Injectors, bigger the better?

[gijoe985]

Is bigger always better with an injector? In other words if I was upgrading, I might as well go big? Worst case I just don't use them to their potential? I just didn't know if I should go with 600-700cc injectors or just buy some huge 1050cc ones so that I'll never have more than I need. Then again, I know I'll never want to use that much hp, so it'd be kinda pointless. I just wanted some thoughts.

 

[kmoore]

First off, you need to update your vehicle profile.

When it comes down to it, it all depends on your tuning capabilities. For an S-AFC for example, the max that I would go with (and plan to) is 650's. Now say you got DSMLink, that is when you get those 1000cc injectors because Link has a wider range of tuning capabilites and is more precise than an S-AFC.

 

[gijoe985]

Updated my profile. Since I have no DSM yet it was easy... Either way, I want a 1g TSI AWD.

I am hoping to get a dsmlink, or at least that is my fuel computer of choice.

 

[mach4g63t]

I might be wrong here, but I think I've also read in the past that you have to be wary of going really big too soon because of the injector pulses that some of the bigger injectors create. They won't be as efficient even when kept in check by DSMLink and won't create as efficient bursts of fuel when operating at low extremes.

 

[awesome_asim187]

Your injectors all depend on what mods you have.

Simple 16g's=550's and above.

 

[97gstjosh]

^ Agreed it just depends on what turbo you want, supporting mods, and horsepower goals.

 

[50trimmed1g]

I am running 660's right now only because the ecu will give lots of timing when you are subtracting a lot of airflow using the safc. I recommend you get the dsmlink and a set of injectors at the same time so you can have the dsmlink chip calibrated for whatever size injector. I wouldn't say bigger is always better, but if I were you I would go with dsmlink and at least some 880's. My 50 trim at 20psi is requiring an idc of 91% which is pretty high.

 

[TSImuchforyou]

yeah i agree and if you need some 880's i have some for sale i just went to 1600cc sucks when you get that big... you need a injector driver haha and 2 fuel pumps

 

[97gstjosh]

Yeah you want your IDC to be between 70-75% never over 80%
I would go with a set of these
Modern Automotive Performance  :: DSM  :: Fuel and Nitrous  :: Fuel Injectors and Drivers  :: Fuel Injectors  :: Fuel Injector Clinic 850cc Injectors (DSM / Evo)

An injector in an engine turns on and off very quickly to control the amount of fuel delivered. The amount of time an injector is turned on and delivering fuel is known as the duty cycle. This is measured as a percent, so 50% duty cycle indicates that the injector is held open and held closed for an equal amount of time. When the engine needs more fuel, the time that the injector stays on (its duty cycle) increases so that more fuel can flow into the engine. If an injector stays on all the time, it is said to be static (wide open, or 100% duty cycle). INJECTORS SHOULD NOT GO STATIC IN A RUNNING ENGINE! If an injector is static in a running engine (open 100% of the time), that injector is no longer able to control fuel delivery. It is just "along for the ride". This could be an indication that the injector is too small for the needs of the engine. Injector duty cycle should usually not exceed 80% in a running engine at any time.

 

[gijoe985]

I guess I was just commenting on bigger=better because I know that there is a direct formula that tells you how large injectors you will need to get X amount of HP at what BSFC/duty cycle. I was just figuring, if you are going to make the investment, and I'd like to get dsmlink as well, I might as well get oversized injectors so that if I one day want to increase my turbo size or whatnot, I will have the fuel to power it. So I guess my question was whether it would hurt performance by having the large injectors before I need them.

I understand you guys need to know what mods to calculate what is "needed." Long and short is, would going bigger hurt at all? I am assuming 850-1050 wouldn't hurt much on a 200-300hp engine. But lets say we put 2000cc injectos on an egine that only breathed enough to produce 200hp. What's that do? Would the injectors not function (being that this is hypothetical and crazy, we're assuming that we can program them correctly) because the are operating at such a low duty cycle?

I'm just trying to learn some injector theory. Thanks for working with me.

 

[wret]

The extra capacity doesn't hurt but larger injectors require more advanced fuel control techniques. 550's can be handled with a MAFT or other piggyback. At around 650's, your going to need an SAFCII. Larger injectors require EPROM chip program change such as keydiver or dsmlink.

 

[dsm-onster]

Exactly. And to add, up to 1150 cc injectors have been proven to idle just fine w/ dsmlink. No more skill than the same for 550s is required to tune up to 1150cc where dsmlink or other eprom flashing is employed. So if you plan on going dsmlink, look at the difference in price between the fic 1000cc injectors and 650cc injectors, and decide if never upgrading injectors again is worth the extra 50 bones.

Several have noted idle issues with 1600cc injectors, though. Spray pattern does become an issue at this point.