[DKX4///M]

As a former tuner, engine builder, and lifr long enthusiast, I've always tried my best to absorb and learn everything I could about a multitude of topics. My thirst for knowledge, love of reading, and over 12 years experience as an ASE certified A tech (by 18) moving up to the manager of a newer high performance sport compact shop in Free port (Area 220 aka Second to none)

....This hands on experience, ability to read and learn what I didn't know combined with a physics major / engineering minor let me take my tuning abilities to a new level...

Not only could I tune from a blank slate (usually better and faster than the competition) But my tunes were known to be safer and better for engine longevity as well...Understanding basic physics allowed me to know not just what do do, but why, and sometimes even how, finding new creative ways to get the same results with easier methods and/or higher degrees of safety....

Enough tooting my own horn, simply looking to give you some back ground on myself, and leave it to the reader if he wants to listen or takes ....While the specific system Im designing is for a small "Wet shot" of N02, the same general rules apply to N/A engines, turbo cars (especially pushing high boost levels)...

Calculating fueling requirements for any application 101
Since running a wet shot (w Low boost, and Bootmode 3 Nitrous map) I needed fuel and stealing from OEM fuel system considering the stories of failure and its inability to supply the needed Fuel...I decided to build a stand alone fuel enrichment (S.A.F.E. System as NX Express calls it).... Very simple really...

Parts needed:
1. In Tank or In Line High pressure pump, or Low pressure/High Volume pump...Note :N02 running through the line @ over 1000psi needs a high pressure pump and preferably a time to postpone the fuel solenoid opening vs N02 solenoid....Obviously without N02 will hit engine first and without time to richen a catastophic pre-detonantion is almost guaranteed.

2.HP Fuel Pressure Regulator (By-pass Style) Adjustable between 40-120psi w boost reference Vacccum Line

3.Fuel cell preferably with Level Sender or safety shutdown, Return Port, and Sea-Foam for "Anti Slosh Purpose (Not Needed but highly recommended) As chances are, under heavy acceleration usually happens to be same time extra fuel is needed...

4. SS Braided fuel hoses to run to fuel solenoid and bypass line....Rubber OE Fuel line will expand at such high pressures making delivery unpredictable.

Now lets get a little more specific... Fuel Requirement 101

To calculate needed extra fuel we need a few things but since this is only pumping as a N02 booster to avoid messing with factory fuel system, I will use general rules of thumb and when tuning N02 an old fashioned Wide Band 02 gauge will help me determine proper fuel pressure later on.

Other gauges that make life much easier are EGT gauge, as cylinder temps skyrocket when approaching a dangerously lean mixture...SO hot they chemically fuse elements...A common reason cars used to fail emission inspections were lean LAMBDA chemically fusing the atmospheres Nitrogen and Oxygen (NOX) and with high temps often cause plug damage, erratic and uncontrolled explosions as opposed to a slow complete controlled burn of the Air / Fuel Mixture....This premature explosion is whats commonly referred to as detonation, knock, ping, pre-ignition and and depending on severity and engine durability, its commonly catastrophic and often causes engine failure or severe damage with as little as one knock event...

Now,to finally get started, you need to know a few things...The more specific the better...

1. BSFC - short for brake specific fuel consumption, basically the amount of fuel a specific engine requires to make 1 BHP for 1 Hour

A.Rule of thumb (and this is to start, fine tuning comes later)
-Naturally aspirated Engines typically have BSFC around .5 lbs per hour of 93 ..Octane (AKI)
-Ethanol and Methanol are higher due to there lower Potential Energy, usually around double for 100% Methyl Alcohol. So 1.8-2 pounds/hr

To get specific BSFC you really would need a dyno, so well work with generalities....

*** Forced Induction / N02 cars require need about .6-.7+ lbs/hr per Crank HP***
N/A Engines slightly less...

2. Volumetric Efficiency of the platform...while not needed, it makes for a much more specific end result and saves time tuning using tiny adjustments later, simply put the higher the "volumetric efficiency" of an engine the less fuel, as its burning more efficiently. It takes 14.7 parts air at sea level to burn one part petro based fuel. Hypothetically 100% VE would leave no hydro carbon emissions...As far as I know this does not yet exist...Moving on....


Although they need MUCH more Meth, sometimes up to 2lbs per hr per BHP. This is due to the lower potential energy and "specific heat" a relatively large amount is can remain un-burned, absorbing heat and dissipation. Hence why it's so great as a race fuel....

