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Noah Holcomb's Avatar
 
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For those with efi and 450+ rwhp, what injectors are you running?

How much power and torque does your car make and at what rpm?

What size injectors do you run?

What is your static fuel pressure at idle?

Do you use a rising rate fuel pressure regulator or a standard fuel pressure regulator?
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Old 07-01-2008, 05:54 AM
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Old 07-03-2008, 09:00 PM
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Use whatever supports your max power w/o more than 85% duty cycle (and not less than 60%).
Do not use rising rate BPR. It's a band-aid and a bad one. It makes mapping PITA and is generally unreliable component. Use 3 bar system pressure and standard BPR. Use (if EFI supports it) low-impedance injectors.

I believe 500cc injectors would be plenty for 450hp with room to spare.
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Old 07-04-2008, 12:11 PM
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P.S. According to my calculations, 3.3L engine running 1.0 bar of boost and delivering 425hp at 6200 RPM with intake temp of 50 deg. C would need 460cc injectors @ 80% duty ratio to sustain 12.7 AFR.


Pump will flow 132L/h and air mass flow would be 47lbs/min.

So my guess was pretty good.
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Old 07-04-2008, 12:17 PM
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I'm using Mototron (Siemens) high impedence injectors. I think they're 60lb injectors but I'm only running 38psi fuel pressure so they're flowing a lot less than that.

Fuel pressure regulator is a standard Edlebrock EFI regulator.

RWHP is 475 and torque is just under 400. I don't have a pic of the final dyno run on this computer, but I think I posted it on my engine rebuild thread.
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Last edited by David; 07-04-2008 at 12:30 PM..
Old 07-04-2008, 12:18 PM
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55ib injectors car is still getting dyno tuned so can't give you any more info.
Old 07-04-2008, 02:29 PM
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Old 07-04-2008, 11:45 PM
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60lb Mototron injectors, low impedance, stock 3.2 FPR/damper/fuel rail/fuel pumps. Duty rate no more than 65% at WOT, 6500 rpm, 1 bar, 525 rwhp. Good idle - not great.
Old 07-05-2008, 07:07 PM
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Delphi Racing 72 lb. Low Impedance
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Old 07-05-2008, 07:18 PM
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Quote:
Originally Posted by Gumba11 View Post
Delphi Racing 72 lb. Low Impedance
Began with 83 lb/hr with adjustable fuel pressure 35 to 55 lbs 3.5 liter tt built by Norwood. Initial set up on first running 1.0 bar dyno run 495 HP at the wheels stopping @ 5000 RPM maximum on new motor. Now fuel pressure raised and exchange to 96 lb/hr Multec for higher fuel pressure setting and adjusted for 1.2 bar to 1.3 bar boost now motor has over 1000 miles on it. This was done before I bought it. Not on dyno yet but feels strong. I'll post once I get some dyno time and a Motec connection the shop did not have on my last visit for a power tune.
Old 07-05-2008, 08:00 PM
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The bigger injectors you have the harder it is to make it idle well. So you want low-Z injectors (so they can open/close quickly). You want them sized so your max power corresponds with roughly 85% duty ratio. Less duty ratio and idle suffers even more. More duty cycle and injectors start running hot and there is no headroom.
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Old 07-06-2008, 03:54 AM
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Injectors

Type: Siemans DEKA VI
Flow: 4.8 to 5.0 gm/s static flow at 300 kPa
Tip: Extra Extended Tip (17.5mm)
Spray: Pencil type, no bend

For a comparison, the stock k-jectronic injectors are flowing around 3.9 gm/s at 300hp(flywheel)@5500 RPM.

The formula I use for sizing injectors is:

Flow (gm/s) = (target flywheel HP)*0.0790/(number of cylinders)

I was shooting for around 400HP at the flywheel, so that comes out to 5.2 gm/s, which is how I arrived at my injector size.

For 650HP at the flywheel, you get 8.55 gm/s (67.7 lb/hr), so the injector size depends on how much power you want.

