Brembo said:

I even went over 100 percent and when I took engine performance class for ASE, the prefossor said it's impossible. Well in my mind that duty cycle is calculated number and does not 100% show exact duty cycle. L

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In theory your professor is probably right but in real life he’s wrong. I’ve hit over 100% more times than I’d like to admit in my Subaru and on stock turbo/injector STIs it’s not that uncommon. I’ve seen people post logs with 110+ IDC

Don't quote me on this but I think anything over 100% duty cycle is just a representation of how much fuel your engine is demanding. The duty cycle is derived from a calculation. A 105% dt doesn't mean your injectors are giving 105% effort. Here is a quote from injector-rehab.com:

"I have seen it more than once that people report they ran a duty higher than 100%... it is not possible. Your injector has completely maxed out and only ran 100%, you just ran it past its operating range and the calculation shows that. It is impossible to physically run an injector HIGHER than 100%."

You can't hit over 100%. Anything over is just a calculated overflow and squirting into the next cycle. The injector is basically completely open at 100%. You cant open it anymore. Look at the square wave on an oscilloscope and it will just be a straight line.

80-85-90 DC (pump gas)
225-240-255 - 370/390cc injectors
275-290-305 - 450cc injectors
335-360-380 - 550/555cc injectors
365-390-415 - 600/608cc injectors
455-475-500 - 725/740cc injectors
515-550-580 - 850cc injectors
605-645-685 - 1000cc injectors
640-680-715 - 1050cc injectors
790-840-890 - 1300cc injectors
1005-1065-1130 - 1650cc injectors
1035-1100-1165 - 1700cc injectors
1215-1295-1370 - 2000cc injectors
1310-1390-1470 - 2150cc injectors

Walbro 255 w/ stock 5/16" feed line is good to at LEAST 425whp.
5/16" line in general has been proved past 500 for a while (Supras)

Some info:
http://www.dsmtuners.com/threads/bosch-044-install.512827/page-3

My $0.02 -->
1) Voltage drop fuel pump to ensure proper voltage.
2)Ensure there are no flow restrictions. All fittings and lines are 5/16"+
3)Get bigger injectors. For 375whp goal I'd go ID1050's for plenty of future growth..
Aeromotive's fuel rail has a 5/8" fuel bore. If you haven't upgraded from stock fuel rail, I'd eventually look into it. With a 5/8" bore, that's something you'd only have to buy once and then you can forget about it.
Good luck.

First injectors I bought back in 07 were 1000cc
Never maxed them out. Bought 1600cc ...never used them. Sold those and now have 2150 that have sitting for 2-3 years

Moral of the story. Buy big injectors (if your wallet allows)

Better to run oversized than undersized

The problem with big injectors how they work at low pulse widths. That effects idles and general driveability. Some big injectors have real problems with linearity at low pulse widths so if you care about anything other than WOT performance you need to look at all the factors. If you not running E85, there's little need.

As mentioned above, ECU's will gladly tell you that your IDC is > 100% but unless you've figured out how to break the laws of physics it just means you need more fuel, your injectors have gone static, and your AFR is going lean.

Vegas smith said:

Is it me, or is your fuel pressure set to 37psi?

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It was set to 40 and I increased to 43

tk106 said:

It was set to 40 and I increased to 43

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Right, but you aren't changing the fuel pressure value inside link so your computer still thinks the car is at 37psi and that is jacking up your tune.

So the down and dirty is conventional theory don't run an injector over 80% for safety sake. Sure you can but your taking out a theoretic safety buffer. An injector cannot duty over 100% because at 100% duty the injector is straight on.
Yes you can bump fuel pressure up to get duty cycles lower and this is ok if the rest of your fuel system is up to the task.
Personally if I were you with how cheap injectors under 1000cc are and you have link I'd just get new injectors. So what if you made more with an safc2 what were your duty s on That?
The safc2 tricks the ecu air flow to compensate for the larger injectors link is more comprehensive so your going to have much more to take into account and a lot larger source of data to draw upon.

Vegas smith said:

Right, but you aren't changing the fuel pressure value inside link so your computer still thinks the car is at 37psi and that is jacking up your tune.

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I did change it in link.

Not on the log you posted.

Thanks everyone!! I will see where we're at after 3rd gear WOT pull to red line.

Vegas smith said:

Not on the log you posted.

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post #18 or am I just crazy??? Fuel tab, correct?

Think I inputted 529cc for some reason. I'll correct it. Thanks Vegas!

