injector swaping

[rc10ps85]

i realize this questions old and retared but i seached a little bit with no answer. If you swap larger injetors on will the STOCK ecu be able to adapt to the changes. therefore allowing say 14 psi no intercooler. and also not running rich as crap at a cruise/idle?? thanks

-Pete

[Chris86NA2T]

there are no efi systems that i have ever heard of that automatically adjust for bigger injectors. the computer needs to know how much fuel is going through the injector when its pulsed.

[rc10ps85]

some how i was thinking that the 02 sensor on a 20 year old EfI system was going to have a major effect on pusle width. just needed some one to tell me yes you are being a tard. my answer sure you can run 14psi without being lean but itll be rich always

-Pete

[Evil Z31]

Chris86NA2T wrote: there are no efi systems that i have ever heard of that automatically adjust for bigger injectors. the computer needs to know how much fuel is going through the injector when its pulsed.

Actually most do, to an extent. :lol:

If the injectors are within the LTFT's perameters, then it can sense the increase in fuel and trim it back. :wink:

[crowbar]

Most people claim about 10% control for the ecu. So 270cc injectors could be replaced with 300cc injectors (approx) and still do a closed loop around the O2 and achieve near-stoic. They would probably be always pushing on the rich side, and may not pass emissions, but you will get a decent idle.

But some poeple here also claim that the ecu does not learn this, and therefore the open loop conditions would be 10% richer. In other words, it will inject the fuel as per the program in the ecu.

So if you want to have a nice idle, you might try that. But it will not help you with those boost goals.

A trick to help out the slightly rich condition from the 300cc injectors at idle would be to trick-out the fuel temp sensor. Change this so the ecu thinks the fuel is cold. It will lean out the fuel a bit since it thinks it is dense. This would help the idle. But there must also be a mechanism to change this so the ecu thinks the fuel is hot during boost. The ecu will enrichen the mix then.

Even combined with something like a rising rate fuel pressure regulator, and with slightly larger injectors, you will run into a limit. The stock ecu will only open the injectors for only so long a duration. This 'ceiling', and the max fuel flow, is the maximum you will push the ecu's limit.

[Steve88t]

The Z31 already runs quite rich under boost. I would be very cautious about going larger on injectors and hoping it will compensate under any condition.

Lets just say you can get a little more fuel out of the stock injectors and that larger ones w/o other changes is not a wise idea.