Fuel Pressure: Up, Up and Away!
Oct 25, 2005 | 11:04 PM
#21
Originally Posted by vanillagorilla
Yeah, pulse width is pulse width. I've already established I'm at a 100% duty cycle. I just had no idea we were privelaged enough to have boost referenced fpr's. It makes sense why the pressure rises. I thought my fp was rising because of the restriction the injectors were producing. I can sleep now. However my fp will drop though with a stock pump with bigger injectors and more boost. Or will it?
Parish I see what your saying makes sense. Maybe a better question would be how much injector can the stock pump support?
Last edited by 02sierraz71_5.3; Oct 25, 2005 at 11:14 PM.
Oct 25, 2005 | 11:14 PM
#22
i think if you take the 42's up to 100% you will run the stock pump out of fuel. if anyone is going to upgrade injectors i wouldn't go with anything less than the 42's. its a good injector that plugs right in. a fuel pump upgrade is prety cheap. if you think you will be going over 400rwhp it is best to just do it.
Oct 25, 2005 | 11:18 PM
#23
I just say its 100% b/c anything after that is trivial, as you can't hold an injector open over 100% of the time.
Parish, you're saying that as long as the fuel pump can flow it, my pressure will rise with the boost? So is it safe to say that as long as the fp is rising with the boost, I won't lean out? That doesn't make too much sense, because the pumps ability to flow drops as pressure goes up. Does anyone now the the flow rates (free flow and flow at a given pressure) of the stock pump? I'm curious to see how far this pump will take me.
Parish, you're saying that as long as the fuel pump can flow it, my pressure will rise with the boost? So is it safe to say that as long as the fp is rising with the boost, I won't lean out? That doesn't make too much sense, because the pumps ability to flow drops as pressure goes up. Does anyone now the the flow rates (free flow and flow at a given pressure) of the stock pump? I'm curious to see how far this pump will take me.
Oct 25, 2005 | 11:26 PM
#24
the stock pump will take you to 400rwhp. maybe ~425 with nitrous and maybe 450na. that question has been answered.
the max flow potential of the pump will go down as the presure goes up. what that sugests to me is the more boost you have to run the less peak hp the pump will support. doesn't really matter though. if you think you are going to go over 400rwhp then get a gauge and watch it or just get a pump.
the max flow potential of the pump will go down as the presure goes up. what that sugests to me is the more boost you have to run the less peak hp the pump will support. doesn't really matter though. if you think you are going to go over 400rwhp then get a gauge and watch it or just get a pump.
Oct 25, 2005 | 11:31 PM
#25
Originally Posted by vanillagorilla
I just say its 100% b/c anything after that is trivial, as you can't hold an injector open over 100% of the time.
you just hit the nail on the head! I have been saying this forever!
100% is still 100% no matter how you slice it!
Oct 26, 2005 | 08:21 AM
#26
[QUOTE=vanillagorilla]I just say its 100% b/c anything after that is trivial, as you can't hold an injector open over 100% of the time.
QUOTE]
thats the thing duty cycle is a measure of time and an injector if operating will always be opening and closing the longer its open the more heat and the quicker you are to burning it up. 100% DC doesnt mean its open all the time or it is neccisarily at its max I called Delphi when I upgraded mine and they went into depth on this and actually what the stock injectors will flow, I was told they rate them very conservatively so when they say 25lb/hr @ 4bar (stock 5.3) its actually only around %70 of thier maximum actuall flow(not duty cycle).
Duty cycle is a measure or standard it is not imperical, nor does it relate to actual flow
QUOTE]
thats the thing duty cycle is a measure of time and an injector if operating will always be opening and closing the longer its open the more heat and the quicker you are to burning it up. 100% DC doesnt mean its open all the time or it is neccisarily at its max I called Delphi when I upgraded mine and they went into depth on this and actually what the stock injectors will flow, I was told they rate them very conservatively so when they say 25lb/hr @ 4bar (stock 5.3) its actually only around %70 of thier maximum actuall flow(not duty cycle).
