Whats better running 850 primaries and 1300 secondaries. The advantage here is I guess you would never run out of gas unless you have ALOT of boost, but wouldnt such huge secondaries really not atomize the fuel?

Then having 850's all around but you can not get to the level of the 1300's sooo what if

What if you got 6 x 720's would that be enough to be at the same level and not be dumping fuel?

 

This of course may be different due to a number of things, but I'll tell you what I've got.

Tuned to about 10.5(+/-) AFRs at 15 psi on 93. At 7350 RPM I'm getting 82% cycles with 850/1600s. I don't have anything higher in my logs that I'm looking at. I will be tuning with 100 in the spring to an undetermined boost pressure.

 

Your going to tune to 100 Octane? Why 10s? I heard 11's is just as safe.
My reasoning behind the question is the whole dumping fuel, and it not getting atomized. Maybe 6 smaller injectors would be better than 4 huge ones. Just a thought, thanks for adding .02

 

Anyone else?

 

If you're concerned about atomization, that will be dependent on the nozzle design of the fuel injector. According to Mazda, the injectors in the RX-8 have a different nozzle design to improve fuel atomization (does anyone else see the irony in the word 'atomization'? If you broke it down to atoms, it wouldn't be a molecule of fuel anymore. But I digress...)
So you might want to look into RX-8 injectors, how many cc's they can flow, fitment, etc...

Having a larger array of small injectors should enable you to control the amount of fuel that is being delivered to the engine with more precision vs. a few large injectors. Can you tune well enough to make use of the increased precision?

Adding extra injectors is more weight and complexity in terms of both hardware (fuel plumbing) and software (ECU tuning). Is that the sort of project you're willing and/or able to take on?

-s-

 

not to thread jack, but how did you get the 850's to fit the primary rail? I was thinking of going that route with my fuel mods. How how HP were u able to carry with 850 in the front and back? thank you

 

I think you are making this too complicated. I have been running 850s and 1300s for over 2 years now with no problems. 850s all around is not enough for those wanting to make over ~400 rwhp, and i don't see any need to go with additional injectors.

The 850s are new stock sec's in a modded prim rail, and the 1300s are RC Engineering bored out sec'd that drip right into the sec rail.

 

i'm running 1300s secondary and 850 primary.......works well

 

Many people, myself included, run 1680cc secondary injectors problem free.

 

the larger secondaries like 1680s will not atomize the fuel and therefore you'll make slightly less power.

 

Thats my whole question/ comment. I was at rx7.com and type in 850s all around and made 512 to the flywheel minus 20% drivetrain loss = 409 hp at the wheels. Thats with the injectors at 80% duty cycle.