3: A close approximation of Brake Horse Power target...

- Example: My M2 w/ FBO should be making FLYWHEEL HP in the range of 500-550 with a 50 Wet Shot on around 14PSI (Maybe going higher at the track, but trying not to get to far ahead of myself.) This is based on Older N55's nitrous numbers I found and is more conservative as a few older N55s with forged rods/pistons, WPC treated bearings were making close to 600 crank, 550 wheel... with 50-75 wet shots and water/ methanol for added knock prevention.

4. The Vehicles OEM fuel usage
Obviously you need to subtract this from overall fuel requirement.

Last but not least...

5.Pumping losses as some in line pumps can lose 5-10+ PSI some extreme cases even more... However todays fuel filters are pretty efficient. My Filter I just purchased claims a 1-2 PSI loss at 100 microns which is a fairly good filter...Also HP pumps usually result in less pressure drop than LP (all things being equal)

*Note!! Inline pumps are not good at pulling, so they should be placed as close to fuel source as possible

So now some Basic Math...550 bhp or brake hp, flywheel hp, crank hp etc (Better safe than sorry aka more fuel is 1000x's better than not enough) x's .6 lbs.hr = 330 lbs per hour TOTAL (Obviously at WOT)....Now remember. I'm still using the OEM Fuel system, so I am calculating total fuel required. BMW as most car makers utilize the same basic formula.
1. They calculate the actual BSFC
2. They also run slightly rich from the factory as a rich LAMBDA is much less prone to detonation...12.0-12.2 is a good safety margin, allows decent 10-15* advance, doesn't wreck fuel economy and still can make good power....Although "Leaner is Meaner"...Rich mixtures only cause engine damage over extended time periods as they coat cylinder walls, stoping the oil from lubricating the pistons...

Here I will calculate OVERALL fuel needed and subtract what the stocks pumps supply.

Rule #3 Factory High Performance Forced induction cars can usually can supply approx 10% more fuel than programmed with.

So, figure WITHOUT meth or N02 on lower boost levels (12-14 to start)...So for simplicity, lets say 400 lbs per hour of fuel to push 550 crank....

A lbs of gas = about 6 US Gallons so 400 lbs divided by 6 gals per lbs per hr = 66.67 Gal per Hr...Considering the OEM System is already conservatively supplying close to 40 gal/hr.... I need an extra 25 gallons per hr to be on the safe side. I'm also using water methanol so this is very conservative.

Lastly, we must add some flexibility in here as the amount of fuel needed at 7k RPMS and 14psi w/ N02 is obviously much higher than at 3000 rpms so the regulator comes with a boost reference.'

This is the simplest concept of this whole endeavor...All these numbers are at sea level which is about 14.7 psi of atmospheric pressure....as boost rises the amount of fuel needed has a direct 1:1 correlation...so at 0psi if 20 Gal/hr is needed...And my pump pushes 46gal/hr @ 40psi of fuel pressure (at approx 13.5v), every 10psi of boost should raise fuel pressure 10psi...easy enough

Considering I'm starting slow and working my way up and will be installing the N02 with a pretty big safety margin and in higher temps than present....I picked a pump that at peak performance hypothetically could support 20psi of boost and a 50+ wets hot of N02...

However, I dont plan on ever going even close to that so this name brand pump operating at a small fraction of its potential should enjoy long life....

It's been a while but I think my math and memory serves correct. But hopefully some of you that are looking to learn read this and it will help you in the future as these rules apply to bigger turbos, super high octane race fuels and even stand alone fuel systems...

Because the N55 has long suffered fueling issues, the M2 with its higher boost and more agressive tune will probably be worse...These principals could even be used for those looking to add fuel at higher rpm with the proper cooling mods and a flash or piggyback that is running much higher boost...

The best part about designing your own simple ( yet effective) fuel system is cost, reliability, and giving you FULL control over the AFR without having to be a freakin hacker or dismantling part of our new engine to access DME...

with one well placed nozzle capable of atomizing the fuel preferably close to the throttle body, you can take stress of our oem pump and solve a handful of problems weve all dealt with...My system cost roughly $400 for everything, and using name brand items...In the next post Ill supply links to what I used and why if your considering doing this yourself...Lastly important to note these principles could be spread across all 6 cylinders as opposed to a simple single port...Basically a simplified port injection...

Feel free to ask any constructive questions....Hopefully some of you read this and are now a little more informed.