Fuel injection flow vs HP tables

[bobqzzi]

I've compiled the theoretical HP numbers that common sized injectors can support.  There are 4 variables:

Injector flow rating: amount of fuel an injector can flow at 100% duty cycle (wide open) at a specified pressure (3 bar is assumed)

 Relative fuel pressure at injector:  The fuel pressure the system is set to minus any effects from boost or vacuum.

Duty cycle: the percentage time the ecu signals the injector to be open. Depending on which injectors and who you ask, maximum should be less than 80 or 90%.

Brake Specific Fuel Consumption:  the amount of fuel the engine burns to make one (crank)horsepower for 1 hour in pounds/hour.  This is the "unknown" variable.  I have included values form .45 (really, really excellent) to .60 (mediocre).  I don't believe any value lower than .45 for a 1.8T, BUT some people would disagree with that.

There is no question that the equation from which these values are calculated  is accurate.  (HP= Injector Flow*Duty Cycle*# injectors/BSFC)  What can be questioned are the variables- what is actual fuel pressure? Do the injectors really flow at their rating?  What is the actual BSFC?  The only one we can be completely sure of is the number of injectors.  Fuel pressure is pretty certain.
Injector flow is less so: people may be surprised how much injectors can vary from rated flow.
BSFC: the only guide here is we have here is similar engines where this is actually measured on an engine dyno.  In my OPINION, the farther you get from stock (the more HP), the higher this number is likely to be.


Injector size: 380cc (36lb Hr)

Fuel Pressure  3 Bar                  
BSFC      .45

Duty Cyle   Max HP @ Duty Cycle
80%   256 HP
85%   272 HP
90%   288 HP
95%   304 HP
100%   320 HP

BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   230.4 HP
85%   244.8 HP
90%   259.2 HP
95%   273.6 HP
100%   288 HP

BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   209.45 HP
85%   222.55 HP
90%   235.64 HP
95%   248.73 HP
100%   261.82 HP

BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   192 HP
85%   204 HP
90%   216 HP
95%   228 HP
100%   240 HP
         




Injector size: 380cc (36lb Hr)

Fuel Pressure  4 Bar                  
BSFC      .45

Duty Cyle   Max HP @ Duty Cycle
80%   296.53 HP
85%   315.07 HP
90%   333.6 HP
95%   352.13 HP
100%   370.67 HP

BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   266.88 HP
85%   283.56 HP
90%   300.24 HP
95%   316.92 HP
100%   333.6 HP

BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   242.62 HP
85%   257.78 HP
90%   272.95 HP
95%   288.11 HP
100%   303.27 HP

BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   222.4 HP
85%   236.3 HP
90%   250.2 HP
95%   264.1 HP
100%   278 HP






Injector size: 440cc (42lb Hr)

Fuel Pressure  3 Bar                  
BSFC      .45                  

Duty Cyle   Max HP @ Duty Cycle
80%   298.67 HP
85%   317.33 HP
90%   336 HP
95%   354.67 HP
100%   373.33 HP

Fuel Pressure  3 Bar                  
BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   268.8 HP
85%   285.6 HP
90%   302.4 HP
95%   319.2 HP
100%   336 HP

Fuel Pressure  3 Bar                  
BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   244.36 HP
85%   259.64 HP
90%   274.91 HP
95%   290.18 HP
100%   305.45 HP

Fuel Pressure  3 Bar                  
BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   224 HP
85%   238 HP
90%   252 HP
95%   266 HP
100%   280 HP




Injector size: 440cc (42lb Hr)

Fuel Pressure  4 Bar                  
BSFC      .45

Duty Cyle   Max HP @ Duty Cycle
80%   345.6 HP
85%   367.2 HP
90%   388.8 HP
95%   410.4 HP
100%   432 HP

Fuel Pressure  4 Bar                  
BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   311.04 HP
85%   330.48 HP
90%   349.92 HP
95%   369.36 HP
100%   388.8 HP

