[judec]

I was wondering about the fuel delivery capacity of the HPI system. Made a little utfg research on it. Before posting any question, here are some facts:
- BMW uses piezo direct injection made by Siemens VDO (yepp, I guess the name is familiar to the 335i owners and fans). It makes a complete setup with their HP fuel pump (that's why it's not that easy to replace)
- Some technical data on piezo injectors:

• Working flow range: > 50
• Static flow: > 35 g / s
• Minimum flow: < 2 mg / stroke
• SMD size: ~ 15 μm
• Injections per cycle: up to 4
• Opening / closing time: ≥ 150 μs
• System pressure: 5 to 20 MPa
• Mounting position: Central position
• Spray angle: 90 °

- Technical data high-pressure pump:

• Flow: up to 170 kg / h at 3,500 rpm (depending on the number of pistons 1 ... 6)
• Maximum fuel pressure: up to 20 MPa
• Supply pressure: 0.45 to 0.6 MPa
• Flow control valve: PWM signal, 0 to 2 A,12 V, 200 Hz
• Operating Temperature: - 40° to 130°C

U can d/l the complete SiemensVDO brochure from here. Sorry about the storage, but for unknown reason I was not able to attach the file here.

Now my questions:

1. Seeing the parameters how much HP could this system handle?
2. What is the max turbo pressure for the HPI to be able to deliver enough fuel to maintain the correct AF ratio?

[Dr_Dirt]

We need more data on the max flow the pump can handle.
170kg/h = 170 liters/hour = 45 gal/hour @ 3500 rpms. Seems strange that they give a flow with an rpm and depending on the number of cyclinders.
Do they mean it can flow 90 gal/hour at 7000 rpms? if so the fuel pump should be good for many upgrades to come.

[judec]

imho it's strange that they specify flow values in weight units not volume, but I hoped to pull the attention of somebody wiser like me. I'll try to email them for further specification.

[judec]

Regarding the weight measure used, maybe we could use 1m3=737.22kg @ 60F for vehicle fuel, but it's strange anyway.

I sent them an email. I am really curious about the answer, if they answer at all.

[Dr_Dirt]

Originally Posted by judec

imho it's strange that they specify flow values in weight units not volume, but I hoped to pull the attention of somebody wiser like me. I'll try to email them for further specification.

Somebody wiser-----was that a dis-??

[judec]

sorry, not a native english speaking - dis- what? If U mean disrespect or something against U - nope, I mistyped or U took it the bad way.

"I hoped to pull the attention of somebody wiser like me... ...to take these numbers, understand them, do the math or just simply comment."

[bnj]

As far as I understand the fuel pump capacity is not going to be a restriction. Even if the capacity was 170 liters/hour it would be good for 500hp. But as you pointed out one kg is much more than one liter, so fuel pump capacity should be more than enough.

[bnj]

Originally Posted by judec

I was wondering about the fuel delivery capacity of the HPI system. Made a little utfg research on it. Before posting any question, here are some facts:
- BMW uses piezo direct injection made by Siemens VDO (yepp, I guess the name is familiar to the 335i owners and fans). It makes a complete setup with their HP fuel pump (that's why it's not that easy to replace)
- Some technical data on piezo injectors:

• Working flow range: > 50
• Static flow: > 35 g / s
• Minimum flow: < 2 mg / stroke
• SMD size: ~ 15 μm
• Injections per cycle: up to 4
• Opening / closing time: ≥ 150 μs
• System pressure: 5 to 20 MPa
• Mounting position: Central position
• Spray angle: 90 °

- Technical data high-pressure pump:

• Flow: up to 170 kg / h at 3,500 rpm (depending on the number of pistons 1 ... 6)
• Maximum fuel pressure: up to 20 MPa
• Supply pressure: 0.45 to 0.6 MPa
• Flow control valve: PWM signal, 0 to 2 A,12 V, 200 Hz
• Operating Temperature: - 40° to 130°C

U can d/l the complete SiemensVDO brochure from here. Sorry about the storage, but for unknown reason I was not able to attach the file here.

Now my questions:

1. Seeing the parameters how much HP could this system handle?
2. What is the max turbo pressure for the HPI to be able to deliver enough fuel to maintain the correct AF ratio?

If the injector capacity is 35g/s (assuming the capacity is given at the system pressure), this is 126kg / hour, i.e. 277lbs/hr. This can support whatever hp. If the 35g/s means the capacity of all the 6 injectors, it would be enough for almost 500hp.

[boostedbavarian]

great thread judec..

