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So you want to mod your EJ20?


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#1 Evil_VZ-T

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Posted 19 August 2008 - 10:24 PM

Hey guys,
* please PM if there is anything that should be added or corrected*

Here is a simple guide to those people out there wondering where to start with modifying their EJ20/25T’ engines. I will cover the 3 main sources for a complete combustion to take process. The principle of “do it once, do it right” will come into play.

NOTE: Im not saying that this is the cheapest or easiest method at all. Just that it works and you wont have to redo or change it due to poor quality

FUEL

Fuel pumps, The first thing to do when deciding to upgrade your fuel system. These bad boys are the backbone in the fuel system. Without them we wouldn’t be able to get fuel from the tank to out beloved engine. One that is capable of pumping more fuel per minute is optimal for later stages of fuel delivery. Walbro and Bosch are the Major brands doing the rounds in modified Subaru tanks.

As some of you may or may not know in Subaru engines (particularly early model Ej20’s) cylinder #2 is prone to run leaner under high boost and RPM applications than the other cylinders in the engine. This is due to the design limitation of the Stock fuel system. This results in cylinder #2 being starved of fuel.

A semi parallel fuel rail mod can fix this very easily by running additional fuel lines in between each bank.
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A full Parallel mod can be done which has been done on many members cars. its a pretty easy DIY, but mick at Techworz in ACT can do this modification for the $300ish mark. (not including FPR. Using Two left hand rails with no fuel pressure regulator. this setup can easily be achieved. (see below posts for MARV's comments)
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Next on the list are fuel pressure regulators. These little buggers can increase fuel pressure as boost rises. The pressure set can determine how the fuel is sprayed out of the injectors. “Too Low” pressure will cause the spray pattern to form a dribble and the fuel will be located and ignited on one part of the piston. “Too High” pressure will allow a big wide mist to come out which will be directed towards the outside of the combustion chamber and cause a possible misfire due to the sparkplug not being able to reach the fuel. The optimum pressure should produce a fine mist that covers the whole combustion chamber allowing for a complete burn. Some brands that are used today are SARD, HKS, Etc..

Injectors, now the rule goes that you want 25 percent more flow than what you need. Early Ej20T came with 380cc injectors which are great for the 160KW mark. MY97-98 STis and GT-B Legacys had the correct 440cc yellow top injectors, but MY99-00 had a different side-fed injector. You can make the 99-00 injector work in an EJ20G (MY89-96 EJ20), but you need EJ25D fuel rails off a gen2 NA 2.5L Liberty/Legacy.
From MY01-on they used top-feed injectors (380cc, 440cc, 550cc) which has a wider range in aftermarket injectors.



A basic guide is:
160Kw’s 380cc
180Kw’s 440cc
200Kw’s 550cc
230Kw and up 650cc



SPARK
Now once all these components have been upgraded its now time to look at Spark

A common fault is the aged Coils breaking down and failing when the boost is raised. An upgrade to Bosch HEC716 coils is a great option. Up rated ignition leads are a must when the coils are changed. Resistance in the ignition leads can lead to poor spark and engine misfire. Spark plugs are next and gapping them is they key to a good ignition. If the gap is too small the spark won’t have enough to completely burn the fuel in the chamber. If its too big the spark may get blown out by the compressed air being forced into the engine from the turbo charger. A gap of 0.7mm is recommended for the EJ20T and slightly smaller if boost is substantially higher than factory.

By changing these components you will now know that your ignition system is great and will not fail you any time soon.
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"courtesy of TZlegacy"


AIR
This is the unit that give us the power, the rule is more air = more fuel = power.

The stock Subaru intake tract is very restrictive due to a resonator located in the inner guard adjacent to the airbox. The simplest method is completely removing the resonator and airbox from the intake and attaching a Pod filter to the end of the Air Flow Meter. This does however give the engine a mighty roar as you stomp on the loud pedal but increases the risk of sucking in hot under bonnet air. A custom Cold air induction is great. This compromises of stainless or mild steel pipe work which goes from the turbocharger, through the hole in the side of the engine bay and ending inside the inner guard where cold air can be sucked in. You can buy kits which re locate the AFM inside the guard which also aids in positioning and cost effectiveness of buying expensive stainless steel. Such Companies as Techworkz and Amauto can make custom kits to suit any application.

The infamous duel 90 degree bends just before the Turbo are restrictive. due to the sudden change move direction the air has to travel. this causes turbulence and the air does not get sucks in as efficient as it could. As Marv has stated a Gen2 Airbox can be installed to still have the Stock style box and it can also work with those who have FMIC piping to suit the inverted core.

