CHRIS P

Could anyone tell me about using 850 primaries as I have read about there use in the past.
On comparrison of the two there seems to be quite a difference in length, i have seen somehere about adding washers or machining down the housing, is it a case of doing one or the other?
Is this a good upgrade?
any advise?
Cheers chris p

rynberg

You don't need larger injectors unless you are consistently running over 12 psi of boost. Most people just upgrade the secondaries to 1200 or 1300 cc as it is easier. Note that you will have to have a stand-alone ecu (Haltech, PFC, AEM) to handle injector size changes. You will also need a higher flowing fuel pump to handle the higher flowing injectors.

CHRIS P

I've got a power fc, curently inj duty is at 89% and rising. I'm monitering fuel pressure, but as yet seems stable, is there a reason to not upgrade the pimaries to 850's or is it ease of access?

rynberg

I know there are modifications to using 850cc injectors as the primaries. You will also have to spend more time tuning it to get the car to idle well and drive well at low speed. It is much easier and common to upgrade the secondaries.

BoostedRex

If you decide to upgrade the secondaries, I suggest that you go with the 1600cc one's from Bosch as they are a stock part. The 1300cc injectors are 850's that were modded, and with any modded part you have more of a chance of failure of some type. Just my .02 though. Hope that helps.

Zach

ttpowerd

http://www.wvinter.net/~flanham/wlan...el/850pri.html

That should help a lot in your search for installing 850s in the primary slot Good luck!

rotorbrain

i dont think ive heard of anybodies 1300s failing. . . i might be wrong though. . . what if you upgraded both sets and had 1300s all the way around. hahahahahahahahahahahahaha. . . yess. . . fuel for everyone!!!!!

paul

SleepR1

You will need to upgrade the fuel rails for this mod.

Quote:

The 1300cc injectors are 850's that were modded, and with any modded part you have more of a chance of failure of some type.

The 850-cc Nippondensos are merely bored out to 1300-cc. They're completely reliable.

SleepR1

Nope, not worth the hassle for primaries.

Quote:

any advise?

What are you trying to accomplish? Do have mods that require enriching the fuel? Primaries are not used in high-rev throttle application; they function for idle and low-speed throttle. Upgrading to 850 primaries will result in very rich air-fuel-ratios at idle; motor won't want to idle.

wptrx7

the motor won't idle?

luigi

SleepR1

No it won't want to idle very well with 850-cc primaries. It's a PITA. You have to adjust the AFRs (air-fuel-ratios) with an Apex Power FC or Haltech, so the idle AFRs are lean enough to use with the 850-cc primary injectors. It's stupid, really. Unless you have a drag car like Ray Lochhead's (running 2 kg/cm2--29 psi), there's no point in upgrading the primaries to 850-cc. Ok...nuff typed

Wade

iTrader: (1)

SleepR1,

What you say isn't exactly correct, the primaries are on at ALL times vs. the secondaries which are only on at higher load. So there is a reason to upgrade the primaries (they aren't off at high load). For example, using 850cc primaries would give 25% more fuel delivery potential at high load, and 50% more at lower load. This is a substantial increase and in a healthy FD should be good for well over 400 rwhp.

Also, there should be no issues with idle or low speed drivability with 850cc primaries, aside from ECU tuning which would be required with any injector change (larger secondaries included).

Wade

SleepR1

But won't you need to upgrade the fuel rails with 850-cc primaries and 1300-cc secondaries?

Nameless

No you dont. Stock 850's can fit in the primary slots, and 1300's are bored out 850s, so it will definitely fit in the secondary slots. No need for a rail right?

Wade

iTrader: (1)

It isn't necessary to "upgrade" the fuel rails when using 850cc secondaries in the primary rail (though additional o-rings should be used or the top of the primary rail should be shaved slightly). No rail mods are needed at all to use upgraded/modified 850's in the secondary rail.

Chris P asks about using washers on the top of the primary rail, this shouldn't work because the lower o-ring seal of the injector wouldn't be sufficient.

Wade

wptrx7

i am purchasing 850 with a a fuel rail is this unnecessary? i was under the impression that having a fuel rail for the primary injector secures it better? i know about the idle issue and know that tunning is required (and some times the best you can hope for is idle at 1000 rpms).

luigi

rxrotary2_7

you can get a motor to idle with 160LB injectors as the primary IF NEEDED. as far as just tossing in 850's into the stock rail....take a look at both sizes of injectors. (physical size, not flow rate) they are different.
wade is right. adjustability is requires with either upgrade of primary or secondary. ther MUST be a way to control the injector pulse.

silver3rdgen

I run/ran 4 850's. NO modification to the fuel rail what so ever. I run a Haltec E6K, upgraded fuel pump and FPR. My car idled fine (doing a rebuild currently) and felt great at low rpm throttle inputs as well. I'm about to upgrade to 1600 secondaries and keep the 850s as primaries.

Jason

iTrader: (5)

FYI for everyone.
If you are worried about fitment issues you can always take your primaries and have them reworked to 850's or even 1000cc if you want. Thats what I did on my car.
I do have an extra set of reworked primaries in stock if you want to send me yours as a core exchange.

Jason

M104-AMG

iTrader: (8)

FYI, I have stock 850cc secondary injectors in my shaved primary rail, and with Steve Kan's tuning (PFC), she idles fine all the time and handles 14psi of boost all day (Cosmo fuel-pump).

:-) neil

GARCO MOTORWORKS

I mill the rails for people all the time so they must be able to make them work at idle .My car has 850 primarys and the car idles fine hot or start up cold .I have also removed the hot wax rod set up and the car starts fine in hot or cold weather .I suggest milling the rail instead of using two o-rings for the seal .

VegasFD

RC told me that the stock primaries could be bored out all the way to 1300cc's. Chuck used to have 950cc modified primaries advertised on his site. And RC told me that Chuck was a customer of their's. If I ever decide to upgrade the primaries, I might go that route for simplicity's sake.