Suggested Order of Modifications *UPDATED 12-17 Now here*
Posted: Thu Jan 31, 2008 6:32 am
Okay, so in another thread someone suggested an order of modifications post.
So here is what I would say. If anyone makes a suggestion I'll update the list and order with it.
Here We Go!
1) Routine Maintenance - Make sure shes good before you start to modify. This includes oil changes, lube jobs, ALL fluids (tranny, differential etc.)
2) Suspension
Power is nothing without control, just ask me!
Here is a comprehensive list of suggested suspension setups.
Courtesy of Jamal.
Any GC8 suspension parts are a direct bolt-in.
Lower arm bars, A-arms, STB, etc
3) Brakes
You better be able to stop well before attempting that 130mph top speed. And I'll admit, the stock SS brakes are fairly good.
Here is a comprehensive guide to brake setups
Once again, courtesy of Jamal
4) Wheels and Tires, well, at least Tires
You need the stickies to keep the shiny side up. ( A well learned mistake on my part)
Some bigger wheels will provide better performance, like 16" rims.
ALL Subaru Legacy, Forester, Outback, Impreza Rims will work, MINUS the SVXs and 05+ STis, they had a 5x114.3 bolt pattern, while all others had 5x100.
Make youre own decision on Tires.
I happen to have 17" WRX rims with Bridgestone Potenza RE92s... I dont like the RE92s... IMO
I think good tires need a bit more emphasis. All the brakes and suspension in the world aren't going to do jack if you're driving around on crap rubber.
5) Gauges
You need to know what is happening in your engine before you do too much.
An exhaust and IC is fine without, but you know your going to want to run higher boost if you put those one.
Autometer makes some of the best gauges available. Most other major brands can be spendy and not have as good of a bang-for-buck ratio.
Generally its suggested that a 30-0-20 is the way to go for a Vacuum/Boost Gauge. That way you know whats happening when not on the boost. (Vacuum measures the amount of pull the engine is producing to suck in air from the outside.)
>Sidenote: I have seen a fair few Autometers that come from the factory reading either 1 psi high or 1 in hg low, which does not lead me to believe that they are consistently a quality product. VDO and Isspro are my two favorite gauge makers.
6) De-Snork and De-resinate (Coffee-Cup Mod)
Remove the snorkus from the fender, this increase the flow of air.
The coffee-cup mod just sounds cooler!
Info on this
7) Intercooler
Now for some fun!
The intercooler cools the air that passes from the turbo to the intake manifold. Ever notice cars have more power when its cold out? Thats because cooler air is denser, allowing for more Oxygen molecules to be forced into the cylinders which creates more power.
It is not suggested to run more than 10lbs of boost without an intercooler.
The main ICs that are in use are Top Mount Intercoolers (TMICs) These sit on top of the engine and cool the air using the air that passes through the hoodscoop.
The easiest TMIC to put on a Legacy Sport Sedan is a Saab 900 IC.
It doesnt look the best, but it works.
>I disagree...the 04-07 FXT and 06-07 WRX Topmount is a much cleaner fit imho...and not hard to install (I've done one)
The next most popular is a 2006 WRX/Forester XT TMIC. These look like they are stock (or near stock) and work good. However the pipes that attach them to the turbo can be tricky if you are using a stock IHI VF-11 turbo due to the angle of the outlet from the turbo (its a 45* angle while WRXs and FXTs use a 90* outlet).
NOTE: The coolant reservoir tank must be moved in order to use the FXT TMIC mentioned above. If not it is possible that it could be damaged and you may need to buy another one.
And when it comes to piping... Use some kind of material that is able to withstand pressure and heat, dryer "slinky hose" will not work.
don't use radiator hose for the 06/07 WRX TMIC install.
get a silicone hose from here for your install to the vf11 if you do it that way..
Then you have Front Mount Intercoolers... These are the big radiator looking things that mount inside the front bumper. These can be a B*tch to install, especially compared to a TMIC.
HOWEVER they cool the air more. And look funny, and considering that the new STis still use a TMIC... Its probably a little overkill. (yes the Evos use a small FMIC but were talking about Subies).
These produce a significant increase in power (from what I hear).
>A frontmount will not produce a huge amount more power compared to a topmount until you start dealing with very large turbos and lots of CFM. They also can be a bit laggy on smaller turbos...i.e. IHI VF Series
>I am not in 100% agreement with everything documented - I felt no additional lag going from stock to a FMIC on the ej22t on the tiny VF11.
