Hey Guys,
I'm planning on going single in the next year or so (probably change my mind 10 times too), and I was wondering if my 1300's will support a T04S at about 15-18psi? Whaddya think? Thanks.

 

no.. get 1600's or 850/1300 combo

 

Thanks.

 

There are many running 550/1300 at 15 lbs, but that's the top of the scale if you are using the 85% duty cycle rule.

At 13.8 lbs I'm at 70% cycle ....... I won't go over 85%. Going to 18 will make you need more than the 550/1300 combo - the 850s or 1600s that mjw mentioned would be the way to go. However, you'll also want race gas over 16 lbs.

Beast

 

i know someone with 4 850's and he's running 15-16 on a kkk27.... whats wrong with a high duty cycle?

 

There is nothing wrong with a high duty cycle, as long as it doesn't reach 100%. If you are using most of your duty cycle, you are getting better control over the range, hence it will run better on partial throttle and idle.

If you would only reach 60% duty cycle, your injectors are too big, and you will be overfueling most of the time. You can't ontrol injectors very well in the low duty cycle range, so stick with something in the 75-85% duty cycle.

I personally haven't modded a turbo 13B before (manly piston engines like the Nissan Skyline 6), so can any body tell me what the rule of thumb is for a 13B turbo with 350hp on 12psi running a bigish turbo? I am taking stabs in the dark with injectors at the moment.

Can anybody help with my setup?

 

I currently run 1300's at 12psi, but sometimes the cold weather gets it up to 14psi. At 12 the highest duty cycle I've seen is 69%, and 77% for 14psi. My car runs 313 whp, but it's also very rich. I need to get it tuned again. I would like to keep my 550 primaries, just so I could still drive around town.

 

550/1600 or 850/1600 is my advice.

Brian

 

Nipondenso makes 680cc and 720cc injectors if your looking for something bigger than 550cc and smaller than 850cc...check the SRmotorsports site

 

The issue with injectors going over 85% is that past that range, they are basically 'on' all the time. You begin to lose granularity and you run up against mechanical limits as things turn on and off. There is not much difference between 85% and 100%, and when you're flowing that close to the top of the ability of the injector to stuff fuel into the combustion chamber, you run the risk of running lean due to running out of gas, or you will have lean 'pockets' due to poor spray patters, AND your injector begin to get hot because they constantly have juice to them. This is a rule of thumb only - many have hit 100% briefly with no ill effects, but you are removing your safety margin. Rotaries are very unforgiving vs. piston motors when you breach safety margins.....

That's the rule, YMMV.

Beast

 

1300s are bored out 850s, aren't they? I have heard that the failure rate is higher for the 1300s. 1600s are readily available (and cheaper, too.)

 

The 1300s are bored out 850s, and I've heard rumors of some failures, but never actually seen proof. Mine were cleaned by RC 5K miles ago and had perfect 1350 flow rates and Excellent spray patterns.

1600s are built that way, but require resistors and different fuel rails, all of which will make it more likely you will fail a CA visual emmissions inspection. That is the primary reason I have not switched over. At least with the 1300s you can get way with it looking stock.

Beast

 

I run 14lbs and have a duty cycle of 76% on the stockers full non-seq.

Im running 1300cc seconds.. and stock primaries.

Josh

 

Sorry i am kinda new at this, but when do the seconds kick in, and do they add to the primaries?? I get everything else tho.....

 

Yes, the secondaries 'add' to the primaries when activated. If you have the datalogit with PFC you can actually configure when this occurs.

Beast

 

I am getting ready to put 850's in my primary. Will these make it a rough idle that will be hard to drive for street? I also have 1300's in my secondary and have had no problem for well over a year.

 

can someone post EXACTLY what I need to change in my datalogit or commander when I put in the 850s in the primary rail? I have them at home with the milled rail...I am also running 1200s in the secondaries. Is this pretty much all I can do without having to get new fuel rails and lines and pressure regulator? Maybe put in 1300s in place of the 1200s? that all I got left?

 

My experience with the larger injectors in the stock system is that you may run out of pump or be limited by the stock fuel system lines ... even with an upgraded intank unit.

With an upgraded pump that flows a butload of fuel I found about 7 psi drop at idle from the firewall to the outlet of the secondary rail. What this means is that you will get less pressure at the secondaries than you might think, especially if you monitor fuel pressure somewhere other than at the secondary rail. I had to run my firewall location pressure up to about 45 psi at idle to get the secondary fuel rail pressure where I wanted it. Also found the pump pressure falling off until rewiring it to see full voltage, was about 1.5 to 2 volts low using the factory wiring. That's a big hit on fuel pump capacity! Rewiring the pump and upping fuel pressure to compensate for the factory fuel system pressure drop reduced injector duty cycle well over 10%!

Running 550/1600 with adj pressure regulator at 45 psi idle at firewall, 19 psi boost, 11.5 AFR, mid to hi 80% inj duty cycle in cold weather.

 

Surge..,

Search the PFC forum here and you'll find the answer to the PFC settings, it's been well documented. You may have to play with some settings to get the inj transition smooth.

 

Wow. This is a lot more than I asked for, but thanks to everyone that has contributed. All the info is greatly appreciated! Thanks.