almost every time i compare stage kits, mostly cobalt-addiction vs. intense, i will compare the pulley sizes w/ the injector size. ie: cobalt-addiction stage 3 has 2.7 w/ 42.5's. intense stage 4 has 2.7 w/ 60's.

same pulley size, but different injectors?! these type of differences "scare" me away from buying a stage kit, and somewhat make me think that CA or intense don't know what they are doing. I JUST DON'T WANT TO BLOW MY S**T up! lol

is there a guide on this site that says which size injectors you should have with which size pulley?

or just tell me to shut up and buy a stage kit cause they all know what they hell they're doing.

 

Think of it this way. Running a 2.9 and lower with 42lb injectors is like playing Russian roulette. The tune has to be PERFECT or you run the risk of blowing the engine up. Main reason why people run 60lb injectors with anything under then a 2.9"

 

if i wannted a 2.9 pulley what size injectors would i need

 

The biggest problem I see on this forum is people asking "what injectors with x pulley?" when that's not how it works.

Main thing to keep a eye on is Injector Duty Cycle, Intake Air temperatures, Combustion Temperatures (reading through EGTs) and making sure that the size injectors you get are adequate for what your fuel pump is rated at so it's not overstressed trying to maintain a certain amount of fuel being sent to your fuel rail and keeping a steady fuel pressure.

Tip: Buy a interceptor gauge, buy a wideband unit and get a EGT probe/unit for monitoring. Start tuning from there.

 

What is an EGT guage

 

Exhaust Gas Temperature is what EGT stands for.

Probe is what measures the temperature in your exhaust stream. The gauge/unit/display is what tells you what the temperature is.

 

It has nothing to do with the tune being perfect or not, you can use a stock tune and it already has values in the VE tables and MAF values for the higher airflow (obviously other tables referring to fueling need to be modified however depending on injector size). Now i'm not saying the stock tune is/isn't perfect but by tuning perfectly in my mind I would think of having the VE tables set as close as possible to achieving stoich AFR at cruise and have a good AFR commanded at WOT in the PE tables. So regardless wether you are using 60's or 42's or even stock, the injectors have to be able to supply the fuel needed for these new cells in the VE that you will be hitting.

Now to explain what your exact question is about. You can use the stock pulley and run 60# injectors if you really wanted to as long as you calibrate your injectors to flow the appropriate amounts of fuel to achieve the desired AFR. My immediate thoughts would be that the two companies you have mentioned may have found that with the AFR they are trying to achieve they only required the injectors they are listing. Personally, and I think many others agree that with a 2.7 or 2.8 you may never need to use the fuel delivering capabilities of the 60 pound injectors but it doesn't affect anything at all if your IDC's never get anywhere near max. There are other things that come into play when using larger injectors but for the most part a 42 and 60 will behave identical when flowing X amount of fuel it's just the 60's have the ability to supply ~ 30% more fuel. For me this becomes critical to think about since it becomes very cold here in the winter and I could potentially be flowing a lot more air into the engine than in the summer; my injectors need to be able to capable of handling the higher flow.

Intense could be using the 60's simply because they can... not as a necessity because as I've said, you may never use the full ability of them with a 2.7 but it's sure nice to know that if you ever did hit a higher amount of airflow that you aren't going to lean out. It's never bad sales either to say to a customer that they are already fully equipped to use a smaller pulley should they desire, easier to sell that smaller pulley this way. Just some of my thoughts anyways....

 

I agree with what you said.

My only thing that people need to recognize is that 60 lb injectors are too large for the stock fuel pump to keep up with supplying fuel for.

 

I'm inclined to agree with the fuel delivery from the pump too. That's a lot of extra fuel for a stock pump to supply.

 

Bingo.

 

If you were running stock pulley and 60's how would they be too big. The fuel pump wouldn't have to work any harder or less hard. I think the 60's are fine with this fuel system. You can argue, why does 4th cylinder lean out, saying that the injector gets less pressure and then fuel but a liquid in a container can't be a higher pressure on one side or the other. Doesn't make sense.

 

Has anyone tried installing a intank pump or even an in-line pump?

 

We're not saying pressure, we're saying flow.

Also, I wasn't referring to a stock car with 60 lb injectors. The people running them are running smaller pulleys.

 

ok here it is simple 42lb injecters are for 2.9 and bigger to be safe. any pulley size under a 2.9 you will need 60lb injectors to be safe so if you want a intenses stage 3 with the 2.7 pulley 60lb injectors are what you want to be safe i still dont understand why cobalt addiction have 42lb injectors with a 2.7 pulley thats pretty much an engine bomb...

 

i think a stage 2 tune and a 2.8 can be gotten away with 2.7 is pushing..stage 2 tune is pretty rich.

 

Yes... this is all fine... but I think the original poster was looking for the why not just simply to be told "you should do this and this".

 

Its because its a returnless fuel system. It tries to maintain ~42 psi fuel rail pressure. If it was a return system, you could use a rising rate pressure regulator and increase the fuel pressure as boost increases, that way you could counter act the injector shrinkage that occurs because of boost pushing against the injectors. With a rising rate pressure regulator 42 lbs injectors could prolly support a 2.7"-2.6" pulley.

 

not trying to be a dick but a 2.7 2.6 pulley on 42lb injectors is car suicide

 

Blown.. what were you running when you blew yours up?

I agreee with ssaddiction... it is car suicide...

 

not 100% true.

 

Do people read on here? He was saying, that IF you could INCREASE FUEL PRESSURE AT THE RAIL, you would be able to run 42lb injectors and a smaller pulley, not that you can do it with stock fuel pressure management.

It all goes back to monitoring and tuning the individual car, I don't care what you should be able to run, look at IDC, AFR and EGT, when those are all happy, then you have a good setup. Until then, you have a setup that needs work, like mine.