“Techworkz Cai”
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EXHAUST
The exhaust system, Its job is to extract the exhaust gas’s and exit them out the rear of the vehicle as quick as possible. Too restrictive and the engine will choke in higher RPM/Boost. Too free and the engine wont have the back pressure to allow the gas’s to be sucked out.

Please refer here for a more indepth view > http://www.subyclub....hp?showtopic=54

A 3” system from the back of the turbocharger is the best option, Don’t stuff around with Catback or diffback systems as it will cost you more in the long run if you decide later that you want to complete the system resulting in a full 3” system. A free flowing muffler is must as the standard item is very restrictive due to multiple baffles as it tries to meet noise regulations. Any local exhaust place will be able to make up a system for your needs.

some workshops insist on a 2.5" from the diffback to add to a 3" system. this is to aid i midrange performance and form a "venturi" effect much like a carburettor. This happens because as the pipe diameter gets smaller the air speed is increased. which is great for an exhaust system.

This guide to basic performance is simple and has been tried by many fellow Subaru owners and proven that it works.
MY02 Liberty B4

#2 Soop

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Posted 19 August 2008 - 10:27 PM

Quality post!
TSM

#3 boost

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Posted 19 August 2008 - 10:35 PM

Great post mate.. You mention the stock muffler being restrictive.. This depends on the system really.. I have a full three inch exhaust from a massive bell-mouth dump pipe.. I have recently replaced the cannon with a standard liberty twin-tip.. the difference in power is negligible, even at 15psi boost.. The difference in noise and 'arrest me' factor is incredible.. Stock sound with high flow.. Not saying it's the ultimate set-up but a stock rear muffler on a full 3" system is a good way to quieten it all down.. The other way is called VAREX...
AWD + BOOST = SEXY TIME

#4 Soop

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Posted 19 August 2008 - 10:36 PM

Boost, Did you notice any increase in bottom end/mid range torque? I'll have more to say on the matter in my next installment of the exhaust thread.
TSM

#5 Evil_VZ-T

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Posted 19 August 2008 - 10:38 PM

Really? Im not sure how well the RS one is, but when i had the GX muff on my 3" system to pass rego, up top the car had no go. it wouldnt boost higher than 10psi because the gas simple couldnt get out quick enough. Im very tired at the moment as i just got back from a school retreat a few hours ago and im mentally drained. so excuse the poor english in the above post
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#6 Soop

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Posted 19 August 2008 - 10:40 PM

AUDM RS' came with a GX muffler. Just thought I'd put that out there...
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#7 Not Marv

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Posted 20 August 2008 - 08:11 AM

A good introduction, but I have some suggestions.

Still, I dips me lid to you Lance for writing this up.

A semi parallel fuel rail mod can fix this very easily by running additional fuel lines in between each bank. This method is being used on many members car in the RSLC and substantial numbers have been made using this setup.
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Only Bazza uses the semi-parallel fuel rail mod and he's a mad bastard (anti-lag + launch control on a built 2.5 with a GT35R = very expensive and illegal on the street). A full parallel fuel rail set-up is easy to do once the intake manifold is off and fairly cheap at around $400 including Sard regulator and gauge.

preMY99 classic shape WRX came with 440ccs and share the same rail design (side feed). Later models were produced with a top feed arrangement,


Sorry Lance, but that is only half right. MY97-98 STis and GT-B Legacys had the correct 440cc yellow top injectors, but MY99-00 had a different side-fed injector. You can make the 99-00 injector work in an EJ20G (MY89-96 EJ20), but you need EJ25D fuel rails off a gen2 NA 2.5L Liberty/Legacy. From MY01-on they used top-feed injectors (380cc, 440cc, 550cc).

The stock 90deg Subaru intake tract is very restrictive due


Fixed :) You can make the 90deg intake work very well by removing resonators and going to a Gen2 NA Liberty airbox so that the only 90deg bends are at the turbo entry. Adrianvos has this set-up and many consider it to work better than an under-manifold entry (UME), which still has quite a few doglegs and step-downs. GC8s with UME benefit greatly from a silicon intake pipe like the APS or PSR one, but the general consensus is that GD UMEs don't really require this due to better designed power steering pump taking up less room.

A 3 system from the back of the turbocharger is the best option, Dont stuff around with Catback or diffback systems as it will cost you more in the long run if you decide later that you want to complete the system resulting in a full 3 system. A free flowing muffler is must as the standard item is very restrictive due to multiple baffles as it tries to meet noise regulations. Any local exhaust place will be able to make up a system for your needs.


