figuring out turbo fuel requirements ***long***
Nov 4, 2004, 12:45 AM
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figuring out turbo fuel requirements ***long***
***Super Long Post***
so i'm going through turbo threads and reading about how you need a fuel pump and a fpr/fmu/injectors/etc. people just recommend "xxx"cc injectors or "xxx":1 fmu discs/springs/whatever. i'm sure most are just copying other turbo kits out there. i'm thinking it's a smart thing to do since you're copying something that's proven. but when people are piecing parts together for a custom kit, i'm sometimes left with a feeling that n00bs are just gonna go out and buy this stuff and figure it's gonna workout somehow when it possibly just might not. it's not like they're not gonna get this stuff installed without someone experienced(damn, i hope not) but i personally hate carrying a lot of stuff that i don't know what they do specifically. so here's my take on fuel related parts. a lot of stuff may be wrong, but i'd rather have a discussion on the boards and have some record of information about these things here. kinda makes things "convenient" for people in the future.
FMU == Fuel Management Unit
this is a turbo specific part. it's "boost sensitive." the FMU senses boost by "T-ing" into a vacuum line between the intake manifold and fuel pressure regulator. when the FMU senses boost in the intake manifold, its pinches the fuel return line to build pressure in the fuel rail/system and therefore forcing more fuel delivery through the injectors. some of these units are adjustable through different means and deliver fuel proportionate to boost pressure. say for instance a FMU has a 12:1 setting. this means that it will raise fuel pressure 12 psi for every 1 psi of boost it senses. furthermore, if you were boosting 7 psi, this would mean that the FMU has raised fuel pressure 84 psi. thats around a potential 122psi at the fuel rail while at 7psi.
FPR == Fuel Pressure Regulator
in stock form it is not boost sensitive. lancers run a stock idle fuel pressure of 38psi and it rises, according to vacuum, to maybe around 47psi. might be a bit more as i haven't had a stock fpr in a long time. the fpr is attached to the manifold through a vacuum hose. sensing through the vacuum hose, the fpr has a diaphram that regulates fuel delivery according to vacuum. it accomplishes this in the same way as the FMU, except a FPR is "vacuum sensitive."
Adjustable Fuel Pressure Regulator
STATIC - a static adjustable FPR can have it's idle pressure adjusted higher or lower. the proportion at which fuel delivery increases over vacuum is the same as a stock fpr. say a stock fpr has idle fuel pressure at 38 psi and has peak fuel pressure(at peak torque? discussable) at 47 psi. the difference is 9 psi. so say you have an adjustable FPR and set it's idle fuel pressure to 44 psi. this would mean it's peak fuel pressure will be 53 psi(@0psi vacuum).
RISING RATE - a rising rate FPR works the same as a static adjustable FPR except that the proportion of fuel delivered under vacuum has increased. if a rising rate adjustable FPR has a rate of 1.7:1, it will deliver 1.7 psi fuel for every 1 psi of vacuum. so say you set a rising rate fpr to an idle fuel pressure of 38 psi (as in the last example). this would mean it's peak fuel pressure would be 53.3 psi([1.7*9] + 38 = 53.3) instead of 47 psi. these units also claim that they react faster than stock FPR's.
RISING RATE & BOOST SENSITIVE - some adjustable FPR's are both rising rate and boost sensitive. it will deliver fuel under vacuum at 1.7:1, but under boost will deliver 1 psi fuel for every 1 psi of boost(1:1). some units can also adjust the fuel delivery ratio higher. if using this for the purpose of upgrading your ride with a turbo, you will also need injectors as a 1:1 rate under boost will probably not be adequate fuel for the added amount of air. a type of fuel control will also be needed.
Injectors
just go to http://www.rceng.com/technical.htm for equations on finding the maximum horsepower ratings for an injector size. if you've got questions, ask them in this thread.
