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| Stock fuel rail modified by Alex Rodriguez Motorsports. -8 AN fitting |
As the horsepower requirements increase, the fuel requirements increase. The fuel system, and that is an important set of words, needs to be adequate enough to supply enough fuel. If you don’t supply enough fuel, you will inevitably end up with a dead engine. Another very important thing to note is fuel flow vs fuel pressure vs voltage.
Fuel System:
Fuel Tank
Fuel Pump
Fuel Pulsator
Fuel Pump Control Module (FPCM)
Fuel Injectors
Fuel Rail
Fuel Pressure Regulator (FPR)
Fuel Filter
Fuel Lines
ECU
Fuel Pressure
System Voltage
Fuel Surge Tanks
If any part of the fuel system is not adequate, you are just asking for problems. So pay careful attention to it. About 90% of the time we are on a dyno with a car, the fuel system is the limiting factor. Build the fuel system with enough capacity for your horsepower goals.
The questions to ask
- How much horsepower are you looking to make?
- What kind of fuel do you use?
- How much money are you willing to spend?
- How is the car used?
How much horsepower are you looking to make?
Horsepower. Just about everyone wants a 500, or 600, or 1000 hp car. Assuming everything else with handle it, lets just focus on the fueling requirements of the engine.
RB26, we have 6 injectors. The factory injectors are low impedance, and they have a resistor box in the circuit. This is important, as most modern injectors are high impedance, and can eliminate the resistor box. HOWEVER, if you eliminate the resistor box, with a normal ECU, and low impedence injectors, you will probably burn out the injector drivers. So make sure what you have, before you go eliminating parts.
A fairly safe rule of thumb on a 6 cylinder engine on gasoline is about 1 hp per cc at the engine. So a stock 440 cc(485 cc at 43 psi) injector is enough for about 440 hp (485 hp) at the engine on an RB26. In real life you can push it harder, or see less depending on the condition of the entire fuel system.
What kind of fuel do you use?
The Injector Dynamics fuel flow calculator is a departure from traditional online calculators which rely on Brake Specific Fuel Consumption (BSFC). There are two sources of error inherent in BSFC based fuel flow calculations. First, BSFC is a rarely measured parameter which few will have access to, and second, being a measure of efficiency, it is dependent on any factor that would affect the overall efficiency of the engine. For instance, a high boost engine running pump gas may require 10-15 degrees less ignition advance than the same engine running race gas. This reduction in timing, and the corresponding reduction in power will have a direct and proportional effect on fuel efficiency, or BSFC. For the reasons stated above, fuel flow calculations based on an estimated BSFC value are so error prone, that the are often meaningless. The Injector Dynamics fuel flow calculator is not based on efficiency. It works by estimating airflow based on a few known parameters, and then calculating fuel flow directly from exhaust lambda. The result is a far more accurate estimation, which allows you to pick the right injector the first time. To choose the best fuel injector for your application, enter the required parameters, click the submit button, and note the injector duty cycle required for the conditions you have specified.
To convert lbs. / hr to gal. / hr. – Divide by 6
To convert cc / min to gal. / hr. – Multiply by .015873
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| Lambda and AFR for Gasoline, E10, E85, and Ethanol |
AMS Brushless Fuel Pump assembly – $2000
NISMO/APEX/Tomei Fuel Pump ~$400
Bosch 044 Fuel Pump – ~$250
Walbro Fuel Pump ~$100
Fuel Injectors ~$600-$800
Billet Fuel Rail ~$400
Fuel Pressure regulator – $120-$250
AN Fittings – $10-$20 each
Stainless Line – 6 ~$6-$10 a foot
From Michael on his fuel system cost
Fuelab Prodigy 1300hp pump 550.00
Fuelab electronic regulator 400.00
Tomei rail 370
Id1700cc injectors 1500.00
Flex sensor 180
Pre pump fuelab 75 mic filter 155
Post pump fuelab 6 mic filter with check valve 210
Fuel cell 220
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| Factory fuel pump in its small sump. The return line puts fuel back to the inlet of the pump . Fuel Pulsator is also visible |
Buy USA Legal R32 Skylines at Importavehicle.com!
Buy-R.com for Nissan Skyline GT-R and GT-R parts.
Fuel Tank
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| OEM R32 GT-R Fuel tank modified with twin -8 feeds, and 044 Bosch Pumps intank |
Gas Cap – R32 Nissan Skyline GT-R – 17251-79915
Gas Cap – R33 Nissan Skyline GT-R – 17251-79920
Sender Unit- Fuel Gauge
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| R32 GT-R Fuel tank capacity and fuel tank specifications |
- 72 liters
- 19 gallons.