Duty cycle is a measure or standard it is not imperical, nor does it relate to actual flow
Oct 26, 2005 | 04:23 PM
#27
[QUOTE=02sierraz71_5.3]
what the heck did you just say? 
an injectors flow rating is given with the injector at 100%. they slam it open and see how much it flows.
no one really talks about over heating an injector, i have seen it mentioned before but injectors are just soo reliable that it doesn't seem to be an issue.
there has been questions on how well an injector flows in the 85-100% range, some say there may be a prestatic flutter when the injector flow actualy drops. they say this happens somewhere in the 85-100% range. in the real world people run their injectors up to 100% often and dont seem to have any problems.
duty cycle is an exact number. it is caculted from time open/time avaliable to be open. at 6000rpm there is only 20ms between cycles so if the injector gets to 20ms it will be at 100%.
Originally Posted by vanillagorilla
I just say its 100% b/c anything after that is trivial, as you can't hold an injector open over 100% of the time.
QUOTE]
thats the thing duty cycle is a measure of time and an injector if operating will always be opening and closing the longer its open the more heat and the quicker you are to burning it up. 100% DC doesnt mean its open all the time or it is neccisarily at its max I called Delphi when I upgraded mine and they went into depth on this and actually what the stock injectors will flow, I was told they rate them very conservatively so when they say 25lb/hr @ 4bar (stock 5.3) its actually only around %70 of thier maximum actuall flow(not duty cycle).
Duty cycle is a measure or standard it is not imperical, nor does it relate to actual flow
QUOTE]
thats the thing duty cycle is a measure of time and an injector if operating will always be opening and closing the longer its open the more heat and the quicker you are to burning it up. 100% DC doesnt mean its open all the time or it is neccisarily at its max I called Delphi when I upgraded mine and they went into depth on this and actually what the stock injectors will flow, I was told they rate them very conservatively so when they say 25lb/hr @ 4bar (stock 5.3) its actually only around %70 of thier maximum actuall flow(not duty cycle).
Duty cycle is a measure or standard it is not imperical, nor does it relate to actual flow
an injectors flow rating is given with the injector at 100%. they slam it open and see how much it flows.
no one really talks about over heating an injector, i have seen it mentioned before but injectors are just soo reliable that it doesn't seem to be an issue.
there has been questions on how well an injector flows in the 85-100% range, some say there may be a prestatic flutter when the injector flow actualy drops. they say this happens somewhere in the 85-100% range. in the real world people run their injectors up to 100% often and dont seem to have any problems.
duty cycle is an exact number. it is caculted from time open/time avaliable to be open. at 6000rpm there is only 20ms between cycles so if the injector gets to 20ms it will be at 100%.
Oct 26, 2005 | 04:59 PM
#28
[QUOTE=parish8]
what the heck did you just say?
an injectors flow rating is given with the injector at 100%. they slam it open and see how much it flows.
no one really talks about over heating an injector, i have seen it mentioned before but injectors are just soo reliable that it doesn't seem to be an issue.
there has been questions on how well an injector flows in the 85-100% range, some say there may be a prestatic flutter when the injector flow actualy drops. they say this happens somewhere in the 85-100% range. in the real world people run their injectors up to 100% often and dont seem to have any problems.
duty cycle is an exact number. it is caculted from time open/time avaliable to be open. at 6000rpm there is only 20ms between cycles so if the injector gets to 20ms it will be at 100%.
Im talking about injector duty cycle take a look at the chart I posted by red hard supra. The way I understand it from Delphi is that the flow rating is conservative the injectors can actually flow well over thier rating they do this because the less time it is open the less heat is built up. The longer the injector is open(more duty cycle) the more heat, less reliable and greater likely hood of failing. An injected engine wouldnt run right with a constant stream of gas hence there is no such thing as an injector operating at its maximum flow it would then overheat and be broken, it has to have a cool down time this is where duty cycle comes into play. I think people get confused and think duty cycle is an absolute number and its not 100% duty cycle on my 31 lbers is refereing to how long they are open not the amount of fuel they are flowing. So if the engine is calling for more fuel the duty cycle can go over 100% meaning the injector is having to stay open alot longer than what is optimum for good performance to supply the right amount of fuel.
