Why go rotated when you can save money with a GT65?

This was originally written up in April 2008 on NASIOC, but its relevance continues to this day.  Plus, given how everyone is trying to save money these days, $1899 for a 450+ whp turbo is a much smarter purchase than spending well over $2500 for a rotated turbo kit that puts out the same amount of power and even spools slower.

This was the maiden voyage for our GT65 stock location turbocharger and for being internally gated 512 whp is pretty impressive. Not only did it impress on the dyno but also took the NASA Time Attack Unlimited class (TTU) win on both days at Virginia International Raceway.

The GT52 has done so well we figured it was going to be really hard to beat. With that said we are not out to replace it but instead offer something larger for those who are on the edge of purchasing a rotated kit. The biggest difference between the 52 and the 65 would be a more heavily modified Garrett turbine wheel and a 65 lbs compressor wheel stuffed into a 3” compressor cover, a heavily ported 8cm turbine housing, and 19 psi internal gate fitted standard. Unlike the GT52 the GT65 requires TGV deletes and a 3” silicon inlet for installation.

The fuel used was Sunoco 110 and also the Hydramist was injecting windshield washer fluid rated at -20C. Peak power toped out at about 6400 rpm where boost was 23.4 psi, the AFR at 11.7, and ignition timing at 25 degrees in the Hydra data log. This is pretty conservative but it’s my road racing map. For drag racing with a fuel such as VP C16 we could pick up about 15 hp. While the peak boost hit 26.4 psi it was not holding all the way to redline but for an internally gated turbocharger it was doing really well and in the “real world” it holds quite well. Spoolup is decent but ever since I installed the Cosworth cams I’ve lost about 300 rpm of my spoolup that I just can’t seem to regain with tuning of the AVCS. Running 1000cc RC fuel injectors and the Hydramist water injection kit fuel injector duty cycles were nice and safe at 78%.

I am also running a modified 2007 RS intake manifold but since I changed a number of parts I’m not sure what gains or shifts in the power curve may have occurred. It’s a nice manifold with long runners and a large plenum. It does take extensive modifications including custom machined manifold spacers (so fuel injectors can clear AVCS solenoids), custom fuel rail brackets, and some welding to close off the EGR ports. It’s also much taller with the spacer but as long as there’s a hood scoop it clears.

I had two bad misfires that popped up on the last two runs. I tweaked out the dwell on the Hydra map and fixed the misfire at around 7100 but then on the next pull I got one at about 7400 rpm. Looking at the logs all was well with no sign of detonation so it might just be time for some new plugs as I didn’t experience any of this while racing.

This was also the maiden voyage for the production Element Tuning turbo-back exhaust system. What separates our downpipe from the rest is that we chose to do something new with the divorced wastegate design. I penned this design almost 5 years ago but finding a manufacturer to produce the system with the quality we wanted proved difficult until now. Since the majority of Element Tuning customers have extensive modifications such as larger bolt-on turbochargers like the GT52 or GT49 we designed this exhaust system to exploit that by running the 3” dowpipe’s centerline on the exhaust wheel and the 2” wastegate dump tube’s centerline with the wastegate flapper valve. To do this is difficult however and required us to intersect the 3” DP with the 2” dump tube. You basically end up with almost the volume of a 5” DP and then the wastegate dump tube follows all the way down to the bottom of the exhaust system where we then angled the dump tube to create a low pressure area, therefore creating a Venturi Effect which further aids in proper wastegate flow.

The other item we altered from the norm was a divider at the turbocharger flange. The reason we did this was that we found in testing that it hurt wastegate performance since the majority of the aftermarket turbochargers swing open in a fashion that dumps wastegate exhaust directly into the divider hurting flow. This is often why “bellmouth” designs have better boost pressure control. Also by forgoing this divider, the system will work with turbochargers that have a divided exhaust housing from the factory.

I don’t think we can make the internal gated setup any better than it is without risking boost creep and most likely the customer interested in the internal setup is likely only going to run a maximum of 23 psi for pump gas. Since my car is also fitted with an Element FEW Competition Uppipe, we’ll weld up the internal gate and fit a TurboSmart Ultra Gate and see if we can hold about 26-27 psi to redline. This should net us in theory another +45 whp which would put peak power at 557 whp which would make me extremely happy for the first shot at the Element GT65 bolt-on turbocharger.

Modifications:

Intake: 3” Silicon inlet, Subaru RS Intake Manifold
Element 4-1 Header
Element Fuel Surge Tank
Aeromotive A1000 fuel pump
TurboSmart E-Boost 2
TurboSmart Megasonic BOV
Clutch Master’s Element Spec Clutch
RC 1000cc Low Impedance Fuel injectors
Custom Fuel Rails
Ported TGV Housings
Front Mount Intercooler core, Element GT65 piping kit
JIC Suspension custom valved and sprung for Element Tuning
Prodrive GC010 18×9.5 Wheels
Hankook Ventus Race Tires 275/35-18
Seibon Carbon Doors, Hood, and Trunk
Sparco Seats, Steering Wheel, and Harnesses
StopTech 355mm BBK
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