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Top > EJ20 & EJ25 Guide > TOMEI Technical Report on EJ25

TOMEI POWERED EJ25 R&D REPORT vol.1

Production R&D Engineer Noriyoshi Komatsu
Marketing & Advertisements Naoki Yamamoto
 

Preface
   
Tomei Powered has begun research and development operations for the Impreza EJ20 engine beginning in 2003 and has been continuing until this day. In April of 2007, the full detailed specifications were determined for the EJ series complete engine. The ultimate objective of our research and development for these engine components is the assemblage of the complete engine.

Many hours are dedicated to engineering these products which make up the vital components of the complete engine kit. Features such as longevity and endurance are the major benefits brought to the end user of the automobile tuning industry.

In order to answer to the demands of the3 Subaru enthusiasts all over the world, we have decided to research the EJ25 engine, and proceed with the development of parts for this application. We have completed the first part of this R&D process, which is included in this report. @
Research and Development Process of Tomei Powered
(repeat cycle until performance meets demand)


CONTENTS
   
CHAPTER 1 Analyzing the Stock Engine
CHAPTER 2 Prioritize R&D Subjects
CHAPTER 3 Product R&D
Exhaust Manifold
Bolt-on Turbocharger
Poncam
 
EJ207 Head Modification
 
CHAPTER 4 Summary
CHAPTER 5 OTHER EJ25 COMPONENTS
 
Connecting Rods
Head Gasket
 
Belt Guides
Valve Spring
Valve Spring Seat
Timing Belt
Baffle Stiffener
Individual Throttle Bodies
     
CHAPTER 6 Proceeding Vehicle R&D Projects
PROJECTS
CONCLUSION
   
   


CHAPTER 1 Analyzing the Stock Engine
Disregarding the existence of the TGV and the turbocharger size, we have determined the components surrounding the long block of the EJ25 to be similar with the JDM GDB applied A. However the long block is known to be dissimilar in many essential ways and is expressed below in a chart.
EJ25
EJ20
BORE x STROKE
99.5~79.0mm
92.0~75.0mm
COMPRESSION RATIO
8.2
8.0
CONNECTING ROD
(center to center length)
130.5
130.5
IN CAMSHAFT
240|@9.6mm
240|@8.9mm
EX CAMSHAFT
240|@9.8mm
240|@9.5mm
AVCS ANGLE
20
40
The most clear and striking aspect that was revealed after this test was the power drop after 5,500 RPM, displayed on the graph. We are planning to prioritize solving this issue as well as increasing overall performance for this project.
 

CHAPTER 2 Prioritize R&D Subjects

STOCK EJ255 ENGINE
Considering the fact that the horizontally opposed EJ engine requires to be completely pulled out of the chassis in order to swap the internals; we have deeply taken in to account several factors when performing the R&D. These factors include tuning difficulties, cost, and effectiveness.

Since Tomei does not produce air suction filters and muffler systems, we have resulted in using products from a rival manufacturer. Although vehicles equipped with the EJ25 are all over the world, and each account has their separate octane rating, we had no choice but to perform the test with the Japanese fuel octane standard.


CHAPTER 3 Product R&D - Exhaust manifold 1 -
Prototype Product Details
Careful thought and consideration have gone into the decision for the prototype unit.
  @Researching equal and non equal length
Pros and cons of equal and non-equal length.
 
Pros
Cons
Equal Each cylinder condition in uniformity.
(More precise settings can be achieved)
Pipes leading to junction are longer in length
(decreased turbo response)
Non Equal Pipes lading to turbo can be kept short as possible.
(increased turbo response)
Disrupts cylinder uniformity
 
The ECU setting can compensate for each of the enginefs cylinder characteristic differences, improving efficiency to a certain point. The stock ECU is incapable of this function.
Considering the next modification one may perform after changing the exhaust manifold is a turbo upgrade, we have decided to go with the unequal length design; similar to our GC8 manifold. The reason for this decision is that we have made turbo response as the priority above all factors.

CHAPTER 3 Product R&D -Exhaust manifold 2 -
  AVarious piping layout
 
The GDB equal length manifold resulted in a long design due to its complicated layout. To compensate for this structure, the pipe diameters were decreased to 38mm. However, the exhaust pressures were too high at the upper RPM range, and the gas flow suffered significantly. This restriction of flow can be noticed more clearly especially if a larger turbocharger has been installed. Also, the 2.5 liter engine has more exhaust pressure than the GDB 2.0 liter unit. The main pipe was made to be 42.7mm and the support piping at 60mm due to the limited space.
The center piping of the 2.0 liter non-equal exhaust manifold was bottlenecked to 55mm, which further engine bench testing will prove if the gbottle neckh was necessary.

