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Old 01-05-2004, 02:07 PM   #1
Kingpin
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Default 740CC injectors for free?

Its a tough choice on which injector to buy for your WRX. Buy STI Pink injectors? $300-$550 and you get an extra 100cc worth of fuel. PE 650 or 850's? $600-$800 a set and because these are mechanically slow you need tuning or a flash to make them work correctly. Other companies sell an option for $450 and another that requires you to solder in a resistor pack. You can skip all of this and make your own 740CC injectors for free.
The Stock Blue 440CC injectors and the STI pink 540s are identical other then the end cap and the color so either injector will work for this mod. There is no advantage to having the Pink STIs once modded so sell them, Make some cash and mod your stock injectors. There are a few ways to accomplish the mod but what needs to happen is the end cap of the injector needs to be removed. You can grind it off or cut it off. Does not matter really. You can use a band saw or a dremel tool and a vice. Take your time and cut the silver end cap off where the nozzles (holes) are.
Since you are removing the end cap you dont need to send these off to have them matched. There will be no adjustment a injector shop can do anyways since they are sealed units. What you are doing is removing the flow restrictor (end cap). The biggest advantage is that the stock ECU is calibrated for the correct opening time compensation for these injectors (dead time). PE's are twice as slow and need more dead time. All of the issues that the PE's bring to the table are absent with these injectors.

Questions:

How much will the injectors flow once modified?
740-750CC

What about the spray pattern?
You end up with a find disk pattern

What about the idle?
Rock solid idle as stock once AFR's are tuned.

What about reliability?
They are stock Denso injectors and you are just removing the end cap containing the sized holes.

Do I need a fuel pump?
Yes, Pressure at the injector is reduces since the injector body can now flow more fuel. You need a fuel pump capable of handing 740CC injectors. Walbro is fine.

What if I dont have engine management will these work on a stock ECU?
NO, You will nearly double the fuel flow so you will need a Utec, SAFC, Link, Gems, Flashed ECU or other EM to calibrate these injectors.

I am still worried about equal flow. How Can I be sure this works?
You can send the injectors To Venom performance in California or RC engineering for testing once the mod is complete. Venom will even do the mod for you and test each one but the cost is nearly $300.

Why are you posting this information and not selling modified injectors?
Because it costs nothing to do this mod and its better to give back to the community. If you do not want to perform this simple mod yourself there are companies out there that will take your $200-$300. Maybe one of the members will try this, report back and offer to mod your injectors for a reasonable price? $50? This way its worth his time to do it and you save a ton of cash in the process by not having to spend $450+ on injectors. Work as a community guys

How many cars have you tuned with these injectors and how long have people been running them?
Kingpin has tuned 7 cars with these modified injectors. All idle smooth, All run fantastic and all have low IDC's One customer has 5000 miles on his set now with out issue.

Hope you guys try this and report back. I would not suggest something that I do not believe it. Some of you can flow test them if you wish and let us know the results. Let the flood gates open!


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Old 01-05-2004, 02:16 PM   #2
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Great info Mike! I am going to have to get bak my stock injectors and try this!

Dave-
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Old 01-05-2004, 02:20 PM   #3
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Awesome! Just when I was getting ready to upgrade injectors. Put in the Walbro 2 weeks ago. In a month I'm sure it will just be referred to as the 'injector mod'!

How do you know how much to grind off?
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Old 01-05-2004, 02:23 PM   #4
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Do we cut off all the silver or just the bottom?
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Old 01-05-2004, 02:24 PM   #5
Kingpin
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Quote:
Originally posted by Zackbo
Awesome! Just when I was getting ready to upgrade injectors. Put in the Walbro 2 weeks ago. In a month I'm sure it will just be referred to as the 'injector mod'!

How do you know how much to grind off?
Zack, Just Grind off the end of the injector. Hold one in your hand and you will see the silver end. The length of that silver cap sits in a grommet so dont take that off... Just the end where the holes are drilled.

Look at the pic that Dave just posted... Notice how there is a "cap" that has the holds in it welded on the end? You can almost see the seam in this picture.. Grind that off so the cap pops off OR simply grind the end off.
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Old 01-05-2004, 03:01 PM   #6
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wow holy cripes kingpin, amazing...question tho, the seven cars youve tuned with these injectors so far, had they all been flow tested before going in?

wonder how long they'll last, mile wise...

Last edited by Enigma76; 01-05-2004 at 03:06 PM.
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Old 01-05-2004, 03:02 PM   #7
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Thanks. I'll be all over it this Saturday. Green Brackets of Death, here I come! Does anyone know where I can get a map to get me by until I'm tuned? If I even knew some values to put in the 0% column I could go from there. I've increased my fuel pressure by 10psi, so the 740cc's are gonna be more like 850+.
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Old 01-05-2004, 03:09 PM   #8
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Enigma. They are stock injectors and no mechanical part is touched. Only the holes(discharge area) is being increased so they will last as long as a stock injector.