- Most of the time E to full is about 17 gallons.
- I never like running cars too low on fuel, as you suck up any trash in the bottom of the tank, and fuel is used to cool and lubricate the fuel pump.
- 65 liters
- 17 gallons
- I don’t think it will take anywhere near 65 liters(17 gallons US), even though that’s what all the books say. I think normally I wouldn’t get much more than about 13-14 gallons US(50 liters) in the tank.
- 65 liters
- 17 gallons
- 65 liters, anyone see a trend?
Holley has a product called Hydramat. The Hydramat acts as a reservoir, and will help prevent fuel starvation. Here is what they have to say about it.
- Fuel reservoir system designed to reduce fuel starvation issues present in hard cornering, acceleration, stopping, inclines, and low fuel conditions
- Available in various shapes and sizes for installation in stock fuel tanks and/or racing fuel cells
- Patent pending design that solves the problems associated with traditional fuel pick-ups in stock fuel tanks as well as racing fuel cells
- Greatly reduces the potential for air to enter into the fuel system which can result in poor engine performance and/or engine stalling
- Perfect for vehicles experiencing fuel starvation during hard cornering, acceleration, stopping, inclines, and low fuel conditions
- Surface tension and fluid wicking allow the HydraMat™ to continue to draw fuel from the tank or cell even when part of the mat uncovered
- As an area of the HydraMat™ is uncovered, tiny pores in the media seal off through surface tension, forcing fuel to be drawn from other areas of the mat where fuel continues to be available
- Unique internal reservoir assists in keeping fuel available at the pickup even under extreme fuel slosh conditions
- Eliminates the need for specialty reservoirs, sumps and pick up pumps saving cost and greatly reducing complexity
- Also acts as a 15 micron pre-filter eliminating the need for a separate filter before the fuel pump
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| Perished top tank vent. This tank leaked from here when filling. |
Some people, when having to change the fuel tank, have installed a S13 240SX fuel tank. It is metal, the filler neck needs to be swapped over. Mostly the non- GT-R R32 have fuel tank rust issues. Some people have said that they split R32 GT-R fuel tanks, but it is mostly the vent lines on the tank that leak.
Fuel Pump
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| Endless R32 GT-R fuel system with two Bosch 044 pumps and a surge tank. Full article here. |
The stock R32 GT-R fuel pump is/was 190 l/hr or 50 gallons an hour. However that one rating isn’t really enough to tell you everything you need to know about a fuel pump. The problem is that fuel flow decreases with pressure. Normal fuel pressure in most older return type fuel systems is around 3.05 kg/cm or 43 psi at idle.
OEM Fuel Pump Assembly R32 GT-R – 17042-05U00
The Stealth 316 page, is one that I have been referring to for years. Has tons of great information on fuel pumps, and fuel flow.
In the April 2004 issue of Turbo & High-Tech Performance magazine, a stock R33 Skyline GT-R fuel pump was tested to flow 252 lph at 43.5 psi and 13.5 volts. All three of those numbers are important. Flow, at pressure and voltage. Just one number alone may be impressive, but you need to see the whole chart, at pressure and voltage to make good fuel system decisions.
At a point, many fuel pumps have relief valves that open, and you get no more fuel. This is also something very important to know.
Most of our Nissan Skylines are at least 25 years old. At that age, things wear out, or will eventually wear out. On our NISMO #500, we decided to get preemptive and ordered a NISMO fuel pump to replace the OEM fuel pump. We see it as cheap insurance. The NISMO pumps are great pumps, drop in, and have low failure rates. Stock R32 is rated at 195 L/hr . Nismo replacement is rated at 276 l/hr. More fuel pump info – Stealth 316. The single NISMO pump, at OEM voltages is good to about 500 wheel horsepower and 75 psi fuel pressure. Above that you need to start thinking about some complex fuel systems.
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| AMS Performance Brushless fuel pump vs, Walbro, Bosch, and Bugatti pumps |
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| Bosch 044 as a reserve pump in R34 N1 Super Taikyu car |
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| Frenchy’s Performance Fuel Pump for stock R32 GT-R fuel tank |
The Frenchy’s Performance fuel pump setup we decided on for our R32 is a dual pump, dual power -8 supply and feed.
R32 GT-R intank fuel system kits. Unique design, easy installation, plug and play with factory harness. First ever kit to incorporate a baffle inside the tank to prevent surge. All components are E85 safe and many options are available: single pump or twin pump, -6 or -8 fittings, screw on or push on hose fittings, wiring kit. The single pump can support up to 500hp at the wheels and the twin pump up to 1000hp. The kits come with genuine Walbro F90000267 pumps. Comes with a fuel level sender calibrated to work with the factory gauge. All stainless steel hardware, anodised aluminium components, milspec wiring, Siemens sensor.
