mrx

Hallo,

i read in some posts that many of you think that a 5th injector setup is not good for high boost appication (>10psi)

can you explain why???

and please don't tell me that it is **** because it is **** because you know someone who think that this is ****... tell me facts only please!

i can imagine that bigger injectors and a standalone are more accurate then a 5th injector at all... but WHY exactly did this 5th injector setup work so bad?!
I drove a 5th injector setup about 1 1/2 years on aprox. 16psi without problems of leaning out or detonation or something on a stock engine with reduced compresstion - so i don't understand why many of you say that this won't work.
Ok it will not give the max. power but it works or not?

Maybe someone can explain it technical!

Thanks
Malte.

Johnyquest

Supposedly (or maybe not) the reason that the 5th injector setup doesn't work at high boost is because at high boost having an exact mixture becomes rather critical. The intake manifold is designed to disperse air equally (or mostly equally) to all four cylindars. When you begin to inject fuel into the IM / chargepipes, the intake manifold is forced to attempt to try to now equally disperse not only the air, but supply each cylinder with the fuel you are squirting into the stream. The #1 (or #4 i forget, the one closest to the throttle body) usually leans out because the fuel droplets have trouble making the tight turn into the runner, causing a lean condition and detontation / melted pistons.
This really starts to get bad at high boost not because of the boost, but because of the massive amounts of fuel you are asking the 5th injector to supply. When you get up there in the boost, the large amount of fuel starts not to vaporize, i.e. form droplets, and once this happens, there is no chance of the IM equally dispersing it and supply all cylinders with fuel. Droplets / liquid fuel do not flow in the same way air does, hence the IM inability to work with it.

In a nutshell, this should explain things. Too much fuel = liquid fuel ending up in IM = uneven fuel distribution = cylinders lean out = blown motor.

Hope that helps!

mrx

Hi,

thats a good point... but what is if i install a 6th or 7th injector (theoretical) before the throttle body... or isn't the injector the problem? maybe it is only the absolut amount of fuel in the intake manifold...

Greets
Malte.