You're not going to be able to make the corrections with just fuel pressure. You need a new tune to run the larger injectors.
Bigger injectors runs flat
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 857
Likes: 1
From: Morrisonville Illinios
Bigger injectors runs flat
We have finaly gotten around to putting 30# ford SOV injectors in to replace the 24# and bolted on the custom siemes runners. Now it will idel and start but as you drive down the road it falls flat(punch it)!! The heads are 113 castings that have been worked over bigger valves, springs and machined out along with intake, it has a 58MM TB and long tube headers witn 3" exhaust no air, egr or cats and comp cam and custom ECM by PCM(Alvin) The fuel pressure was setting around 47psi with the older injectors and it had a bunch of torque and would downshift almost immediately and try to spin the tires when you would pass
. BUT Now with the bigger injectors it will fall flat and not downshift
. I have set the fuel pressure back down to 40psi and it still falls off and it is starting to downshift some but falls off. ??? put the older injectors(24#) and see what happens or set the fuel pressure a little lower?
Trying to get it runnig welll for FUNFEST!
Any and all ideals would be appreciated. WRO87
. BUT Now with the bigger injectors it will fall flat and not downshift . I have set the fuel pressure back down to 40psi and it still falls off and it is starting to downshift some but falls off. ??? put the older injectors(24#) and see what happens or set the fuel pressure a little lower?Trying to get it runnig welll for FUNFEST!
Any and all ideals would be appreciated. WRO87
Team Owner
Joined: Jan 2003
Posts: 20,324
Likes: 250
From: Summerland B.C. Canada
Your going to need Alvin to redo your tune. 
I'll bet it's pig rich under WOT and the ECM is having fun trying to correct the BLM's during closed loop.
Take tequilaboy's advice and crank the pressure down. Short term help till you get a new prom.
I'll bet it's pig rich under WOT and the ECM is having fun trying to correct the BLM's during closed loop.
Take tequilaboy's advice and crank the pressure down. Short term help till you get a new prom.
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 857
Likes: 1
From: Morrisonville Illinios
OK GANG THANKS!!!
. I had set the pressure down some but NOT ENOUGH! Now setting at 29# and it will get up and run and bark the tires when it upshifts. 86 you are right about rich
. It is a lot better now. Taking it in to have muffler eliminators put on then trying to get set up with the tuner so he can dial it in on the DYNO. If you guys are at the FUNFEST
Saturday look me up in the FORUM lot and the adult beverage will be on me for the assist.
87' vert black and camel interior with gold bbs wheels.
WRO87'
. I had set the pressure down some but NOT ENOUGH! Now setting at 29# and it will get up and run and bark the tires when it upshifts. 86 you are right about rich . It is a lot better now. Taking it in to have muffler eliminators put on then trying to get set up with the tuner so he can dial it in on the DYNO. If you guys are at the FUNFEST Saturday look me up in the FORUM lot and the adult beverage will be on me for the assist.87' vert black and camel interior with gold bbs wheels.
WRO87'
Melting Slicks
Joined: May 2007
Posts: 2,382
Likes: 2
From: Kathleen FL
There is a direct correlation to how much fuel pressure you can run vs. the injectors you have. You can take the stock value of the factory 22# injectors and multiply it with a stock fuel pressure of 40 psi. So the product between them is 880. For reasons of being flamed, I would think that it is accurate to a point so don't go trying to run 88 lb injectors with only 10 psi of fuel pressure and vice versa!
The coefficient I am talking about is 880. To use it, simply divide this number by the size injectors you currently have, assuming they are rated at 40 psi.
As demonstrated in post #5, one theoretically should be able to run 30 lb injectors with roughly a fuel pressure of 29.3 psi without making any changes to the injector flow constant in the ECM. Seems totally legitimate as long as either value isn't to extreme.
The coefficient I am talking about is 880. To use it, simply divide this number by the size injectors you currently have, assuming they are rated at 40 psi.
As demonstrated in post #5, one theoretically should be able to run 30 lb injectors with roughly a fuel pressure of 29.3 psi without making any changes to the injector flow constant in the ECM. Seems totally legitimate as long as either value isn't to extreme.
Pro
Joined: Jun 2007
Posts: 626
Likes: 2
From: Coquitlam British Columbia
This is interesting...have a 90 Vert...24lb Accels and AFPR are coming in from Summit(Multecs are on their last legs) and my stock pressure on the rail is 45 psi at present. In using the above theory; my pressure should be 41.25 lbs...at least I have a starting point now to play with pressure once installed.
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Melting Slicks
Joined: Jan 2002
Posts: 2,238
Likes: 4
From: Milan
We have finaly gotten around to putting 30# ford SOV injectors in to replace the 24# and bolted on the custom siemes runners. Now it will idel and start but as you drive down the road it falls flat(punch it)!! The heads are 113 castings that have been worked over bigger valves, springs and machined out along with intake, it has a 58MM TB and long tube headers witn 3" exhaust no air, egr or cats and comp cam and custom ECM by PCM(Alvin) The fuel pressure was setting around 47psi with the older injectors and it had a bunch of torque and would downshift almost immediately and try to spin the tires when you would pass . BUT Now with the bigger injectors it will fall flat and not downshift . I have set the fuel pressure back down to 40psi and it still falls off and it is starting to downshift some but falls off. ??? put the older injectors(24#) and see what happens or set the fuel pressure a little lower?
Trying to get it runnig welll for FUNFEST!
Any and all ideals would be appreciated. WRO87
. BUT Now with the bigger injectors it will fall flat and not downshift . I have set the fuel pressure back down to 40psi and it still falls off and it is starting to downshift some but falls off. ??? put the older injectors(24#) and see what happens or set the fuel pressure a little lower?Trying to get it runnig welll for FUNFEST!
Any and all ideals would be appreciated. WRO87
-Beppe-
P.S. Burning a new chip with the correct injector size will cure the problem, even with the same 47 psi pressure.
Waiting for the new chip, the Tequila advice is right
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 857
Likes: 1
From: Morrisonville Illinios
Ok Gang Here Goes! We had it on the dyno last week finally and the A/F was pretty close on the money if anything a lean. We had this intake made up to get more air in since we where thinking that with more air more fuel? Well we already had the fuel pressure up to 48# with the 24# injectors with the older style runners and we reasoned that since we where increasing the air in we might need a little bigger injectors (bought them cheap for a matched set that had just been done). Well like a lot of things changed too much at once put the bigger runners on and the 30# injectors, it would start but you knew it was rich, driving it it was like hitting the wall it would fall flat and not even try to downshift/upshift just go along so we started to set the pressure down but not enough. (Guess I should have gone back and read the TPI book again)All we where trying to do is to get it to run so we could take to the shop for muffler replacement(eliminators) and then back to the dyno for a retune. When we get the tune done will post the results since we have the one from earlier for comparison but with the SOP we can feel it (should have seen my sons grin).
Well we will be at FUNFEST Since it less than an hour away and maybe we can hook up with some of you so we can talk shop.
wro87
Well we will be at FUNFEST
Since it less than an hour away and maybe we can hook up with some of you so we can talk shop.wro87
