injector flow rate
Thread Starter
TECH Veteran
iTrader: (6)
Joined: Nov 2003
Posts: 4,397
Likes: 0
From: Tallahassee, FL
injector flow rate
Injector Flow Rate vs. KPA Vac: This value is the Injector Flow rate in g/sec. It is used to tell the VCM the size of the injectors and also how flow rate varies with manifold vacuum (ie. varying pressure characteristics).
When looking at the table though, it has gallons per second as the variable and rpms hosting as the independent variable. How would increasing the gallons per second of fuel rate give you a leaner condition. My values across the entire table are 3.13 per any amount of vacuum.
If I'm loosing you. I'm lost on the part where adding fuel makes you run leaner. What am I overlooking?
Thanks,
Kyle
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
if an injector can flow 3 gallons per second, and you need 3 gallons of fuel in 1 second, then the PCM commands the injector to stay open for 1 second
if you set the that same value to 6 gallons per second, and you need 3 gallons, it keeps it open for .5 seconds ... higher the value the shorter period of time the injector pulse width... shorter the time the less fuel that's delivered (unless you scale the injectors 100% perfect ... which I know I had a hella time doing so w/my FMS 42#)
so if you go from an injector that flows 3 gallons/second to one that flows 6 gallons/second, if you leave the values in the IFR table alone, the PCM will keep the injector open for a full second, but instead of delivering the 3 gallons it expected it's now delivering 6 gallones...
so if you change the IFR to 12 it will keep the injector open for .25 seconds to flow 3 gallons, however the injectors take .5 seconds to flow 3 gallons, so the PCM thinks you flow more than you actually do, so you go lean (only delivering 1.5 gallons)
if you set the that same value to 6 gallons per second, and you need 3 gallons, it keeps it open for .5 seconds ... higher the value the shorter period of time the injector pulse width... shorter the time the less fuel that's delivered (unless you scale the injectors 100% perfect ... which I know I had a hella time doing so w/my FMS 42#)
so if you go from an injector that flows 3 gallons/second to one that flows 6 gallons/second, if you leave the values in the IFR table alone, the PCM will keep the injector open for a full second, but instead of delivering the 3 gallons it expected it's now delivering 6 gallones...
so if you change the IFR to 12 it will keep the injector open for .25 seconds to flow 3 gallons, however the injectors take .5 seconds to flow 3 gallons, so the PCM thinks you flow more than you actually do, so you go lean (only delivering 1.5 gallons)
12 Second Truck Club
iTrader: (1)
Joined: Jun 2004
Posts: 1,395
Likes: 0
From: The Chicken Ranch, California
Yeah, what horist said. 
I was/am trying to get a post going over on the HP Tuners site in the Basics forum that explains what the tables do in layman terms (I know I don't understand half the stuff in the help files). Unfortunately, the Basics forum is at the very bottom and no one goes down there. The IFR table is the only table I could explain. Here is what I said about it:
I was/am trying to get a post going over on the HP Tuners site in the Basics forum that explains what the tables do in layman terms (I know I don't understand half the stuff in the help files). Unfortunately, the Basics forum is at the very bottom and no one goes down there. The IFR table is the only table I could explain.
Here is what I said about it:
Injector Flow Rate vs. KPA Vac: (IFR Table) decreasing values makes the VCM think the fuel injectors are smaller therefore keeping them on for a longer period of time which increases fuel flow and makes the engine run more rich. Increasing values does the exact opposite. This is a good starting point for getting LTFT's slightly negative.