Fuel Pressure  4 Bar                  
BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   282.76 HP
85%   300.44 HP
90%   318.11 HP
95%   335.78 HP
100%   353.45 HP

Fuel Pressure  4 Bar                  
BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   259.2 HP
85%   275.4 HP
90%   291.6 HP
95%   307.8 HP
100%   324 HP

Injector size: 580cc (55lb Hr)

Fuel Pressure  3 Bar                  
BSFC      .45

Duty Cyle   Max HP @ Duty Cycle
80%   391.11 HP
85%   415.56 HP
90%   440 HP
95%   464.44 HP
100%   488.89 HP

BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   352 HP
85%   374 HP
90%   396 HP
95%   418 HP
100%   440 HP

BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   320 HP
85%   340 HP
90%   360 HP
95%   380 HP
100%   400 HP

BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   293.33 HP
85%   311.67 HP
90%   330 HP
95%   348.33 HP
100%   366.67 HP





Injector size: 580cc (55lb Hr)

Fuel Pressure  4 Bar                  
BSFC      .45

Duty Cyle   Max HP @ Duty Cycle
80%   452.98 HP
85%   481.29 HP
90%   509.6 HP
95%   537.91 HP
100%   566.22 HP

BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   407.68 HP
85%   433.16 HP
90%   458.64 HP
95%   484.12 HP
100%   509.6 HP

BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   370.62 HP
85%   393.78 HP
90%   416.95 HP
95%   440.11 HP
100%   463.27 HP

BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   339.73 HP
85%   360.97 HP
90%   382.2 HP
95%   403.43 HP
100%   424.67 HP







Injector size: 755cc (72lb Hr)

Fuel Pressure  3 Bar                  
BSFC      .45

Duty Cyle   Max HP @ Duty Cycle
80%   512 HP
85%   544 HP
90%   576 HP
95%   608 HP
100%   640 HP

BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   460.8 HP
85%   489.6 HP
90%   518.4 HP
95%   547.2 HP
100%   576 HP

BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   418.91 HP
85%   445.09 HP
90%   471.27 HP
95%   497.45 HP
100%   523.64 HP

BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   384 HP
85%   408 HP
90%   432 HP
95%   456 HP
100%   480 HP





Injector size: 755cc (72lb Hr)

Fuel Pressure  4 Bar                  
BSFC      .45

Duty Cyle   Max HP @ Duty Cycle
80%   593.07 HP
85%   630.13 HP
90%   667.2 HP
95%   704.27 HP
100%   741.33 HP


BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   533.76 HP
85%   567.12 HP
90%   600.48 HP
95%   633.84 HP
100%   667.2 HP

BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   485.24 HP
85%   515.56 HP
90%   545.89 HP
95%   576.22 HP
100%   606.55 HP

BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   444.8 HP
85%   472.6 HP
90%   500.4 HP
95%   528.2 HP
100%   556 HP





Injector size: 880cc (83lb Hr)

Fuel Pressure  3 Bar                  
BSFC      .45

Duty Cyle   Max HP @ Duty Cycle
80%   590.22 HP
85%   627.11 HP
90%   664 HP
95%   700.89 HP
100%   737.78 HP

BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   531.2 HP
85%   564.4 HP
90%   597.6 HP
95%   630.8 HP
100%   664 HP

BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   482.91 HP
85%   513.09 HP
90%   543.27 HP
95%   573.45 HP
100%   603.64 HP

BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   442.67 HP
85%   470.33 HP
90%   498 HP
95%   525.67 HP
100%   553.33 HP






Injector size: 880cc (83lb Hr)

Fuel Pressure  4 Bar                  
BSFC      .45

Duty Cyle   Max HP @ Duty Cycle
80%   683.38 HP
85%   726.09 HP
90%   768.8 HP
95%   811.51 HP
100%   854.22 HP

BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   615.04 HP
85%   653.48 HP
90%   691.92 HP
95%   730.36 HP
100%   768.8 HP

BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   559.13 HP
85%   594.07 HP
90%   629.02 HP
95%   663.96 HP
100%   698.91 HP


BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   512.53 HP
85%   544.57 HP
90%   576.6 HP
95%   608.63 HP
100%   640.67 HP





Injector size: 1008cc (96lb Hr)

Fuel Pressure  3 Bar                  
BSFC      .45

Duty Cyle   Max HP @ Duty Cycle
80%   682.67 HP
85%   725.33 HP
90%   768 HP
95%   810.67 HP
100%   853.33 HP

BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   614.4 HP
85%   652.8 HP
90%   691.2 HP
95%   729.6 HP
100%   768 HP

BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   558.55 HP
85%   593.45 HP
90%   628.36 HP
95%   663.27 HP
100%   698.18 HP

BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   512 HP
85%   544 HP
90%   576 HP
95%   608 HP
100%   640 HP






Injector size: 1008cc (96lb Hr)

Fuel Pressure  4 Bar                  
BSFC      .45

Duty Cyle   Max HP @ Duty Cycle
80%   790.76 HP
85%   840.18 HP
90%   889.6 HP
95%   939.02 HP
100%   988.44 HP

BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   711.68 HP
85%   756.16 HP
90%   800.64 HP
95%   845.12 HP
100%   889.6 HP

BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   646.98 HP
85%   687.42 HP
90%   727.85 HP
95%   768.29 HP
100%   808.73 HP

BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   593.07 HP
85%   630.13 HP
90%   667.2 HP
95%   704.27 HP
100%   741.33 HP






Injector size: 1680cc (160lb Hr)

Fuel Pressure  3 Bar                  
BSFC      .45

Duty Cyle   Max HP @ Duty Cycle
80%   1137.78 HP
85%   1208.89 HP
90%   1280 HP
95%   1351.11 HP
100%   1422.22 HP

BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   1024 HP
85%   1088 HP
90%   1152 HP
95%   1216 HP
100%   1280 HP


BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   930.91 HP
85%   989.09 HP
90%   1047.27 HP
95%   1105.45 HP
100%   1163.64 HP

BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   853.33 HP
85%   906.67 HP
90%   960 HP
95%   1013.33 HP
100%   1066.67 HP





Injector size: 1680cc (160lb Hr)

Fuel Pressure  4 Bar                  
BSFC      .45

Duty Cyle   Max HP @ Duty Cycle
80%   1317.69 HP
85%   1400.04 HP
90%   1482.4 HP
95%   1564.76 HP
100%   1647.11 HP

BSFC      .50

Duty Cyle   Max HP @ Duty Cycle
80%   1185.92 HP
85%   1260.04 HP
90%   1334.16 HP
95%   1408.28 HP
100%   1482.4 HP

BSFC      .55

Duty Cyle   Max HP @ Duty Cycle
80%   1078.11 HP
85%   1145.49 HP
90%   1212.87 HP
95%   1280.25 HP
100%   1347.64 HP

BSFC      .60

Duty Cyle   Max HP @ Duty Cycle
80%   988.27 HP
85%   1050.03 HP
90%   1111.8 HP
95%   1173.57 HP
100%   1235.33 HP

[mj6234]

How does ignition timing play into these calculations? Does fuel density matter?

[elitedübs]

whats BSFC mean/stand for?

[whizbang18T]

B.S.F.C is brake specific fuel consumption - How much fuel you are using per horsepower per hour

http://www.rceng.com/technical.htm

it's in the original post as well

[bobqzzi]

How does ignition timing play into these calculations? Does fuel density matter?

Depends on what you mean.

As far as the equation is concerned, they are irrelevant.  remember- BSFC is the actual amount of fuel an engine burns to make 1HP for one hour. How it does it makes no difference.