Found PTE 1000s on here. Any objections to these? Thanks!!

http://www.dsmtuners.com/threads/precision-1000cc-injectors.515827/

None I run fic 750 which are the same style and I never had an issue dialing them in.

tk106 said:

Found PTE 1000s on here. Any objections to these? Thanks!!

http://www.dsmtuners.com/threads/precision-1000cc-injectors.515827/

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I view used injectors as taboo.
Risky at the least.

Used injectors require paperwork.

If there is one thing you do not mess with, it's fuel going into our engines.
At the very least, send them out for testing. Get them flowbenched so you know what you're getting and know what you're putting on the car.
Knowledge is power.

What the typical cost to have them tested?

Bleakley said:

80% - 95% IDC (Pump gas)

350-450whp - 555cc injectors

My $0.02 -->
1) Voltage drop fuel pump to ensure proper voltage.
2)Ensure there are no flow restrictions. All fittings and lines are 5/16"+
3)Get bigger injectors. For 375whp goal I'd go ID725's. ID850's for plenty of future growth..
Aeromotive's fuel rail has a 5/8" fuel bore. If you haven't upgraded from stock fuel rail, I'd eventually look into it. With a 5/8" bore, that's something you'd only have to buy once and then you can forget about it.
Good luck.

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Correct me if I'm wrong. One can put down 350-450whp with 555 injectors? And are you saying 80-95% IDC is acceptable?

1 - How do I do that? I did notice my voltage dropping to 13.0v at the top of my pull.
2 - All lines are stock except for -6an off of rail to FPR. I do have another braided line with -6an's but need the fittings to connect from filter to rail.
3 - Rail is stock. I'll look into upgrading when I get fittings for line. Do you know the inner diameter of -6an?

Thanks

tk106 said:

Correct me if I'm wrong. One can put down 350-450whp with 555 injectors? And are you saying 80-95% IDC is acceptable?

1 - How do I do that? I did notice my voltage dropping to 13.0v at the top of my pull.
2 - All lines are stock except for -6an off of rail to FPR. I do have another braided line with -6an's but need the fittings to connect from filter to rail.
3 - Rail is stock. I'll look into upgrading when I get fittings for line. Do you know the inner diameter of -6an?

Thanks

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One cannot put down 450whp with 550cc injectors.

A lot of people run up to 90% idc. It's just preference. You could theoretically run 99-100% idc but you wouldn't have any margin for error if the car overboosted or something. The number you'll see thrown around a lot is don't go over 80%.

You're always pulling through Vegas!!

tk106 said:

What the typical cost to have them tested?

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FIC charges 25.00 per injector to flow test and clean FYI.

The cost of used injectors and paying to get them cleaned/ flowed usually negates any cost savings. Might as well buy them new unless you just run then as is. As for fueling, our stock lines/rail is more than adequate for 550+hp. The fuel filter banjo is the only real restriction.

I have a set of precision 1000's that are ready to drop in, no nonsense. 150 shipped.

I sent you a PM


Edit: Just realized that my add is linked above and that you already saw it.

Bleaky- These days, paypal is what makes online trading possible. The buyer has about 6 months to decide if they are happy or not. To rip someone off, you would have to be an absolute fool, but it doesnt mean people dont try. So anyway, I think to call anyone's offering "Taboo" just like that is a bit thin. At the same time, maybe you are jaded after having dealt with someone ethically underhanded?? An important part of online trading, to save yourself wasted time really, is to feel out the person you are possibly dealing with. Look for their posts from the past and access their overall presentation, check out their recent activity. Establish communication, see if they can maintain smooth communication that makes sense. After spending a minute or two doing that, you can reasonably decide weather the offering is "Taboo" or not...... OK, Im done now. Sorry for the rant. Had to do it.

Here is another thing many people are missing: fluid penetration. There's a reason that boosted cars have 1:1 fuel pressure increase. If you up that base pressure with only 17 psi and stay away from the zone that your walbro starts to tank on volume output, your fuel pump wouldn't cause any problems. However, if the fluid penetration increases too much from the increased fuel pressure, you can run into wall-wetting, worse atomization, lower mpg, fuel/ring wash, etc.

Now, if you only gonna bump em a little, you might be okay, but if you're sitting on a stock engine setup (stock compression and cams) you should just leave the fuel pressure alone and buy some larger injectors. I hope this explanation of some fuel injection theory (engineering etc) makes sense.