Injector Flow Rates -

Hi all -

Anyone able to state what injectors they are using on their FI setups? and whether they are batch fired (in pairs) or sequentially fired.

If you can state the flow rate in lbs/hour or preferably cc/min together with your rail pressure and if you know it, your HP fuel pump flow rate. (Litres/hour)

Any info greatly accepted - I'm just trying to get my head round a problem at the moment.... /ubbthreads/images/graemlins/confused.gif
 
In the ford Mustang 5.0, I think the injectors are sequentially fired. Stock injectors are 19 lbs/hr. I don't know how that translates to cc's. Those injectors are good for about 300hp of fuel flow. The 5.0 Cobra models used 24 lbs/hr injectors. I will be using 30 lbs/hr injectors because they should support 450hp.

I don't know anything about the single stack setups, but I do know that not all fuel injectors are made equal. There are some that controll the fuel a lot better at low duty cycles. If you need a big injector to support the power you can make, you need it to be accurate at low duty cycles so that it will idle well.
 
Thanks for the reply Daniel - I seem to remember that the injectors we use flow about 500cc / min when full on so maybe 400cc at 80% duty cycle - (might have been 500cc at 80% - can't quite remember) - however - I seem to remember the number of 36lbs? being quoted when they were supplied and I believe 400cc/min is good for about 80BHP - so 8x80 means they should be good for about 640Bhp - I think?

Bit late now..... and my brain hurts! /ubbthreads/images/graemlins/confused.gif
(yeah yeah James - it's only a little pain... /ubbthreads/images/graemlins/grin.gif)
 
I think they were rated at 100% duty cycle, because 36 lbs/hr is less than twice the flow of 19 lbs/hr injectors which are good for about 300 hp.

On the other hand, they might have rated them at a very high fuel pressure, like 65 psi. Most injectors are factory rated at about 40 psi, but the retailers will look at the flow chart and choose the highest spot, then take that flow and extrapolate power from an efficient engine that is using that much fuel. In reality, you always need a bigger injector than those inflated numbers would suggest because you don't want to run 100% duty cycle or super high fuel pressures at peak power.

Fuel injectors are made in lots of sizes, I know that 38 and 42 lbs/hr are common. That might be the size you have.

Most mustangs over here in the states run between 38 and 50 psi fuel pressure. A popular upgrade is a walbro 255 liter/hr fuel pump. Of course supercharged cars have more of everything, bigger injectors, higher fuel pressure, dual pumps, and oversized fuel lines.

As long as your regulator can controll the fuel pressure, it does not matter if your pumps are too large. With that in mind, I am going to use dual 190 liter/hr pumps with one wired to a RPM switch. That way, I will have more than enough volume with out wasting a bunch of electricity pumping fuel through the bypass.

It's overkill, I could probably just use a 255 liter/hr pump, but I have heard that they can be noisy, and they draw a lot of amps to move all of that fuel.

What kind of compression are you running and what RPM are you turning? 640 horse power is a lot for a 347.

Most good 347's around here are making less than 500 hp. Some are higher, but they are mostly race only engines.
 
Hi again -

We are not making 640Hp - my thoughts were that the injectors should flow enough fuel for up to 640BHP.

We are making approx 530+ at 6000rpm (or used to be)..

Engine should run to 7500 but we have an rpm limit issue at the moment! (and not by choice).. /ubbthreads/images/graemlins/confused.gif

Compression is about 10.8:1 if I remember correctly.

Fuel rail runs at 55 psi.

I am going to stick my Bosch Wideband Lambda meter on ot this weekend (Wiscombe Hillclimb) and log whats going on.
 

Lynn Larsen

Lynn Larsen
Daniel,

If your injectors get to 80% IDC you need to switch to larger injectors. They should NOT be "on" constantly.

Regards
Lynn
 
Paul,

Why not get Roy to hire Fraser for the day. You might then get 640 BHP!!! /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif

Regards,

J.P

P.S For what its worth my rail is 45psi, I'll check what injectors are running.

It'll be very interesting to compare maps, maybe at the track day.
 
Have been corresponding with Michel Guerts at Motec most of this week and have fitted the Motec AF meter for this weekend. We may visit Motec in the near future just to check and there may be a vistor or two at the club track day..... /ubbthreads/images/graemlins/smirk.gif

As a side note - I was speaking to Keith Baker earlier in the week and his Ultima Can Am now makes 610BHP and 580ftlbs and is road legal!! - God help us all!! - he says a visit from Frasier is due to 'improve its road manners!'

i'll bet it is..... /ubbthreads/images/graemlins/grin.gif
 
It's always good to be safe with your fuel system.

55 psi is a bit high. Since you have a motec, I would adjust the pressure down and bump the duty cycle up. If you run out of fuel you need bigger injectors.

A fuel pump has a flow curve that decreases as the pressure increases, and current draw goes right up with preasure also. Using a lower pressure and larger injectors will allow your pump to deliver more fuel and last longer. At 530 hp, you need pretty good flow.

In Mustangs, the pump is the next bottle neck after the injectors. The fuel rails are a distant third and lastly the fuel line from the pump is the last restriction. Most Mustangs making 530+ should probably upgrade the whole system, from the pump to the fuel injectors.

Since your car was built from the beginning to support big power, your fuel pump and injectors are the only likely bottlenecks.
 
Paul,

Another thought. we're running two Bosche fuel injection pumps to guarantee enough flow to the injectors. Peter Knight was under the impression that the injectors would draw fuel faster than one pump could handle. I think we ran 2 pumps on the dyno.

I'm not expert. BUT whats the voltage like. Min of 13v apparantly.

You'll need that 7500RPM if you are to beat me to that sub 12 sec run at Brighton! /ubbthreads/images/graemlins/grin.gif
 
Paul,
Go to www.pro-flow.com
Look under "Meter sizing"
Scroll down to "suggested injector sizing...."
This will give you an approximate HP for NA or Supercharged engines for what injectors you using.

Hope this helps.
 
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