Thompson Motorsports was the supplier for the bottom end, with a 5.3L GM block bored to 3.905″ housing an OEM GM LS1 3.622″ stroke crank. Spinning on the crank are K1 4340 forged H-beam rods with ARP2000 fasteners. Sitting on top of those rods are forged Diamond Racing -2.0CC flat-top pistons with a moly skirt coating.
PRC did the head work, providing a “Stage 2.5″ CNC-ported set of 5.3L LS heads with 62cc combustion chambers. Oversized stainless 2.02″ (intake) and 1.575″ (exhaust) valves are bounced around by PRC .650” dual valvesprings and stainless retainers. Texas Speed bumpsticks round out the internal power package, with a combination of their 233/239 .595”/.603” 114LSA +2 units.
If you’re doing the fancy engine builder math, the final product comes in at 5.7L.
Like many before him, why stop at a 26% increase in displacement when you can also have forced induction? This Turbosmart 45mm Comp-Gate is used to control the VS Racing billet 7875 journal-bearing turbo.
Erin took GM truck manifolds and hacked off the collectors. Then, he welded 2.25″ mild steel tube to them with V-bands. More 2.25″ tubing was used as a crossover into a custom merge collector and then into the T4 flange that the turbo is attached to. A lot of wastegate priority was built into the exhaust setup as Erin only runs a low 10psi of boost.
The exhaust gases all make their way into a homemade downpipe that starts with 3” round tubing, expands to 3.5” round using a cone adapter, and then to 3.5” oval in a vertical orientation for clearance between the engine and the frame rail.
And when Erin does, this Turbosmart Raceport 50mm BOV prevents the intake charge from annihilating the throttle body or backing up to the turbo and making a real mess of things. Fortunately, the LS setup is using a MAP sensor for measuring, which means the BOV can simply dump to the atmosphere when called on.
6 comments
Nice to see some DefSport parts being used in anger. Cool build.
BTW – did you ever get the Astra power steering pump to quiet down? Based on my recent MR2 experience, I think maybe using Redline D4 ATF in it could have been the cause for the loud pump. It seems they like this special thicker hydraulic fluid blend (Pentosin makes one).
I found that mounting the pump a little higher in the car helps believe it or not.
It’s not all that loud, I couldn’t hear it over all of the other noise the car makes. I just sounds like a small turbine engine on startup then turns into an electric forklift noise after it settles in.
I never found it to be all that loud, especially compared to all the other noise the car makes. It sort of resembles a jet turbine starting up 😂
Mike – it’s mounted up about as high as it can be in the trunk of an S13. The SW20 MR2 installation has it down in the frunk just above the steering rack – but it has a big rubber condom over it to help muffle noise.
I probably wouldn’t have minded it on the track, but for a sometimes street driven car it seemed annoying to me. Then again, I had a hatch S13 so maybe it was a bit more open.
Any chance of seeing how the wastegate flow was prioritized? This is the 2nd recent MotoIQ car-ticle with a similar size turbo and gate. I feel I am running a near identical setup to this particular car though and similarly put extra effort into making wastegate flow entry a relatively shallow angle from my exhaust flow path. Truck manifolds, v banded, near equal length 2.25 inch up pipes, merge into 3″ before tapering down to undivided T4 flange. I have a precision gen 2 7675 CEA .96 a/r with full 3.5″ turbo back exhaust. This is on a 5.3 with ~10:1 compression and timing backed off for tuning, 12* base timing. I’m having trouble with boost creep with a precision turbo 46mm wastegate dumping to atmo. I have a 3psi spring in it and in full throttle 4th gear pulls from 40-100ish it can hold boost steady at 3.5 psi up to 5500rpm, on the way past that to my ‘safe for tuning’ limiter of 6000rpm it loses control and boost spikes to ~8psi, it will likely be even worse with a proper redline. I was contemplating going to a PW66.