Quote:
Originally Posted by scubasteve
20g sounds kinda like a build motor...hmmm not sure Im up for that quite yet
Ive read enough to get the idea that continuing to increase boost also increase heat which makes a less dense air charge = less that will fit in a cylinder....
but for the rest of it, I will take your word for it.
Whats your take on aftermarker upipe, maybe PNP headers to get a few more ponies?
|
A turbo has a range of compression efficiencies. Basically, it's the amount of air (flow) vs. the amount of boost (pressure). For some ranges of flow and pressure, the turbo does a good job of compressing the air... get outside that range and, like you said, the turbo is just a hairdryer heating up the intake charge. you can squeeze a little more power out of upping the boost, especially with a good intercooler, but really it's better to run a larger turbo in its sweet spot than to over boost a smaller turbo.
So while the 20g is a medium/large turbo, it's perfectly okay to run it at lower boost levels safe for a stock bottom-end EJ255. Because it will flow a ton more than the VF43, that same boost level is actually a bunch more power. Plus, you won't need to taper as much towards red line. I would bet a 20g at 16 or 17 psi will be over 250whp. At 18psi, close to that 300whp you're looking for. The stock STi cat-back might be a bit of a limit, but not terribly so. Your non-STi heads are far more the reason you're not getting STi power levels. Of course there will be some spool issues... the STi turbo is a wicked fast spooling turbo. So, your boost will come on a bit later with a 20g. But that can be combated with choosing the proper hot-side.
If you're not racing the car, the TD05-20g is a crazy awesome turbo on a 2.5l block. Spools like the STi turbo, but will get you to that 300whp level with proper supporting mods. However, this turbo is known to run high EGTs when WOT for long periods. Both MikeK and I have run it... it's an awesome turbo, but at the track, you'll start melting stuff like timing belt covers. On the street, it's unlikely to be an issue because you're not going full-throttle lap after lap, but it's something to be aware of.
The far more popular TD06-20g is a bigger hot-side version of the same turbo. It will spool later, make a bit more power, and run cooler. It's probably a little big for an unbuilt EJ255 w/ non-STi heads, but not by much. I bet there are tons of people running that turbo on the same block as you.
And there are probably like 40 other variations/tweaks of similar sized turbos... I'm just not up on the latest and greatest since I'm not turbo shopping for a Forester these days.