Injector Innovation update Part 2
Ok so the first 12-hole Denso 270cc injectors i tried popped up lean codes towards the end of a tank of gas (300+ miles). The car idled and ran fine but this worried me so after speaking with Charlie he thought to go up a size on the injectors because i have some performance modifications. The codes didnt pop up when i was accelerating just around town or normal 3rd gear, 50-60mph conditions.
P0171: Fuel System Too Lean (Bank 1)
P0174: Fuel System Too Lean (Bank 2)
The first time i cleared the codes (just pull the clock fuse under the hood) thinking it was just a freak occurrence or maybe something was left loose, the codes came back after another 150 miles or so. I promptly limped the car back home, took apart the airbox/throttle body and triple checked everything to make sure i was not having any air leaks to cause a lean code.
I arranged a new setup from Charlie to try.
So now we are on variation 2 of this modified injector setup. Now I am running Bosch 18-hole 315cc 14mm injectors with 11mm adapters into the fuel rail. These injectors seem to have solved the lean issue and because of the very fine atomizing of fuel from the 18-hole setup, this increase in flowrate does not seem to have any detrimental effect. These injectors spray in a cone pattern, the car idles and runs fine all the way to redline, so far no complaints after 300 or so miles. From what i understand the OEM 250cc injector (91-96) and 270cc (97+) is small and it is run at a high duty rate.
Im sure there are more scientific ways to go about this but im just trying to share what i have learned messing with injectors etc.
Flowrate is measured at how much fuel an injector flows at an industry standard 43.5 psi, because the OEM injectors are older needle style injectors they do not atomize as well as a modern 4,12, or 18 hole injectors so they shoot "two streams" which is a dated technology. The game nowadays is how fine/dense of a mist and small the particles of fuel can get. The fuel rail/fuel pressure regulator controls this ~43.5psi condition for the injectors so flowrate can be varied to a certain extent when increasing how finely the fuel is atomized. My understanding is that as we increase the atomization efficiency and mist density of fuel in the motor we can safely run a slightly larger flowrated injector. The ECU cannot physically see the larger flowrate but because the difference is not much it compensates in the fuel table. I am running a Uni-Filter, DF scoop, and full SOS exhaust setup, so i believe these modifications make the case for larger injectors even more convincing.
For example the Prospeed RDX injectors are 410cc flow rated at 43.5psi, this is too much a of a difference for the stock ECU to handle. it cannot effectively trim the fuel tables enough to compensate for the increased flow. Hence there was a chip for 91-94 and additional tuning required for 95+.
Im sure someone more versed than me will correct me on some of this, but hey at least im out here trying:redface:.
Some notes about installing Osidetiger's RC-DEVIL Bosch 18-hole kit:
-3 washers now shimming up the fuel rail on each post (12 total), this is the max height possible anymore and the nut wont have enough to thread on.
-use a bit of fresh motor oil when pressing in o-ring (14mm to 11mm) adapters into fuel rail
-ziptie adapters to fuel pressure regulator vacuum line
-use new crush washers on fuel line
-you must rotate the front bank of injectors 90-degrees to plug in as the plugs foul against a harness. Injectors spray in a perfect cone so it doesnt matter the position (no need to really align with marks on the fuel rail like OEM injectors)
I have 400 miles on this setup and so far no codes or problems. Im pretty happy with this setup however i dont have any great data besides, i installed it, ran it, pullled the spark plugs and "read" them with a nice light brown color. Everything seems to be operating/burning fine and it seems to make power everywhere. I have not done air/fuel ratio as the original OBD2 o2 sensors are not wideband so they do not show that information. I think this setup is pretty darn good and the motor runs like a sewing machine.
So far i know for sure this setup will work on 1995-1996 NSX for sure, im fairly certain it will work on 91-94 NSX with the same injectors just send Charlie pictures. If anyone has a 1997+ and wants to try it ill be happy to install for them and help.
left: Blue old 270cc Denso injector
right:Gray 315cc Bosch injector and new adapter
Notice there are 3 washers stacked to shim up the fuel rail on each post. (4 posts, 12 washers total).
shown here is the rear bank, on the front bank you will rotate the injectors 90 degrees to get them to clear the harness
Left:
blue 12-hole Denso
right top:
gray 18-hole Bosch
