Fueling upgrade ?????
- Thread starter alanep70
- Start date
they're not signs , theyre requirements 
when you opt for more power , and start pushing the ct9 to its limits or perhaps get a hybrid / larger , you get larger injectors , and ofcourse , larger fuel pump , i reckon the fpr's need would depend on the tuning route u wish to take .
when you opt for more power , and start pushing the ct9 to its limits or perhaps get a hybrid / larger , you get larger injectors , and ofcourse , larger fuel pump , i reckon the fpr's need would depend on the tuning route u wish to take .
GTti
Member +
What are your reasons for this? I can see none?
I would be supprised if anyone could name one reason other than age for the replacement of the fuel pump!
If you modify your car PROPERLY you will never be required to change the fuel pump or the regulator. You just need the correct size injectors (If you exceed max duty cycle on stock injectors and an ECU or method of controlling injector opening time.)
The fuel pump maintains a pressure between the fuel supply and the high pressure filter and pressure regulator. If you're using an Adjustable FPR then you'll only be increasing the base pressure slightly to provide greater pressure to the injector (Hence a small addition of fuel). A stock fuel pump will be perfectly capable of providing these sorts of pressures.
1) A larger injector will provide more fuel under the same rail pressure (stock)
2) A AFPR will provide a smaller injector (stock) will more fuel rail pressure
3) Fuel pump technically has nothnig to do with either of the above
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jayc-glanza17
Fresh Recruit
i didnt think you needed a larger fuel pump.
but what about the warlbro ones?
i know what a fuel pressure regulator does, yet not 100% sure
on how it operates, anyone with a proper definition?
i would suggest no bigger than 330cc injectors, that sound about right gti?
as is said what are you going for? hybrid?tdo4 or bigger?
but what about the warlbro ones?
i know what a fuel pressure regulator does, yet not 100% sure
on how it operates, anyone with a proper definition?
i would suggest no bigger than 330cc injectors, that sound about right gti?
as is said what are you going for? hybrid?tdo4 or bigger?
GTti
Member +
You need an AFR sensor to be able to see what the ratios of fuel to air are at various load intervals.
With a hybrid you'll find that at higher RPM and higher boost the intake charge may be cooler than if it were a CT9 at the same pressures. Thus meaning more air mass, requiring more petrol to keep the AFR's on track.
A fuel pressure regulator controls the pressure of fuel in the fuel rail before the injectors, behind this is the pressure of the pump > regulator which will be greater than the fuel rail. This will modifiy the rail pressure 1:1 on boost. So 1 psi for every 1 psi of boost seen. So if the base pressure is 40psi and you're boosting at 20psi the fuel rail will be at 60psi.
The idea is to slightly increase base pressure to compensate for the leaner AFR's seen at higher load. So you run a little rich through the range, but this is no problem on a modified car.
A rising rate regulator (RRFPR) modifies the pressure depending on boost/vacuum greater than 1:1, so 1:2 or 1:2.5 etc, this is not what you want and will screw up the fuel MAP and make it difficult to tune. Also not really compatible with aftermarket ECU's.
The amount of people that advise to get a RRFPR here is crazy...
With a hybrid you'll find that at higher RPM and higher boost the intake charge may be cooler than if it were a CT9 at the same pressures. Thus meaning more air mass, requiring more petrol to keep the AFR's on track.
A fuel pressure regulator controls the pressure of fuel in the fuel rail before the injectors, behind this is the pressure of the pump > regulator which will be greater than the fuel rail. This will modifiy the rail pressure 1:1 on boost. So 1 psi for every 1 psi of boost seen. So if the base pressure is 40psi and you're boosting at 20psi the fuel rail will be at 60psi.
The idea is to slightly increase base pressure to compensate for the leaner AFR's seen at higher load. So you run a little rich through the range, but this is no problem on a modified car.
A rising rate regulator (RRFPR) modifies the pressure depending on boost/vacuum greater than 1:1, so 1:2 or 1:2.5 etc, this is not what you want and will screw up the fuel MAP and make it difficult to tune. Also not really compatible with aftermarket ECU's.
