ADJUSTABLE FUEL PRESSURE REGULATOR MADNESS
Thread Starter
Racer
Joined: May 2000
Posts: 411
Likes: 0
From: Krakow
I have adjustable fuel pressure regulator (AFPR). I want to set best pressure point. But I hear that every engine (especially modified one) need another fuel pressure to work best. I have L98, so pressure change at WOT should be noticeable.
I know one method: set pressure - drive with stopper, set pressure - drive with stopper, set pressure - drive with stopper, set pressure - drive with stopper... Something boring.
I heard that another more elegant and finer method is tune pressure via observing data from scanner: observe O2 sensor data or BLM.(???)
So there is question: If I want tune my AFPR with scanner, what I should exactly do, for what data I should look at and how that data should be. I think answer for that question will be help not only for me.
Thanks
Jerry from Poland
My mods:
CORVETTE 1988 automatic Z52 35-th anniversary (75000 miles)
Open air lid
K&N filter
MAF screens removed
Plenum porting
No cats, no mufflers
Adjustable fuel pressure regulator
AIR pump removed
EGR off
I know one method: set pressure - drive with stopper, set pressure - drive with stopper, set pressure - drive with stopper, set pressure - drive with stopper... Something boring.
I heard that another more elegant and finer method is tune pressure via observing data from scanner: observe O2 sensor data or BLM.(???)
So there is question: If I want tune my AFPR with scanner, what I should exactly do, for what data I should look at and how that data should be. I think answer for that question will be help not only for me.
Thanks
Jerry from Poland
My mods:
CORVETTE 1988 automatic Z52 35-th anniversary (75000 miles)
Open air lid
K&N filter
MAF screens removed
Plenum porting
No cats, no mufflers
Adjustable fuel pressure regulator
AIR pump removed
EGR off
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
If you have a scan tool it should show Block Learn Modifier (BLM) cell values. The values are set based on O2 sensor data at part throttle in closed loop mode. As engine conditions change the ECM choses one of the 14 available cells (cell #15 is used at WOT and is always 128, the nominal value) to help set fuel injector pulse width. The nominal value is 128 +/-6. This means that the pulse is at the standard value. As you modify the engine and more air can pass through more fuel is required for any throttle position as seen by lean O2 sensor readings. So, the ECM increases the BLM cell values till the fuel/air ratio is ok agian.
As a starting ping, you can increase/modify fuel pressure till you get nominal readings for all BLM cells. Then you can fine tune fuel pressure for best power at WOT by using the O2 sensor readings. AT WOT the ECM records O2 sensor data even though it does not then use it to adjust fuel injector pulse width.
For a good explanation and much other useful information see if you can get hold of "How to Tune & Modify Chevrolet Fuel Injection" by Ben Watson.
As a starting ping, you can increase/modify fuel pressure till you get nominal readings for all BLM cells. Then you can fine tune fuel pressure for best power at WOT by using the O2 sensor readings. AT WOT the ECM records O2 sensor data even though it does not then use it to adjust fuel injector pulse width.
For a good explanation and much other useful information see if you can get hold of "How to Tune & Modify Chevrolet Fuel Injection" by Ben Watson.
Intermediate
Joined: Nov 2000
Posts: 27
Likes: 0
From: Michigan
Originally Posted by 65Z01
If you have a scan tool it should show Block Learn Modifier (BLM) cell values. The values are set based on O2 sensor data at part throttle in closed loop mode. As engine conditions change the ECM choses one of the 14 available cells (cell #15 is used at WOT and is always 128, the nominal value) to help set fuel injector pulse width. The nominal value is 128 +/-6. This means that the pulse is at the standard value. As you modify the engine and more air can pass through more fuel is required for any throttle position as seen by lean O2 sensor readings. So, the ECM increases the BLM cell values till the fuel/air ratio is ok agian.
As a starting ping, you can increase/modify fuel pressure till you get nominal readings for all BLM cells. Then you can fine tune fuel pressure for best power at WOT by using the O2 sensor readings. AT WOT the ECM records O2 sensor data even though it does not then use it to adjust fuel injector pulse width.
For a good explanation and much other useful information see if you can get hold of "How to Tune & Modify Chevrolet Fuel Injection" by Ben Watson.
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As a starting ping, you can increase/modify fuel pressure till you get nominal readings for all BLM cells. Then you can fine tune fuel pressure for best power at WOT by using the O2 sensor readings. AT WOT the ECM records O2 sensor data even though it does not then use it to adjust fuel injector pulse width.
For a good explanation and much other useful information see if you can get hold of "How to Tune & Modify Chevrolet Fuel Injection" by Ben Watson.
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Huh!?!
Seriously,65Z01, sounds like good info, but how do I look for nominal readings at all BLM cells using my scan tool??
Thanks