---How to use all this--- (or at least I think)
-i'm going to use the Fuel Injector Worksheet on rceng.com to work all this out-
Desired Horsepower
so now we wanna shoot for a basic 200whp using a turbo. first, we're gonna want to convert this 200whp to crank hp. i use 15% as drivetrain loss(personal preference), i multiply 200 * 1.15 . that comes to 230 crank hp. we enter that to box one asking for desired horsepower.
Injectors
of course, we're going to use 4 injectors. so put that in the next box. i don't know how this works if you're going to be adding injectors to the fuel system as i believe some of the '04 lancers might use that as an option.
Brake Specific Fuel Consumption
there's another java app below the first one for finding this. just put in basic lancer info in there and you get a BSFC of (.53). you can convert injector cc ->> lbs/min by dividing injector size by (10.5). our stock injectors are 240cc. system fuel pressure is 38psi and our injectors don't see over 75% duty cycle for this particular app.
Maximum Injector Duty Cycle
for max injector duty cycle, put 80%.
System Fuel Pressure. This is where it's kinda tricky.
if you're using:
stock FPR with FMU - take how much boost you're going to run and multiply it by the FMU ratio. then add 47 psi. enter this into the fuel system pressure box.
Static/Rising Rate FPR with FMU - take how much boost you're going to run and multiply it by the FMU ratio. then add the base PSI(@0psi vacuum) you have set the FPR at. enter this into the fuel system pressure box.
Boost sensitive Static/Rising Rate FPR - take the amount of boost you're going to run and add that to the the base PSI(@0psi vacuum) you have set the FPR at. enter this into the fuel system pressure box.
stock fpr - enter 47 into the fuel system pressure box.
Tadaaaa!!!
So now you can press the "Press to Calculate Static Flow" button and the worksheet will tell you how big of injectors you will need to run to achieve the desired crank horsepower. Tadaa!!!
Other Notes:
Fuel Pumps
upgrading fuel pumps will be a necessity. usually just grabbing a 255 walbro is the thing to do since your FPR will regulate fuel at the rail. if you're pushing more power than an evo (the very few and probably proud) you're gonna wanna know how much the pump is actually flowing at different fuel system pressures. here's Road///Race Engineering's Fuel Pump Flow Rates Info. You have to make sure that if you set the base fuel pressure high, that with the added pressure, your pump will have sufficient output to supply your injectors.
Air Fuel Controller and the standalone Engine Management System
for stock cams and relatively low boost, an AFC will suffice. stock ignition timing maps were made specifically for the characteristics of the stock cam. under low boost, torque curves won't be affected enough to have to retard timing. when you start upping the boost and you start getting knock no matter how rich you make that particular part of the RPM range, you've reached the limits of the stock maps.
once boost is high enough to create knock on stock maps, you can trade the AFC in for a standalone EMS. now that ignition timing is adjustable, you can adjust it to suit your new torque curve appropriately. this can also result in being able to raise your Air/Fuel ratio leaner in conjunction with adjusting ignition timing to extract more power. if you've come this far, i hope you'd have had learned quite a deal about tuning your baby, or you've got the money to get your baby tuned professionally.
Measuring Fuel Pressure at the Rail @0psi Vacuum
this is measured by hooking up your fuel rail to a fuel pressure gauge and unhooking the vacuum line to the (a)fpr and plugging the intake manifold end with your finger. then take the reading from the gauge. this reading 'unhooked' will be higher as there is no vacuum pressure from the intake manifold to reduce fuel pressure at the fpr. the reading will be 0psi vacuum since that port is now open to the atmosphere. altitude may change readings due to lower atmospheric pressure.