The amount of people that advise to get a RRFPR here is crazy...
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gorganl2000
Lifer
gtti is makes a good point
here's my take
Ok…fuel pump selection is a little technical…I’ll see if I can do an example based on some reading I did a while back from a reputable site/source when I was doing my research on this topic
Let’s say 330cc injectors---seems popular on here….lol
Lets do a conversion from cc to lph (litres per hour)
(size of injector*minutes in hour*number of injectors)* conversion rate
(330*60*4)*0.001 = 79.2 lph @100% duty cycle
And let’s say u plan to run 22 psi (1.5bar) max….. as a lot of people probably wont go past this except the chosen few…lol
Assuming a base fuel pressure of 43.5 psi (3 bar)..again most of us use this…….u need a pump that can handle about 80 lph @ 65.5 psi of pressure (base pressure + full boost pressure)…..i think the stock pump may well be good for that based on the above calculation
Flow will be variable depending on certain factors such as fuel line size, fuel pressure supply, voltage levels, etc.
Again reality and theory don’t always go hand in hand……so keep that in mind
And what is the stock pump’s fuel rating???.........lol
However, most people just upgrade their pump to a 255lhp walbro when doing upgrades for safety (let’s wack a new pump in there)…because a new walbro is comparatively cheaper than a new oem pump and flows more at the same time….and also because its been done by everyone on here, so why be different (keeping up with the Jones or their friend has one or I get one free or whatever…lol)..and because they are available right on here from our traders at good prices……..so I guess it’s the sensible thing to do for some
PS---if my calculations are off……please let me know….so o can correct the formula I’ve seen…..i’m always looking to learn and improve
here's my take
Ok…fuel pump selection is a little technical…I’ll see if I can do an example based on some reading I did a while back from a reputable site/source when I was doing my research on this topic
Let’s say 330cc injectors---seems popular on here….lol
Lets do a conversion from cc to lph (litres per hour)
(size of injector*minutes in hour*number of injectors)* conversion rate
(330*60*4)*0.001 = 79.2 lph @100% duty cycle
And let’s say u plan to run 22 psi (1.5bar) max….. as a lot of people probably wont go past this except the chosen few…lol
Assuming a base fuel pressure of 43.5 psi (3 bar)..again most of us use this…….u need a pump that can handle about 80 lph @ 65.5 psi of pressure (base pressure + full boost pressure)…..i think the stock pump may well be good for that based on the above calculation
Flow will be variable depending on certain factors such as fuel line size, fuel pressure supply, voltage levels, etc.
Again reality and theory don’t always go hand in hand……so keep that in mind
And what is the stock pump’s fuel rating???.........lol
However, most people just upgrade their pump to a 255lhp walbro when doing upgrades for safety (let’s wack a new pump in there)…because a new walbro is comparatively cheaper than a new oem pump and flows more at the same time….and also because its been done by everyone on here, so why be different (keeping up with the Jones or their friend has one or I get one free or whatever…lol)..and because they are available right on here from our traders at good prices……..so I guess it’s the sensible thing to do for some
PS---if my calculations are off……please let me know….so o can correct the formula I’ve seen…..i’m always looking to learn and improve
gorganl2000
Lifer
255lhp walbro is a popular choice for GTti owners, I peak at 25psi max boost on the GTxx with base pressure of 2.9BAR.
Stock FPR
Stock Pump
Large injectors
Microtech ECU
20 years young
good stuff
its generally the injectors that really need to be upgraded and supporting ecu in terms of power ........additonal items like fpr, pump, etc. are really a safety net
somehow a lot of starlet will ever need a 255lph fuel pump,,,
but everyone has their choice to make
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gorganl2000
Lifer
an even more simple formula used to calculate fuel pump size is to just multiply the set power level by a factor ranging from 0.4-0.7 from what 've seen.....turbo application then near to 0.7 side of things
but dont forget the result is at 100% duty cycle...and u always want a little room for safety
but dont forget the result is at 100% duty cycle...and u always want a little room for safety
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