I think it should be noted that TMICs will get heatsoaked when sitting in traffic - I've seen temps over 135* in my Impreza while stuck in NYC traffic (which is why I'll be going FMIC on that car by summer).
Also...
OEM Air-water TMICs came on JDM/EDM BC Legacys & Libertys.
AWICs have the potential to cool charge temps below ambient temps if used with a ice water tank.
A pump, heat exchanger, & associated wiring/plumbing will have to be used/done with a AWIC set-up.
I'm starting to see cheap AWICs & heat exchangers on e-bay which may make these a good performing budget I/C option.
9) Manual Boost Controller/ Fuel Cut Defender
This allows you to turn up the amount of pressure exerted by the turbo.
Only use one of these if you have the supporing mods (IC and Exhaust) otherwise you could mess something up, there is a reason that Subaru only set it at 8.7PSI of boost from the factory.
These work by intercepting the flow from the output of the turbo to the input of the wastegate actuator (the thingy that bleeds off exhaust pressure). They basically trick the wastegate into thinking there is less boost than there actually is.
Turbo XS has the best reputation, however many generic one are fine because they are all fairly simple.
At this stage it may be okay to install a Fuel Cut Defender... If you turn the boost past 14lbs the ECU cuts fuel and you literally hit a wall on the power band. When I got my new car the fool had the boost solenoid hooked up backwards... and No IC... At 4200RPM in 4th Gear at WOT I hit Fuel Cut... And when you do... You know it!
So... there are quite a few of these... On this board there are instruction on how to make your own FCD... Electical or Mechanical...
OR you could simply use a Check Valve (go to Home Depot).
NOTICE: Do not overboost... and the VF-11 cant really do anything much above fuel cut if anything. So use these at your own risk. And if you go to high your car will run to lean (to much air for the amount fuel)... So you need to upgrade your fuel system...
Short Version: Dont go over 14lbs on the stock fuel system.
11) Bigger Turbo
You have an itsy-bitsy IHI VF-11 turbo that can only hold like 12psi to redline... It can peak at about 15 I BELIEVE (correct me if I'm wrong).
So now that youre ready... Put on a bigger one!
One of the most popular ones are TD05-16gs...
It is a very nice turbo from what I hear...
yea you can use a WRX td04 but its not really that worth it because it is a small upgrade and hard to install due to the differences in intake setup.
A JDM VF-8 is probably the easiest upgrade, almost bolt in and there are very noticable differences. However they can be hard to come by.
Here is the order from smallest to largest on the turbo scale:
VF11
TD04
VF10
VF8
VF12
TD05-16G
Yes there are other but you can look those up.
>The VF11 runs out of efficiency around 12 psi too...running any higher boost levels just means a whole heap of warm air is going into your motor, and your EGTs are going through the roof!
12) Engine Management
If you read some more into this thread you see that this becomes a hot topic for placement.
Regardless… here it is.
Piggy-Backs - The most common one is a PP6… Perfect Power 6. It can do quite a bit for yours cars performance. And allow you to upgrade a lot.
So Turbos, Injectors, MAFS… You name it.
HOWEVER. All it can do is modify the ECU signals to do what you want. BUT it cannot however replace them. SO you still have to fart around with MAFs even though you have a MAP system to… and you’re still stuck with the pesky IAC shit.
Standalones – There are a lot of these. I do know that John (kleinkid) has gotten some damn good results with the Autronic made for an early WRX.
Link makes some. And there are a lot. Someone else could really do a better job here than me.
>Fuel and timing correction are necessary as you delve into the realms of higher boost. I have found (from personal experience with wideband experimentation) that the stock Legacy Turbo MAF runs out of range at ~15psi, at which point the injectors go into "freakout mode" and cut off the fuel. A Perfect Power will allow for fuel load signal correction. A standalone starts from ground zero with tuning, and does away with the factory ecu.
So yeah, could someone take over the EM section?
13) Injectors
One of the more common minor upgrades are 440cc JDM Legacy RS (AUDM Liberty RS) injectors.
I have heard conflicting info on these, I have heard that you must use USDM N/A Legacy Fuel Rails… BUT According to John (kleinkid) you don’t.
You can also use others like WRX and STi Injectors. The WRX injectors are grey I believe and the STis are Yellow.
