notes I believe, they would help anyone by providing more of a "how to".
Closed loop around stoich is more to keep the old tech cats alive, closed loop cools the cat as it cycles rich every few seconds. You'll get better mileage by turning it off and tuning cruise to a lean afr. Worse thing about closed loop on the PFC is that it can start coming on at idle and low speeds.
Last edited by twokrx7; Jul 28, 2007 at 07:47 PM.
BDC Motorsports
Joined: Jun 2002
Posts: 3,667
Likes: 6
From: Grand Prairie, TX
BDC Motorsports
Joined: Jun 2002
Posts: 3,667
Likes: 6
From: Grand Prairie, TX
BDC,
Lean AFR cruising works just fine for a street port if you kill the closed loop, give it a try. I was able to run upwards mid to high 16's and even some 17:1 at cruise with no issues on my street port motor, no cats tho. You just have to tune the tip in right to prevent a lean stumble upon throttle tip-in, I've documented this many times on this forum over the years. We documented it well in Chuck's notes I believe, they would help anyone by providing more of a "how to".
Closed loop around stoich is more to keep the old tech cats alive, closed loop cools the cat as it cycles rich every few seconds. You'll get better mileage by turning it off and tuning cruise to a lean afr. Worse thing about closed loop on the PFC is that it can start coming on at idle and low speeds.
Lean AFR cruising works just fine for a street port if you kill the closed loop, give it a try. I was able to run upwards mid to high 16's and even some 17:1 at cruise with no issues on my street port motor, no cats tho. You just have to tune the tip in right to prevent a lean stumble upon throttle tip-in, I've documented this many times on this forum over the years. We documented it well in Chuck's notes I believe, they would help anyone by providing more of a "how to".
Closed loop around stoich is more to keep the old tech cats alive, closed loop cools the cat as it cycles rich every few seconds. You'll get better mileage by turning it off and tuning cruise to a lean afr. Worse thing about closed loop on the PFC is that it can start coming on at idle and low speeds.
B
"Elusive, not deceptive!”
Joined: May 2007
Posts: 930
Likes: 13
From: Slidell, LA
If you are bored while cruising try observing what the best speed is obtained from a 20% injector duty-cycle. My thought is that this will give us the strongest power for a set duty-cycle. I found that I was fastest (81mph) at about 15.2AFR. My best MPG was 22 with 6 other 7’s going to Deal’s Gap cruising 90.
Last edited by Barry Bordes; Jul 29, 2007 at 03:59 PM. Reason: add info
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