Is running FOUR 850cc injectors a problem?
 

Is there any idle/starting problem with this?
Is there other problems like tuning or reliability?
How much boost can I run on the stock twins with this?

Is there any idle/starting problem with this?------>No. Not with an aftermarket ecu like a PFC and a tuner who knows what he is doing.
Is there other problems like tuning or reliability?-----> No.
How much boost can I run on the stock twins with this?------->safely, 375 rwhp? four 850s should be enough for anything the stock twins can dish out.

Hmmm interesting. I'm looking for 15psi on stock motor/twins. I have all other supprting mods except these injectors.

Do you run FOUR 850cc set-up>? what is your duty cycle like?

I am running this setup with an upgraded pump, on a single turbo at 13PSI putting down 360RWHP.

Duty cycle gets up to about 91% at the very top range.

No problems. :)

Ditto that,

My duty cycle rarely gets above 80%. Stock twins running .94 bar, and in cold weather just above 1 bar. Currently getting 333 rwhp.

You need access to good tuning. If you just drop them in and change the PFC injector setting, the car will run very rich under low load.

Jack

Well for what it's worth I'm not very thrilled with my 4x850 setup. When I get the chance I'll be putting 550's back in the primaries and getting a new secondary rail. I haven't been able to get my idle AFRs above 11:1, despite reducing the idle cells using the datalogit. It's also a pain trying to retune all the cruise areas and deal with the throttle tip-in stumbles... If you're going to put in 850's, you NEED a wideband and a datalogit. If you just put them in and change the injector settings using the commander, you can expect about a 8mpg decrease in mileage, and a FOULED engine. While I was waiting to get a professional tune, mine lost compression after about 6 months from the insane amount of carbon buildup. Maybe my experiences aren't the standard, but I'd give it real thought before putting 850's in the primaries.

As far as power, I'll second what everyone else said. With my single turbo @ 13psi I made 315rwhp on a mustang dyno (supposed to be roughly 350 on a dynojet) with duty cycles going into the 90's.

I just talked to Jason at rx-7 store and he doesn't see any problems to tune it for 15psi.

Tailhappy, for those six months you were driving "untuned" , were you boosting at all?

FYI, at 15 psi on the stock twins on stock injectors all around I was at about 98%. You should have plenty of headroom for 15 psi with 850s in the primary spot. Of course, YMMV.

In a way it doesnt matter......his overly large primaries were not dialed in correctly, and they of course function at idle and low load situations, so while babying the car, sounds like he just mucked everything up with all the fuel in his motor. 6 months is a long time to go like that.....I'll bet some nice h2o injection would have cleaned up his motor pretty nicely.

Yes!!! I have not seen that little acronym since the Big List. I used to use it to describe certain female types to my buds, hehe :D

I am currently running 4 X 850cc injectors on my single setup. Getting 410rwhp at 15psi. I have not checked my injector duty cycle but my tuner says its fine. But I am using 100 octane as well as water injection so you may see different results. Idling is a bit rougher then the 550's but other then that everything else is fine.

To Rich:

Yeah man my tuner manage to push 410rwhp from the RX6 turbo!

i'm running that setup with a pump also and I could only run 12psi and thats at 96% duty cycle. Tunning was by Steve Kan so I'm sure he knows what he's doing, also had the fuel filter replaced same day as tuning so I should have no problems with clogs. I dont know thats just my car though, always has issues lol

Thats odd maybe you are running rich. what fuel pump are you running?
I ran 12psi on 550 primarys and 850 secondarys with a duty cycle at about 90%...

IMO: keep your 550 primaries and upgrade your secondaries to 1600cc.

Then be done with it.

Why not just go with 1000cc secondaries, or 1300? ...and you get to keep driveability, right?

well it's supposed to be a nidepenso or what ever it is the biggest they make but who knows if I actually have it, I had suspicions of this shop ripping me off and another thread about a tranny that had a 30 dollar part replaced to fix it seems almost word for word what was wrong with mine and they charged me for a new tranny. so it just keeps building up. So really I dont know if I even have one now

agreed on the 550 pri and 1600 secs

i dont have primarys.
all i have is 850s
Why do 1600cc when runnig the stock turbos? isnt that over kill?

Yeah, I was boosting before I got it "tuned." I did get on a dyno and get the WOT areas ok, but it's damn near impossible (well at least it would be REALLY expensive) to get all the cruise areas tuned while you're sitting on a dyno. It wasn't until I got a wideband permanently installed in my car that I found out just how rich the idle and cruise areas were.

And as someone else said, primaries are used during cruise, with secondaries being for boost. So with hindsight being 20x20, it really doesn't make sense that I put 850's all the way around. Putting in larger secondaries is the _right_ way of doing it, in my opinion. 850 primaries are good if you can't get big enough secondaries to support your power, or if you want to take the easy way out. But that's just my opinion.

Keep in mind, some may run out of fuel with 850 primaries, while others say they're fine, because several of us have different turbos.

And there's no such thing as overkill.... :) Once you start down this path of modding and power-searching, you're not going to stick with those stockers forever! ;)

Congrats to the guy getting 410 with his RX6! That's nice numbers. Pays to get a professional tune, I suppose!