--- --- ---
so that's it from me in a nutshell. this is pretty much an amalgamation of the things i've picked up since i joined here in '02. do i have a turbo lancer? nope. but my two friends/housemates (they're brothers) have an evo and a 2G eclipse GSX so it's not like i haven't worked on a turbo car before. i've also taken a class on turbochargers and fuel injection systems, as well as supporting automotive classes, so it's not like i'm not educated in this field. i'm not stating this to somehow say i'm absolutely right or anything like that. just to say that i'm not a complete n00b. i've probably written some details that are pretty sketchy, too.
mmmmmmm. craving chicken and waffles... lates...
so i'm going through turbo threads and reading about how you need a fuel pump and a fpr/fmu/injectors/etc. people just recommend "xxx"cc injectors or "xxx":1 fmu discs/springs/whatever. i'm sure most are just copying other turbo kits out there. i'm thinking it's a smart thing to do since you're copying something that's proven. but when people are piecing parts together for a custom kit, i'm sometimes left with a feeling that n00bs are just gonna go out and buy this stuff and figure it's gonna workout somehow when it possibly just might not. it's not like they're not gonna get this stuff installed without someone experienced(damn, i hope not) but i personally hate carrying a lot of stuff that i don't know what they do specifically. so here's my take on fuel related parts. a lot of stuff may be wrong, but i'd rather have a discussion on the boards and have some record of information about these things here. kinda makes things "convenient" for people in the future.
FMU == Fuel Management Unit
this is a turbo specific part. it's "boost sensitive." the FMU senses boost by "T-ing" into a vacuum line between the intake manifold and fuel pressure regulator. when the FMU senses boost in the intake manifold, its pinches the fuel return line to build pressure in the fuel rail/system and therefore forcing more fuel delivery through the injectors. some of these units are adjustable through different means and deliver fuel proportionate to boost pressure. say for instance a FMU has a 12:1 setting. this means that it will raise fuel pressure 12 psi for every 1 psi of boost it senses. furthermore, if you were boosting 7 psi, this would mean that the FMU has raised fuel pressure 84 psi. thats around a potential 122psi at the fuel rail while at 7psi.
FPR == Fuel Pressure Regulator
in stock form it is not boost sensitive. lancers run a stock idle fuel pressure of 38psi and it rises, according to vacuum, to maybe around 47psi. might be a bit more as i haven't had a stock fpr in a long time. the fpr is attached to the manifold through a vacuum hose. sensing through the vacuum hose, the fpr has a diaphram that regulates fuel delivery according to vacuum. it accomplishes this in the same way as the FMU, except a FPR is "vacuum sensitive."
Adjustable Fuel Pressure Regulator
STATIC - a static adjustable FPR can have it's idle pressure adjusted higher or lower. the proportion at which fuel delivery increases over vacuum is the same as a stock fpr. say a stock fpr has idle fuel pressure at 38 psi and has peak fuel pressure(at peak torque? discussable) at 47 psi. the difference is 9 psi. so say you have an adjustable FPR and set it's idle fuel pressure to 44 psi. this would mean it's peak fuel pressure will be 53 psi(@0psi vacuum).
RISING RATE - a rising rate FPR works the same as a static adjustable FPR except that the proportion of fuel delivered under vacuum has increased. if a rising rate adjustable FPR has a rate of 1.7:1, it will deliver 1.7 psi fuel for every 1 psi of vacuum. so say you set a rising rate fpr to an idle fuel pressure of 38 psi (as in the last example). this would mean it's peak fuel pressure would be 53.3 psi([1.7*9] + 38 = 53.3) instead of 47 psi. these units also claim that they react faster than stock FPR's.
RISING RATE & BOOST SENSITIVE - some adjustable FPR's are both rising rate and boost sensitive. it will deliver fuel under vacuum at 1.7:1, but under boost will deliver 1 psi fuel for every 1 psi of boost(1:1). some units can also adjust the fuel delivery ratio higher. if using this for the purpose of upgrading your ride with a turbo, you will also need injectors as a 1:1 rate under boost will probably not be adequate fuel for the added amount of air. a type of fuel control will also be needed.
Injectors
just go to http://www.rceng.com/technical.htm for equations on finding the maximum horsepower ratings for an injector size. if you've got questions, ask them in this thread.
---How to use all this--- (or at least I think)
-i'm going to use the Fuel Injector Worksheet on rceng.com to work all this out-
Desired Horsepower
so now we wanna shoot for a basic 200whp using a turbo. first, we're gonna want to convert this 200whp to crank hp. i use 15% as drivetrain loss(personal preference), i multiply 200 * 1.15 . that comes to 230 crank hp. we enter that to box one asking for desired horsepower.
