The side feed injector thread.

[AndyMac]

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.

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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.

Alright, have at me..
__________________
Andrew MacPherson
My turbo projects
1995 RT/10
1990 300zx ttv8
2002 WRX

 

[Viper Specialty]

The simplest means by far, though not the cheapest, is to just have the OEM's resized and balanced professionally. We can have it done for about 150 bucks each. Expensive, but starts to look a little better when you figure than a set of new injectors and rails will run you 1000-1400 easy, plus the addition of lines and fittings... and that isnt even balanced.

 

[AndyMac]

That is still really pricey for an injector upgrade, especially since 500-600 will get you 10 used Subaru injectors. The key word here is used I guess, in that some don't like used parts.

Also, if I'm spending 1500 bucks, I would get new Subaru injectors rather than modify 15+ year old injectors, but that is just me.

Thanks for the info. Are you "in the know" about how they open up the stock injectors?

 

[white out]

I can get Subaru sidefeed injectors up to 850cc. They flow very nicely until ~75psi (ratings are at 43.5psi), above 75psi they don't atomize well. I ran a set of 850s on my STi at 55psi with zero issues.

Nick
- VCAs resident subaru guy

 

[AndyMac]

Are the 850's just modified yellow tops? I thought for some reason they were modded in a similar fashion to what I am doing to the maxima injectors.

Just a note for the VEC guys, I am told that 550's with a cone shaped spray are about as large as you can go without tip-in problems. Maybe the SCT could run the 850s fairly well, but limits that to the genII's.

white out - I'm also a Subaru guy.

Later,

 

[white out]

Yellow tops can be modified up to 850cc and then there are 850cc sidefeeds that aren't modified.
The modified flow very well with a nice spray pattern from a few companies. Most of the home-modified are not clipped well and often not bench flowed/tested to make sure that the injectors are within a close flow rate of
each other.

AndyMac, nice and rare sedona red you have there.

Nick

 

[ROGUE]

You know you can run top feed with rails and retain the stock single feed line and pump?

The easy upgrade from there is dual pumps, -8 feed line, regulator at the rails, and use the stock line as the return.

For $1500 I would definitely be going to rails and a quality regulator with dual pumps.

 

[AndyMac]

white out - Thanks. I have a few spare Subaru 550's around that I may mod to see what happens. These are problem injectors that were causing misfires(common for this injector in a Subaru application) so I don't know what my end result will be.

Rogue - Yes, you could use the stock fuel system with an external rail and top fee injectors, but it kind of defeats the purpose of the injector upgrade (cost vs benefit). The stock 300zx TT injectors will flow about 420cc at 55psi and get you into the range of being able to max your stock fuel pump depending on the BSFC. (600bhp, 10 injectors, 0.6 BSFC, 90% DC, = 420cc/min)

The point I'm getting at is this. If you want to keep the stock pump and lines, get the 300zx TT injectors and be happy. They'll be a lot cheaper and keep a nice factory look. (I'm not a big fan of the external fuel rails anyhow)

IMO, external fuel rails are for people interested in making 4 digit power numbers, or those interested in wasting money.

Later,

 

[AndyMac]

Oh yea, also, you can add dual inlets to the intake and use the factory feed as a return when using the side feeds as well. Am I to understand that it is 1500 for just the rails and fittings? So you still have to buy injectors etc?

 

[white out]

white out - Thanks. I have a few spare Subaru 550's around that I may mod to see what happens. These are problem injectors that were causing misfires(common for this injector in a Subaru application) so I don't know what my end result will be.
Later,

There's actually a company that will pay you for your stock 550cc injectors if you pick up their modded & bench flowed to be within 1% of each other injectors. It's a pretty good deal.
PM me if you want more info on them.

Nick

 

[ROGUE]

Am I to understand that it is 1500 for just the rails and fittings?

Good god no lol. Rails are a couple hundred bucks, injectors vary in price by size somewhat, then just depends on which lines, fittings etc.

For $1500 you should have a fully functioning system that will support well into the 4 digit hp range.

