Hello, I recently purchased a Power FC and Datalogit. I am currently rebuilding my motor and I want to upgrade the injectors. I noticed a lot of people running the stock 550's along with 1300cc secondary’s. I am planning on sticking with the stock twins and to keep the HP numbers around 350. However, I would like some wiggle room if I decide to shoot for more in the future. I don’t want to go to big for tuning / drivability reasons. Any ideas on what would be a good place to start? Also, is it recommended to have the 850's modded to 1300's?

 

550 primaries with the 850 secondaries bored out to 1200 with an upgraded fuel pump with the FP wiring improved is your best choice.
850 --> 1300 have had high failure rates.

 

850/850 with rewired pump would also get you enough fuel for your HP goals. It would be a cheaper alternative, (I have some forsale) but you might have some trouble getting a lean idle. Some people have no problems with this and others have a harder time getting a lean idle.

 

Who is the best company to hvae the mod done by? I am having a hard time finding any injectors over 850cc which are side feed.

 

I really havent had any driveability problems with my primary milled rail with 850 and 1680 secondaries.

I just went big because i knew down the line i would want the extra fuel.

If you just want around 350 than stick with an upgraded pump rewired for more voltage, and like chuck said 550's with 850's bored out to 1200. You would have a nice smooth idle and still get some good mpg.

at 334hp with 850/1680 i was getting 22mpg

 

yeah i think the 850 primaries mainly only have an issue at idle where the MS on time is the least

 

Actually, my idle is good ,but I have driveablity issues, just in vacuum, while light throttle driving. I'm running 4 x 850cc

 

RC Engineering

 

Go with 850's all around you have the capability to make 410whp at 80% duty cycle. Bored injectors have an actual failure rate. Case closed...

 

+1

except I run 1300cc secondaries for 5 years or so now. Street port, 99 twins running sequentially and all supporting mods resulted in 350 rwhp at 15 PSI.

great idle, great part throttle response, good low RPM response for good street manners. Trying to fit 850s into a primary rail 'works' but its kind of a goofy setup as they never fit 100%. Yeah you can mill the primary rails to allow you to install them but the rest of the injector just doesn't sit in there perfectly like the 550s do.