Quite a few people (MSR + HiTech + some of the Tassie boys) are now recommending 3" down to 2.5" from the diff back and a bell-mouth dump pipe (with splitter) on street cars as it improves mid-range hugely. A full 3" generally gives you a lot more up top.

#8 boost

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Posted 20 August 2008 - 10:58 AM

Nice one not marv.. :)
AWD + BOOST = SEXY TIME

#9 fatcat67

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Posted 20 August 2008 - 12:16 PM

"Not Marv", with the full parallel setup you have do you run standard Subaru FPR's at the rails and then 2 pipes for the fuel return T'd back to a single pipe to the tank? Lance is this something you have done yet or are you going Semi-parallel?
As Tony Montana would say:
In this country, you gotta make the money first.
Then when you get the money, you get the power.
Then when you get the power, then you get the women.

#10 Not Marv

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Posted 20 August 2008 - 04:53 PM

*cough*

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#11 Soop

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Posted 20 August 2008 - 05:01 PM

F*ck that must have been one hell of a scratchy throat..... Top stuff that, Iain.
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#12 Not Marv

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Posted 20 August 2008 - 05:28 PM

All that shit came from Pirtek, except the rails. I used x2 passenger side rails (no FPR) and bought some elbows off Vaccine who had cut the stock metal fuel lines down so the stock elbows bolted up to the rails. He'd also swaged the ends of the elbows so the lines won't blow off under the pre ssure (42psi base + 19psi boost = lots of pressure). Please take note and make sure the edges are very rounded and that they cannot in any way cut through the rubber hose. Plenty of people swage them with brake line flaring tools and this leaves a sharp edge. It isn't enough to cut your finger, but it still cuts through the fuel hose, leading to leaks and fires.

#13 Jeff

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Posted 20 August 2008 - 06:33 PM

This thread is a gold mine for anyone with an ej20 thanx for the write up Lance and thanx guys for the additional info

Just Married


#14 Evil_VZ-T

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Posted 20 August 2008 - 09:32 PM

Thanks Marv, i appreciate your input and thanks for correcting me. i knew about the MY99 model having a different side feed and o rings can be used to fit early rails, but its dodgy. hence why i said PRE My99. I wasnt sure what was getting used these days in regards to the parallel mod, i have only seen bazza's diagram and though thats how it goes. Frank, i will be going parallel rails very soon as i will be installing the haltech and bigger injectors to suit. going for 200kw' atw's cheers Lance
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#15 Not Marv

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Posted 21 August 2008 - 07:44 AM

Yeah, I was just specifying that not all post-99 WRXs ran top-feed injectors. For people who can fit them to their rails it's a far better way to go than early 440s due to superior spray pattern and the ability for them to be high-flowed with good results. Personally, I wouldn't de-cap injectors, but if I could find somewhere reputable to get them high-flowed I'd do that over buying new Sards (as the spray pattern of the Sards isn't great and takes a lot of time to tune around to get perfect).

#16 Jeff

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Posted 06 September 2008 - 02:52 PM

Question.... Do you have to use 2 left hand rails or could you just route the fuel line to the opposite side??

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Like this (sorry for the dodgy pic, i've only got mspaint on here)

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#17 JRod

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Posted 06 September 2008 - 09:18 PM

Hey guys,
* please PM if there is anything that should be added or corrected*


A basic guide is:
160Kws 380cc
180Kws 440cc
200Kws 550cc
230Kw and up 650cc



BAHAHAHAHAHAHA. Should I let you know now that I'm still using my factory 440cc injectors and have over 200kws.

In other news, my motor has since stopped working. Possibly due to running too lean.................jk ;)

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As soon as i mentioned 300kw I was in trouble :)


#18 Soop

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Posted 06 September 2008 - 09:39 PM

Whats the injector duty at now Jarrod? 11ty%?
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#19 fatcat67

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Posted 06 September 2008 - 10:28 PM

Jarrod, he did say basic guide. I have read elsewhere that these figures are dependant on quite a few variables. Your variable is that your engine is a freak. Soop, I'm fairly sure the guys at Chiptorque would have tuned with some saftey margin. They don't lock ecu's (can see what they have tuned in) and Jarrod has his wideband running all the time so leaning would be easily spotted. That said, it is definitely at the point where the fuel system need some upgrading.
As Tony Montana would say:
In this country, you gotta make the money first.
Then when you get the money, you get the power.
Then when you get the power, then you get the women.

#20 Soop

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Posted 06 September 2008 - 11:07 PM

Oh definitely, i wasn't meaning to insinuate anything like that. But the injectors must surely be maxed out, from a safety point of view.
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