X HP -> Which Fuel Injectors

[CONSIGLIERI]

Hello friends !

Is there any "Rule" for a range of HP should go with which Fuel Injectors ?

For example, the stock 450cc can handle up to how many hps ?

I've read a lot of topics with questions like: "My car has 400 whp, should I switch my fuel injectors for a 650cc ?"

Thanks !!!

 

[9!'clipseDOHC]

Here is a simple chart:
HP Goal – Min Injector Size (cc/min)*
250hp-....... 550cc
300hp-....... 650cc
350hp-....... 750cc
400hp-....... 850cc
450hp-....... 950cc
500hp-....... 1050cc

Here is a simple calculator on Fuel Injector Clinic's website:
Fuel Injectors FLow Calculator - Fuelinjectorclinic

And this is probably more info the you want but here you go:

What size injectors do I need for my horsepower goal?

Like other selections made in the build process, such as turbo and fuel pump, the flow rate of the injectors will determine the range of horsepower that is possible. Injectors are identified by their flow rate, typically in cubic centimeters per minute, but the rating is based on 100% flow. In actuality the injectors are never open 100% of the time. The length of time they are open while your engine is running is called injector duty cycle (IDC). When IDC exceeds a certain point, horsepower can actually drop as the internal valves of the injectors are asked to open and close faster than they can complete each event and are essentially floating in a partly open/partly closed position. The maximum IDC can vary by manufacturer and design but it is generally between 80% and 90%. Therefore, when upgrading injectors it should be planned that IDC will not exceed 80%. This generally leaves a little safety margin. The table below is based on the mathematics of a duty cycle of 80%. There are several interactive calculators on line. Just google "injector size calculator".

HP Goal – Min Injector Size (cc/min)*
250hp-....... 550cc
300hp-....... 650cc
350hp-....... 750cc
400hp-....... 850cc
450hp-....... 950cc
500hp-....... 1050cc

*Injectors are generally available sized in increments of 50, although some are sized at other increments such as 680 or 720. There are fewer size increments available between 1000 and 1600.

There are several ways to extend the horsepower expected with a given size injectors. One way is running a leaner mixture with race fuel and/or water-alcohol injection. Another is to increase regulated fuel pressure higher than the normal 43.5 psi.

What fuel control upgrades are required with larger injectors?

The greater the increase of the injector size over stock, the more advanced the fuel control system requirement. Mild upgrades can be handled with a piggyback system or MAFT. Injectors with rates up to 650 can be successfully controlled with an SAFCII. Injectors larger than 650 require some programming changes to the ECU to control them effectively.

Injector size - Minimum fuel control requirement
Up to 550-......... MAFT or piggyback
>550 to 650-..... SAFCII
>650-................ EPROM ECU with revised chip such Keydiver/SAFCII or DSMLink

I'm upgrading. Should I just get huge injectors and never have to upgrade again?

The extra capacity doesn't hurt and injector cost is not relative to volume so it might make economic sense to get larger injectors and never have to upgrade again. Just make sure you plan on proper fuel management (see above).

What is stock injector size?

1G turbo- M/T 450, A/T 390
2G turbo- 450 for M/T and A/T

What is the color code for Mitsubishi injectors?

Alright, I've decided to spend some time at work and crunch some numbers on the most commonly used injector and fuel pump sizes. The list below will provide you with the maximum amount of air that a give fuel system component can handle. There are some assumptions that I had to make for the calculation to function. Such as:

1) Everyone is running 93 octane fuel @ a base pressure of 43psi.
2) The Denso stock replacement fuel pump supplys the same flow, at a give pressure, as the stock Mitsubishi pump.
3) Everyone's fuel pump and injectors are working at peak performance.
4) Target AFR is 11:1
5) I can't have everyone's injectors flow tested, so we have to assume that if you bought 550cc injectors, that they flow 550cc/min.

On to the numbers

Injectors

390cc @ 100% IDC will support 27.99lbs/min
390cc @ 80% IDC will support 22.39lbs/min

450cc @ 100% IDC will support 32.30lbs/min
450cc @ 80% IDC will support 25.84lbs/min

550cc @ 100% IDC will support 39.48lbs/min
550cc @ 80% IDC will support 31.58lbs/min

580cc @ 100% IDC will support 41.63lbs/min
580cc @ 80% IDC will support 33.31lbs/min

650cc @ 100% IDC will support 46.66lbs/min
650cc @ 80% IDC will support 37.32lbs/min

660cc @ 100% IDC will support 47.37lbs/min
660cc @ 80% IDC will support 37.90lbs/min

720cc @ 100% IDC will support 51.68lbs/min
720cc @ 80% IDC will support 41.34lbs/min

750cc @ 100% IDC will support 53.83lbs/min
750cc @ 80% IDC will support 43.07lbs/min