This is why gorilla is getting away with the stock injectors and he isnt having fueling problems!!!!
He is degrading the life expectancy of the injectors though as they are probably getting very hot this is why I have asked for the wot pulse width and the rpm range. So we can figure out exactly how far out of the optimum range he is and generally how long the injectors will last before he burns one up and had no fueling what so ever. Hopefully he wont melt one on a wot run and blow a hole in the piston from lots of boost and no fuel.
I talked to chuck at delphi for a couple of hours the guy gave me more info than I can understand nor would I want to know. If anyone has anymore questions Id call the 800 number and ask for him he will talk your ear off
Originally Posted by 02sierraz71_5.3
what the heck did you just say?
an injectors flow rating is given with the injector at 100%. they slam it open and see how much it flows.
no one really talks about over heating an injector, i have seen it mentioned before but injectors are just soo reliable that it doesn't seem to be an issue.
there has been questions on how well an injector flows in the 85-100% range, some say there may be a prestatic flutter when the injector flow actualy drops. they say this happens somewhere in the 85-100% range. in the real world people run their injectors up to 100% often and dont seem to have any problems.
duty cycle is an exact number. it is caculted from time open/time avaliable to be open. at 6000rpm there is only 20ms between cycles so if the injector gets to 20ms it will be at 100%.
Im talking about injector duty cycle take a look at the chart I posted by red hard supra. The way I understand it from Delphi is that the flow rating is conservative the injectors can actually flow well over thier rating they do this because the less time it is open the less heat is built up. The longer the injector is open(more duty cycle) the more heat, less reliable and greater likely hood of failing. An injected engine wouldnt run right with a constant stream of gas hence there is no such thing as an injector operating at its maximum flow it would then overheat and be broken, it has to have a cool down time this is where duty cycle comes into play. I think people get confused and think duty cycle is an absolute number and its not 100% duty cycle on my 31 lbers is refereing to how long they are open not the amount of fuel they are flowing. So if the engine is calling for more fuel the duty cycle can go over 100% meaning the injector is having to stay open alot longer than what is optimum for good performance to supply the right amount of fuel.
This is why gorilla is getting away with the stock injectors and he isnt having fueling problems!!!!
He is degrading the life expectancy of the injectors though as they are probably getting very hot this is why I have asked for the wot pulse width and the rpm range. So we can figure out exactly how far out of the optimum range he is and generally how long the injectors will last before he burns one up and had no fueling what so ever. Hopefully he wont melt one on a wot run and blow a hole in the piston from lots of boost and no fuel.
I talked to chuck at delphi for a couple of hours the guy gave me more info than I can understand nor would I want to know. If anyone has anymore questions Id call the 800 number and ask for him he will talk your ear off
Last edited by 02sierraz71_5.3; Oct 26, 2005 at 05:06 PM.
Oct 26, 2005 | 11:21 PM
#29
[QUOTE=02sierraz71_5.3]
Im talking about injector duty cycle take a look at the chart I posted by red hard supra. The way I understand it from Delphi is that the flow rating is conservative the injectors can actually flow well over thier rating they do this because the less time it is open the less heat is built up. The longer the injector is open(more duty cycle) the more heat, less reliable and greater likely hood of failing. An injected engine wouldnt run right with a constant stream of gas hence there is no such thing as an injector operating at its maximum flow it would then overheat and be broken, it has to have a cool down time this is where duty cycle comes into play. I think people get confused and think duty cycle is an absolute number and its not 100% duty cycle on my 31 lbers is refereing to how long they are open not the amount of fuel they are flowing. So if the engine is calling for more fuel the duty cycle can go over 100% meaning the injector is having to stay open alot longer than what is optimum for good performance to supply the right amount of fuel.
This is why gorilla is getting away with the stock injectors and he isnt having fueling problems!!!!