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| Walbro F90000267 Flow vs voltage |
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| Walbro F90000267 Flow vs Pressure and amperage |
Belt Driven Fuel Pumps
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| RB Mechanical Fuel Pump Bracket (Single) and Full Trigger Kit |
There is a point, that it seems no amount of electric fuel pump will supply enough fuel. Platnium Racing Products (PRP) in Australia developed a system using proven mechanically driven fuel pumps to supply fuel.
Mechanical Fuel pumps. with great power comes the need for dependable fuel delivery. The modern performance car is using so much more fuel to make the average 1000hp street car these days, there is a much simpler and in some ways primitive fuel system available to you right now being the PRP Cam driven Mechanical fuel pump system. No wiring, no current draw, no need for upgraded alternators required to power up the nostalgic 044 or newer version in-tank pump that draws 18 amps, this system is bulletproof. Its quiet, its lite, it is extremely reliable, and this system has been used for decades in Indy, Nascar, sprint car racing you name it, even light aircraft it works, whether you use it for street or track it’s efficient and the way of the future.PRP has designed a billet alloy bracket kit utilizing the cam gear to a drive mechanical fuel pumpThe PRP kit includes:
- Billet bracket and trigger sensor mount as an all in one unit.
- Optional Cam trigger sensors with all sensor ready kits.
- Spider uni type coupling that absorbs shock, reverberation and noise prolonging equipment life.
- Easy to assemble hardware with excellent support, we pride ourselves on being industry leaders with tech, warranty and support.
- This kit has been designed to incorporate the use of any of the leading pumps on the market including Kinsler, Weldon, Waterman, and Enderlie
Fuel Pump Control Module
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| Nissan Skyline GT-R R32 Fuel pump control module wiring diagram (FPCM) |
The fuel pump control module (FPCM) slows the fuel pump speed down at idle/low speed. It is one of those OEM parts that sound great on paper, but in real life, when they fail, car no go. It provides a ground to the fuel pump and is controlled by the ECU.
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| R32 GT-R Fuel pump control module – FPCM, or a very complicated way to make a ground |
Modulator – Fuel Pump Control
- 17001-05U01 (Alt 17001-05U00)
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| Internals of the Fuel Pump Control Module – FPCM. Complicated way to make a ground. |
Fuel Relay
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| Fuel Pump Relay – 25230-C9965 |
Fuel Injectors
444cc at 42 psi in 1989, or 1990, or 1991. Its not 1989 anymore. Lets just say that each cc of injector – on a 6 cylinder car is good for 1 hp or about 444 hp at the motor. The stock injectors are “yellow” tops. They are also low impedance(2 ohm), so there is a resistor pack located on the right side of the engine compartment. In the chart above you can see at 2.55 kg/cm2 (36 psi) of fuel pressure the injector flows about 440 cc. At 3.05 kg/cm2 (43 psi) of fuel pressure it flows about 485 cc. At 3.55 kg/cm2(50 psi) it flows 525 cc. Don’t get too crazy with the fuel pressure. Your fuel pump relief valve might end the fun soon.
Fuel injector cleaning results
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| Injector resistor pack delete from NZEFI |
OEM injectors have a 10.5 mm top.
Most aftermarket rails are 11mm or 14mm.
With an inline 6 fuel rail, it is easy to get an o-ring cockeyed, or an injector not fully seated. Always prime the fuel system and check for leaks after fuel injector replacement.
OEM GT-R Fuel Injector
- 16600-54C02 (Alt 16600-05U00)
Fuel injector connector metal clips
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| Nissan Skyline Fuel injector spring clips |
- B4111-U7600
- If you have ever dropped one down in the black hole of the engine compartment, you know what we are talking about. The design of these things is pretty awful. These are EV1 connectors, so there are some better replacements out there, but depends on how far you want to go into new wiring.
OEM injector replacement o-rings
SEAL O-RIN (16618-78A00)
INSULATOR- (16635-78A00)
RUBR INSUL (16636-V5000)
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| SARD Fuel injector sizes (cc), and dead time for RB26dett. R32, R33, R34 GT-R |
Fuel Rail
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| Stock fuel rail modified by Alex Rodriguez Motorsports. -8 AN fitting |
The OEM GT-R – RB26 rail isn’t bad. It takes a 10.5 mm top fuel injector. Most aftermarket are 11 mm. More recently it is possible to get 10.5 mm adapters or injectors to direct fit the stock rail. It is large feeds from rear, fuel pressure regulator(FPR) is on the front, where it returns to the fuel tank. The Super Taikyu race car had a stock type rail that had been modified with a -6 fitting on the supply, and a -6 fitting on the outlet of the FPR.