Be realistic! Bigger is not better. The reason is that a large flowing injector performs very poorly at idle. The pulsewidth becomes so small that the injector can't handle it. Rather than spraying in a small amount of fuel, it just shuts off.

65 lb/hr is probably the biggest that most people on this board will need. 85 is ay too big, unless you're making over 800HP at the flywheel.

Nothing wrong with designing to run at 100% duty cycle at max power. That's when the injector is running the best! Flow is not interrupted, just one big garden hose of fuel spraying in.

Pay attention to the spray pattern. All injectors are NOT the same. Most multi-intake valve engines actually have two narrow sprays coming out of one injector. Put those in our motor and you have two narrow sprays onto the port walls. Not Good!
Old 07-06-2008, 05:19 AM
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Got Accel 72 pounders in mine with aeromotive pump, FPR, and -10 an line.
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Old 07-06-2008, 05:03 PM
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Checked my records and I have Mototron INJ-GAS-006 injectors. http://www.racetronix.com/L107.html

They flow 63.2 lb/hr at 43.5psi.

When I bought them I thought they were low impedence, but they are in fact high impedence.
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Old 07-07-2008, 05:17 AM
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Beep Beep,Speedy Squirrel. You're right, with the 96lb/hr injectors the idle definatley suffers below 2000 rpm actually below 2300 Rpm hot however strong from there upward. For some reason unbeknownst to me they at Norwood needed to go larger than the 83lb/hr they started with. A member on this board who is familiar with this motor development process wrote me to say they were shooting for a somewhat reliable 800 crank Hp. Waiting to get a final power tune to see how close they got to it.

Last edited by voitureltd; 07-07-2008 at 06:59 PM..
Old 07-07-2008, 06:13 AM
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What is diferent when comparing the Delphi Multec family of injectors ans the Siemens Deka injectors?
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Last edited by Noah Holcomb; 07-08-2008 at 06:40 AM..
Old 07-07-2008, 05:05 PM
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Quote:
Originally Posted by Speedy Squirrel View Post
Pay attention to the spray pattern. All injectors are NOT the same. Most multi-intake valve engines actually have two narrow sprays coming out of one injector. Put those in our motor and you have two narrow sprays onto the port walls. Not Good!
What designs should be avoided then?
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Old 07-08-2008, 06:43 AM
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Most multi-intake valve engines use four-hole disc-type high ohm injectors. Four hole disc design atomizes fuel very well but depending on where you mount them, they might wet the cylinder walls.

That being said, you'll be hard pressed to find a big (>500cc) motorsport injector of four hole disc type. Most are low impedance pintle type injectors with plain "garden hose" conical pattern.

So as long as you don't buy bling-bling six-hole Supra injectors but ordinary Siemens stuff you'll be good.
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Old 07-08-2008, 02:04 PM
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Quote:
Originally Posted by beepbeep View Post
Most multi-intake valve engines use four-hole disc-type high ohm injectors. Four hole disc design atomizes fuel very well but depending on where you mount them, they might wet the cylinder walls.

That being said, you'll be hard pressed to find a big (>500cc) motorsport injector of four hole disc type. Most are low impedance pintle type injectors with plain "garden hose" conical pattern.

So as long as you don't buy bling-bling six-hole Supra injectors but ordinary Siemens stuff you'll be good.

Oh, I get it now. Do you know what angle for the spray cone is optimal?
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Old 07-09-2008, 06:44 AM
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Quote:
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Oh, I get it now. Do you know what angle for the spray cone is optimal?
Hard to say. It depends on where you mount them. I guess it would be best to "test shoot" an injector prior to installation, observe the steepness of cone and then try to mount it in suitable place.

That being said, spray cone optimization is nice but it doesn't have to be 100%-match. It's mostly emission thing. Remember, if you have batch triggered injector at 80% duty-ratio it will spend lot's of it's time spraying into closed intake valve anyway.
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Old 07-09-2008, 10:16 AM
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