how do YOU guesstimate your Injector constants?
Thread Starter
Melting Slicks
Joined: Oct 2002
Posts: 3,193
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From: Cincinnati Oh
how do YOU guesstimate your Injector constants?
how do you guys correct your Fuel Injector constants for most accurate MPG readouts? I have SVO 24#'s and am using the 25.78 correction factor that was calculated from the ford FP of 37psi and my current "base" FP of 43psi or so.
But obviously the FP changes with engine vacuum (ie RPM and driving), so do most people use the base pressure (with the AFPR plugged into vacuum- minimum flow) or a tweaked value that's slightly more to account for acceleration and higher-than-idle RPMs?
But obviously the FP changes with engine vacuum (ie RPM and driving), so do most people use the base pressure (with the AFPR plugged into vacuum- minimum flow) or a tweaked value that's slightly more to account for acceleration and higher-than-idle RPMs?
Safety Car
Joined: May 1999
Posts: 3,651
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From: Atlantis
Cruise-In I Veteran
Hey Jesse,
I think most folks (myself included) adjust the Injector Constant to dial in the INT's and BLM's.
Then the VE (speed density) is adjusted to minimize the adjustments the ECM has to do to maintain the desired mixture.
I believe the mileage calcs. do whatever they want afterwards and most just don't worry about them.
It probably isn't (ok definitely isn't) a good idea to adjust the Injector Constant using the mileage calcs. as a measure of "correctness".
Somehow I feel this may not be the answer you are looking for. I'm sure you knew this already and are looking for another answer....
BTW... THE FUEL PUMP WORKS G-R-E-A-T!!!!!!!!!!!!!!!!!!!!!!!
Thank you,thank you, thank you.
Jim
I think most folks (myself included) adjust the Injector Constant to dial in the INT's and BLM's.
Then the VE (speed density) is adjusted to minimize the adjustments the ECM has to do to maintain the desired mixture.
I believe the mileage calcs. do whatever they want afterwards and most just don't worry about them.
It probably isn't (ok definitely isn't) a good idea to adjust the Injector Constant using the mileage calcs. as a measure of "correctness".
Somehow I feel this may not be the answer you are looking for. I'm sure you knew this already and are looking for another answer....
BTW... THE FUEL PUMP WORKS G-R-E-A-T!!!!!!!!!!!!!!!!!!!!!!!
Thank you,thank you, thank you.
Jim
Race Director
Joined: Jan 2002
Posts: 12,264
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From: O'Fallon Missouri
Last edited by STL94LT1; Jul 10, 2004 at 07:44 PM.
Thread Starter
Melting Slicks
Joined: Oct 2002
Posts: 3,193
Likes: 1
From: Cincinnati Oh
Originally Posted by VetNutJim
Hey Jesse,
Somehow I feel this may not be the answer you are looking for. I'm sure you knew this already and are looking for another answer....
BTW... THE FUEL PUMP WORKS G-R-E-A-T!!!!!!!!!!!!!!!!!!!!!!!
Thank you,thank you, thank you.
Jim
Somehow I feel this may not be the answer you are looking for. I'm sure you knew this already and are looking for another answer....
BTW... THE FUEL PUMP WORKS G-R-E-A-T!!!!!!!!!!!!!!!!!!!!!!!
Thank you,thank you, thank you.
Jim
I didn't think the injector constant was used for much more than mileage calc and knowing what the basic flow was- I guess I just assumed that the ECM would use other variables (o2, lv8, etc) to calculate the change in pulsewidth *relative* to the existing maps and such. But I matched it to what the flow of the current injectors are (SVO 24#'s) to the best that I could- so it should be pretty close to accurate for the ECM's calcs- After all, I'm changing the AFR/%change/LV8 and AFR/Change/Coolant Temp tables to adjust enrichment- aren't we accomplishing the same thing via different means?I'll read the link and see if I can't edjumacate myself a little more...
BTW- glad you could use that pump!
Last edited by Ramanstud; Jul 10, 2004 at 11:07 PM.
Pro
Joined: Sep 2001
Posts: 542
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From: Stuck in the 80's
I have mine (FMS 24#) set at 26.25, that is where I get the BLM's just below 128 most of the time. I think it's good to be a little rich to ensure smooth transition at AE. As for the MPG gauge, I think it would be pretty accurate if your BLM's are close to where they shuold be, although I never scanned my car with the stock injectors to see what the factory BLM's were in comparison.
Safety Car
Joined: May 1999
Posts: 3,651
Likes: 5
From: Atlantis
Cruise-In I Veteran
Hey Jesse,
I'm going to take another shot at it.
The Injector Size Constant is sort of the "rough" tuning parameter.
You "rough it in" with the Injector Size and then fine tune from there with the other parameters.
I believe the fuel calcs are allowed to "fall where they may" and there is no specific adjustment to calibrate the fuel calculator portion of the ECM.
I just checked my fuel calculator. The ECM said I was getting 18.9 avg. MPH.
ACTUAL from fuel entered and miles traveled worked out to be 16.1 MPG. That is "town driving".
I don't know of a way to calibrate the fuel/mileage calculator but that doesn't mean there isn't a way.
Go to ThirdGen.Org , the DIY PROM section and ask there.
Or check with tjwong here, he would likely know.
On ThirdGen page Grumpy and check with him.
Hope something here helped.
Regards,
Jim
I'm going to take another shot at it.
The Injector Size Constant is sort of the "rough" tuning parameter.
You "rough it in" with the Injector Size and then fine tune from there with the other parameters.
I believe the fuel calcs are allowed to "fall where they may" and there is no specific adjustment to calibrate the fuel calculator portion of the ECM.
I just checked my fuel calculator. The ECM said I was getting 18.9 avg. MPH.
ACTUAL from fuel entered and miles traveled worked out to be 16.1 MPG. That is "town driving".
I don't know of a way to calibrate the fuel/mileage calculator but that doesn't mean there isn't a way.
Go to ThirdGen.Org , the DIY PROM section and ask there.
Or check with tjwong here, he would likely know.
On ThirdGen page Grumpy and check with him.
Hope something here helped.
Regards,
Jim
