largest injectors
 

i read yesterday about the 305cc or 330cc injectors on the standard 1.6 ecu(1991 model) will run.
do you have to do any mods......
if so is idle ok and will you see any power gains.

i have the 1.8 injector at present in my 1.6 greddy turbo,intercooled bipes fmu walbro 255 forge boost controller forge wastegate and bov.
186 bhp flywheel @5,500 rpm.

This has been talked about many times now. Some people have good luck with it, some don't. You have to mess with the afm clockspring. Look it up in braineaks diy projects portion. The other guys would know a whole lot more on this than I would, so I will turn it over to them.

Oh yeah I run 330's and they idle fine. You have to toghten the spring in the AFM to get them to idle a little more lean. Mine runs great w/o any problems.

if you have the factory AFM it just takes a drill and a screw driver to idle them. the AFM has a screw to change the idle mixture, just as the TB has a screw to change the idle speed. Tighten the screw and you'll have a richer idle mixture, adversely loosen the screw and see a leaner mixture. When idling my 305cc injectors it took one complete turn looser to have a perfect 14.7 AFR idle. Your really must tune with a wideband or on a dyno.

Is 14.7 the "correct" factory afr? Curious because since the begi fmu mine idled at 15.7 with the original blue tops and the same with the current tan tops. When I adjusted the clockspring tension and idle mix at the dyno and got no change in my wot afr, I adjusted it back to where it was before I touched it. 15.7:1

Mine idled 14.7(ish) with and with out the emanage on 1.8 injectors and BEGI AFPR (base pressure was ~40psi). The 305's caused things to get wonky, as did the RX7 AFM. I was able to get the idle back on track by playing with the emanage.

The ECU will do it's best to get you in around 14.7.

thanks....

thanks

thanks for your info i will see if i can pick up some 305cc injectors from a non-turbo toyota supra.....

For gasoline fuel, the stoichiometric air/fuel mixture is approximately 14.7 times the mass of air to fuel, so yes. but idling at 15.7 just means you're not wasting gas, and as long as the AFR curves and ping control are acceptable there's only an added benefit.

Yeah, it seems ok to me. It's only ~15.7 at ~850 rpm idle. Add the smallest possible amount of throttle (~1000 rpm) possible and it richens to 14.7.

I was curious because I'm working up the energy to bolt on the rx7 afm, and I need a target idle afr.

plus the ecu always trys to aim for 14.7 based on what the 02 sensor and afm tell it.

is it possible to use the slightly larger injectors and just lower base FP to get the correct afr for idle?

no, you cant lower your base fuel pressure beyond that of the control of the OEM FPR. But tweaking the amount of air into the system is overly simple.

my car is newer 1.8 can't do what you do. was going to replace oem fpr with adjustable unit in order to lower fp, figured this would lean it out with bigger injectors(somthing around 300cc)

which year? yes, replacing the factory fpr could work. although depending on your year bumping up from 265cc to 300cc might be ok for the ecu to handle without adjustments, only a 10%-or-so increase.

You also need to remember the spray pattern of th einjectors will be compromised at lower pressure levels.

And at high pressures as well I would expect.

not according to Corky.

1997; planing on trying the ever popular 305cc, i figured lowering fp about 8.5 psi or less would get idle about right.