Does ignition timing affect BSFC?  Yes, certainly, as does every other mechanical/tuning parameter.  The only way to know the actual BSFC is to measure it on an engine dyno.  People who have built all sorts of engines have accumulated a great amount of data over the years, so reasonable estimates can be made for various types of engines.  The very best automotive turbo diesels are around .34-.36 Very large marine diesels are much better than this. http://www.bath.ac.uk/~ccsshb/12cyl/
A turbocharged aircooled Porsche or Chevy might be .65.  The 1.8T is somewhere in between.  I THINK a typical Big Turbo car is around between .5 and .55 based on my limited experience.  There is no way it is below .45.

Specific gravity plays a part too, but most gasolines are pretty close.

[27psiBOOM]

First off  :notworthy: :notworthy: :notworthy:

This is priceless information, thank you!!!  :bowrofl:

I have included values form .45 (really, really excellent) to .60 (mediocre).  I don't believe any value lower than .45 for a 1.8T, BUT some people would disagree with that.

Bob
Would you suggest .45 BSFC to find out the proper injector size on the 1.8T?

I'm running 3.25bar off vaccumm the injectors reach 100% DC at 5500rpms, but would like to lower FP a bit to get a nice 12:1 AFR instead the 11:1 I'm getting right now, but you say 100% DC isn't any good, would you please elaborate a bit more?

[elitedübs]

B.S.F.C is brake specific fuel consumption - How much fuel you are using per horsepower per hour

http://www.rceng.com/technical.htm

it's in the original post as well

yeah, i read it and didn't even put 2 and 2 together, thanks man. i thinkits bed time. :sleep:

[bobqzzi]

First off  :notworthy: :notworthy: :notworthy:

This is priceless information, thank you!!!  :bowrofl:

I have included values form .45 (really, really excellent) to .60 (mediocre).  I don't believe any value lower than .45 for a 1.8T, BUT some people would disagree with that.

Bob
Would you suggest .45 BSFC to find out the proper injector size on the 1.8T?

I'm running 3.25bar off vaccumm the injectors reach 100% DC at 5500rpms, but would like to lower FP a bit to get a nice 12:1 AFR instead the 11:1 I'm getting right now, but you say 100% DC isn't any good, would you please elaborate a bit more?

Given complete control over the management and thus A/F I would certainly use .55 BSFC for a 1.8T- bigger is generally better, because you can run a lower duty cycle...but can't go over 100% if you go to small.

If you are running stock management, thing are a bit more complicated. It's best to have a "chip" that is tuned for a a specific size injector, fuel pressure, and MAF.  Then you can use Lemmiwinks and fuel pressure to fine tune.  Others can offer more useful comments about this.  If you choose an injector not intended by the software maker, then you have to balance WOT A/F with what happens the rest of the time.  Again, others can offer more guidance here.

High duty cycles are not desirable because as you approach 100% you lose control over the injector- it essentially just become a fixed orifice.  It also isnl;t too great for the injectors.  They can overheat and start to fail.

You are rich at WOT and the injectors are wide open- so, if you do turn down the fuel pressure, it will lean the A/F out.  Ideally it would be better to have the software call for the leaner mixture and consequent reduced duty cycle.  But, I don;t know if you have control over that.

[enginerd]

Great post bob,

Calls out the  :bs: like dynoing 300 whp on the stock fuel system.

[Don®]

Thanks for the great info Bob  

[fast_a2_20v]

another thing to keep in mind people is that fuel pump 90% of common pumps have pressure limitations in the 75-80psi range... Safety valves or whatnot... walbro 255 in tank is one which pops to mind, pretty much deadpans at 75psi...

Soooo, you need to keep in mind that if you start with 4 bar or about 60 psi, your going to hit 80psi of rail pressure at only 20psi of boost.

if your pump flow takes a shit on you, the fuel pressure drops, injetor flow drops, and piston welding commences.


so keep that in mind unless you have an arnold swollenpekka size inline pump.

[27psiBOOM]

Let me tell you this info is extremely accurate.