(The gbottleneckh portion increases exhaust flow velocity right before the turbocharger, aimed to increase turbo response.)


 

 

CHAPTER 3 Product R&D -Exhaust manifold 3 -
- Results & Observations
Tomeifs bottle neck design had no effect on the output, with power increasing all the way up to 5,600 RPM. Since the exhaust pressure was made to be similar to the stock specification, the turbo response should not be hindered in any way, but improved. On top of this improvement, more power is expected to be available. A decline in power can be seen at anything above 5,600 RPM due to the overall manifold shape.
It is prospected that the turbine is almost at full capacity since the stock manifold exhibited a trend of higher exhaust pressure and similar power output as our prototype unit. In regards to the gbottle neckh area of the support piping, no notable differences were seen in terms of power and exhaust pressure. However, we had decided to disregard (take off) the bottle neck area to spare room for further tuning advancements. Therefore we will not have any bottle neck designs in our future tested products.
   
 
Main Piping
Pipe Merge Section
Support Piping
Weight
Stock
42.7 Sufficient
45 Sufficient
45
12.4 kg
TOMEI
42.7
60
60
8.9 kg


 

CHAPTER 3 Product R&D -Bolt-On Turbocharger 1-
 
The third step in the STAGE 1 pertains to bolt-on turbochargers. The selection of the turbocharger assembly depended on the following 2 points listed below.
 
 
A)@Space Restrictions
 
The two problems when placing a turbocharger in place of the stock area is 1.) suction pipe near the surge tank, 2.) turbo compressor housing is very close to the block, limiting the size of the housing to 50.5 or 52.6.
 
B) Over 400 Horsepower + Characteristics Similar to Stock Turbo
 
The final decision of keeping the vehicle in the 400 horsepower range was made because we wanted to keep the vehicle at a streetable level. The 52.6 compressor housing was used since it is very difficult to produce 400 horsepower out of a 50.5 housing. The exhaust housing was changed to M77 to fight decreasing response. The final outcome was the M7760 turbo assembly.
 
 
COMPRESSOR WHEEL
COMPRESSOR HOUSING
TURBINE WHEEL
IN DIA
mm
OUT DIA
mm
TRIM
INT. SIDE
EXH. SIDE
OUT DIA
mm
EX DIA
mm
TRIM
VF39(STD)
46.5
60
60
48
40.8
48
53
82
ARMS-M7760
52.6
68
60
53.5
42
49.1
56
77

CHAPTER 3 Product R&D -Bolt-On Turbocharger 2-
The Bolt-on turbocharger was evaluated with these criterias in mind.
  If the boost can keep up at the upper RPM range
If the primary exhaust pressure (engine to turbo) is similar to stock turbo
If the compressor outlet temp does not keep rising depending on impellor revolution.
If stock boost (1.3lg/cm2) has capacity to produce 400hp
Measuring Points
  Engine Power (taking into account surrounding aspects that affect power)@@@@
Boost Pressure @@@@
Primary Exhaust Pressure @@@@@@@@
Compressor Outlet Temperature
  ~ RESULTS & OBSERVATIONS~
  The ARMS-M7760 turbocharger was chosen because its size and dimension allows it to be swapped out in place of the stock turbo placement. However, we have begun to realize that reaching the 400 horsepower mark with this turbocharger may be a bit difficult. According to the graph, with the boost pressure at 1.3kg/cm2, the EVC duty is already at 70%. There is still room to increase boost pressure but this will result in increasing the primary exhaust pressure, which leads to high compressor outlet temperature. Therefore we cannot increase the boost pressure any higher.

CHAPTER 3 Product R&D -Bolt-On Turbocharger 3-
Characteristics of the ARMS M-7760
Primary exhaust pressure is very similar to that of the stock rating at the lower RPM range.
* Power sensation characteristic is not too slow or sudden, but very natural.
* Ease of use and smooth drivability experienced.
Response similar to stock turbocharger
* Increasing turbocharger size usually hinders throttle response, however we have avoided this issue without sacrificing this aspect. This was made possible by carefully selecting the most ideal combination of components.
25 Horsepower maximum power improvement
* Out of all the turbochargers we have researched and considered, this unit provided an improvement of 25 horsepower or more.
* This number was confirmed without sacrificing drivability or response.
Boost maintained at the upper RPM range
* The new turbo setup maintains boost pressure even above the 5,500 RPM mark, which greatly affects the prospected tuning course of this engine.
Completely bolt-on
* This turbocharger will include all necessary accessories such as gaskets and hardware for a straight bolt-on capability. The entire kit is ready to be installed straight out of the box.
     
* The entire testing procedures have been completed, labeling this turbo as the Tomei ARMS M7760. This turbocharger is now in the preparatory stages of production and sales.

