The Wrenchrat Twin-Turbo Kit - Rocket Brand 114 Race Fuel

The Wrenchrat Twin Turbo Kit Engine Setup

The Test
If you look at the numbers in the dyno-day sidebar, you are going to see that the turbos doubled the boost from 10.4 pounds to 21 pounds and picked up an additional 377 lb-ft of torque between 3,500 and 4,500 rpm, right in the sweet spot. We are always saying that torque equals a good e.t. and horsepower makes for a good trap speed. This system does both with a torque peak of 978 lb-ft at 4,300-rpm and a horsepower peak of 936 at 6,400.

After some tuning runs, we made this number using 25 degrees of timing total and 86 primary and 94 secondary jets in the 850 Holley. To control detonation, we used Rockett Brand 114 race fuel and a methanol injection kit from Snow Performance.

To run this combo on pump gas and cruise, we'd need to dial out a lot of exhaust pressure with the wastegates and use an MSD BTM to control timing on the street.

Next Stop
We made whopping power on the first installation of the Wrenchrat kit and opened the door to a lot of questions. Cam, carb, and cylinder head size will be a factor in where and how much power the system makes. In the usual Car Craft fashion, we went for the big number first to have a little fun. In fact, we have an even bigger set of Brodix 233 heads and a 420-inch small-block being assembled right now at Westside Performance as a dyno mule. Using that combo, we are going to get scientific and figure out what the best twin-turbo combination is for street and strip.

The AR ratio in the turbine side is 0.81. This is as large as you can go on the Wrenchrat kit before the housing touches the valve cover.
The AR ratio in the turbine side is 0.81. This is as large as you can go on the Wrenchrat
These are the 67mm twins from Comp Turbo. They have billet compressor wheels, ceramic ball bearings, and are rated to produce 950 hp each.
These are the 67mm twins from Comp Turbo. They have billet compressor wheels, ceramic ball
If you look closely, you can see the recirculation slot right at the tip of the inducer (smaller section of the compressor wheel). This slot moves the surge line on the compressor map, giving the turbo additional flow range.
If you look closely, you can see the recirculation slot right at the tip of the inducer (s

When Wrenchrat advertises the 4-into-2 system, this is what the company is talking about. The headers feed onto a split T4 flange, carrying the exhaust pulse energy into the turbine.
When Wrenchrat advertises the 4-into-2 system, this is what the company is talking about.
The kit also comes complete with a 2-into-1 merge carb hat and a 50mm blow-off valve. The system will also work with an EFI elbow.
The kit also comes complete with a 2-into-1 merge carb hat and a 50mm blow-off valve. The
The Wrenchrat kit comes with a pair of 41mm wastegates and a downpipe merge to properly ventilate gases into the exhaust stream.
The Wrenchrat kit comes with a pair of 41mm wastegates and a downpipe merge to properly ve

From left: George Diagne, Marty Stromberger, Eric Solomon, and Steve Berg working on the '55 at Westech Performance.
From left: George Diagne, Marty Stromberger, Eric Solomon, and Steve Berg working on the '
Even though this kit can be tuned to run on pump gas, we used Rockett Brand 114 for the big-digit pulls.
Even though this kit can be tuned to run on pump gas, we used Rockett Brand 114 for the bi
The Stage 1 Boost Cooler from Snow Performance injects Boost Juice into the carb hat when the vacuum switch reaches a user-adjustable point. The idea is that the methanol mix cools the intake charge for more power and less chance of detonation.
The Stage 1 Boost Cooler from Snow Performance injects Boost Juice into the carb hat when

Throughout all the tests, we used this simple 2-inch cog drive system from Millerspeed to run the accessories. It doesn't slip and frees up a bit more flywheel horsepower.
Throughout all the tests, we used this simple 2-inch cog drive system from Millerspeed to
Toki's blem tires were throwing chunks on the last dyno day, and Ernie Mena from Westech threatened to stop the testing. For this test we used a set of 295/65-15 M/T ET Street Radials.
Toki's blem tires were throwing chunks on the last dyno day, and Ernie Mena from Westech t
Looking at the dyno chart, you can see the copious amounts of torque these turbos are capable of producing. Note the speed of the horsepower gains in a 1,000-rpm window.
Looking at the dyno chart, you can see the copious amounts of torque these turbos are capa