The WRXs are 440cc I BELIEVE… Please Correct me if I am wrong, and the STis are 550cc.
FYI, injectors size is not dependent upon boost level, once I thought it was. I was wrong.
It depends on estimated hp. According to Vikash (vrg3) the rule of thumb on size is double your estimated hp.
Plus a little bit for Murphy (Murphys law… d’oh!).
That is a rough estimate… stock Lego Turbacy… 160chp… Injector size… 370cc 370/160= 2.31
USDM STi… 293chp… injector size… 550cc 550/293=1.877
USDM WRX Blues… 227chp… injector size… 440cc 440/227=1.93
JDM Legacy RS… 220cho… injector size… 440cc 440/220=2
You get it.
Now, the max the Stock ECU can control is 440cc injectors. So you’re gonna need EM if you want larger. SO… go re-read step 12.
14) Fuel System Upgrades
I honestly don’t know that much about this… But eventually, with larger injectors and EM, your gonna run out of fuel… And lean is BAADDDD.
So don’t do it.
A proper tune ought to help sure, but you need Fuel Pressure Regulators and possible Fuel Controllers.
I have heard that TurboXS’ DTec Fuel Controller is pretty good.
I hope someone else can take over this section.
15) Transmission and Drivetrain
Honestly, if your at this step… Your stock trannys probably going to shit on you… Especially with higher mileage trannys. (Not Transvestites… I heard someone say “I blew up my tranny at the drag races” and thought that was funny… okay back on topic)
The stock 5mt for a sport sedan is a decent tranny, especially with the hydraulic clutch, but WRX transmissions are better… AND definitely STi trannys are the shit… But um… yeah an STi Tranny is probably more than your car.
Depending on what you plan on doing, certain gear ratios will benefit you differently. I still have a 3.90 (stock Sport Sedan ratio) why?
Well, I’m too cheap to use what money I have on a different one, and I drive a LOT on freeway. 25mi to school and 25mi back, yeah, I use a shitton of gas.
The most common ones are:
Sport Sedan/ Touring Wagon (5mt and 4eat) = 3.90 Final Drive
1st Gen Legacy (USDM) (5mt and 4eat) = 4.11 Final Drive
STi 6mt = 3.90 Final Drive
JDM Foresters (Not sure on the year) = 4.44 Final Drive
Someone please add to this… It would be greatly appreciated.
FYI, the higher the number final drive the higher the rpm to wheel revolutions ratio is.
Also LSDs. Depending on what you’re doing you will benefit from a rear lsd.
A Limited Slip Differential only allows enough slip so the inside wheel can turn slower on turns. And when on wet or slippery conditions it sends power equally to both wheels, with no regard for traction.
3.90 LSDs were on 1991 USDM Legacy Turbos. 1992-1994 didn’t have them.
Also the overseas one often had VLSDs. Someone ought to be able to shed more light.
One note about axles (okay halfshafts… whateve)… the FWD NA Legacys had beefier front halfshaft than AWD legacys… so, you may consider upgrading to those.
16) Head Swaps
At this point… I would definitely assume you are pushing those weak-ass Phase I SOHC Legacy Turbo Heads past their limit.
You’ve reached block engine build stage… Long and Short Block.
On the long block side… Dealing with Heads there are a lot of different options.
SOHC is commonly refered to for both early BC/BF heads such as the stock Ej22t heads and also the heads on later (phase 2) Ej25s.
DOHC is really a bit of a cluster f**k. Ej20g, Ej20k, Ej20h are all DOHC. These are the most commonly discussed here. Ej205, Ej207, Ej255 and Ej257 are all newer (different ECU signals) and basically ignored on this forum. The early (phase 1) non-turbo USDM Ej25s also have DOHC heads.
Ej20g is BC/BF Legacy and early WRX (v1&2). Legacy heads have stub rockers while WRXs have cam-over-buckets. Both of these engines have the 'elbow' turbo inlet like our Ej22ts.
Ej20k is later WRX (v3&4) and is also cam-over-bucket. These engines have the under the manifold turbo inlet. There is also engines in these years Subaru labeled as Ej20g, but should be treated as Ej20ks because electrically and installation-wise that's what they are.
Ej20h is Legacy twin turbo. Electrically these are way out in left field from most other Subarus. But used just for the hardware, not the electrics, it's basically a Ej20k.
