I am getting very close to starting my Miata engine swapped Triumph Spitfire project and need your suggestions as the path I went down has deviated from the norm. I have installed a small turbo from a forum member (WhiskeyBusiness) and he had recommended that I get some larger injectors as the stock NB injectors were going to run out of headroom at my projected 10 pounds of boost. I am not looking for max power, just a reliable 200 HP at the wheels.
I ended up getting Bosch 320cc injectors that have been serviced and appeared on paper to give me what I needed. They installed easily and should give me the extra flow I will need at my projected power and boost levels. Here are the specs.
Bosch 320CC injector. The part number for the injectors is 0280155831. They are rated at the following flow rates.
320cc @ 3bar/43.5psi
460cc @ 3.8bar/55psi
400cc @ 4bar/58psi
I wanted to get your recommendation whether I should use a stock or the 550 Basemap for getting started? My engine specs are below:
1999 Miata NB engine, 6 speed transmission
t25 turbo- looking at 8-12 pounds boost max
320cc Bosch injectors above
Hydra Nemesis 2.7 and wideband O2
Anyone have any recommendations?
The math I was told was use an Injector that reads 1/10 of the Projected Power, Mega Squirt MATT. is who I would ring up.Aka mad science matt.
What fuel pump will you be running? Pump flow goes downas pressure goes up, so you need to balance that factor in as well. Always have at least 20% more pump than injector.
Bear in mind that unless you are running a fixed pressure, returnless system, boost pressure will increase demands on the pump. 58psi base pressure plus 12psi boost means 70psi in the rail for example. (Conversely, a 58psi fixed system at 12psi boost will effectively only have 46psi worth of flow. The 58psi in the rail has 12psi in the manifold pushing back)
I am a fan of bigger injectors and lower pressure, makes the pump a lot happier and last longer.
Pump right now is the stock Miata 1999 pump, with a fixed pressure, returnless system. According to most of what I have "read" the stock pressure of the returnless system is supposed to be 60 psi.
The pump will always be pushing 60psi, then, and the injectors will flow at whatever 60psi - boost pressure (or + manifold vacuum) will be.
IMO, I'd convert it to a standard boost-referenced system and run it at 3 bar, but that's just because it's known to work just fine.
If fuel pressure does not rise with boost the injectors get smaller as boost goes up, I call that a death spiral.
Returnless system does not cool the fuel rail, also does not purge the rail of any air bubbles, any air in the system must go through the injector displacing fuel.
In reply to bentwrench :
You'd think that, but a rail full of air yet compressed to 60psi makes the air very small, and it blows through the injectors VERY quickly since air is a lot more flowable than liquid.
I did an LQ4 swap a few years back, with a returnless fuel system conversion. Decided to crank the engine with the key to make sure everything worked even though I didn't go in with HPTuners and disable the antitheft in the PCM. The engine actually fire and ran for a second even though the rail was full of air.
As a data point, my MSM with stock injectors, turbo, and fuel system was running 10 psi of boost at 96% duty cycle. So I'd go with bigger injectors. Now I'm running a set of EV14 640cc FlowForce injectors, and all is well.