[judec]

35g/s * 3600 = 126 kg/h / 0.74kg/l = 170 l/h

the veyron burns s/t like 5l/min, 300l/h (full perf, unreal), so yess, it should be enuff for 500+ HP (@ crank). If it is for one piston only, it is a mistake, too much to be true. See quote:

How much gas is that?
Here's a quick calculation, which you can ignore if you hate math:

• 1,000 horsepower is equivalent to roughly 2.6 billion joules per hour. A gallon (3.8 liters) of gasoline contains 132 million joules, so a 1,000-hp engine has to be able to burn just over 20 gallons of gasoline per hour.
• However, car engines are only about one-quarter efficient -- three quarters of the gasoline's energy escapes as heat rather than as power to the wheels. So the engine actually has to be able to burn at least 80 gallons per hour, or 1.33 gallons (5 liters) per minute.
• Let's convert over to metric. Gasoline requires about 14.7 kilograms of air to burn 1 kilogram of gas. Air weighs 1.222 kilograms per cubic meter at sea level. A gallon of gasoline weighs 2.84 kilograms. So the engine has to be able to process 2.84*1.33*14.7 kilograms of air per minute, or roughly 45 cubic meters of air per minute. That's 45,000 liters of air per minute.
• If a V-8 engine is turning at 6,000 rpm, it can inhale a total of 24,000 cylinders' full of air per minute. If it needs to inhale 45,000 liters of air per minute, it works out to roughly 2 liters per cylinder-full. That's a 16-liter engine.

[bnj]

Or you can just plug some numbers here:
http://www.slowgt.com/Calc1.htm#FPHP

[Dr_Dirt]

I found the following info in a fuel injection basics manual that came with my AEM manual.
OK now for my disclaimer.... I don't know if the same rules apply,the BMW system uses the newest direct injection technology which I'm sure AEM did not account for when they wrote this.

************************************************** *****
Fuel Pump Sizing
To achieve proper fuel delivery, you must select the right fuel pump for your vehicle. In most cases, where the engine has been modified only with “bolt on” performance items, there is rarely need for a larger fuel pump or larger injectors. Vehicle manufacturers typically design a “safety factor” into the fuel pump to accommodate the deterioration of the fuel system over time. This safety factor is intended to compensate for a fuel filter that is nearing the end its life, or for deposits in the injector orifice. Our research has revealed that generally there is about a 15%-20% oversize in most factory fuel pumps.
If the engine is enhanced via forced induction or nitrous oxide, the stock fuel pump is inadequate. If the engine’s power is increased more than 15-20% fuel delivery must increase as a factor of the power gain.
The way to determine the proper-size fuel pump is based on the desired brake specific fuel consumption (BSFC) of the engine. This term refers to how much fuel in pounds per hour (pph) the engine consumes per horsepower and is a measure of the efficiency of the engine. It is a useful term in determining the total fuel requirement of the engine.
On vehicles equipped with forced induction or nitrous oxide, higher BSFC’s are required as an added measure of safety to prevent detonation or high combustion chamber temperatures. Below is a guide of BSFC’s with standard CR that AEM uses for various engines that run on gasoline:
• Naturally Aspirated engines have a BSFC of .48 to .50
• Forced Induction engines have a BSFC of .65 to .68
Methanol (alcohol) powered engines require twice the amount of fuel so the BSFC’s are doubled.
Calculating the total fuel requirement of an engine requires simple equations that we outline in the following section. You must know how much power the engine is anticipated to make and we recommend that you guess on the high end. The fuel requirement will be determined in pounds per hour of fuel flow. Since most pumps are rated in gallons/hour you must know the weight of your fuel/gallon. (The vast majority of gasoline based fuels run at 7.25 lbs./gallon.)
The equations to determine your fuel requirement is as follows:
• (Power x BSFC) x (1 + Safety Margin) = pounds/hour
• Pounds/hour / 7.25 = gallons/hour.
An example of this equation is:
• 500 hp gasoline engine using moderate boost with a 30% safety margin
• (500 x .625) x 1.30 = 406.25 lbs./hr.
• 406lbs/7.25 = 56 gallons/hour.
• If the pump that is being considered is rated in liters per hour, use the conversion factor of 3.785l/gallon. The pump described above would be rated at 56 gallons x 3.785 liters = 211.96 liters/hour.
In the fuel pump sizing, always use a safety margin greater than 20%.

[bnj]

AEM is pretty cautious.
I would guess that those BSFC figures are a bit pessimistic considering that N54 should be highly efficient. Also the safety factor is on the safe side considering that "The safety factor is intended to compensate for a fuel filter that is nearing the end its life, or for deposits in the injector orifice." which is not the case with our new vehicles for some time.

[Dr_Dirt]

The complete AEM EFI BASICS manual for your viewing pleasure.