General Injectors and pumps

[Justin DuBois]

I’m looking for the practical wisdom regards injector sizing related to the fuel pump.

I assume there is a practical limit to the size injector you can pair with a fuel pump.

Example: At some point a stock fuel pump/filter/-6an supply wont have enough flow to hold pressure at WOT with a xxx size injector.

What is that practical limit?
What pump do you pair with x size injector?

In my case I’m running -6an supply, stock fpr, stock return.

I’ve been very happy with 380hp using 720cc injectors and a Supra 280lph pump.

If I move to 1000cc injectors (or larger) what else has to change? and practically - how do you know what has to change and by how much?

 

[Stapl3]

I assume there is a practical limit to the size injector you can pair with a fuel pump.

You could put 450s on 3" ID fuel rail with a pump the size of a brick that's regulated to 42.5psi and it should operate as stock. I don't see why not anyways.

My 92 talon has a 450 pump rewired with a BAP, stock lines, stock filter, stock rail, 2150's at 40psi base. E85. No issues.
My 91 talon has a 450 pump rewired with a BAP, stock lines, stock filter, stock rail, 650's at 80psi base. E85. No issues.
If I had to do it over again I'd use a 525 pump.

The stock lines are so closely sized to -6 I think it would be more enjoyable to put the money in the toilet and push the handle just to say you did that instead.

 

[19Eclipse90]

At least regarding pump to injectors, theoretically - and ignoring pressure factors and voltage - the fuel pump should be able to supply enough fuel to the quantity of injectors at their rated / maximum flow rates.

Fuel pump flow rates for imports are usually provided in liters per hour. Injector flow rates usually provided in cubic centimeters and the unspoken per minute.

One cubic centimeter is 1 milliliter. So if you’re running (4) 250cc injectors, that’s potential for 1000cc per minute or 1L per minute. That’s 60L per hour.

If you have (4) 1000cc injectors, that’s potential for 4L per minute or 240L per hour. So, theoretically, a 255LPH pump should be sufficient for that setup.

It’s a simplistic approach and certainly doesn’t cover everything, but in my mind, is a good place to start. It at least shows pretty quickly, for example, that you probably shouldn’t pair 1000cc injectors with a 190lph pump and expect to be able to utilize the injectors to their full potential.

Take it for what it’s worth - and that may not be much once you consider some of the more advanced factors. Forgive me if this is all well understood already but it seemed that’s kind of what you are after.

 

[jdxnc]

Fuel injector to pump or pump to fuel injector size really have no correlation in my mind, it's all based on desired power level of the engine and fuel type. As started above, you could have a 535LPH pump with stock injectors and a proper regulator and run like stock, overkill but it would be fine.

Now with how much technology had advanced since these cars were newish, I won't even bother with low impedence injectors, on a basic street car, either stay with the stock fuel system or jump up to 1000cc hi-z injectors and a Walbro 255 or AEM 320 pump and a quality AFPR, stock lines/filter will be perfectly fine. These's plenty in this to run 10's on the 1/4 mile.

Once you want more power than that, say enough to run mid to low tens, go with 1650-2150cc injector a 525 or 535 pump and upgraded lines. This will take you well into the 9's.

 

[Justin DuBois]

At least regarding pump to injectors, theoretically - and ignoring pressure factors and voltage - the fuel pump should be able to supply enough fuel to the quantity of injectors at their rated / maximum flow rates.

Fuel pump flow rates for imports are usually provided in liters per hour. Injector flow rates usually provided in cubic centimeters and the unspoken per minute.

One cubic centimeter is 1 milliliter. So if you’re running (4) 250cc injectors, that’s potential for 1000cc per minute or 1L per minute. That’s 60L per hour.

If you have (4) 1000cc injectors, that’s potential for 4L per minute or 240L per hour. So, theoretically, a 255LPH pump should be sufficient for that setup.

It’s a simplistic approach and certainly doesn’t cover everything, but in my mind, is a good place to start. It at least shows pretty quickly, for example, that you probably shouldn’t pair 1000cc injectors with a 190lph pump and expect to be able to utilize the injectors to their full potential.

Take it for what it’s worth - and that may not be much once you consider some of the more advanced factors. Forgive me if this is all well understood already but it seemed that’s kind of what you are after.

I'm picking up what your putting down here... I was hoping someone would go with the rough math relating to flow - and you got there. Fuel pump is due to be replaced. I mean its only been (muttering ..2006, carry the one...) 17 years?

 

[Justin DuBois]

Fuel injector to pump or pump to fuel injector size really have no correlation in my mind, it's all based on desired power level of the engine and fuel type. As started above, you could have a 535LPH pump with stock injectors and a proper regulator and run like stock, overkill but it would be fine.

Now with how much technology had advanced since these cars were newish, I won't even bother with low impedence injectors, on a basic street car, either stay with the stock fuel system or jump up to 1000cc hi-z injectors and a Walbro 255 or AEM 320 pump and a quality AFPR, stock lines/filter will be perfectly fine. These's plenty in this to run 10's on the 1/4 mile.

Once you want more power than that, say enough to run mid to low tens, go with 1650-2150cc injector a 525 or 535 pump and upgraded lines. This will take you well into the 9's.

Big 16G Turbo Rebuild and O2 Housing+Downpipe flow improvements, have been introduced since last tune, and everything leaned out 10-11%. The global fuel correction pushed my 720's max Injector Duty Cycle to - 100%, Fuel is not plentiful in this case - which is a good problem to have. ;-)

I've never been to the drag strip (as a driver) - no idea what this one does in terms of 1/4 mile. I try not to launch on the clutch and transmission as a general habit.

I agree regards LowZ, was going to stick with the stockish configurations as long as possible. I'm trying to keep the balance between supply and demand so non-heroic pressures can be used.