How much boost with stock Injectors???

[JoEgsX90]

Running a 190 fuel pump with stock injectors othe mods on my profile....Im getting a SAFC2 and wondering how much boost can i run with the stock 450's??

 

[gsxeclipse97]

Wow that is confusing. So basicly you would be better just buying dsm link cause that way you can adjust timing, and change the maps at the same time without doing guess work to try to correct the ecu with a piggy back system. I currently don't have either so i have never really experimented with an afc. But it seems to me you would have to get some sort of system to counter the fuel cut or you would never be able to run over x amout of boost because the computer will hit fuel cut before you start making more power. So after you get the basics your basicly capped until you get a engine managment system.

 

[the_mork]

You are taking this to level that is not necesssary. You don't need a Dyno to find injectors for a car, so you don't need to go into all this added discusstion about VE or drivetrain loss. Horsepower has everything to do with tuning. You don't get horsepower from nothing. You have to get a start from somewhere. So you are saying that this formula is useless in finding an injector in a close range:

Horsepower X B.S.F.C = LBS/hr (per injector)
----------------------------
No.of injectors X Desire duty cycle

-In most cases a naturally aspirated engine will have a B.S.F.C of .50. This means that the engine will use .50 lbs. of fuel per hour for each horsepower it produces. Turbocharged engines will want to be at .60 lbs. per hour or higher.

-Using these numbers as a guideline, you can select the approximate injector size in the following formula for a four cylinder, naturally aspirated engine at 200 bhp.

-Most injectors will max out at 80% duty cycle and this is the accepted industry standard.

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

So I am going to run a GT14 turbo on my stock 2.0 engine with cams. How would you go about finding the right size injectors. I will be tuning with maf translator if that helps out any.

Sigh, I think you have this backwards. You are the one who is taking this to a level that is not necessary. Horsepower is an unnecessary calculation and using a "calculator" will give you completely unreliable worthless results. If you want to base your injectors on horsepower you would need a dyno.

As for the injector sizing question why don't you tell me how much airflow you want to have? It is a step in your horsepower calculation. It is also as far as you need to go to know what size injectors you need.

Maybe I should clear this up here. I am saying that you can run a higher boost level on 450cc injectors than what some members on this topic are claiming. I should have pin-pointed who I was talking to but this was not for the O.P. If I was to comment on what would be a safe limit for just the O.P.s current setup, I would suggest leaving the boost alone until he gets a logger to make sure he is not going to pop his engine. You are not comprehending this the way I am intending it to sound.

Fine, you weren't very clear and I wasn't very considerate, we agree that the sort of boost you run should not be considered a universally safe number.

You might want ot recheck this. The ECU initiates fuel cut when the calculated airflow goes over a set value. It in no way correspond with maximum IDC. This has nothing to do with a certain boost level. If you have done any ECU tuning you would know this. Why do some hit fuel cut or not you ask with pretty much the same setups??? Say fuel cut is to iniate at 2000HZ. The first car with a leaky throttle body and a couple leaky vacuum lines, when it hits say 15 lbs of boost it has to draw more air through the MAS to compensate for the leaks just to hit that 15 lbs to make the wastegate happy. So it has a beter chance of hiting that 2000HZ the mas reads. Second car has zero leaks and a tight system. It hits 15lbs and will read a lower count of HZ because none of it is leaking out of the already counted for readings. This car will not hit fuel cut so soon so now you can run this at a higher level of boost before it does fuel cut. The IDC comes into play because it coresponds with the mas flow HZ through the ecu. You can hit fuel cut before you run out of injector on a 450cc. This on my part maybe a poor explination on this but it covers the basis.

The number is based on a boost leak free car under normal operating standards anything else will lower your fuel cut ceiling, that does not make it just a silly number that the designers picked out of thin air it makes it a specific number that becomes more conservative as the car falls apart. I also didn't say that it has anything to do with boost, it has everything to do with airflow.

 

[the_mork]

Wow that is confusing. So basicly you would be better just buying dsm link cause that way you can adjust timing, and change the maps at the same time without doing guess work to try to correct the ecu with a piggy back system. I currently don't have either so i have never really experimented with an afc. But it seems to me you would have to get some sort of system to counter the fuel cut or you would never be able to run over x amout of boost because the computer will hit fuel cut before you start making more power. So after you get the basics your basicly capped until you get a engine managment system.

A piggyback system is based on tricking the ecu about what is coming in from the maf, the ecu wont see as much air if you are tuning for bigger injectors so you wont hit fuel cut at the same point.