780cc @ 100% IDC will support 55.99lbs/min
780cc @ 80% IDC will support 44.79lbs/min

850cc @ 100% IDC will support 61.01lbs/min
850cc @ 80% IDC will support 48.80lbs/min

880cc @ 100% IDC will support 63.17lbs/min
880cc @ 80% IDC will support 50.53lbs/min

950cc @ 100% IDC will support 68.19lbs/min
950cc @ 80% IDC will support 54.55lbs/min

1000cc @ 100% IDC will support 71.78lbs/min
1000cc @ 80% IDC will support 57.42lbs/min

1150cc @ 100% IDC will support 82.54lbs/min
1150cc @ 80% IDC will support 66.04lbs/min

1600cc @ 100% IDC will support 114.85lbs/min
1600cc @ 80% IDC will support 91.88lbs/min

Fuel pumps

Numbers will be arranged in the following format:

"X psi = Y lbs/min"

where X = Boost and Y = Max airflow supported by pump

Stock 2g pump

10psi = 33.29lbs/min
11psi = 32.61lbs/min
12psi = 31.90lbs/min
13psi = 31.17lbs/min
14psi = 30.41lbs/min
15psi = 29.63lbs/min
16psi = 28.84lbs/min
17psi = 28.01lbs/min
18psi = 27.16lbs/min
19psi = 26.28lbs/min
20psi = 25.38lbs/min
21psi = 24.46lbs/min
22psi = 23.51lbs/min
23psi = 22.54lbs/min
24psi = 21.54lbs/min
25psi = 20.52lbs/min

Stock 2g pump (Rewired)

10psi = 42.08lbs/min
11psi = 41.51lbs/min
12psi = 40.92lbs/min
13psi = 40.30lbs/min
14psi = 39.67lbs/min
15psi = 39.00lbs/min
16psi = 38.32lbs/min
17psi = 37.61lbs/min
18psi = 36.88lbs/min
19psi = 36.13lbs/min
20psi = 35.35lbs/min
21psi = 34.55lbs/min
22psi = 33.72lbs/min
23psi = 32.88lbs/min
24psi = 32.01lbs/min
25psi = 31.11lbs/min

Walboro 190lph

10psi = 46.48lbs/min
11psi = 45.89lbs/min
12psi = 45.26lbs/min
13psi = 44.58lbs/min
14psi = 43.86lbs/min
15psi = 43.09lbs/min
16psi = 42.28lbs/min
17psi = 41.43lbs/min
18psi = 40.54lbs/min
19psi = 39.60lbs/min
20psi = 38.62lbs/min
21psi = 37.60lbs/min
22psi = 36.53lbs/min
23psi = 35.42lbs/min
24psi = 34.26lbs/min
25psi = 33.06lbs/min

Walboro 190lph (Rewired)

10psi = 60.68lbs/min
11psi = 59.85lbs/min
12psi = 59.01lbs/min
13psi = 58.16lbs/min
14psi = 57.29lbs/min
15psi = 56.40lbs/min
16psi = 55.49lbs/min
17psi = 54.57lbs/min
18psi = 53.63lbs/min
19psi = 52.67lbs/min
20psi = 51.70lbs/min
21psi = 50.71lbs/min
22psi = 49.71lbs/min
23psi = 48.68lbs/min
24psi = 47.64lbs/min
25psi = 46.58lbs/min

Walboro 255lph

10psi = 63.53lbs/min
11psi = 62.88lbs/min
12psi = 62.20lbs/min
13psi = 61.48lbs/min
14psi = 60.72lbs/min
15psi = 59.93lbs/min
16psi = 59.10lbs/min
17psi = 58.23lbs/min
18psi = 57.33lbs/min
19psi = 56.39lbs/min
20psi = 55.41lbs/min
21psi = 54.39lbs/min
22psi = 53.34lbs/min
23psi = 52.26lbs/min
24psi = 51.13lbs/min
25psi = 49.97lbs/min

Walboro 255lph (Rewired)

10psi = 72.15lbs/min
11psi = 71.47lbs/min
12psi = 70.77lbs/min
13psi = 70.04lbs/min
14psi = 69.29lbs/min
15psi = 68.52lbs/min
16psi = 67.73lbs/min
17psi = 66.92lbs/min
18psi = 66.08lbs/min
19psi = 65.22lbs/min
20psi = 64.34lbs/min
21psi = 63.43lbs/min
22psi = 62.50lbs/min
23psi = 61.55lbs/min
24psi = 60.58lbs/min
25psi = 59.58lbs/min

Walboro 255lph HP

10psi = 64.64lbs/min
11psi = 64.19lbs/min
12psi = 63.74lbs/min
13psi = 63.30lbs/min
14psi = 62.86lbs/min
15psi = 62.42lbs/min
16psi = 61.99lbs/min
17psi = 61.56lbs/min
18psi = 61.13lbs/min
19psi = 60.71lbs/min
20psi = 60.29lbs/min
21psi = 59.87lbs/min
22psi = 59.46lbs/min
23psi = 59.05lbs/min
24psi = 58.64lbs/min
25psi = 58.24lbs/min

