Fuel Pressure questions
08-14-2007, 06:42 PM
#12
3rd Gear Member
Thread Starter
Join Date: Dec 2006
Location: South Texas
Posts: 665
RE: Fuel Pressure questions
ORIGINAL: 5.0rick
What brand is your MAF? 70mm sounds like an OEM cobra MAF.
Rick
What brand is your MAF? 70mm sounds like an OEM cobra MAF.
Rick
08-14-2007, 06:46 PM
#13
4th Gear Member
Join Date: Jun 2006
Location:
Posts: 1,892
RE: Fuel Pressure questions
ORIGINAL: 5.0rick
Hi Texas 5.0,
1st and foremost, let me ask the following:
What MAF are you running?
What EEC-IV are you running?
Are your 24# injectors the FMS blue ones?
Let me start by saying that the stock fuel pressure should work fine if your injectors and MAF are designed to work with each other. You should not have to play with the fuel pressure at all.
If you are having problems, you may not have what you think you have. BTW just in case, the 93 Cobra MAF requires the Cobra computer (X3Z) to work correctly ( It has a different transfer).
On your question regarding the fuel pump size, let's look at the math ( this is a guestimate)
19#/hr injector flows 200cc/minute or 12000cc/hr. There are 1000cc in 1 liter, so you could say 12 liter/hr. That is for 1 injector at 100% duty cycle. Multiply by 8 injectors and you get 96 liters/hr at 100% duty cycle. Now, let take a more realistic duty cycle like 92%. 96 liter/hrX 92%=88.32 liter per hour. So basically, the stock fuel pump will roughly support19# injectors (8 of them) at 92% duty cycle. These numbers are not exact, but you get the idea.
Using the same calculation, the stock fuel pump will support the 24# injectors at 73% duty cycle (which is still an overall flow of 88 liters/hr). 24# injectors flows 252cc/minute.
BTW,with a Brake Specific Fuel Consumption of .5, the 19# injectors and 88 liter per hr fuel pumpsupport around 290HPinstead of the 330HP I mentioned earlier.(the fuel pump being the limiting factor, that is if you wish to push the injector duty cycle past 92%)
Where in Texas are you? I am in Round Rock, just north of Austin.
Regards,
Rick
ORIGINAL: Texas5.0
I am not making more than 330 at the flywheel and I have the correct mass air for 24#'s.
I guess the question I am asking is not as easily answered as I thought. My problem right now is that I am running around 22psi on my new 24 # injectors. I just bought an adjustable fuel pressure regulator and got to thinking about the entire fuel delivery system. I was wondering if the stock fuel pump would have enough pumping ability to get the system up to 42 pounds with the mods that I have and with 24 pound injectors and the new adjustable FPR.
ORIGINAL: 5.0rick
If you are making more than 330 HP@ the flywheel, then you will need to step up from 19# injectors to 24#s. If you move up on your injector size, you will also need a new Mass Air Flow sensor (MAF). Fuel pressure on your stock regulator should be ~47 psi with the vacuum disconnected (that is what my 89 is set to with the stock pressure regulator per my Autometer gauge).
Rick
If you are making more than 330 HP@ the flywheel, then you will need to step up from 19# injectors to 24#s. If you move up on your injector size, you will also need a new Mass Air Flow sensor (MAF). Fuel pressure on your stock regulator should be ~47 psi with the vacuum disconnected (that is what my 89 is set to with the stock pressure regulator per my Autometer gauge).
Rick
I guess the question I am asking is not as easily answered as I thought. My problem right now is that I am running around 22psi on my new 24 # injectors. I just bought an adjustable fuel pressure regulator and got to thinking about the entire fuel delivery system. I was wondering if the stock fuel pump would have enough pumping ability to get the system up to 42 pounds with the mods that I have and with 24 pound injectors and the new adjustable FPR.
1st and foremost, let me ask the following:
What MAF are you running?
What EEC-IV are you running?
Are your 24# injectors the FMS blue ones?
Let me start by saying that the stock fuel pressure should work fine if your injectors and MAF are designed to work with each other. You should not have to play with the fuel pressure at all.
If you are having problems, you may not have what you think you have. BTW just in case, the 93 Cobra MAF requires the Cobra computer (X3Z) to work correctly ( It has a different transfer).
