ARMS_Technical Report

What type of EJ is the ARMS M7760 suited for? To find the answer to that question, we prepared a completely stock EJ207, a heavily modified 2.2 liter version of the EJ207, and the EJ255. Each of these engines were put through numerous rigorous tests. We checked power numbers with the use of the factory exhaust parts, and with the TOMEI Powered EXPREME turbo manifolds and downpipes. Furthermore, with the EJ25, we expanded our test by porting the heads to test improvement over the factory unit.
As you can see in the dyno graphs, the M7760 works very well with each engine. This is due to the pre-turbo backpressure being kept at the same level as the factory unit. In addition to the great spool up and response, there are no power spikes. This insures the drivability of the car to be as good as Subaru intended.
As for the peak power, compared to the factory turbo with the EXPREME turbo manifold and downpipe, the M7760 made an additional 25 horse power more at the same boost pressure (1.3～1.4kg/cm2).
TOMEI achieved 400 horsepower on the EJ255 by head modification and opening up the exhaust. 400 horsepower is good MAX for this set-up, and that we proved the versatility of the M7760 with these comparisons.

Powerful even with the standard displacement

The test engine is the EJ207 with the factory turbocharger and exhaust parts, the dyno graph, as expected, is linear and smooth. With the EXPREME products installed, there was in increase in low end torque and response. Finally, with the M7760 installed, the low end torque slightly drops compared to the factory turbo with the EXPREME products, but it is still ahead of the run with the factory exhaust system. Beyond 4000 rpm, however, the M7760 overtakes either set up and proves its capabilities.

Bringing out the best in increased displacement

This graph shows the modified 2.2 liter EJ207. This set up demonstrates the improvements in the low end torque that many EJ owners are looking for. The most notable attribute of this set up is that the horsepower does not taper even at redline. The power is seamless and constant. The boost for this engine is also set at 1.3kg/cm2, and unlike the stock turbo, the boost is consistent all the way to the 7600rpm redline.

Maintaining high output at high RPM

The test engine for this graph is the EJ255. TOMEI has expanded its tests to include the installation of PONCAM cams and head porting. There is a substantial increase in torque with the installation of the EXPREME set, while the addition of the M7760 completes the equation by allowing the engine to breathe at higher rpm and creating 360ps. With the addition of PONCAM cams and a reworked GDB head, TOMEI was able to squeeze out 400ps out of the engine at 1.3kg/cm2. We feel this is the ideal set up for a street EJ25.

All OF OUR PRODUCTS ARE DEVELOPED ON THE ENGINE DYNO

At TOMEI Powered, we take parts development very seriously. All of the products we sell have gone through hours of rigorous testing on the engine dyno to ensure the effectiveness and durability of each product. The engine dyno is a very effective tool in parts development as we can alter load and rpm while measuring A/F ratios and Exhaust temperatures to see how everything works with one another. In testing turbochargers, we record and analyze the backpressure both before and after the turbo. We perform all of our tests in the strictly controlled environment of our sound proof engine dyno room. This allows us to maintain consistent air intake and water temperatures so that we can study consistent results.

EJ25 MODIFICATION STAGES

The horizontally opposed EJ25 is known for being troublesome in terms of modifications, especially when it comes to swapping the camshafts and engine internals. The engine assembly is required to be taken out of the vehicle in order to reach inside the engine. For the end user, it is most effective to first modify the intake system considering the high degree of difficulty and expense involved in fully tuning a boxer. Tomei Powered recommends a turbocharger upgrade after the intake system has been modified.

Head Intake Port Comparison

EJ207 Combustion Chamber Modification

Stock	Power drop above 5,500 RPM	328 HP

EXPREME Exhaust Manifold	Simple bolt-on exhaust manifold upgrade	345 HP

ARMS M7760	Despite size limit, most efficient turbo design achieved	369 HP

PONCAMS	Increased intake air volume with most ideal duration	385 HP

Head Modification	Air intake restriction eliminated, objective cleared	400 HP

*EJ25 is equipped with a restrictive head design resulting in the air intake to be maxed out at 6000 RPM. Tomei Powered has utilized a modified EJ207 head, boring out the combustion chamber diameter to match the cylinder diameter; all done to achieve superb results.

Misc. PRODUCTS

FUEL PUMP

Fuel Pump, Filter, Retainer, Insulator, Wire Harness,Wire terminal, Hose, Hose Band, Rubber Cushion, Tie Wrap

PART#

183020

$220.00 (USD)

INJECTORS

SIDE FEED 740cc (EJ25)
*850cc suited for 2.0L / 2.2L applications

PART#

193023

$640.00 (USD)

CONNECTING RODS

FORGED H-BEAM CONNECTING RODS

PART#

125008

$970.00 (USD)

THE TEST ENGINES

The new ARMS M7760 turbo is designed as a direct replacement bolt-on turbo for all EJ motors that utilizes the “single scroll turbine”. More specifically, the EJ20, EJ25, and the modified versions of these motors. We have not encountered any issues with the EJ207; however, with the EJ255, the TGV (Tumble Generation Valve) might become a bottleneck in regards to peak power. The TGV is designed to create tumble in the combustion chamber to lower Hydrocarbons during cold-start. In a serious tuning application, we suggest either removing the system or use the GDB EJ207 manifold as we did in our testing.