He is degrading the life expectancy of the injectors though as they are probably getting very hot this is why I have asked for the wot pulse width and the rpm range. So we can figure out exactly how far out of the optimum range he is and generally how long the injectors will last before he burns one up and had no fueling what so ever. Hopefully he wont melt one on a wot run and blow a hole in the piston from lots of boost and no fuel.
I talked to chuck at delphi for a couple of hours the guy gave me more info than I can understand nor would I want to know. If anyone has anymore questions Id call the 800 number and ask for him he will talk your ear off
whoa!!!! not sure who this chuck guy is but he needs to go back to school.
let me say again. the injectors are rated at wide open(100%duty cycle).
if you see 100% duty cycle on your logger then the injector is wide open, that is known as "static". static means the pintle or disk or whatever is in there in no longer moving. it is just held open. some say going static is bad for the injector but most say it doesn't hury anything. once you are at 100% duty cycle there is no more fuel to be had from those injectors. they can not give any more than 100%.
at 6000rpm there is 20ms thru 2revolutions. 2 revolutions is how far the motor turns before the cycle starts over. if the computer asks for 22ms of pulse width then it will be asking for a longer pulse width then there is time for. that is when the duty cycle can show over 100%. in reality there is only 20ms(at 6000rpm) for the injector to be open so going 22ms or over 100% duty cycle isn't posiable.
i used to have some great links on fuel systems and how they work but i seem to have lost them. i will try and find them.
Originally Posted by parish8
Im talking about injector duty cycle take a look at the chart I posted by red hard supra. The way I understand it from Delphi is that the flow rating is conservative the injectors can actually flow well over thier rating they do this because the less time it is open the less heat is built up. The longer the injector is open(more duty cycle) the more heat, less reliable and greater likely hood of failing. An injected engine wouldnt run right with a constant stream of gas hence there is no such thing as an injector operating at its maximum flow it would then overheat and be broken, it has to have a cool down time this is where duty cycle comes into play. I think people get confused and think duty cycle is an absolute number and its not 100% duty cycle on my 31 lbers is refereing to how long they are open not the amount of fuel they are flowing. So if the engine is calling for more fuel the duty cycle can go over 100% meaning the injector is having to stay open alot longer than what is optimum for good performance to supply the right amount of fuel.
This is why gorilla is getting away with the stock injectors and he isnt having fueling problems!!!!
He is degrading the life expectancy of the injectors though as they are probably getting very hot this is why I have asked for the wot pulse width and the rpm range. So we can figure out exactly how far out of the optimum range he is and generally how long the injectors will last before he burns one up and had no fueling what so ever. Hopefully he wont melt one on a wot run and blow a hole in the piston from lots of boost and no fuel.
I talked to chuck at delphi for a couple of hours the guy gave me more info than I can understand nor would I want to know. If anyone has anymore questions Id call the 800 number and ask for him he will talk your ear off
whoa!!!! not sure who this chuck guy is but he needs to go back to school.
let me say again. the injectors are rated at wide open(100%duty cycle).
if you see 100% duty cycle on your logger then the injector is wide open, that is known as "static". static means the pintle or disk or whatever is in there in no longer moving. it is just held open. some say going static is bad for the injector but most say it doesn't hury anything. once you are at 100% duty cycle there is no more fuel to be had from those injectors. they can not give any more than 100%.
at 6000rpm there is 20ms thru 2revolutions. 2 revolutions is how far the motor turns before the cycle starts over. if the computer asks for 22ms of pulse width then it will be asking for a longer pulse width then there is time for. that is when the duty cycle can show over 100%. in reality there is only 20ms(at 6000rpm) for the injector to be open so going 22ms or over 100% duty cycle isn't posiable.
i used to have some great links on fuel systems and how they work but i seem to have lost them. i will try and find them.
Oct 26, 2005 | 11:24 PM
#30
14 Second Truck Club
Joined: Aug 2003
Posts: 3,775
Likes: 0
From: Tucson, AZ
Originally Posted by vanillagorilla
Ok, that's about what I see at 6psi. I feel better now. Time for an upgraded fuel system. 
Bring on the boost and broken trannys.
Bring on the boost and broken trannys. 