2 of the cars where flow tested and they came back around 740CC. If you cut the end off it will be nearly impossible for these to not be equal in flow. You will see what I mean if you do it.

Zack... Can you turn the pressure down? You are going to be moving a crap load of fuel with 10 psi increase and the mod. If you need that much fuel great. If not I would reduce the pressure. Values about -7 to -10 will be a good start in that 0 column. Just use a Scan tool to get the trims.
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Old 01-05-2004, 03:16 PM   #9
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Any clue whether the different spray pattern will cause an issue?

/Andrew
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Old 01-05-2004, 03:16 PM   #10
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frickin awesome kingpin, MAD props to you guys coming out with this mod to the public for free!
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Old 01-05-2004, 03:31 PM   #11
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Andrew... Like I said.. 7 cars. No issues. Solid idle. Smooth mapping. The pattern is like a nice cone.

Enigma. Not my idea. Just passing on information that others are charging for. If parts where needed or custom machine ect then I can see a large price. But since a guy can do this in his garage it should be free information passed to the Club.
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Old 01-05-2004, 03:39 PM   #12
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Kingpin --

Very cool. I'm just trying to figure out the implications of removing the restrictor cap other than increased flow.

/Andrew
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Old 01-05-2004, 03:43 PM   #13
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Post up a pic of a modded injector.
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Old 01-05-2004, 03:55 PM   #14
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Quote:
Originally posted by Kingpin
Enigma. They are stock injectors and no mechanical part is touched. Only the holes(discharge area) is being increased so they will last as long as a stock injector.

2 of the cars where flow tested and they came back around 740CC. If you cut the end off it will be nearly impossible for these to not be equal in flow. You will see what I mean if you do it.

Zack... Can you turn the pressure down? You are going to be moving a crap load of fuel with 10 psi increase and the mod. If you need that much fuel great. If not I would reduce the pressure. Values about -7 to -10 will be a good start in that 0 column. Just use a Scan tool to get the trims.
No, I can't lower it. I've permanently modified the stock RRFPR. After doing the math, it looks like they will flow approx. 830cc's with the added pressure. I wonder if that will be enough on the stock turbo My IDC's should be in the 40's tops Looks like the money I had saved up for injectors can go towards the TXS tuna. I'm gonna need it now, even before the turbo upgrade.
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Old 01-05-2004, 03:58 PM   #15
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Kingpin, do you have a map for me on modded 740's for my 1820? I was just talking with you about a touch up for my ECUTEK and this might be the perfect time

Dave-
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Old 01-05-2004, 04:31 PM   #16
inpreza kid
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good info. does anyone have pics of the injector with the endcap cut off? interested to see what the injector tip looks like before i do this mod.
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Old 01-05-2004, 04:48 PM   #17
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This is most disturbing to me. I've been getting injectors modified for folks, making about $40 a set, and to find out that Venom charged me $292 for these, and my injector shop is charging me $200 to do this is .... well its embarassing.

IF its the same modification. I know my shop is cutting off the caps, but I was told they are reflowing them as well. If I'm reading this correctly, there is no reflow occuring, and they just work.
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Old 01-05-2004, 05:09 PM   #18
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Cronic. We have maps for these injectors for the US and JDM STI ECU's including the AF481 and AG970. Send the ECU back if you want me to update it!
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Old 01-05-2004, 05:23 PM   #19
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Wow - shocking to say the least. There must be SOME risk associated with this, it seems too easy...
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Old 01-05-2004, 06:25 PM   #20
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Quote:
Originally posted by T-WRX
Wow - shocking to say the least. There must be SOME risk associated with this, it seems too easy...
Risk? How about voiding your warranty.
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Old 01-05-2004, 06:28 PM   #21
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Quote:
Originally posted by alster
Risk? How about voiding your warranty.
If you need 740cc injectors, chances are you're way way past what even a liberal-minded dealer will cover
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Old 01-05-2004, 06:44 PM   #22
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Quote:
Originally posted by alster
Risk? How about voiding your warranty.
Warranty.. thats a good one.
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Old 01-05-2004, 06:45 PM   #23
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Someone post a pic of a modded injector please i'm curioius to see what it looks like under the salt shaker cap.
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Old 01-05-2004, 06:51 PM   #24
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Quote:
Originally posted by alster
Risk? How about voiding your warranty.
Modding your car in general voids warranty. If you are worried about warranty, you shouldnt be modding your car.

Quote:
"Enigma76: wonder how long they'll last, mile wise... "
Darthchicken has been running these for a long time and he hasnt had any issues. IF this is the same mod. My guess is yes it is.

I'd be interested in seeing a pic of a modded injector on here. Or a pic that has a line showing exactly where you are cutting off the cap. Do you clean the injectors after cutting? Awesome info kingpin. Thanks
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Old 01-05-2004, 07:09 PM   #25
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Are either of thses the correct spots? Or am i not comprehending this?

Sorry for the crappy pic but i have no photoshop on this pc and used paint..
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