I have bored out the injector holes pretty well and i remember seeing a post about making sure that the topfeed injector nozzle was not too much lower the the intake valve and i have got the injector about half way in the the plug and the nozzle is already considerably lower than the stock sidefeed was, is it ok to leave them at this depth as long as the rail to injector clips are used and the rail is bolted to the mani? i am afraid that if i sit them flush to the wires that the injector nozzle will be close to coming out of the intake in the bottom, thanks
jason
is this ok? or does it have to be lower?
I'm interested in this too, so... BUMP!
Go beyond the "bolt-on".
im going to say better pics are going to be needed for ANY type of accurate assesment and help
The way I figure it, if the nozzle is already as far down as the side-feed's were, and the o-ring is sealing okay, it's all okay!
Go beyond the "bolt-on".
cool thanks what will the inector do if its alll the way down at the front of the manifold? inconsistent spray pattern on the valve?
thanks
jason
I figure it'll act alot like when the injector is mounted more upstream in the runner, only the reverse. Some builders that run high RPMs mount it fruther upstream to aid fuel/air mixing under higher revs, since the air-charge is moving so quickly under that engine speed that if the injector were closer the valve, the fuel wouldn't mix properly with the air-charge. The reason the injectors are mounted so close to the valve on factory systems is to prevent puddling at low RPMs, which is where a stock or street engine would spend alot of time, which would result in poorer fuel efficiency & emissions.
If just one of the injectors is to close to the valve, an improper spray pattern will result on that cylinder & result in uneven fueling in the engine. As a result of that, the ECM will continuously try to adjust to compensate, but never really achieve balanced fueling. I don't know if it'll overload the ECM, but I have heard a story about a middle-aged lady that took ownership of a brand-new Lebaron Turbo & ran too low of octane fuel in it, which resulted in the SMEC (Single Module Engine Controler) having a nervous breakdown from trying to compensate for all the knock it saw. She wound-up taking it back to the dealer for service, the SMEC was replaced & she was told to specifically run a certain octane fuel (93) from then on. So I guess it's better to play it safe than sorry.
Go beyond the "bolt-on".
Quote:
The reason the injectors are mounted so close to the valve on factory systems is to prevent puddling at low RPMs,
Please don't repeat that statement as it's completely inaccurate. When the OHV pfi intake was first put into use the common injector firing strategy was to trigger multiple injectors at a time with each crankshaft reference pulse. In the case of the OHV all 4 injectors were fired 2x per crank revolution giving 4 injection events for every 1 intake event. Fuel was directed into the intake port while the valve was closed and heat from the valve and ports acting on the mixture of liquid and atomized fuel would vaporize some of the light end hydrocarbons prior to the valve opening.
Quote:
cool thanks what will the inector do if its alll the way down at the front of the manifold? inconsistent spray pattern on the valve?
If you were working for GM and trying to get the best emissions possible, you'd more than likely set injector height by referencing the spray angle of the injectors, calculating the distance from tip of spray cone to the point where the diameter of the base of the cone is equal to the largest exposed diameter of the back of the intake valve, then setting the distance from the back of the intake valve to the injector mounting point necessary to provide the correct pattern. What you should consider, however, is that people swap injectors all the time without ever worrying about spray angle or pattern and generally have acceptable results anyway. As far as the possible downside of installing the injectors too deep you might find the spray cone is too narrow and causes higher emissions, you might find some issues with excess carbon buildup in the intake over the long run, you might find some low speed and / or cold engine driveability issues or you might find that you have no problems whatsoever.
-->Slow
slowolej wrote:Quote:
The reason the injectors are mounted so close to the valve on factory systems is to prevent puddling at low RPMs,
Please don't repeat that statement as it's completely inaccurate.
From your complete post, I see that you have
indeed had fortune to do more reading than me on the subject. But please... Let's not start arguement over this^ again.
Go beyond the "bolt-on".
