Okay, I’ve been PMing back n forth with a couple guys about the topfeed conversion, and I have one more thing I need to straighten out, and that’s which injectors to use. I honestly don’t know what my fuel pressure will need to be, but I’m going to be running 8psi on a T3 turbo, nothing fancy. I’m going to be tuning with a Cartech FMU, and so far from what I understand, the Ford redtops have been said to be my best option, but I’ve heard that getting idle fuel pressure dialed in can be a bit of a pain. One of the guys I have been talking to has mentioned stock LD9 injectors as an option that some guys have used as well. I could use some input before I get too far into this. I already bought the 2200 rail and stock injectors, as well as a spare manifold assembly to do the mock up, but I haven’t bought the injector harness or different injectors yet.

Redtops and browntops seem to be the most popular

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Cavgold96 wrote:Redtops and browntops seem to be the most popular

Yeah, I get that part, but the one thing I see people complain about is that, with the redtops anyway, they're running pig rich when they're not in boost. I don't know about the browntops, I don't know if they're bigger or smaller. I want to be able to tune the car without HPT or a stand alone because I don't have regular access to a computer. I don't even own a computer, I go to the library or a friend's house. It was mentioned to me that although the injectors on an LD9 won't handle boost on that particular motor, they should work fine for my LN2, considering the small amount of boost I'm going to be running. They're what, 320cc? I have no idea how big the Ford injectors are.

If i'm not mistaken the stock LD9 injectors aren't 320cc the GM S/Cer injectors for the LD9 are 310cc, again, if i'm not mistaken. I'm unsure about the red and brown tops though. I wish you luck though!


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Ah, maybe that's what he was suggesting, was the S/C injectors. Apparently they're physically about the same size as the 2200's injectors so they should fit no problems.

stock is 252cc on a LD9

you scratch my ride IMA EAT YO CHILDREN

You will be so much better off if you can get the pcm tuned. Spark should be adjusted as well as fuel. Even if you have to pay someone to do it. But...

If you're going to use fuel pressure only to make this work, then you need to get an FMU which provides enough range in pressure from idle to boost. If you're running at 8 psi boost, you can say you're making roughly 50% more power (just for calculations) and that you'll need roughly 50% more fuel, max.

To supply 50% more fuel and still keep the fuel delivery stock at idle and non-boost conditions, you need a range of about 54 psi. If you pick 90 psi as a top pressure (dayam, that's high) then you'll have a starting pressure of about 36 psi. So you can find an injector which will flow almost the same amount of fuel at 36 psi as the stockers at stock pressure. I think 90 psi is a little high. And I know that you generally don't want to run injectors below 20 psi to ensure a good spray pattern. So I'd go with a range from 22 to 76 psi. Since 22 psi represents the pressure at key on, engine off, you need to find injectors which flow the same as stockers at 22 psi.

Stock LN2 injectors are 17 lbs/hr @ 43.5 psi. The math shows 23.9 lb/hr injectors will flow 17 lbs/hr @22 psi. Sounds like you're looking for a set of injectors from a 1992-95 Vette / Camaro / Firebird LT1. As far as using injectors from the 2.4 or Eco, those engines use a higher fuel pressure than yours. The injector may flow 24 lbs/hr @ 55 psi, but it actually flows less fuel than your stockers when you drop pressure to 22 psi.

There's some auctions on SleazeBay for 24# injectors right now.
HTH

-->Slow

Thanks for the info, Slow. That makes a bit more sense. As far as the ECU tuning, it's something I WANT to do, but there isn't anyone locally to me with the software I need. The only person that I know I can trust to do the tune and has the softare to do it, is Shifted. But that's about an 8 hour drive for me and if I got him to tune it for me, I'm sure he would want the car there, which means I'd have to tow the car there (it'd be dumb to drive the car on a stock tune), and I have no way to do that.

Now, If I can get my laptop fixed without breaking the bank, that's a whole different story. It's sort of in a perpetual reboot, provided I can even get it to boot up in the first place. It got to the point where it just starts up for a few seconds and then shuts itself off so I'm betting the hard drive needs to be completely wiped and rebuilt. Granted, if I got the laptop fixed, I can get the HPT software and tune the car myself.

So, yeah. That's all I got.

I'm about a 17 hr drive, so that doesn't help, either.

I've been using the same laptop for years. It's ugly, it's slow, but it works.

I need to find a new (used) one, though. I'm going to step up to USB tuning hardware. The old one has parallel / serial ports only. Local computer shows always have decent laptops for cheap $$.

-->Slow

I am also looking to turbo my cavalier with about 8 psi I am making my own headers and down pipe and will be using a kkk turbo off of an Audi s5000 that was tapped in the rear end by a large truck. It is a 2.2L I5 though I have every aspect of the project figured out except the fuel system specifics and where to run the oil feed line from. I have been asking around and i hear that the old (1986) ford thunder bird 2.3 I4 turbo runs about 8psi stock and its injectors are optimal but this was one person and am unsure if it is true. I was also pretty sure that the Gm Ecu was not modifiable in the standard way a Honda can be tuned or re-flashed with new fuel maps. i also heard that using a check valve will solve the problem with the map sensor reading boost. But if the Ecu can be tuned with new fuel maps would it be still be required that a piggyback system be used. and if the ecu cannot be modified than which piggyback system is the most effective as far as cost and ease of installation. And finally doesn't the fuel pressure stay at a constant it sounds like it varies with load on the engine

You can find the flow numbers for those injectors on the 'net.
Oil feed line from back of block. Search boost forum for posts and pics.
GM computers were being tuned before Honda. Gotta pick the right GM computer and tuning software.
MAP sensor not reading boost = engine computer not delivering right fuel or spark.
Fuel pressure will vary with load if measured with a standard gauge.

hth
-->Slow