I'm needing to upgrade my injectors. My mechanic has given me the option to redo the system and upgrade to a top feed injector rather than the stock side feed injectors. Who has done this and why?

Is it better? What brand would you recommend? Any info will be great!!!!!!!

 

Do you have a method to control these different injectors? ECU?

 

There are more sizes available in top feed, I believe 850cc is the biggest you can go when it comes to side feed. I'm running all top feed injectors and most single turbo FDs are. There's several good brands for injectors, Denso is really popular, Bosch and KG are also very good options. You'll need an aftermarket ECU to control the injectors, such as Power FC, AEM, Motec, etc... Fueling is usually the limiting factory when it comes to making power.

(PS: your mechanic is right...)

 

[fact]you should've searched[/fact]
[fact]I'm bored and felt like spoon feeding you[/fact]

you can get the stock 850s bored out to 1300ccs, available here
http://www.rx7store.net/product_p/ni...o%201300cc.htm

for top feeds, the sky is the limit, I'm looking at Injector dynamics injectors, but they're pretty expensive for the 2200s, get 2 1000cc secondaries and you'll be set for a while. The beauty of the ID injectors is the fact that you don't need resistors (not encouraged) or an FJO injector driver (an extra 150 dollars) that you would need with *inexpensive* bosch 1600 cc secondaries. This of course assumes you're using a PFC (the most common aftermarket FD ECU), I can't tell you if you would need the resistors/injector driver with something like a haltech or Microtech.

I almost wonder if were gonna start seeing people running top feed 725 primaries and 1000 secondaries... seems like a good choice once prices start coming down.

anyways, you'll need:
top feed secondary rail
FPR
probably a fuel pump, at the least the oem one rewired
lines
pigtails
and a programmable aftermarket ecu of some sort
possibly the FJO driver or resistors

it adds up, FAST, see if you can find some of this stuff used on here.

edit: does your mechanic REALLY know what he's talking about? Doing this is a bit of a pain in the *** with the LIM attached to the motor and the motor in the car.

 

How much power do you want to make? What fuel do you want to use? And what ECU are you using?

 

I have a PFC ECU, so computer will not be an issue. I'm only wanting 350 rwhp since I drive my car most days of the week, but I will be happy breaking 300 rwhp for the time being. I have all the mods needed to acomplish this (some still in the box), but since I installed most the mods I'm running out of fuel at 7.5 psi. though I am running a bit rich till I install the radiator in order to keep the motor cooler, I feel I should have been able to get back to the stock boost. (but that's why I have a mechanic and am not the mechanic)

My mechanic is good and I'm not questioning him, I've been going to him for 7 years now plus he's a friend (which some times is not good for my pocket book, since he won't let me go the cheap way), but since I haven't herd anything about replacing injectors in the 3 years I've had an RX7 I was wondering what others thought about the convertion since its pretty expensive.

Thanks

 

With a free flowing exhaust, and upgraded Intercooler, you should be pretty close to 300 just with the PFC. Oh and turn up the boost a bit, of course. My setup is running 14lbs with the NS twins, and gauging from my other turbo FC that was 305hp dyno'd it feels pretty close to that.

 

You must be running very, very rich if your maxing out of fuel at 7.5 psi. Theres probably a lot of room to work with in your set-up. Go get it tuned properly.




walbro 255hp pump
intake
down-pipe
mid-pipe
cat-back
pfc/w auto harness
pfSMIC
tuned to 13psi
stock injectors 366 fwhp and 309 whp ( a five speed with these mods should see 320+whp)
at 85% injector duty cycle MAX

 

rewire your harness, walbro/bosch/denso fuel pump, maybe a rising rate FPR, up the fuel pressure a bit, and with the stock injectors you won't have a problem hitting 350. The stock injectors at 85% injector duty cycle are good for that much. Add a meth injection system and you'll be golden.

 

OK here's good way to upgrade your fuel system and not break the bank,

Use your stock secondary injectors as your new primaries (you'll need to modify your stock primary rail to do this)
Buy new secondary injectors (1600cc or so), either Bosch or Denso
Buy a new secondary rail from KG
Aeromotive or Weldon Racing fuel pressure regulator
Denso (Supra TT) or Walbro 255lph fuel pump

Alot of these parts you can get used for cheap and in great condition.

I would go ahead and get a second fuel pump though, and here's some things to consider why:

1: When running your fuel lines you could run a line from each pump to a rail instead of splitting one line to feed two pumps.

2: Yes two pumps is overkill for what your wanting to accomplish but you will be well under 85% injector duty cycle and if you want more power in the future (trust me, you will) you already have a fuel system to handle over 500rwhp.



And remember... proper tuning is the key!

 

85% duty cycle and make 350whp with stock injectors? I'm at about 86% duty cycle @ 10psi, untuned. Most tuned FD's I see here on rx7club that make anywhere from 330-350whp say they're maxed out 95-100% duty cycle @ 15psi.

If stock injectors can really support that much power, I think its time I get a tune

 

like I said, rewire that fuel pump for proper and constant voltage across all ranges and bump fuel pressure a tad

 

https://www.rx7club.com/showpost.php...4&postcount=25

 

Another option is Xcessive Man's single 4 port rail. Can simplify the whole system, although having a pump for each rail is also a good idea. Utilizes 4 top feed injectors.

What are the opinions on that route (as I am entertaining it when I rebuild my motor soon..)?

http://www.xcessivemanufacturing.com...?pid=79&step=4

 

Here's a fuel system calculator that helps compare different fuel system setups for the rotary.

http://www.wannaspeed.com/index.php?...d=19&chapter=1

 

Looks like to use that 4 port rail you'll need a custom/modified lower intake manifold.

It's a good idea though, running 6 injectors total is for when you really want to make a ton of power.

 

nice, I always just used the one on the rotary performance page, but this one is a bit more in dept, now if only it had a way to calculate for e85 (I know I know, 40% more fuel.)

 

I was going to buy it along with the Xcessive LIM. The way I read it, I can use that rail and completely get rid of the secondary fuel rail. Is that correct? That way, I would still only be running 4 injectors, but off of one rail.

 

In for later

 

Not exactly. the 4 injectors would be located in the secondary location of the intake. The primaries are located much closer. The advantage to running 4 secondaries is that you can run 4 smaller injectors instead of 2 larger injectors. Should be able to smooth out the transition easier. Or... you can obviously make more power with 4 bigger injectors and more boost.

 

^that, plus I would still run 2 injectors in the primary slot so there's less distance for the fuel to travel at low speeds where the air isn't moving as fast. It may not make a difference, but why risk driveability problems? also If you plan on running 4 secondary injectors, I believe someone managed to make it work with the PFC buy using the FJO injector driver, 1 in to the driver and out for 2 injectors.