Help a brother out
Thread Starter
Burning Brakes
Joined: Oct 2001
Posts: 1,033
Likes: 0
From: Tracy California
St. Jude Donor '05
Help a brother out
Ok, here's the story I'm trying to get my engine tune dialed in and I'm all out of ideals. I'm hoping one of you guys more familiar with this type of stuff might see something and/or possibly have a susgestion.
My AFR curve is wierd! You can see it here. The fuel pump was upgraded prior to this pull with a 500HP Bosch unit. Here's a Diacom trace of the pull.
So far all I know is that the curve follows the pulse width changes. Could that mean my pump is still to small? The injectors are FMS 24# units. Are the injectors too small?
What would be some examples of the pulse widths in the lower RPM range for a NA 383?
Thanks for taking a look.
KM
My AFR curve is wierd! You can see it here. The fuel pump was upgraded prior to this pull with a 500HP Bosch unit. Here's a Diacom trace of the pull.
So far all I know is that the curve follows the pulse width changes. Could that mean my pump is still to small? The injectors are FMS 24# units. Are the injectors too small?
What would be some examples of the pulse widths in the lower RPM range for a NA 383?
Thanks for taking a look.
KM
Instructor
Joined: Oct 2000
Posts: 152
Likes: 0
From: des plaines, il
Re: Help a brother out (88-406)
Um, I don't really understand your question - but looking at the AFR curve you posted, your ECM needs to be reprogrammed to straighten out the fuel curve. Not sure what that has to do with the pump.
Melting Slicks
Joined: Apr 2001
Posts: 2,099
Likes: 218
From: Ca.
Re: Help a brother out (88-406)
Lower rpm/higher tq and the pulse widths will be higher....however at 6000rpm your pulse width is 100+%! You need to look at the higher rpm-as there isn't as much time for the inj. to pulse. OK, found it! The formula is (inj. pulse widthXrpm)divided by 600=inj. duty cycle. The easiest to look at is 6000rpm. 10ms is 100%; 8ms is 80%, etc.
You need bigger injectors...
You're maxing out the maf at about 5000rpm-no biggie-but you do need to program the PE % change to f/a ratio vs rpm; as stated above....that will adjust the f/a ratio at wot. Oh yea-you weren't closed loop at idle...do you have long tube headers without heated O2 sensors?
Otherwise no knock which is good!
Also what is your fuel press. set at? The fms 24# usually can keep up given enough press.
You need bigger injectors...
You're maxing out the maf at about 5000rpm-no biggie-but you do need to program the PE % change to f/a ratio vs rpm; as stated above....that will adjust the f/a ratio at wot. Oh yea-you weren't closed loop at idle...do you have long tube headers without heated O2 sensors?
Otherwise no knock which is good!
Also what is your fuel press. set at? The fms 24# usually can keep up given enough press.
Thread Starter
Burning Brakes
Joined: Oct 2001
Posts: 1,033
Likes: 0
From: Tracy California
St. Jude Donor '05
Re: Help a brother out (drive it)
Drive it
Thanks for the reply. My fuel pressure is 45ish, and yes I have long tube headers and an unheated o2. From looking at the data, it just seems like it wants alot more fuel.
Maybe I should be looking for bigger injectors! I wonder how others seem to be able to get away with the 24's?.
KM
Thanks for the reply. My fuel pressure is 45ish, and yes I have long tube headers and an unheated o2. From looking at the data, it just seems like it wants alot more fuel.
Maybe I should be looking for bigger injectors! I wonder how others seem to be able to get away with the 24's?.
KM
Melting Slicks
Joined: Apr 2001
Posts: 2,099
Likes: 218
From: Ca.
Re: Help a brother out (88-406)
First get some heated O2 sensors. Then see where your blms are when closed loop. You really need to tune to blms 128 +/_ 4 to 6 before you try to tune wot, as it bases part of it's calc's off the closed loop #'s.
Then, yes-you may need bigger inj.
More power =more fuel needed! :) Again, that needs to be tuned in the prom......
[Modified by drive it, 12:56 AM 11/8/2002]
Then, yes-you may need bigger inj.
More power =more fuel needed! :) Again, that needs to be tuned in the prom......
[Modified by drive it, 12:56 AM 11/8/2002]
