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Old 03-10-2005, 02:16 AM   #1
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Default fuel injectors

Hey gang, I am planning some mods for my 02 SE this spring. I'm planning on a FWI, new pcm, new plugs, wires, fuel filter, pcv, and 180* t-stat. While I am at it I was contemplating on adding the 42.5 pnd/hr fuel injectors.

My question is this, If I do decide to go with the new injectors how hard are they to install?. Would I need to add a new fuel pump, pressure regulator, and fuel rails also??? Any help on this matter would be appreciated!!



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Old 03-10-2005, 04:24 AM   #2
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Larger injectors are generally on an "as needed" basis. If you're not outflowing your stock injectors, don't worry about upgrading. Spend that money on mods that'll get more air into it, then later you can worry about fuel.

Aside from that, I've never done it on an 02 but my '93 took about 10min to do. You shouldn't need any of that other stuff but you will need an a/f calibrator.
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Old 03-10-2005, 11:32 AM   #3
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From your list, the injectors look like no gain and a waste of money. I agree. Spend your money elsewhere.
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Old 03-10-2005, 02:33 PM   #4
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You don't need them unless your looking at adding some kind of forced induction. Zooomers girlfriend'* N/A GT has about 250whp with stage 2 heads, stage 3 cam, stroker kit and is running a mid 12 sec 1/4 mile. Zooomer went only to 25 lbs. injectors.
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Old 03-10-2005, 11:03 PM   #5
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The general rule of thumb for injector sizing is approx. 2 hp. per pound of fuel per hour for an N/A engine and 1.75 hp. per pound for a boosted engine. 25 lb injectors should support approx. 262 hp. at 100% duty for a supercharged engine. Of course the flow rate can be changed by raising or lowering the base fuel pressure. Raising the pressure somewhat to gain fuel capacity (within reason) does a better job of atomizing the fuel and a smaller injector that has a little more "on" time is a little more efficient since the injector dribbles fuel just as it starts to open and as it closes. Small changes in flow capacity can usually be compensated for by the ECM or PCM which will change the Block Learn adjustment to correct the fuel air ratio for cruise conditions. Usually the stock system can adjust for 10%-15% change in fuel delivery without a problem. Mine are 30% larger than stock (26#) and it seems to be right at the limit of the ECM'* ability to control since block learn is down to about 100 under some conditions. This is on an older LN3 3800.
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Old 03-11-2005, 01:12 AM   #6
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In other words, no reason, and no performance gain for the author of this topic.
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Old 03-11-2005, 12:27 PM   #7
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ok i get it no gain. didnt really want to do it anyway.

I think I messed up and posted the same topic twice. If i did i most sincerely apologize.



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Old 03-12-2005, 06:55 PM   #8
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i saw another forumla too. its HP=flow* duty cycle/bsfc* 6 cylinders. I worked it out and it told me the stock injectors should be good for about 280 hp assuming an 80 percent duty cycle and a .5 bsfc.
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Old 03-12-2005, 07:18 PM   #9
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Quote:
Originally Posted by jachin
i saw another forumla too. its HP=flow* duty cycle/bsfc* 6 cylinders. I worked it out and it told me the stock injectors should be good for about 280 hp assuming an 80 percent duty cycle and a .5 bsfc.
Ehh.. 36# injectors * .80 (dc) / .5 (bsfc) * 6 (# of injectors) = 345hp

Here'* a chart I made up a while back using a 95% duty cycle:

Naturally Aspirated

Injector BSFC Theoretical HP limit

21 0.45 276
21 0.47 264
21 0.49 253

24 0.45 315
24 0.47 302
24 0.49 290

26 0.45 342
26 0.47 327
26 0.49 314


Supercharged


Injector BSFC Theoretical HP limit

30 0.55 323
30 0.57 311
30 0.59 301

36 0.55 387
36 0.57 374
36 0.59 361
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Old 03-12-2005, 07:20 PM   #10
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aah i didnt read the sig, i assumed it was S1.
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