Injectors
of course, we're going to use 4 injectors. so put that in the next box. i don't know how this works if you're going to be adding injectors to the fuel system as i believe some of the '04 lancers might use that as an option.
Brake Specific Fuel Consumption
there's another java app below the first one for finding this. just put in basic lancer info in there and you get a BSFC of (.53). you can convert injector cc ->> lbs/min by dividing injector size by (10.5). our stock injectors are 240cc. system fuel pressure is 38psi and our injectors don't see over 75% duty cycle for this particular app.
Maximum Injector Duty Cycle
for max injector duty cycle, put 80%.
System Fuel Pressure. This is where it's kinda tricky.
if you're using:
stock FPR with FMU - take how much boost you're going to run and multiply it by the FMU ratio. then add 47 psi. enter this into the fuel system pressure box.
Static/Rising Rate FPR with FMU - take how much boost you're going to run and multiply it by the FMU ratio. then add the base PSI(@0psi vacuum) you have set the FPR at. enter this into the fuel system pressure box.
Boost sensitive Static/Rising Rate FPR - take the amount of boost you're going to run and add that to the the base PSI(@0psi vacuum) you have set the FPR at. enter this into the fuel system pressure box.
stock fpr - enter 47 into the fuel system pressure box.
Tadaaaa!!!
So now you can press the "Press to Calculate Static Flow" button and the worksheet will tell you how big of injectors you will need to run to achieve the desired crank horsepower. Tadaa!!!
Other Notes:
Fuel Pumps
upgrading fuel pumps will be a necessity. usually just grabbing a 255 walbro is the thing to do since your FPR will regulate fuel at the rail. if you're pushing more power than an evo (the very few and probably proud) you're gonna wanna know how much the pump is actually flowing at different fuel system pressures. here's Road///Race Engineering's Fuel Pump Flow Rates Info. You have to make sure that if you set the base fuel pressure high, that with the added pressure, your pump will have sufficient output to supply your injectors.
Air Fuel Controller and the standalone Engine Management System
for stock cams and relatively low boost, an AFC will suffice. stock ignition timing maps were made specifically for the characteristics of the stock cam. under low boost, torque curves won't be affected enough to have to retard timing. when you start upping the boost and you start getting knock no matter how rich you make that particular part of the RPM range, you've reached the limits of the stock maps.
once boost is high enough to create knock on stock maps, you can trade the AFC in for a standalone EMS. now that ignition timing is adjustable, you can adjust it to suit your new torque curve appropriately. this can also result in being able to raise your Air/Fuel ratio leaner in conjunction with adjusting ignition timing to extract more power. if you've come this far, i hope you'd have had learned quite a deal about tuning your baby, or you've got the money to get your baby tuned professionally.
Measuring Fuel Pressure at the Rail @0psi Vacuum
this is measured by hooking up your fuel rail to a fuel pressure gauge and unhooking the vacuum line to the (a)fpr and plugging the intake manifold end with your finger. then take the reading from the gauge. this reading 'unhooked' will be higher as there is no vacuum pressure from the intake manifold to reduce fuel pressure at the fpr. the reading will be 0psi vacuum since that port is now open to the atmosphere. altitude may change readings due to lower atmospheric pressure.
--- --- ---
so that's it from me in a nutshell. this is pretty much an amalgamation of the things i've picked up since i joined here in '02. do i have a turbo lancer? nope. but my two friends/housemates (they're brothers) have an evo and a 2G eclipse GSX so it's not like i haven't worked on a turbo car before. i've also taken a class on turbochargers and fuel injection systems, as well as supporting automotive classes, so it's not like i'm not educated in this field. i'm not stating this to somehow say i'm absolutely right or anything like that. just to say that i'm not a complete n00b. i've probably written some details that are pretty sketchy, too.
mmmmmmm. craving chicken and waffles... lates...