I have heard that the 20h heads flow better because they were designed for twin turbo flow. AND they also have an extra set of oil and coolant return lines for the second turbo… which we have no use for and must plug. Doug Vincent has had damn good success with Twin Turbo heads.
USDM phase 1 Ej25 heads are losely based on Ej20k heads. They only need existing bosses drilled and tapped for turbo oil and coolant lines.
The above heads are mostly interchangable because they all accept the same intake manifolds. The 'bolt in/plug-in" deal would be any of the above heads with an Ej20g intake manifold. For our cars the Ej20g intake manifold is prefered becasue it uses comapatable sensors and IAC. It is by all means not the only option.
The Phase 2 SOHC Ej25 head is a very good flowing head, but because it has no provisions for a turbo it seems mostly avoided.
The phase 1 SOHC head is what you have already got on a Ej22t.
Phase 1 and 2 refers to a mild redesign of the block by Subaru about '98. It appears mainly to adrress some problems that cropped up when Subaru 'factory stroked' the Ej20/22 series into the Ej25. Headgasket problems are the most notable. There are numerous improvements but the major ones were a change in the position of the thrust bearing on the crank, the size of the rod journals on Ej25s and structural improvements. As far as heads go there is little to concern yourself with as far as phase1 or 2.
SOHC small valve (EJ22T), SOHC large valve, and DOHC heads make power in different RPM ranges.
Head choice should consider, drivability, RPM limit, power level, turbo choice, compression ratio, boost limit, and just about everything else. It’s a system and all parts need to work together. The best place to start is figure out how you will use the car, and be realistic, building a track car to drive to work every day could be miserable.
To over simplify… bigger valves and more cams tend to produce power at higher RPMs.
17) Short Block Builds
At some point your going to want to build that short block…
Rarely do the bottom ends of these engines go… why? They already have a forged crank and forged rods.
The pistons however are pressure cast, thus not as strong as forged.
…
I have wayyy more on short blocks… but I’m damn tired and I’ll finish it tomorrow.
I hope this helps someone out, it would have helped me.
-Spencer
BTW this is like, my most informative post ever!
KEY
Anything in Brown are additional notes made by Nick (555BCTurbo)
Anything in Green are notes made by Jamal
Anything in Yellow are notes made by dscooby
Anything in Blue are notes made by or derived from SubaruNations experiences. :-D
Anything in Violet are notes made by BXSS
So here is what I would say. If anyone makes a suggestion I'll update the list and order with it.
Here We Go!
1) Routine Maintenance - Make sure shes good before you start to modify. This includes oil changes, lube jobs, ALL fluids (tranny, differential etc.)
2) Suspension
Power is nothing without control, just ask me!
Here is a comprehensive list of suggested suspension setups.
Courtesy of Jamal.
Any GC8 suspension parts are a direct bolt-in.
Lower arm bars, A-arms, STB, etc
3) Brakes
You better be able to stop well before attempting that 130mph top speed. And I'll admit, the stock SS brakes are fairly good.
Here is a comprehensive guide to brake setups
Once again, courtesy of Jamal
4) Wheels and Tires, well, at least Tires
You need the stickies to keep the shiny side up. ( A well learned mistake on my part)
Some bigger wheels will provide better performance, like 16" rims.
ALL Subaru Legacy, Forester, Outback, Impreza Rims will work, MINUS the SVXs and 05+ STis, they had a 5x114.3 bolt pattern, while all others had 5x100.
Make youre own decision on Tires.
I happen to have 17" WRX rims with Bridgestone Potenza RE92s... I dont like the RE92s... IMO
I think good tires need a bit more emphasis. All the brakes and suspension in the world aren't going to do jack if you're driving around on crap rubber.
5) Gauges
You need to know what is happening in your engine before you do too much.
An exhaust and IC is fine without, but you know your going to want to run higher boost if you put those one.
Autometer makes some of the best gauges available. Most other major brands can be spendy and not have as good of a bang-for-buck ratio.
Generally its suggested that a 30-0-20 is the way to go for a Vacuum/Boost Gauge. That way you know whats happening when not on the boost. (Vacuum measures the amount of pull the engine is producing to suck in air from the outside.)
>Sidenote: I have seen a fair few Autometers that come from the factory reading either 1 psi high or 1 in hg low, which does not lead me to believe that they are consistently a quality product. VDO and Isspro are my two favorite gauge makers.
6) De-Snork and De-resinate (Coffee-Cup Mod)
Remove the snorkus from the fender, this increase the flow of air.