Most “billet” rails are smaller internally than the OEM rail. If pretty colors are your thing, then go right ahead with the billet rail. If you want to double feed the rail, or add other ports, then billet may be what you want. However up to 800+ we don’t see an issue with a modified stock rail.
Fuel Pressure Regulator
Fuel Pressure. Normal fuel pressure in most older return type fuel systems is around 3.05 kg/cm or 43 psi at idle with the vacuum line disconnected. The OEM fuel pressure regulator is a 1:1 regulator. How that works is this. As 1 psi of pressure is in the plenum, where the injector fires, it raises the fuel pressure 1 psi to overcome this pressure. So at 43 psi base pressure, plus 10 psi of boost, your actual differential fuel pressure is still 43 psi, but your fuel pump needs to supply fuel at 53 psi. At 20 psi of boost, 63 psi of fuel pressure, 30 psi of boost, 73 psi of fuel pressure. If you didn’t raise fuel pressure vs boost pressure, you would end up with a lot less fuel though the injector. Some great fuel pressure and flow charts here. As you can see as pressure increases, flow decreases. At a point, many fuel pumps have relief valves that open, and you get no more fuel. This is also something very important to know.
It is VERY important that you don’t lose this boost reference line. NOTHING else should be tapped off this line. If you need to add boost gages, or BOV control, do not under any circumstances use this line. Failures in real life happen. If you add one additional item on this line, you are adding three additional points for failure.
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| DO NOT. DO NOT put a t in this line. You just added at least four more failure points. If you lose this line, your car will probably blow up. I don’t care what they did in Japan, I don’t care what the instructions say. Use the back of the balance tube for anything you need to get a decent vacuum and boost reference. |
Fuel Filter
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| OEM R32, R33, R34 GT-R fuel filter. OD of fitting 8 mm |
Somewhere in there, in the fuel system there should be a filter. Maybe two or three. The first line of defense is on the fuel pump. A screen. From there you will probably have another filter inline. These filters help prevent getting anything clogged in the injectors. The injectors themselves actually have small screens in them, but that really is a last line.
RB26 Fuel Filter Part numbers
Fuel Lines
Fuel lines pass the fuel. OEM lines will support OEM power well. Once you go up from OEM then you need to do some figuring.
OEM fuel filter – OD of lines 8 mm.
Tank top – Supply and return OD 8 mm
AN line sizes
ID= Inside diameter
OD= Outside diameter
-4 hose has an I.D. of 1/4″ or 6.35 mm
-6 hose has an I.D. of 3/8″ or 9.52 mm
-8 hose has an I.D. of 1/2″ or 12.7 mm
-10 hose has an I.D. of 5/8″ or 15.87 mm
-12 hose has an I.D. of 3/4″ or 19.05 mm
-16 hose has an I.D. of 1″ or 25.4 mm
-6 AN line to about 500 hp
-8 AN line to about 800 hp
-10 AN line to about 1100 hp
E85 compatible 8 mm fuel lines
We have actually had the fuel lines in the tank fail in an R33 GT-R. When they failed, with a full tank of fuel, the car would run fine. However as the fuel load decreased, the car would run progressively worse, until it would just shut off under boost at a point. We finally figured out that the lines in the tank were collapsing. The R33 uses a saddle tank. It is taller and narrower than an R32 GT-R tank. It is behind the seat vs under the trunk in an R32.
Since Sam asked us to post photos of using the HICAS lines as fuel lines, here are a few photos of the R32.4. This will obviously only work if you delete HICAS. We don’t mind HICAS, think it is just a misunderstood system, with mostly steering wheel gasket issues. Fix those steering wheel gaskets, and it is a good system.
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| -8? AN fittings adapted to the HICAS lines. |
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| Using old HICAS lines as fuel supply lines. OEM line was used as a return. |
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| HICAS lines went to a Y, with a filter on the outlet, that then feed the back of a modified stock style rail. The quick disconnect in the picture is for the release bearing. |
ECU
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| Look, it is a magic box, dissected partially. |
It all is controlled with some magic box, the ECU(engine control unit) This magic box takes voltages from one source, chews them up, and spits out other voltages and grounds. A magic box is only as good as its inputs. It is only as good as the numbers that are put into it. Our current advice on ECU, are use whatever your tuner likes. If you pick something they don’t have experience with, you are just paying them to learn, and perhaps hate what you have given them. With a magic box they are used to, they can get started, and troubleshoot any issues that might come up.
