turbodreamz22

I come from evos and sti's and turbo Hondas which only use 1 set of injectors.

So I get confused when I hear that there are primaries and secondaries in te rx7.

What is the reason for this? I am new to the rotary world

Help!!

gsl-se addict

iTrader: (3)

The best way to think about it is this:

For a given amount of HP, you need to supply a given amount of fuel. It depends on the car, but a 4 banger may have 4 injectors and a V6 may have 6. Now with our cars, we only have two rotors. If you do one injector per rotor, the injectors would need to be large (the GSL-SE did this and used 680cc injectors). Starting with the 2nd gens, they ran the primary/secondary injectors (total of 4). The advantage of using 4 smaller injectors compared to two huge injectors is that they have better fuel control at idle and low loads. So, you have two small injectors running at idle/low loads (good control) and then the other 2 come on when needed.

Kent

KaLo_FC

Thats good to know, I always thought that both injectors fired at the same time. So does this mean you would upgrade the secondary injectors and leaving the primaries stock when turning the boost up to keep good idle? since the secondaries kick in when needed? and of course this would be after taking care of the fuel pump and other maintenance items before turning the boost up. one more question, what tells the ECU to kick the secondaries in? the maf?

Sorry, im also a noob! havent gotten my RX7 yet, but its on the way!

gsl-se addict

iTrader: (3)

I know it is RPM based on the 2nd gens. I haven't messed with FDs much, so not sure there. Could be RPM, throttle position, boost, or some combination.

You can also think of these like a 4-barrel carb. Two small primaries to handle low loads and then open the two large secondaries when you stomp on it

Often people will just increase the secondary injectors some will up the primary injectors too. It depends on the build, what kind of HP you are looking for, and what you are using to control it all.

KaLo_FC

ok cool, well to give you more info its a S5 FC, going to be stock Turbo but I will run a really good exhaust and intake and want to up the boost to about 15 psi. FMIC and meth. Not sure if i will need to upgrade the injectors, if not..then I will at least get them rebuilt. and im for sure getting a nice FPR and a new fuel pump and filter.

I want close to stock HP, going to be a DD and this is my first RX7.

Aaron Cake

iTrader: (1)

FC injector staging is both RPM and load based. 3800 RPM and 2" of vacuum.

No point running the stock turbo at 15 PSI. It just starts blowing heat around 14 PSI anyway. You'll find peak power is made somewhere between 12 and 14 PSI.

Use an RTek ECU, upgrade the secondary injectors to 720CC.

Evil Aviator

If you truly want to run 15psi (see below), then you will need to upgrade the injectors to keep the engine from blowing up. The other items on your list are also a good idea. The size of the injectors depend on the hp level, tuning quality, and ECU. For example, the Rtek chips are a popular low-budget upgrade, but the different models are specific about the size of injectors that they will operate:
http://digitaltuning.com/?pid=rtek7

If you want close to stock HP then don't double the boost level. If you run 15psi and downtune the engine to 200hp, then all you will get for your work is worse gas mileage.

KaLo_FC

thanks for the info guys! looks like im just going to be running 10-12 psi then! this should be safe with meth right? the reason why is because I dont want to deal with tuning for now. Its going to be a DD and I will be driving it alot...

any suggestions on what boost pressure I should run?

Im guessing I probably need something better to control boost since I will have a close to
free flowing exhaust and a nice Intake with a performance filter.

I think I have hijacked this thread lol sorry! , I will post a build project thread

turbodreamz22

thanks

Evil Aviator

It depends if you are willing to port the wastegate:
http://fc3spro.com/TECH/HOWTO/KWG/kwg.html

Aaron Cake

iTrader: (1)

If you want the car to be reliable with higher boost, then you need to properly address fuel. The 720CC/RTek combination I mentioned is a very good choice and with minimal tuning will drive fine, since the RTek is essentially a tunable stock ECU. You only need to alter the load areas as you are adding boost/fuel.

Stock boost pressure, if you "don't want to deal with tuning".

Boost controllers cannot lower boost past what the wastegate would naturally achieve. You use a boost controller to raise boost, not lower it.

KaLo_FC

Aaron cake <---

Yes i know boost controllers only turn up boost. I was Thinking about external wastegate, i mentioned i will need better boost control since i will have better exhaust and intake. That obviously means it will probably boost creep wirhout wastegate porting. But will that be enough? I never ran a rx7 turbo before.