The coffee-cup mod just sounds cooler!
Info on this
7) Intercooler
Now for some fun!
The intercooler cools the air that passes from the turbo to the intake manifold. Ever notice cars have more power when its cold out? Thats because cooler air is denser, allowing for more Oxygen molecules to be forced into the cylinders which creates more power.
It is not suggested to run more than 10lbs of boost without an intercooler.
The main ICs that are in use are Top Mount Intercoolers (TMICs) These sit on top of the engine and cool the air using the air that passes through the hoodscoop.
The easiest TMIC to put on a Legacy Sport Sedan is a Saab 900 IC.
It doesnt look the best, but it works.
>I disagree...the 04-07 FXT and 06-07 WRX Topmount is a much cleaner fit imho...and not hard to install (I've done one)
The next most popular is a 2006 WRX/Forester XT TMIC. These look like they are stock (or near stock) and work good. However the pipes that attach them to the turbo can be tricky if you are using a stock IHI VF-11 turbo due to the angle of the outlet from the turbo (its a 45* angle while WRXs and FXTs use a 90* outlet).
NOTE: The coolant reservoir tank must be moved in order to use the FXT TMIC mentioned above. If not it is possible that it could be damaged and you may need to buy another one.
And when it comes to piping... Use some kind of material that is able to withstand pressure and heat, dryer "slinky hose" will not work.
don't use radiator hose for the 06/07 WRX TMIC install.
get a silicone hose from here for your install to the vf11 if you do it that way..
Then you have Front Mount Intercoolers... These are the big radiator looking things that mount inside the front bumper. These can be a B*tch to install, especially compared to a TMIC.
HOWEVER they cool the air more. And look funny, and considering that the new STis still use a TMIC... Its probably a little overkill. (yes the Evos use a small FMIC but were talking about Subies).
These produce a significant increase in power (from what I hear).
>A frontmount will not produce a huge amount more power compared to a topmount until you start dealing with very large turbos and lots of CFM. They also can be a bit laggy on smaller turbos...i.e. IHI VF Series
>I am not in 100% agreement with everything documented - I felt no additional lag going from stock to a FMIC on the ej22t on the tiny VF11.
I think it should be noted that TMICs will get heatsoaked when sitting in traffic - I've seen temps over 135* in my Impreza while stuck in NYC traffic (which is why I'll be going FMIC on that car by summer).
Also...
OEM Air-water TMICs came on JDM/EDM BC Legacys & Libertys.
AWICs have the potential to cool charge temps below ambient temps if used with a ice water tank.
A pump, heat exchanger, & associated wiring/plumbing will have to be used/done with a AWIC set-up.
I'm starting to see cheap AWICs & heat exchangers on e-bay which may make these a good performing budget I/C option.
9) Manual Boost Controller/ Fuel Cut Defender
This allows you to turn up the amount of pressure exerted by the turbo.
Only use one of these if you have the supporing mods (IC and Exhaust) otherwise you could mess something up, there is a reason that Subaru only set it at 8.7PSI of boost from the factory.
These work by intercepting the flow from the output of the turbo to the input of the wastegate actuator (the thingy that bleeds off exhaust pressure). They basically trick the wastegate into thinking there is less boost than there actually is.
Turbo XS has the best reputation, however many generic one are fine because they are all fairly simple.
At this stage it may be okay to install a Fuel Cut Defender... If you turn the boost past 14lbs the ECU cuts fuel and you literally hit a wall on the power band. When I got my new car the fool had the boost solenoid hooked up backwards... and No IC... At 4200RPM in 4th Gear at WOT I hit Fuel Cut... And when you do... You know it!
So... there are quite a few of these... On this board there are instruction on how to make your own FCD... Electical or Mechanical...
OR you could simply use a Check Valve (go to Home Depot).
NOTICE: Do not overboost... and the VF-11 cant really do anything much above fuel cut if anything. So use these at your own risk. And if you go to high your car will run to lean (to much air for the amount fuel)... So you need to upgrade your fuel system...
Short Version: Dont go over 14lbs on the stock fuel system.
11) Bigger Turbo
You have an itsy-bitsy IHI VF-11 turbo that can only hold like 12psi to redline... It can peak at about 15 I BELIEVE (correct me if I'm wrong).
So now that youre ready... Put on a bigger one!
One of the most popular ones are TD05-16gs...
