how much power will the SPFI system susport? is there anyway to tune it ? would it even be worth the effort to swap it on my EA-81 vs the weber

Tuning can be done through several methods. To increase fuel delivery in proportion to boost one could use a RRFPR (rising rate fuel pressure regulator) that increases fuel pressure as the boost rises delivering the needed fuel in proportion to the added air. Another method is to use an airflow converter. This device takes the incoming MAF signal and increases or decreases it in proportion to a table that you enter. The table is plotted to RPM and or boost. This way you can lie to the computer telling it that more or less air is present at a given point so that it adds more or less fuel. Should you need 10% less fuel at idle (due to larger injectors) and 5% more at 4k RPM with 14PSI boost you can set that up accordingly. I have this same combo on my 300+ HP Impreza and it gives me great flexability in tuning.

 

I would go with FI over carb any day. You get configurability you just can't get with carbs and everything just works better overall. Of course the main problem you face is getting the timing signal that the ECU needs to know when to fire each injector in a MPFI system. Of course SPFI simplifies much of that.

i think it's easier to max out our smaller engines with a weber than with SPFI. that's my hearsay though..

ya, I'm the same way I just would like to keep the EA-81 for now. as I'm planing on either a EA-82t, ER-27, EJ-XX swap in a couple of years( I hope not that long but I say plan for the worst hope for the best)

I'm planning to switch my ea81 over to SPFI but I will be using Megasquirt http://www.bgsoflex.com/megasquirt.html instead of the factory ECU. This will allow more room for tuning, future development like a progressive 2 port throttle body with different infectors and possibly best of all no MAF. I will also be able to use a regular EA81 distributor with this. Also I believe it will help simplify the installation.

I've thought about using the megasquirt but what about the injector what size is that? when will that run up of steam so to speak. but really what cc is the injector

After watching archemetis go through making his webber fit and work only to really not be happy with its ultimate performance I'm sticking with my SPFI. Its simple, its solid and has given me no troubles. As for performance the computer should make up for any changes you do, to a certain point. It will adjust for more air flow if you flow the intake and heads. With a weber you will be under the hood for hours tuning it.

 

Now going FI on an carb'ed engine is kind of a whole different deal. In your case it would be easier to make a weber fit then monkeying with a computer and sensors on an engine that wasnt designed for them. Even the hours you spend tuning it wouldnt surpase the hours you will be spending figuring out how to adapt SPFI to your EA81

 

I guess how difficult of a job are you up to is the real question?