Walboro 255lph HP (Rewired)

10psi = 74.29lbs/min
11psi = 73.86lbs/min
12psi = 73.43lbs/min
13psi = 73.01lbs/min
14psi = 72.58lbs/min
15psi = 72.15lbs/min
16psi = 71.72lbs/min
17psi = 71.28lbs/min
18psi = 70.85lbs/min
19psi = 70.42lbs/min
20psi = 69.99lbs/min
21psi = 69.55lbs/min
22psi = 69.12lbs/min
23psi = 68.68lbs/min
24psi = 68.24lbs/min
25psi = 67.80lbs/min

Denso US EVO 8 Stock Pump

10psi = 39.96lbs/min
11psi = 39.10lbs/min
12psi = 38.12lbs/min
13psi = 37.31lbs/min
14psi = 36.39lbs/min
15psi = 35.45lbs/min
16psi = 34.48lbs/min
17psi = 33.49lbs/min
18psi = 32.49lbs/min
19psi = 31.47lbs/min
20psi = 31.47lbs/min
21psi = 29.35lbs/min
22psi = 28.26lbs/min
23psi = 27.15lbs/min
24psi = 26.02lbs/min
25psi = 24.87lbs/min

Denso EVO 8 Stock Pump (Rewired)

10psi = 51.23lbs/min
11psi = 50.36lbs/min
12psi = 49.48lbs/min
13psi = 48.60lbs/min
14psi = 47.72lbs/min
15psi = 46.85lbs/min
16psi = 45.97lbs/min
17psi = 45.09lbs/min
18psi = 44.20lbs/min
19psi = 43.32lbs/min
20psi = 43.32lbs/min
21psi = 41.55lbs/min
22psi = 40.67lbs/min
23psi = 39.78lbs/min
24psi = 38.90lbs/min
25psi = 38.01lbs/min

Denso Supra 260

10psi = 70.70lbs/min
11psi = 70.06lbs/min
12psi = 69.42lbs/min
13psi = 68.77lbs/min
14psi = 68.12lbs/min
15psi = 67.45lbs/min
16psi = 66.78lbs/min
17psi = 66.10lbs/min
18psi = 65.42lbs/min
19psi = 64.73lbs/min
20psi = 64.03lbs/min
21psi = 63.32lbs/min
22psi = 62.60lbs/min
23psi = 61.88lbs/min
24psi = 61.15lbs/min
25psi = 60.41lbs/min

Denso Supra 260 (Rewired)

10psi = 82.91lbs/min
11psi = 82.38lbs/min
12psi = 81.83lbs/min
13psi = 81.28lbs/min
14psi = 80.73lbs/min
15psi = 80.17lbs/min
16psi = 79.60lbs/min
17psi = 79.03lbs/min
18psi = 78.46lbs/min
19psi = 77.88lbs/min
20psi = 77.08lbs/min
21psi = 76.71lbs/min
22psi = 76.11lbs/min
23psi = 75.51lbs/min
24psi = 74.91lbs/min
25psi = 74.30lbs/min

Although these are the maximum values that the fuel system components can support, I do not advocate running the fuel pumps at their maximum flow. I also don't recommend running your injectors above 80% IDC. Why, you might ask.....

Lets say you are running on the 190lph Walboro @ 20psi and are flowing about 37lbs/min of air. At that point you are within the tolerance of a perfectly functioning pump. For some reason your voltage drops because of a bad alternator, or the boost starts to creep for some reason. Now you are pushing more air than the pump can support and the car starts running lean. At that point there is a chance of melting something, which we would all like to avoid.

Anyway, I just thought I would crunch some numbers so that everyone has a reference.

Also, if anyone sees any errors, let me know and I will make the appropriate corrections. There was a lot of numbers to crunch and transpose, so it is possible that I made a mistake.

EDIT -> Added additional data for injectors (750cc, 850cc, 950cc and 1000cc). Also, please note that these flow rates are calculated at the fuel pump outlet and not after traveling through the system. Just another reason not to try and approach the maximum limits listed above.

I just added the US EVO 8 stock pump and the Denso Supra 260 as requested.

I also adjusted the injector calculation because I screwed up the mass of 1 gallon of water in my calculation, which led to the incorrect mass of 1 gallon of fuel being used.

 

[gofer]

Injector size is NOT relative to horsepower, this is a common misconception, it relative to the airflow of the turbo. You find how much the turbo you want to run can flow, then pick an injector thats big enough to support it.

Injector/Fuel Pump Supported Airflow

 

[airmail96]

With that question I think it depends more on what fuel your using and how much air your flowing.