Fuel Pressure 3 Bar
BSFC .55

Duty Cyle Max HP @ Duty Cycle
80% 244.36 HP
85% 259.64 HP
90% 274.91 HP
95% 290.18 HP
100% 305.45 HP

I got 302whp on 440cc @ 3.25bar, runing good AFR numbers and almost 100% DC so 0.55 BSFC seems accurate  :driving:

[mj6234]

Don't AGUs have a limitation on injection time to 16.32 ms where the DBW cars do not?

[Dizzy]

Don't AGUs have a limitation on injection time to 16.32 ms where the DBW cars do not?

I believe this is correct.  What were nebulight's and Steve's numbers on 440's?  Steve did like 388whp on some high fuel pressure, and I think nebulight's was similar.

[27psiBOOM]

yes they do but it wasn't confirmed, seems like vag-com only reads 16.32ms but injection period keeps on raising, and with bobqzzi info this should be true for 0.55 BSFC

[Don®]

Here's a useful Utility...

Racers Math - 1

[27psiBOOM]

Here's a useful Utility...

Racers Math - 1

Don your the man  :bowrofl:

So according to that formula stock fuel pumps (90lt/hr) can only handle 265-270HP for a 0.55 BSFC, and almost 750HP for a Walbro 255lt/hr !!!!  

[enginerd]

So according to that formula stock fuel pumps (90lt/hr) can only handle 265-270HP for a 0.55 BSFC, and almost 750HP for a Walbro 255lt/hr !!!!  

you never really get 255 l/hr out of a walbro. They are more like 500 hp ish pumps.

[Don®]

So the Stocker should be good for at least 350 hp...

[fast_a2_20v]

walbro 255's typically run out of juice around 550-600hp but it depends on how big of injectors and how much base pressure your running. that is certainly not a "safe" level for them and you need to have your wits about you because fuel pressure might be dropping off etc etc.

[Dizzy]

So would a fuel pressure gauge in cabin be a good idea?  I don't exactly like the idea of pressurized fuel in the cabin, lol.

[Don®]

:bowrofl:

[bobqzzi]

walbro 255's typically run out of juice around 550-600hp but it depends on how big of injectors and how much base pressure your running. that is certainly not a "safe" level for them and you need to have your wits about you because fuel pressure might be dropping off etc etc.

I concur

My walbro 255 started coming up short about 480hp and 25psi- but that was at @12.5 volts.  So, at 13.8volts..a bit on the high side of 500bhp.

This is with 83 lb/hr injectors, 50psi base pressure.

I thought I read that these pumps had an internal bypass at 75psi- but have no idea if it is true.  Anyone know?

[enginerd]

walbro 255's typically run out of juice around 550-600hp but it depends on how big of injectors and how much base pressure your running. that is certainly not a "safe" level for them and you need to have your wits about you because fuel pressure might be dropping off etc etc.

I concur

My walbro 255 started coming up short about 480hp and 25psi- but that was at @12.5 volts.  So, at 13.8volts..a bit on the high side of 500bhp.

This is with 83 lb/hr injectors, 50psi base pressure.

I thought I read that these pumps had an internal bypass at 75psi- but have no idea if it is true.  Anyone know?

If they guys at walbro ever run my pump on their test bench, I shoudl have a nice curve for the stock pump. Maybe another week

bypass at 75 psi would be a disaster. 4 bar base fuel and 20 psi of boost = 78 psi

Dizzy, I have run autometer digital fuel pressure gauges with good results. They use a transducer to measure fuel pressure, and you just tee into the line with the sensor. only wiring run into the cabin. They even have one with an analog output that you can log with an LM1 or other logger. I had to make pins to fit in the connector but the signal was there.

[enginerd]

Bump for the dyno master flex

http://www.elitedubs.com//modules.php?name=Forums&file=viewtopic&p=8863#8863

[Matt_Arruda]

Pricless info, great refferance tool.
I dynoed the car @ 42 psi base fuel on 96lb injectors 80% duty .55 BSFC made 430 WHP Chart is stating 558 HP assuming its flywheel HP. This was done on a Land and Sea dyno if that helps. Great info none the less looks like I got some bugs to work out again great reffeance tool