It is a very nice turbo from what I hear...
yea you can use a WRX td04 but its not really that worth it because it is a small upgrade and hard to install due to the differences in intake setup.
A JDM VF-8 is probably the easiest upgrade, almost bolt in and there are very noticable differences. However they can be hard to come by.
Here is the order from smallest to largest on the turbo scale:
VF11
TD04
VF10
VF8
VF12
TD05-16G
Yes there are other but you can look those up.
>The VF11 runs out of efficiency around 12 psi too...running any higher boost levels just means a whole heap of warm air is going into your motor, and your EGTs are going through the roof!
12) Engine Management
If you read some more into this thread you see that this becomes a hot topic for placement.
Regardless… here it is.
Piggy-Backs - The most common one is a PP6… Perfect Power 6. It can do quite a bit for yours cars performance. And allow you to upgrade a lot.
So Turbos, Injectors, MAFS… You name it.
HOWEVER. All it can do is modify the ECU signals to do what you want. BUT it cannot however replace them. SO you still have to fart around with MAFs even though you have a MAP system to… and you’re still stuck with the pesky IAC shit.
Standalones – There are a lot of these. I do know that John (kleinkid) has gotten some damn good results with the Autronic made for an early WRX.
Link makes some. And there are a lot. Someone else could really do a better job here than me.
>Fuel and timing correction are necessary as you delve into the realms of higher boost. I have found (from personal experience with wideband experimentation) that the stock Legacy Turbo MAF runs out of range at ~15psi, at which point the injectors go into "freakout mode" and cut off the fuel. A Perfect Power will allow for fuel load signal correction. A standalone starts from ground zero with tuning, and does away with the factory ecu.
So yeah, could someone take over the EM section?
13) Injectors
One of the more common minor upgrades are 440cc JDM Legacy RS (AUDM Liberty RS) injectors.
I have heard conflicting info on these, I have heard that you must use USDM N/A Legacy Fuel Rails… BUT According to John (kleinkid) you don’t.
You can also use others like WRX and STi Injectors. The WRX injectors are grey I believe and the STis are Yellow.
The WRXs are 440cc I BELIEVE… Please Correct me if I am wrong, and the STis are 550cc.
FYI, injectors size is not dependent upon boost level, once I thought it was. I was wrong.
It depends on estimated hp. According to Vikash (vrg3) the rule of thumb on size is double your estimated hp.
Plus a little bit for Murphy (Murphys law… d’oh!).
That is a rough estimate… stock Lego Turbacy… 160chp… Injector size… 370cc 370/160= 2.31
USDM STi… 293chp… injector size… 550cc 550/293=1.877
USDM WRX Blues… 227chp… injector size… 440cc 440/227=1.93
JDM Legacy RS… 220cho… injector size… 440cc 440/220=2
You get it.
Now, the max the Stock ECU can control is 440cc injectors. So you’re gonna need EM if you want larger. SO… go re-read step 12.
14) Fuel System Upgrades
I honestly don’t know that much about this… But eventually, with larger injectors and EM, your gonna run out of fuel… And lean is BAADDDD.
So don’t do it.
A proper tune ought to help sure, but you need Fuel Pressure Regulators and possible Fuel Controllers.
I have heard that TurboXS’ DTec Fuel Controller is pretty good.
I hope someone else can take over this section.
15) Transmission and Drivetrain
Honestly, if your at this step… Your stock trannys probably going to shit on you… Especially with higher mileage trannys. (Not Transvestites… I heard someone say “I blew up my tranny at the drag races” and thought that was funny… okay back on topic)
The stock 5mt for a sport sedan is a decent tranny, especially with the hydraulic clutch, but WRX transmissions are better… AND definitely STi trannys are the shit… But um… yeah an STi Tranny is probably more than your car.
Depending on what you plan on doing, certain gear ratios will benefit you differently. I still have a 3.90 (stock Sport Sedan ratio) why?
Well, I’m too cheap to use what money I have on a different one, and I drive a LOT on freeway. 25mi to school and 25mi back, yeah, I use a shitton of gas.
The most common ones are:
Sport Sedan/ Touring Wagon (5mt and 4eat) = 3.90 Final Drive
1st Gen Legacy (USDM) (5mt and 4eat) = 4.11 Final Drive
STi 6mt = 3.90 Final Drive
JDM Foresters (Not sure on the year) = 4.44 Final Drive
Someone please add to this… It would be greatly appreciated.
