Welly Posted May 3, 2022 Share Posted May 3, 2022 Hi all, first post and new to the forum so apologies if this isn't in the right place. Been doing modifications for a very long time indeed, however, totally new to the Subaru boxer and looking for guidance. In the process of replacing my Brother's turbo on his 2003 WRX which I believe is a PPP model (not sure how to confirm however). The turbo extracted is a TD04, and certainly has thrust bearing play and needs attention. We have to go on in it's place a good condition VF35. Simple enough swap, however, I have some concerns with regards to fuelling, especially as I have no idea what the WRX PPP stock injectors or pump are, or capable of. Fuelling and a map will come at a later date, but for now this need to be 'safe' (word used cautiously) on stock pump and injectors. What's the score here? Also, how is boost controlled on these engines? Can't see that there is any kind of solenoid for controlling boost, and the actuator is piped to the boost outlet nipple with a T off to what I assume is a MAP sensor. Seems that the wastegate is the control mechanism? Quote Link to comment Share on other sites More sharing options...
Welly Posted May 3, 2022 Author Share Posted May 3, 2022 Disregard boost control question, tracked down a very useful article here: https://cobbtuning.atlassian.net/wiki/spaces/PRS/pages/615088215/How+Subaru+s+Factory+Boost+Control+System+Works Quote Link to comment Share on other sites More sharing options...
savage bulldogs Posted May 3, 2022 Share Posted May 3, 2022 Some of my non classic spec is a bit sketchy but I believe the Prodrive Performance pack on a bug /blob wrx should have a certificate, blue tmic to turbo Y pipe , sports cat ,or maybe just the pre cat removed from the up pipe (like in sti's ) and possibly a sticker on the ECU (or some sort of prodrive identification serial number). I believe the in tank pump is different but don't know what markings it should have on it , unfortunately. As for straight swapping from a tdo4 (290 max hp ) to a vf35 (360 max hp) without a remap would be a bit risky imo . As the vf35 would flow quite a bit more air at the same boost pressure. The maf , map and o2 feedback to the ECU might pull things in check a bit on the stock ECU boost pressure but it more likely just fuel cut and pull timing. Because of the different rpm boost threshold (spool point ) and increase in flow .... Or worse still could melt something. The stock 2ltr wrx blue injectors are good for around 330hp , pending on supporting mods. So with just a new pump (just to be safe) and a remap ,you should see around 320 to 330 hp without stressing anything too much . If its really a case of get you out of trouble and the car moving for a couple of weeks until the remap ? You could set up "actuated boost" by by passing the boost control system and running at wastegate spring pressure but even then I'd want it to go on a dyno pull before using boost . These engines don't really like changes in airflow without being mapped tbh . Quote Link to comment Share on other sites More sharing options...
Tidgy Posted May 7, 2022 Share Posted May 7, 2022 100% will need a map for the new turbo, will prob need a 3 port boost sol as well to allow porper boost control. be wary of whaty cob say about mapping, they have a very different way of tuning in the US 1 Quote Link to comment Share on other sites More sharing options...
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