CHAPTER 3 Product R&D -Bolt-On Turbo Graph & Photos
Turbine Test Results
 
1.3 kg/cm2 Boost setting

CHAPTER 3 Product R&D - Poncam 1 -
AVCS Structure Research
  Upon comparison of the AVCS functionality range between the EJ255 and EJ207 engines, we have found that they are different. The component was then disassembled and analyzed / compared, to find out that the hardware was completely identical. This brought us to realize that everything was controlled by the ECU. The maximum AVCS advancement angle for the EJ207 RA Spec-C unit is 45 degrees, with over 2.0mm of piston to valve clearance (p-v clearance).
Selection of camshaft specifications for testing
Since the AVCS function is present, A great amount of duration is not necessary since the AVCS function is existent, so 2 types of conditions were brought clear.
  ~ A setup with the most lift
  ~ A setup with the most duration
     
   
IN
EX
DURATION
LIFT
P-V CLEARANCE @ 45
DURATION
LIFT
P-V CLEARANCE
STOCK
240
9.6
2.96(ATDC 10)
240
9.8
7.85(BTDC 0)
TESTED
252
10.4
2.23(ATDC 5)
252
10.4
260
9.8
2.22(ATDC 5)
264
10.0
77
    The retardation and center angles are set at stock (IN-125 EX - 115)

CHAPTER 3 Product R&D - Poncam 2 -
Measuring Points
  EEngine Power (taking into account surrounding aspects that affect power) @@@@
EBoost pressure
EIdeal AVCS angle advancement
  * It has been confirmed that the turbocharger cannot maintain boost at the higher RPM levels, therefore the value of 1.3kg/cm2 was decided.
RESULTS & OBSERVATIONS
4 types of tests were performed including stock settings
  252-252

Shared same qualities as stock at the lower RPM range. As 5,200RPM as the boundary, some power improvements were exhibited.
  260-264
The graph looks similar to the 252-252 spec, but is offset at the higher RPM area.
  252-264 Shares same characteristics as the 252-252 in the lower range, and 260-264 at the higher RPM range.
All tested versions exhibited a peak of 6,000 RPM boundary limit, which is believed to be caused by the lack of intake air at that RPM range. The duration cannot be increased without the modification of the intake components (surgetank or intake plenum, intake port/polish, etc). If we were to change the camshafts, the next candidates will be 252-252, 252-264 however considering the balance of the intake and exhaust sides, 252-252 might be more desirable.
The camshaft specifications can be made up by changing the AVCS duration, but we have provided 2.0mm margin of safety for inappropriate settings and also in case any of the teeth on the timing belt accidentally skip. Increasing the lift may result in interference with the camshaft journal caps.

CHAPTER 3 Product R&D - Poncam Data & Photo -
Camshaft Test Line Graph
 
 

CHAPTER 3 Product R&D - EJ207 Head Modification 1 -
Head Structure Inspection
  Due to the air intake restriction we had experienced earlier during the camshaft testing, we have decided to inspect the EJ207 and EJ255 head assemblies. As seen in the photo, the EJ207 head was equipped with larger ports. The similarities of the IN/EX valves enabled us to compare the intake ports of these two heads by swapping each unit.
 
*
The EJ207 required alterations to the combustion chamber due to different cylinder bore diameter.
 
*
Since the same camshafts cannot be used for both applications, the EJ207 head was fitted with Poncam (IN250-9.6 EX256-9.8).
Intake Port Comparison
 
EJ207 Combustion Chamber Modification
  We have prioritized the flow bench test results because of the differences in the camshaft specifications, and engine bench tests were performed as well. This test was performed as backup to confirm the special engine changes (high RPM range power output) and the power figures were used as a reference.

CHAPTER 3 Product R&D - EJ207 Head Modification 2 -
Results & Observations
  According to the flow bench results, the differences between the EJ255 and EJ207 heads were further increased as the cam lift became bigger. The EJ207 head proved to have 10% better flow than the EJ255 with the use of the prototype camshaft (10.4mm lift). According to these findings, the differences in terms of performance becomes more clear as different factors such as intake port size, higher lift camshafts, and turbo sizes come into play.
  The engine bench test reflects directly with the flow bench results, with no proof of any power drop at the higher RPM range; even though both units were equipped with similar camshaft profiles. The stock engine provides great engine response but lacks power at the higher RPM range. To surpass 400 horsepower, head modification is necessary. There two options for this; to modify the ports on the EJ25 head, or divert to using the EJ207 head.
Flow bench test results
Problems
  * EJ25 Head Modification
 
Jig templates and computer programs are required for the Numerical Control Machine (NC Machine) to make each port even flow. This will all require a good deal of time and expense.
  * EJ255 Head Modification
 
Since the ports do not to be modified, the combustion chamber diameter need to bne increased. There is a sufficient amount of hand labor involved but to increase efficiency and accuracy, the Numerical Control Machine is required to be used. Also, since the pick up sensor for on the camshafts are different, the stock ECU cannot be utilized with this head.
     