Last edited by rhyzin; Sep 30, 2005 at 03:57 PM.
Nov 4, 2004, 11:00 AM
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BSFC is weird and i still don't really get it. i'm having trouble understanding the equation because if hp was a kind of unit and you're multiplying it out by lbs/hr, why don't you hp carry over to the answer so it would be something like 31.25 hp lbs/hr? i don't see how the units for injector duty cycle cancel out the hp units in the numerator. it's not really important at all for anyone to understand, but i hate not understanding.
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May 28, 2005, 03:04 PM
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Originally Posted by rhyzin
BSFC is weird and i still don't really get it. i'm having trouble understanding the equation because if hp was a kind of unit and you're multiplying it out by lbs/hr, why don't you hp carry over to the answer so it would be something like 31.25 hp lbs/hr? i don't see how the units for injector duty cycle cancel out the hp units in the numerator. it's not really important at all for anyone to understand, but i hate not understanding.B.S.F.C = lbs/(hp * hr)
so you are not multiplying hp by lbs/hr.
Sep 30, 2005, 09:11 AM
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Originally Posted by datdjrobp
if you guys can find a place to host an excel spreadsheet, i think i might have something useful....
Sep 30, 2005, 03:23 PM
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does this look right to you guys? i took the formulas from the site above and incorporated them into an excel spreadsheet to show requirements for various boost levels....
Sep 30, 2005, 03:44 PM
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wow. having read this thread, i made a mistake.
[*] fuel at the rail is 47psi, not 38. this is what the rail will flow at 0psi vacuum(14.7apsi)
as for your spreadsheet...
[*]the RRFPR raises fuel 1:1 -> PSI:BOOST (eg 1psi=39psi, 2psi=40psi, 3psi=41psi, etc.)
[*]not really wrong, but using a RRFPR and a FMU? very iffy but i guess doable.
that's all i can see wrong between the 2 of us. other than that, it's good. at first glance i wondering why the numbers went down as boost went up. then i realized the speadsheet was trying to make 230chp with 1psi of boost i'm retarded. so after this, the hard part would be to find the turbo that supports the horsepower.
[*] fuel at the rail is 47psi, not 38. this is what the rail will flow at 0psi vacuum(14.7apsi)
as for your spreadsheet...
[*]the RRFPR raises fuel 1:1 -> PSI:BOOST (eg 1psi=39psi, 2psi=40psi, 3psi=41psi, etc.)
[*]not really wrong, but using a RRFPR and a FMU? very iffy but i guess doable.
that's all i can see wrong between the 2 of us. other than that, it's good. at first glance i wondering why the numbers went down as boost went up. then i realized the speadsheet was trying to make 230chp with 1psi of boost
i'm retarded. so after this, the hard part would be to find the turbo that supports the horsepower.
Sep 30, 2005, 03:59 PM
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Originally Posted by rhyzin
RISING RATE - a rising rate FPR works the same as a static adjustable FPR except that the proportion of fuel delivered under vacuum has increased. if a rising rate adjustable FPR has a rate of 1.7:1, it will deliver 1.7 psi fuel for every 1 psi of vacuum. so say you set a rising rate fpr to an idle fuel pressure of 38 psi (as in the last example). this would mean it's peak fuel pressure would be 53.3 psi([1.7*9] + 38 = 53.3) instead of 47 psi. these units also claim that they react faster than stock FPR's.
did i miss something then?
and....yeah, i guess i'm kinda retarded. so it's either an FMU and pray or an FPR and bigger injectors?
Sep 30, 2005, 04:06 PM
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a straight rising rate fpr only works under vacuum. it does not work under boost. the example in that paragraph is for an NA application. the 1.7*9 is not under boost. the 9psi is the difference between idle vacuum and 0psi vacuum where 0psi vacuum is 100% efficiency of intake manifold. so when there's 0 vacuum, the rrfpr will be delivering 53.3psi fuel at the rail which i believe is around peak torque in an NA application.