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The VIPER Garage  |  How To Instructions  |  How-to section  |  My side feed injector thread.
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Author Topic: My side feed injector thread.  (Read 4315 times)
AndyMac
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« on: October 24, 2010, 05:04:11 PM »

I'd like to get a thread together with information on side feed injectors, stock and larger replacements. Trying to avoid top feed injector swap info here, but if it is relevant, go for it.

So, the stock fuel system runs at 55psi. The fuel pressure is regulated in the tank, which means this setup has only 1 line from the tank to the motor. (the feed line)

Facts:
Gen 1 stock injectors - 25lb/hr (black tops)
Gen 2 stock injectors - 29lb/hr (red tops)
Internal fuel rails in the intake are -8 AN (1/2")

A good side feed injector upgrade is the Subaru yellow top injector. They will flow close to 60 lb/hr at 55 psi. The down side is that they are really expensive new. Cost at the dealer is 150 per injector, which is 1500 for injectors plus tax. If you look on the Subaru forums, you can get 4 shipped for 150 - 200 bucks. This will require new injector connectors, and obviously some kind of engine management to compensate for the extra flow.

The Subaru injectors aren't a direct drop in, I believe that an O-ring swap from the original injectors would be enough. I'm also thinking that the tip may need to be filed down a bit to fit.



Here you see (left to right):
1) late model Nissan 300ZX TT injector. 370cc
2) Subaru yellow top injector 550cc
3) Stock Gen II injector 305cc
4) Nissan Maxima injector 240cc

These are all high impedance injectors, and all should fit without too much issue.

Soooo, why is the Maxima injector there you might ask? Well, I got 24 of them for 100 bucks. I wanted to try resizing the injectors to flow more and had some success thus far. I had some pics, but they are super fuzzy, so you'll have to imagine it.

The bottom of the injector has a plate micro welded to the injector with several small holes in it. This atomizes the fuel as well as limits the amount injected. If you remove the plate, the flow goes from 240cc to 550cc. Obviously the pattern isn't as good anymore, but it is similar to the stock Viper injector now. I rigged up a flow bench to test the flow rate before and after, and initial testing is good. I modded 20 of the 24 and plan to flow them all and see what the variance is between them.

I was thinking if there was a wide spread, I can use the individual cyl trim in the VEC to compensate for them.

I realize that this isn't for everyone, but I will give it a try and report back.

As a neat note, the TT 300zx injectors can be modded in the same way, but result in the same end flow rate. Nissan probably used the same base, just changed the restrictor plate and color. They are also really expensive too, so the Maxima injectors are the obvious choice for this test.
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Andrew MacPherson
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AndyMac
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« Reply #1 on: October 24, 2010, 05:09:08 PM »


  Here you can see the modified Maxima injector in the center with the cut down connector. The left is a stock Maxima, and the right is a stock Viper injector. I used the stock Maxima top O-ring and the Viper lower O-ring to get it to seal in the rail.



  I had to spread the hold down tabs a bit and grind the injector body slightly to get the fit the way I wanted.



  I ran them this summer with no issues, other than I couldn't go past 10psi without maxxing my fuel system out. :)
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Andrew MacPherson
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« Reply #2 on: October 26, 2010, 09:58:11 PM »

Great info.
I'm thinking 550cc would be about as big as you will be able to go since the stock lines and internal rails won't be able to flow enough to run anything larger. 
You might be able to rig up a rising-rate FPR in the stock system for a little more fuel press. at higher boost levels, but if you are pushing it that close to the edge you should already be looking at a top-feed setup. 
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« Reply #3 on: October 26, 2010, 10:37:11 PM »

Not sure of the flow rate (volume) of the Paxton FMU but it's actually not a bad idea for higher boost levels as the injectors lose efficiency at boost.  Not sure what Manifold pressure the injectors are rated at, but it's probably atmospheric pressure or less.  Adding a pound or two of fuel pressure for each pound of boost is actually a good idea.

I read some Mopar Performance injector research back in the late 80s and 90s on the injectors for the 300bhp turbo 2.2s.  They found that above 14psi none of the injectors they tested perfomed well so they had special injectors invented for 14# and higher boost.  They were about $75 each.  Increasing fuel pressure should allow the injectors to operate closer to their design efficiency compared to trying to operate at stock fuel pressure.
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AndyMac
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« Reply #4 on: October 27, 2010, 05:45:05 AM »


 I've been looking at a lot of options for a fuel system that are simple and cost effective. The fuel rails in the intake are pretty big and should be adequate for a while. There are access plugs on the end of the intake for the fuel rail which could be removed to incorporate a return style system as well as additional feed lines.

  A 255 Walbro in the tank with a BAP and a couple of external 255's inline with an FMU giving me a total fuel pressure of 100-120 psi would probably go a long way. I've been told that the dual walbros and an FMU supported 800whp with 60lb/hr injectors.. /shrug

  My biggest issue right now is that for every psi of boost, I loose 1 psi of fuel pressure. So at 10 pounds of boost, I have 42-45psi of fuel pressure.

  I really should just put 3 Walbros in the tank and run a couple 3/8 lines to the manifold, use a regulator and FMU through the stock fuel line for return. This seems like a pretty straight forward cheap/simple/capable system.

  Good discussion.
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Andrew MacPherson
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« Reply #5 on: October 27, 2010, 04:35:56 PM »

hey andy im running my gen 1 with suburu wrx ijectors part #16600aa170 555cc  sti i mean and the paxton fuel set up no bap 10 psi making 800 rwhp (also heads,exhaust,headers, ported intake 1.7's rods, all on vec 2
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gen 1 805rwhp 888 torgue monster
AndyMac
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« Reply #6 on: October 27, 2010, 06:08:56 PM »

hey andy im running my gen 1 with suburu wrx ijectors part #16600aa170 555cc  sti i mean and the paxton fuel set up no bap 10 psi making 800 rwhp (also heads,exhaust,headers, ported intake 1.7's rods, all on vec 2

  Very impressive! Thanks for the confirmation on the fuel system. It is truley amazing what the system is capable of considering the restrictions in the fuel line.
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Andrew MacPherson
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« Reply #7 on: October 27, 2010, 06:17:06 PM »

your welcome but i to am curious about tapping into both side feed rails on my intake
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