CHAPTER 3 Product R&D - EJ20 Head Modification Data & Photo -
Comparisons Between Two Head Assemblies
 

CHAPTER 4 Product R&D - Summary -
 
Reflecting back at the research and development performed so far:

up to 328 HP
Displayed power drop after 5,500 RPM
up to 345 HP
Increase exhaust efficiency by swapping manifolds
up to 369 HP
Target horsepower unachievable due to turbo limitation.
up to 385 HP
Increased air intake combined with precise timing control
up to 400 HP
Eliminated restrictive air intake problem. Objective reached.
   
Tomeifs product research and development involves a definitive schedule for each project, which each point of concern is effectively solved one by one. Each step is tested thoroughly to ensure that a solution is brought forth to any concerns that may arise during the entire process. The quality and performance exhibited from Tomei Powered products reflects the countless hours spent on rigorous research and testing.

CHAPTER 5 - Regarding Other EJ255 Components 1 -
CONNECTING RODS TIMING BELT

* H-Beam
* Rod & cap made from different material
* Oil ports
* ARP bolts
* Knockpins to prevent dislocation

More..

* Longevity against heat & water
* Prevents belt slippage prone to EJ engines

More..

 
  HEAD GASKET BELT GUIDES (COMING SOON)

* Super grommet construction improves surface pressure
* Exclusive rib design
(Improved seal around water seal)
* 2 thickness available for different compression

More..

Since the boxer engines are horizontally opposed, there are incidents of camshafts not lifting. This product firmly secures the belt vibration to prevent unwanted troubles.
 
VALVE SPRINGS BAFFLE STIFFENER

* Elliptical design adopted for high lift cams
* Improved valve movement

More..

* Circulates oil and prevents build up
* Strengthens crankcase

More..

 
VALVE SPRING SEAT INDIVIDUAL THROTTLE BODIES

* Easily adjust valve spring seat load
* Prevents surging

 

* Increased capacity surge tank
* 48mm throttle bodies for high response
* A must for the big EJ fanatics

CHAPTER 6 Proceeding Vehicle R&D Projects - Arise -
 
ENGINE EJ207
PISTON TOMEI Forged 92.5mm
CONNECTING RODS
TOMEI Forged H-Beam
CRANKSHAFT TOMEI 79mm Stroke
CAMSHAFT TOMEI IN 250-9.60mm, EX 256-9.80mm
DISPLACEMENT 2123cc
HEAD GASKET TOMEI 1.2mm 93.5 Bore
COMPRESSION 8.0
TURBO TOMEI ARMS B8446
INJECTORS TOMEI 850cc
EX. MANIFOLD TOMEI EXPREME
CATALYTIC TOMEI EXPREME
Used as the R&D vehicle for the EJ20 engine components since 2003, the Tomei / Arise Impreza has been competing in various time attack events. This engine was built as research for the Tomei complete engine emphasizing on reliability as well as great performance. Becoming the winner of the 2007 Hyper Car Meeting 10 lap race (AP Battle Open Class), it proved to be an all around player.

CHAPTER 6 Proceeding Vehicle R&D Projects STPOWERED
 
ST Powered is a Tomei Powered authorized dealer catering to Singapore / Indonesia / Malaysia / Thai. Their democar, equipped with a EJ25 along with various components that make up this research and developme t report. The stroker kit, which is still under development, was fitted into this chassis as the test vehicle. ST-Poweredfs continuing support in providing us with valuable data and feedback makes them one of our prominent dealers. They have recently taken 2nd place in a renowned time attack event, and their success can be best celebrated with the Tomei stroker kit.
PROTOTYPE PISTONS@ 99.75
PROTOTYPE CRANK 81.0mm STROKE
PROTOTYPE CON ROD 128.8mm
TURBO@@@@@TOMEI ARMS B8446
EJ26 In Development
 

IN CONCLUSION
 
The final objective in Tomei Poweredfs researching and development of engine products is the complete engine. Only the necessary components are developed to reach each projectfs target objective.
For this EJ25 project, countless trials and errors have been repeated, but we have created the best engine that a customer can use with the utmost satisfaction.
Special thanks goes out to Mr. Michael Ferrara of Dsport Magazine, which he has generously agreed to support us by exposing our hard work into his publication. This will be the stepping stone to informing the entire world about Tomei Powered, and our passions.
Some aspecs are difficult to state by text, so if there are any inquiries concerning this report please feel free to contact us anytime.
Lastly, we would like to thank everyone for the opportunity, and especially for the future opportunities to come.

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