TwinTriangles

Anyone running 850 primaries and 1300 secs have any input on tunability or is this a farely good setup ?
My mods are as follows:
Pettit Large Street Port
3mm apex seals
silicon coolant seals (?)
dp, mp, N1 catback
K&N intake
Greddy FMIC
blue printed/balanced stock turbos w/clipped blades
Power FC tuned @ 14psi
HKS SSQV
Vac. Hose Simplification w/no emissions
1300cc secondary inj.
Supra fuel pump
AEM Ignition amp
Koyo Rad.
Apexi AVCR

Im asking because Im looking to get a little more fuel possibly, right now I see about 75% duty cycle but am looking to upgrade to gt40r or maybe gt35r. Would I need to maybe port some 850's out to like 1000cc or will 850cc be ok. I'd probably run 16-17psi with a single turbo...?

finnicky7

Just buy the 1600's same price more fuel. The 1300's are over-rated, if you go with 1600's you will more than likley never need more. Kgparts.com normally has good prices.

widebody2

1300s and 850s is good for 47x hp at 85% duty cycle. I have that setup. The car has just a basic single map in it right now and the idle is pretty bad. Its going for tuning within a week, so hopefully the bad idle can be tuned out.

TwinTriangles

Do you think its the 850 primaries making a bad idle or is it just needing to be tuned ? I would buy 1600's and a fuel rail but I already have been running my 1300's for 2 years, So i could get a set of stock 850's for way cheaper than buying 1600's plus a fuel rail if it will supply what I need.

470 something sounds like pleanty to make with a gt35r @ 85% duty cycle. And I could still get 850's ported by RC for cheaper than 1600 setup if I needed to.

widebody2

I think its the 850ccs causing the lumpy idle but I have heard that, that problem can be tuned out. I've heard of tons of people getting a lumpy idle with the 850 primaries. I was in the exact same situation as you, converting to single while already running the 1300s and I went with the 850s because it provides plenty of fuel and was way less expensive...you don't NEED a rrfpr, aftermarket rail, and 1600s, that stuff adds up. If you can wait like a week I will let you know if the problem was fixed by the tuning. I'm dropping the car off friday probably. PM me to remind me to let you know

TwinTriangles

Great! Thanks for your help, BTW what turbo are you running now ?

Snook

iTrader: (12)

My car idles perfect with 850s and 1600s
at 14-15psi 4th gear pull to redline on cold nights I'm seeing 82% duty cycle! (pump gas)

widebody pm me with any updates!!

kuroi FD

lol Surgemonster where are you pulling 4th gear to redline whats that 140+, dont get a ticket big guy.

TwinTriangles

Ok, Im going to give them a try and see what happens. Thanks for the info & widebody keep us posted on your results also.

RX794

Talk to Boostn7 about this fuel injector combination, he's been using this same fuel injector combination for a long time in his FD. He's probably got more info on this than injector combination with the PFC than anyone else out there.

rx7tt95

Ran 850's all around for a year with the Power FC. Had been running 550/1300's...new engine combo will necessitate the 850's in the primary slot. If your idle is lumpy, it's tuning or dirty injectors. My 1300's were just cleaned by RC. Before cleaning they were 1280 something with a good flow pattern. Came back at 1308 with excellent flow pattern. Another trick to eek out a bit more fuel is to bump the base pressure slightly. You'll get better atomization. I'd run a nice big fuel pump with that combo, dual Walbros, the Porsche GT-1 Bosch pump, Barry Grant, etc...

TwinTriangles

Good idea, thanks for the info guys

DCrosby

How bad is it to tune, with 550's and 1680's !? That's a major Jump from Pri, to Sec....

And if you're running 850 & 1680 what sort of change in fuel milage did you see if any !? Not that milage is that much of a concern, but it does add up over time....

-DC

Rx7aholic

iTrader: (22)

Where are u guys finding the 1300cc to buy? I have search many places on the net and still can't find new 1300, Also I spoke to rx7.com regarding port injectors they told me it's not a good idea to port injector because they will eventually fail? Don't know true that is.

TwinTriangles

I got my 850's ported to 1300cc by RC. Put it this way, Ive been running these 1300's for 2 years with no problems whatso ever. I know the discrepancy but personally have had no problems with mine.

Herblenny

iTrader: (13)

I'm also interested in this topic..

I have flowed 1200s, new 1600s, 550s, and 850s.. So, what combination would be the best.. and also anyone have a base map?? I guess sounds like 1600's and 850s are the way to go?? I'm going to go with stock twins non-seq first and than T76BB.. I don't want to jump into single until at least I know how non-seq works..

rx7tt95

Stick with the 550/1600's for the twins and switch to the 850's when the single goes in. If someone is afraid of the 850's in the primary slot, get an adjustable FPR, tap the stock secondary rail (1/4" NPT to 6AN) and bump base pressure by 10psi. Again, make sure you have a high flow high PRESSURE pump. But you'll be able to handle 450ish at the rear wheels with a good solid idle and decent fuel economy.

Once I get my car back together, I'll more than likely post a map to the Datalogit list for others to start with.

maxcooper

No one makes new 1300s (well, not side-feed RX-7 injectors in that size anyway). They are all modified 850s.

I've got an 850/1300 setup in my car now, too. It is still at the shop, though, so I haven't gained enough experience yet to know how well the injector combo works. I have read about some issues with big primaries, but I have also read a lot of reports where there were no issues, so it seems clear that it can work just fine.

-Max

rallimike

iTrader: (1)

I run 850s and 1300s with no problems.

TwinTriangles

Yea it kinda makes sense that there shouldn't be any problems using 850's, its only 300cc bigger and reallistically anything should be tuneable. I think Jason runs 1000's in primary. Anyone know what that horsepower website is that can calculate estimated fuel requirements for different HP numbers ?

bencb44

iTrader: (2)

do you have to modify the fuel rail at all to put the 850's in the primaries position?

maxcooper

There is a limit to tunability -- you only have so much resolution to work with. For instance, if you need 1.5ms of injector open time per cycle for a good idle and you can only choose 1ms or 2ms (due to the limited resolution of your fuel injection control computer), you won't be able to achieve the idle you want. However, that is just a hypothetical example of what kind of limits exist -- those aren't empirically gathered measurements (but rather just round numbers I made up) and I don't mean to imply any specific limits with the PowerFC and 850cc primaries. This example is just an illustration -- nothing more. I don't know the resolution of the PowerFC, and I believe that it is possible to get a decent idle with 850cc primaries and a PowerFC based on the reports from people who are running this setup.

I have a web page for calculating fuel system capacity:
http://maxcooper.com/rx7/how-to/fuel_system/calcs.html

-Max

rx7tt95

there are two ways to install 850's into the primary slot. The first and easiest is to use an additional 0-ring near the bottom of the injector. You'll then have two o-rings and for some, that's worked. The other method is to machine the primary injector manifold down .125" from the top (where the injector is inserted) which will allow the bottom o-ring to seat properly and seal.

TwinTriangles

I thought I read something about that. What do most people do that have 850's primary, use two o-rings? How safe is that really ?

SlingShotRX7

Why bother with the 850 primaries???
Keep your 550 Primaries, and the money
you gonna spend on them use to get 1600secondaries
and fuel rail and regulator. Believe me
eventually.. You gonna get the 1600s. why not
save on the labor, and do it once..

btw. There was a thread, stating alot of reworked
850's to 1300s were sticking prone causing
Engine failure.. DO a search and you'lll seee.

goodluck