FYI, the higher the number final drive the higher the rpm to wheel revolutions ratio is.
Also LSDs. Depending on what you’re doing you will benefit from a rear lsd.
A Limited Slip Differential only allows enough slip so the inside wheel can turn slower on turns. And when on wet or slippery conditions it sends power equally to both wheels, with no regard for traction.
3.90 LSDs were on 1991 USDM Legacy Turbos. 1992-1994 didn’t have them.
Also the overseas one often had VLSDs. Someone ought to be able to shed more light.
One note about axles (okay halfshafts… whateve)… the FWD NA Legacys had beefier front halfshaft than AWD legacys… so, you may consider upgrading to those.
16) Head Swaps
At this point… I would definitely assume you are pushing those weak-ass Phase I SOHC Legacy Turbo Heads past their limit.
You’ve reached block engine build stage… Long and Short Block.
On the long block side… Dealing with Heads there are a lot of different options.
SOHC is commonly refered to for both early BC/BF heads such as the stock Ej22t heads and also the heads on later (phase 2) Ej25s.
DOHC is really a bit of a cluster f**k. Ej20g, Ej20k, Ej20h are all DOHC. These are the most commonly discussed here. Ej205, Ej207, Ej255 and Ej257 are all newer (different ECU signals) and basically ignored on this forum. The early (phase 1) non-turbo USDM Ej25s also have DOHC heads.
Ej20g is BC/BF Legacy and early WRX (v1&2). Legacy heads have stub rockers while WRXs have cam-over-buckets. Both of these engines have the 'elbow' turbo inlet like our Ej22ts.
Ej20k is later WRX (v3&4) and is also cam-over-bucket. These engines have the under the manifold turbo inlet. There is also engines in these years Subaru labeled as Ej20g, but should be treated as Ej20ks because electrically and installation-wise that's what they are.
Ej20h is Legacy twin turbo. Electrically these are way out in left field from most other Subarus. But used just for the hardware, not the electrics, it's basically a Ej20k.
I have heard that the 20h heads flow better because they were designed for twin turbo flow. AND they also have an extra set of oil and coolant return lines for the second turbo… which we have no use for and must plug. Doug Vincent has had damn good success with Twin Turbo heads.
USDM phase 1 Ej25 heads are losely based on Ej20k heads. They only need existing bosses drilled and tapped for turbo oil and coolant lines.
The above heads are mostly interchangable because they all accept the same intake manifolds. The 'bolt in/plug-in" deal would be any of the above heads with an Ej20g intake manifold. For our cars the Ej20g intake manifold is prefered becasue it uses comapatable sensors and IAC. It is by all means not the only option.
The Phase 2 SOHC Ej25 head is a very good flowing head, but because it has no provisions for a turbo it seems mostly avoided.
The phase 1 SOHC head is what you have already got on a Ej22t.
Phase 1 and 2 refers to a mild redesign of the block by Subaru about '98. It appears mainly to adrress some problems that cropped up when Subaru 'factory stroked' the Ej20/22 series into the Ej25. Headgasket problems are the most notable. There are numerous improvements but the major ones were a change in the position of the thrust bearing on the crank, the size of the rod journals on Ej25s and structural improvements. As far as heads go there is little to concern yourself with as far as phase1 or 2.
SOHC small valve (EJ22T), SOHC large valve, and DOHC heads make power in different RPM ranges.
Head choice should consider, drivability, RPM limit, power level, turbo choice, compression ratio, boost limit, and just about everything else. It’s a system and all parts need to work together. The best place to start is figure out how you will use the car, and be realistic, building a track car to drive to work every day could be miserable.
To over simplify… bigger valves and more cams tend to produce power at higher RPMs.
17) Short Block Builds
At some point your going to want to build that short block…
Rarely do the bottom ends of these engines go… why? They already have a forged crank and forged rods.
The pistons however are pressure cast, thus not as strong as forged.
…
I have wayyy more on short blocks… but I’m damn tired and I’ll finish it tomorrow.
I hope this helps someone out, it would have helped me.
-Spencer
BTW this is like, my most informative post ever!
KEY
Anything in Brown are additional notes made by Nick (555BCTurbo)
Anything in Green are notes made by Jamal
Anything in Yellow are notes made by dscooby
Anything in Blue are notes made by or derived from SubaruNations experiences. :-D
Anything in Violet are notes made by BXSS
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