There are threads about this all over, but maybe a few people could weigh in since I can basically go wherever I want at this point. I want to add power, with the least amount of boost possible to help cripple along my intercooling system as it is. 2013 GT500 pump, large single pass Roush HE, probably a 2013 GT500 fan, fencing, etc.. with the M90 lower intake.
Currently through stock cats I'm seeing anywhere from 7.5 to low 9's for PSI depending on weather. 82mm pulley on the 1.9. I don't know where Justin got his dyno graphs from, but I think that was sqwerl's stock engine with no cats, at just under 8 psi he was nearly 450 at the wheels on 93. I'm going to assume I'm making around there, 430 or so right now on 91. Currently my IAT's are well in hand 90% of the time, and I can accept the car running a bit slower on a 100F day, of which I get 3 a year.
The plan is to remove the cats and possibly add some blower cams, this might cause a gross drop in the boost by 1-1.5 psi. Has anyone got experience ditching catalysts and/or adding cams such as the comp 127205 (small cams) and the effects on boost on an otherwise stock engine? I've seen it mentioned in many threads but it's always in the midst of a bunch of other stuff happening, pulley changes, etc...
My concerns with camshafts:
- I could need heavier springs. The failure rate of cam drives with heavier springs seems fairly significant.
- I would need phaser limiters. Lito is trying to get me to use limiters even with my stock camshaft when I build the engine. This isn't a bad idea, so I've built the cost into what I'm doing.
- I would need retainers, locks.
If I were to do 127205's I could conceivably leave the heads alone, but I don't want to do it and see a statistically insignificant difference in horsepower gain and boost loss. I might be better off spending my money elsewhere, especially if I see a false increase in IAT's. I've finally been able to register at the comp forums, seems like they have a knowledgeable moderator in there that isn't just answering yes to every question about buying a comp part.
I've addressed my planned boost elsewhere but I'll repeat it here, 69mm pulley, Brian says that's good for 11 PSI. I've always seen slightly higher numbers than he had, for one reason or another, so we'll say 11-12.