ECU: Nissan Skyline GT-R 2020 Upgrades – Engine Control Unit : Engine Computer – Your car just came over from Japan, and while checking it out you notice that your ECU has some kind of sticker or badge on it. What is it? What does it do? Is it OK to run on pump gas in the US? Do I need to tune my car? Can this ECU be retuned? The factory ECU is not OBD II. It uses Nissan’s proprietary diagnostic connector, known as Consult : Read More
Oxygen sensors or 02 sensors. Old cars don’t have wideband oxygen sensors. The R32 uses a small oxygen sensor, the R33 and R34 use a larger sensor. The wiring on them is slightly different. The connectors are the same, but different. https://www.gtrusablog.com/2017/12/nissan-skyline-oxygen-sensor-02-sensors.html
R32 Nissan Skyline GT-R 02, Oxygen Sensors
22690-05U21 front
22690-05U22 rear
R34 Nissan Skyline GT-R 02, Oxygen Sensors
22690-24U02 front
22690-24U03. Rear
Fuel Pressure
Fuel pressure is important. The problem is that fuel flow decreases with pressure. Normal fuel pressure in most older return type fuel systems is around 3.05 kg/cm or 43 psi at idle with the vacuum line disconnected from the fuel pressure regulator (THIS IS IMPORTANT). Most modern non return systems run about 50 psi base pressure. This supposedly helps with fuel atomization.
Fuel Flow vs Pressure Calculator
Fuel Pressure Regulator Vacuum Line : Where to Tap an RB26 For A Vacuum or Boost Sign
System Voltage
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| Fuel pump hotwire or direct power kit for a Nissan Skyline GT-R |
This is something else that isn’t given much thought normally. A battery in a vehicle is designated as 12 volts. This voltage is potential, or standard voltage, but in real world a vehicle that is running is taking its electrical power from the alternator. The alternator is producing a voltage/current, normally in the 13.5 volt range. As a straight measurement, voltage is generally easier to measure than amperage, as amperage normally requires the meter to be in line with the supply and load. As above the FPCM actually slows the OEM fuel pump down, by supplying less voltage at low speed. This quiets the pump down a little. On an all stock car it might be fine, but on a modified car, it is a good thing to eliminate.
As an example, the Toyota Supra Denso pump at various voltages from 12v to 18 v showing the relationship between flow and voltage pretty clearly.
Poor People Racing has developed a fuel pump direct power kit. This fuel pump hotwire kit provides alternator voltage directly to the fuel pump though a fused relay. This is a plug and play solution with the right connectors. Sure you can make your own, but this makes it easy. Watch the install video below.
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| R34 N1 Super Taikyu Fuel cell, surge tank, and 044 reserve pump |
They sound great on paper. However in my real world experience, nearly every single one manages to reek of fuel. On a race car, not a big deal, but on a street car, it is normally enough to have someone not happy with the car.
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| Dual 044 in an externally mounted Surge tank. Patrick’s setup |
Most of the time you see them mounted in the trunk of the car. The issue with the trunk being, there is no airtight barrier between the trunk and interior. Some guys, like Patrick, have a surge tank mounted under the car, but you don’t see them much there. Stainless lines over time will have some permeability based on our experience. The ethanol in pump gas seems to put a bit of a hurting on most lines. The latest and greatest stuff may last a bit longer, but if you have lines that are 5 or 10 years old, you may have a permanent 91 cologne.
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| Dual 044 in an externally mounted Surge tank. Patricks setup |
We do see people do surge tanks in all hard line, and that is fine, just need to be supported properly. They also need to allow for some expansion and contraction, and rough roads. On a hard oil line to a turbo on the R34 race car, we actually developed a crack, that flashed to a fire at Sebring. We lost a bolt that helped support the line. Never had that issue before or after, but Sebring is a rough track.
When we race we want to minimize failure points. Adding a surge tank to most systems, just adds many times to the complexity. In order to get fuel to the surge tank you need a lifter pump (normally oem). Then you have one, two, fifteen pumps in the surge tank, or an externally mounted pump that has the suction side on the bottom of the surge tank. In the surge tank will be a lot quieter than externally mounted. A couple 044 in the trunk sound like you have a swarm of angry bees chasing you.
With one setup we had with a Weldon pump, it was louder than front row center at an AC/DC concert. You had to wonder if the 2.8 liter 4 inch exhaust, GT42R RB26, with the 280 cams was running, over the racket that the Weldon produced.
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| Trunk mounted surge tank |
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