I'm fishing for philosophy here.

Realistically, as far as my tuning is concerned, the only change to my setup will be the added displacement.

For now, I'm going to retain my heads and the vf30 st4 that I have. I will also be using the pde up and down pipes and 3" Stromung (resonator-less) exhaust. As a side note, since strapping that on, I've noticed some WG fluttering that I've never had before. I wonder how the addition of the SB will affect this. Another side note is that I have the TUNA for AFR.

The only modifications I'm planning on right now are both of the Kingpin fuel system hacks. I'm going to change my stock WRX injectors to push 740cc's and also make my stock WRX FPR flow the fuel with an additional 10psi.

I haven't made up my mind yet. Obviously doing both would probably be overkill. All I know is that both my UTEC and Delta Dash logs are showing high 90%-100% IDC. The DD has actually logged 113%!

Anyhow, the facts as I know them are that the engine will be sucking in (and blowing out) quite a bit more air. Therefore, the current fuel map I have will be too lean, uniformly. The boost map will also be too high. I'm not as certain about timing, but my assumption is that it shouldn't change. It seems as though, once I've gotten to my targetted mixture, that the spark should be occuring exactly where I have it now. Please correct me if I'm wrong.

The immediate questions that I have are how should I begin tuning my fuel? Should I just do the ctrl-u and add a percent or two across the board? Should I even bother with the higher flow of fuel? There's no doubt that I will be un-tuned as soon as the engine is in, I just don't want to make things any harder than they have to be. Another question is, how much will the MAF voltage actually change? My fear here is that the new MAF voltage will completely skew my assumptions and make tuning the fuel a bear.

Thanks for reading this.

*This is cross-posted on WRXHackers.

 

I thought you already had larger injectors Pat. Or am I confusing you with Chris? I know he has PE800s with his STi shortblock, but I thought you had STi pinks... anyways. If you already have injectors large enough for the VF30 (pinks are fine, 650s are good too) than you are fine. You will make more torque than before, but no more peak horsepower. In fact, you may make slightly less because you will be making peak power at a lower RPM. I am also putting a VF30 on an STi shortblock, using a reflashed WRX ecu and STi injectors. I expect to make about 330 hp at the crank, because that's what a VF30 can do, but like I said it may be less as I'll be flowing that much air at lower RPM. Anyways, back to the point.
You will need a complete retune once you add the shortblock. It won't require any more fueling or make more power, it just makes it sooner in the powerband. I the combo is perfect for autocross, and I'll be testing that theory in a lot of events in Reno this year. Good luck with your season, and I'll keep you guys posted on mine as well.

 

I have the pinks, but for whatever reason that I just can't seem to cure right now, I'm MAXXXXing out mine. I doubt it's very accurate but the DD is saying up to 113% IDCs.

I'm expecting that the extra .5L of displacement will create immediate leanness on the map I have with all of that additional air; so with just the pinks, I was querying everyone as to how much I should bump up the entire map to make up for all the additional oxygen (or is my deduction misguided?)

You know, now that I think about it, because of the different dimensions of the combustion chambers in addition to the stock heads, I wonder if the timing would be all ate up. If it were, I doubt it would be by much.

 

A VF34 can indeed max out STi injectors. Play around with the fuel injector calculator Wingless Wonder posted recently (it's stickied somewhere around here) and you'll see that 330-340 hp is really the limit on them. But, that's the effective limit- you can keep them there for as long as they are working properly. You will need to enrichen your fuel curves from where boost starts to build on the new motor up to the point where boost starts to taper off (about 5000 rpm probably, based on very rough preliminary calcs I painstakingly did in my head one day during a long drive ).