I personally don't ever like maxing out a system, especially one that is as vital as fuel. The last thing you want is a pump to start failing, lose a little pressure with the injectors at max flow, have it go lean and roach the motor. All because you didn't want to spend another couple hundy to do it right.

Besides getting the fuel out of a hot intake manifold is always a bonus.

 

[Viper Specialty]

For $1500 you should have a fully functioning system that will support well into the 4 digit hp range.

Using new parts? No way... if you are talking about a full system, front to back.

Injectors: minimum 60/ea for decent injectors
Rails: closer to 400 min
Pump: 300-1000+
Fittings: easily 1-2 dozen fittings x30-60 each
Filters: 100+ x2
Regulator: 150-300 easy

Even for a half-assed system you are looking at 2K. Easily 3K for a NICE system. I have even seen some creep into the 5K range if you start getting fancy with PWM drivers, Weldon D2345's, balanced injectors, etc.

 

[ROGUE]

VS, i'm not the type to send my car to someone else to build and install things. Shop around, don't pay retail, and you can have a very nice system up and running for $1500.

No point in arguing, it is what it is.

 

[white out]

If you don't change rails, it can be done for ~$1500. Otherwise you are going to need some serious discounts.

Nick

 

[Viper Specialty]

VS, i'm not the type to send my car to someone else to build and install things. Shop around, don't pay retail, and you can have a very nice system up and running for $1500.

No point in arguing, it is what it is.

None of my prices included building or installing anything. I know what these parts cost even at wholesale levels, and most of my prices are what you would find on the internet. I also know very well how quality plays into price, from both an experience standpoint, and an engineering standpoint.

I stick with my comment. Unless you are buying firesale, garbage, leftovers, or used parts, your pricing is not realistic. I cannot stress enough how different levels of quality can impact things. For example, a cheap system is usually dual walbros. No hanger setup? Pickup issues in the can often times. Hanger setup? Now you have pickup issues on low fuel levels. Almost ALL large pump or multi-pump setups cook fuel in a return system. Poor quality pumps? System fails. Car burns. Poor filters? Pump Fails. Poor fittings and lines? Gas smell, system leaks. Single pump? Very loud. A system needs to be designed well, not slapped together, or it WILL have some type of a downside. Just because you can do it that cheap, doesnt mean its a great idea. Just because you can make it work, doesnt mean it works as well as it could.

My point is not to argue with you, but when you post that, people start to think that is what you should ALWAYS be able to do it for. Very, very wrong. That price would be the exception, not the rule.

 

[AndyMac]

I got the injectors modified and installed today. I used the stock Maxima top o-rings and the viper lower o-rings. I had to shave a bit off the top of the injectors for the hold downs to clear. Even then, I had to spread the tabs on the hold downs to fit.

Also, I had to modify the connector on the injector body so I could use the stock viper injector connectors.

Had it out for a run and it seems to be working fantastic.

You must be registered for see images attach

Later,

 

[CWhiteRun]

RacePartSolutions - Fast Parts At Discount Prices....NOT RSI! I love RSI too, but they are two separate companies. Reasonable and REALISTIC prices for fittings, fuel side items, and every clamp and coupler imaginable. Plus...they used to do a 10% discount on top if you were a member of the theturboforums.com. Just because some of us own a Viper and want to modify it does not mean we should have to pay out the nose to do it.

 

[BOTTLEFED]

Great thread


Just to add another possible side-feed injector, 93-95 RX-7 used a 850cc (81#) in their secondaries. You can usually pick up a good pair for $30-50. Be careful though, the rotaries are known for cooking injectors, so sometimes the plastic casing is brittle and cracking.

 

[AndyMac]

Great thread


Just to add another possible side-feed injector, 93-95 RX-7 used a 850cc (81#) in their secondaries. You can usually pick up a good pair for $30-50. Be careful though, the rotaries are known for cooking injectors, so sometimes the plastic casing is brittle and cracking.

My friend is a rotary nut, and he gave me a couple to screw around with. The rx-7 injectors will NOT work in our intakes. I can't remember the specifics, but if you want, I can get them back and take some pics. It would have been nice, but just won't work.

Later,