So, I'm planning to go with a bigger turbo. While the Disco Potato makes my mouth water, I'm thinking I need 400 whp with the biggest, broadest powerband possible. I've been looking into the GT2871R, HKS' GT-RS and a few other turbos.
To help fight off lag, I'll be going high-compression, too. I'm thinking 10.5:1 or maybe as high as 11:1. Unlike you, we can get 93-octane gas at the pump here, and my dad has an airplane, so I can get 101-octane low lead at the airport, too.
Anyway, my question is this: What would you run on Project Silvia with higher compression if you were going for 400 whp?
Brandon Dawson
Kent, Wash.
First, you don't need a bigger turbo to beat your uncle's Camaro. If you really had been studying Project Silvia, you'd know it ran a 12.89 with the Potato turbo, a cat, a stock downpipe elbow, a stock exhaust manifold, stock cams, 17 psi of boost and Falken Azenis street tires.
If I had a beef with your uncle, I'd ditch the cat, get a 3-inch downpipe elbow, some cams, some drag radials, a softer rear suspension, a heavier flywheel, and I'd send the ECU back to Jim Wolf for a dual-map switch that let me run an optimized 100-octane map.
Now, if you're really more obsessed with 400 hp than with your uncle's F-body, that's another thing. Either the GT2871R or GT-RS will work well, as they're actually the same turbo. Beware the danger of chasing dyno numbers instead of actual performance, though. I've seen far too many guys blow up perfectly good cars trying to get 10 more horsepower they were never going to use.
You, in particular, are going to blow your car up with your misguided high-compression/high-boost idea. Making more than 200-hp per liter takes a lot of boost, and that absolutely requires the kind of low compression the SR20DET already has. The best you can hope for is that you'll have to retard your timing so much to avoid detonation that you'll end up making less power than you would have with low compression.
Now the real shocker: high compression won't do much for your turbo lag. All else being equal, the higher expansion ratio will actually extract more energy from the combustion event, leaving less energy in the exhaust to drive the turbo. High compression will improve off-boost performance somewhat, so you'll reach spool-up speed slightly sooner, but the difference won't be as big as you're hoping.
Save yourself a few grand. Stick with an internally stock SR20DET and shoot for 350 at the wheels. The extra 50 hp isn't worth the money.
Rally Bred?Short of getting a magnifying glass and a sidekick named Watson, I've done everything searching for the answer to this question, but to no avail. It's a question that comes up often on forums, and the naysayers always discredit the defenders by saying there's NOTHING similar between these two cars.
So, as a former WRX owner and current defender of Subaru honor, I need this question answered: Just how "rally bred" is the WRX? What similarities and differences lie between the road-going Subaru WRX and the World Rally WRX WRC?Allan RansomAppleton, Wis.
You're looking in the wrong place with the WRC car; the true answer to the rally breeding of both the WRX and the EVO lies in Group N. Group N is as close to a showroom stock class as rally will ever have, and there are strict rules limiting the modifications of every aspect of the car. The short version of the Group N rules is basically this: You can add a cage, skid plates, and change springs and dampers. Virtually everything else has to remain stock.