On your question regarding the fuel pump size, let's look at the math ( this is a guestimate)
19#/hr injector flows 200cc/minute or 12000cc/hr. There are 1000cc in 1 liter, so you could say 12 liter/hr. That is for 1 injector at 100% duty cycle. Multiply by 8 injectors and you get 96 liters/hr at 100% duty cycle. Now, let take a more realistic duty cycle like 92%. 96 liter/hrX 92%=88.32 liter per hour. So basically, the stock fuel pump will roughly support19# injectors (8 of them) at 92% duty cycle. These numbers are not exact, but you get the idea.
Using the same calculation, the stock fuel pump will support the 24# injectors at 73% duty cycle (which is still an overall flow of 88 liters/hr). 24# injectors flows 252cc/minute.
BTW,with a Brake Specific Fuel Consumption of .5, the 19# injectors and 88 liter per hr fuel pumpsupport around 290HPinstead of the 330HP I mentioned earlier.(the fuel pump being the limiting factor, that is if you wish to push the injector duty cycle past 92%)
Where in Texas are you? I am in Round Rock, just north of Austin.
Regards,
Rick
you list of mods its all that rough... so u could probably get by with a stock pump... BUT!!!!!!!!!!!.... let e explain this too u i think ull open your mind a little... u are board line rite now... since you pump is not brand new i bet its not running 100% like it used to... so your even ore board line... when your engine goes line everything well start to **** up... ull have to replace a lotta gaskets and u might f*ck up you piston and rings... which is lots of money... oh and you valve and seals dont like running really lean either... so if u do that and u dont caught to problem you looking at seveal hunderds if not a thouasand or so buck worth of problems to fix... or you could but a new pump... and a 255lph which is what i have will support my 500hp easlily.... and guess what it only cost 100 buck shipped and i took me a whole 1.25hrs to pump in( that is with not help and never do a pump be so u might be faster)..... so u make the choice... 100 bucks and 1hr or so of work or 1200 bucks if u get unlucky and **** hits the fan...
im an *** i know... but i just dont want you to **** up your car.... DONT CUT CORNERS!!! my way of thinking is that close is just to close... and true me ull be close... and hell lucky is offering a pump sell on a pump so i dont see why u wouldnt wanna do it... if u were close id would even install if for u...
08-14-2007, 06:54 PM
#14
3rd Gear Member
Thread Starter
Join Date: Dec 2006
Location: South Texas
Posts: 665
RE: Fuel Pressure questions
Hey crazy... I'm not trying to be a ***** but your post takes more time to read than what it is worth. Your spelling and grammar is, well, crazy. People will take what you have to say much more to heart if you give the appearance thatYOU care about what you are writing.
"when your engine goes line everything well start to **** up... ull have to replace a lotta gaskets and u might f*ck up you piston and rings... "
I'm not sure what that means. I think you are trying to tell me that I need to get a larger fuel pump.... Anyway thanks for the help.
"when your engine goes line everything well start to **** up... ull have to replace a lotta gaskets and u might f*ck up you piston and rings... "
I'm not sure what that means. I think you are trying to tell me that I need to get a larger fuel pump.... Anyway thanks for the help.
08-14-2007, 07:10 PM
#15
4th Gear Member
Join Date: Jun 2006
Location:
Posts: 1,892
RE: Fuel Pressure questions
ORIGINAL: Texas5.0
Hey crazy... I'm not trying to be a ***** but your post takes more time to read than what it is worth. Your spelling and grammar is, well, crazy. People will take what you have to say much more to heart if you give the appearance thatYOU care about what you are writing.
"when your engine goes line everything well start to **** up... ull have to replace a lotta gaskets and u might f*ck up you piston and rings... "
I'm not sure what that means. I think you are trying to tell me that I need to get a larger fuel pump.... Anyway thanks for the help.
Hey crazy... I'm not trying to be a ***** but your post takes more time to read than what it is worth. Your spelling and grammar is, well, crazy. People will take what you have to say much more to heart if you give the appearance thatYOU care about what you are writing.
"when your engine goes line everything well start to **** up... ull have to replace a lotta gaskets and u might f*ck up you piston and rings... "
I'm not sure what that means. I think you are trying to tell me that I need to get a larger fuel pump.... Anyway thanks for the help.
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