what are the pros and cons of these systems?......

 

I don't have either, but here is what I have observed.
PROS

STS - Cheaper initial cost, adjustable boost, easy to install, Good power all around, better mpg, very reliable.

Radix - A bit more complete, 3year warranty, available powertrain warranty, great bottom end tq, and good hp, super reliable.

Cons

STS - No intercooler, so can only run so much boost

Radix - Pricey, can only run so much boost efficently

 

Radix is one of the most complete kits out there - bar none. Complete with tuning, intercooling, larger injectors, and higher flow fuel pump. I sold mine and bought the STS because it could not get me where I wanted to go. I'm shooting for 15lbs of boost on a free flowing 408. Radix would run out of breath before it hit that.

Your boost will be limited more with a Radix. 10+ for sure, but I never could hit 11lbs. Once you start spinning it that high, your efficiency would take a big dive. Turbo can take you a bit higher.

The turbo, if you get above 6-7lbs of boost will require bigger injectors and possibly an addit'l fuel pump. These don't come with the kit. Needed for sure, if you wanted to go higher. An intercooler will make it much more efficient. does not come with it, again. Also, tuning, their cost does not include tuning.

So overall, I think the costs even out, with the STS costing a little more, but that is a going all out costs. The base system is substantially less.

I think the base systems for both, 6-7lbs of boost, would be a pretty equal run at the track, but that is yet to be proven. I've ridden in both.

 

boost for boost, I would have to put my money on the Radix truck at the track.

 

Does STS have CARB approval? If you're in CA, that's a big selling point for the radix.

 

I'm hearing that's a couple of months away still, but they should get it from what I hear.

 

They've paid their fee, they went through the first round of testing ('cleanest turbo we've ever tested' said the commission), and they needed to move a couple of small components before they would be issued the CARB cert. The second, follow-up test was last month. The CARB cert is really a formality - the STS is a post-cat system, the cleanest of all possible scenarios.

 

I bought the Radix because:
Complete kit
Detailed instructions - easy install
Look great - matches exterior of my truck
Warranty/emissions
Been available for a long time - tons of feedback
I've had a Roots type blower before and I'm addicted to the off-idle torque/power

I didn't buy the STS because:
There wasn't alot of feedback when I wanted to buy (however there was an explosion of feedback right after)
Didn't really come with everything needed to install for the amount of boost I'd want
I have a lowered truck and drive through relatively high water once a year
Dont like the idea of all that plumbing (rubbing/clearance issues - there may be none, I dont know)

I am a "weekend mechanic" and I would say I did a pretty nice Radix install pretty easily, and put about 1k miles within a few weeks of installing it with absolutely no problems.

 

Only Radix truck in my area to compete with me at the track is an SS Silverado with a 75shot of nitrous and even then I bet I get him

 

While turbos sound neat, I love the way the Radix wails when you're on it. Nothing else sounds like it.

My lame 2-cents.