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Old 02-05-10, 06:19 PM   #1
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Lightbulb Exciting New Head Option for EJ205/EJ257 Hybrid Builds!

We are excited to announce that we have a great new option for the 2.0/2.5 hybrid folks! As most people know, when you run a 2.5l shortblock with 2.0l heads, the compression ratio is too high to run safely and efficiently. The common approach to resolve this is to use a thicker head gasket to try to bring the compression ratio down. While this can bring the overall compression ratio down, it is by no means ideal. The resulting combustion chamber shape remains inefficient since you're leaving the 2.0l chamber in the heads untouched. You are in essence shrinking the quench area and introducing several sharp edges to the combustion chamber that can build up heat and cause knock. This makes the engine less efficient than a full EJ257 with EJ257 heads.

Instead of using a thicker head gasket, we decided to try something a bit different. We worked closely with our machine shop to actually map out the combustion chamber of the EJ257 STI head and create a CNC program to replicate the exact same chamber every time. Using this program, we then set up the 2.0l head castings in the CNC and machine out an exact copy of the 2.5l combustion chamber into each 2.0l head casting. We are then able to use a quality OEM head gasket and maintain the exact compression ratio of a complete STI engine. This greatly improves the quench area and overall efficiency of the engine because you now have the exact same combustion chamber as a full EJ257.

We have done several hybrid builds with this approach now and have seen great results not only in overall power output, but especially in terms of crisp, smooth off-boost drivability and torque. We've also seen a significant increase in fuel economy as compared to a standard hybrid build. From a tuning standpoint, the difference is so significant that we had to spend quite a bit of time building new base maps for these builds. Under low load conditions, these setups can run as much as 15-20 degrees more timing advance than a hybrid build with a thicker head gasket. This was a great thing to see as we end up with a timing curve much more similar to an STI rather than a 2.0l WRX.

This service is available for any EJ205 heads and its $400 for a set of heads.

Thanks
-- Ed

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Last edited by EQ Tuning; 03-04-10 at 11:17 AM.
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Old 02-05-10, 08:50 PM   #2
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Default Re: Exciting New Head Option for EJ205/EJ257 Hybrid Builds!

A picture is worth a thousand words...

Do you have CNC porting for these heads as well?
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Old 02-06-10, 08:29 AM   #3
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Default Re: Exciting New Head Option for EJ205/EJ257 Hybrid Builds!

Ed you folks make me happy! Does the cost include pulling/reinstallation of valvetrain, or is this for a bare head? Bare head I assume... Is there I way to do this with valvetrain intact? I assume that wouldnt be safe.
Do you also deshroud around the valves?

Last edited by sleepybear; 02-06-10 at 09:45 AM.
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Old 02-06-10, 10:31 AM   #4
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Default Re: Exciting New Head Option for EJ205/EJ257 Hybrid Builds!

Quote:
Originally Posted by NSFW View Post
A picture is worth a thousand words...

Do you have CNC porting for these heads as well?
Indeed! We have a set of test heads that really show the changes made. I'll make sure to take a picture of those sometime next week. Its amazing to see how much of a difference it makes.

We don't have CNC porting available yet, but we can do a killer bowl blend, hand port and gasket match.

-- Ed
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Old 02-06-10, 10:36 AM   #5
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Default Re: Exciting New Head Option for EJ205/EJ257 Hybrid Builds!

Quote:
Originally Posted by sleepybear View Post
Ed you folks make me happy! Does the cost include pulling/reinstallation of valvetrain, or is this for a bare head? Bare head I assume... Is there I way to do this with valvetrain intact? I assume that wouldnt be safe.
Do you also deshroud around the valves?
The price is for bare head castings. Pulling them apart and re-assembling will add about $100 to the price. We generally do a 5 angle valve job on most of these heads as well, so they get torn down anyway.

I'm not sure what you mean about deshrouding around the valve? You're probably more referring to what happens with a valve job and bowl blend?

Thanks
-- Ed
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Old 02-06-10, 10:51 AM   #6
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Default Re: Exciting New Head Option for EJ205/EJ257 Hybrid Builds!

Quote:
Originally Posted by EQ Tuning View Post
The price is for bare head castings. Pulling them apart and re-assembling will add about $100 to the price. We generally do a 5 angle valve job on most of these heads as well, so they get torn down anyway.

I'm not sure what you mean about deshrouding around the valve? You're probably more referring to what happens with a valve job and bowl blend?

Thanks
-- Ed
Sorry Ed, I mean the ring lip thing around each valve face on the combustion chamber. if your looking at the cc there is a lil rigde around the paramiter of the valveseat. I know Im a n00b. lol
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Old 02-11-10, 12:38 PM   #7
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Default Re: Exciting New Head Option for EJ205/EJ257 Hybrid Builds!

Quote:
Originally Posted by sleepybear View Post
Sorry Ed, I mean the ring lip thing around each valve face on the combustion chamber. if your looking at the cc there is a lil rigde around the paramiter of the valveseat. I know Im a n00b. lol
Ah I see what you're talking about. That ridge does get cleaned up with a valve job and bowl blend but I don't believe it gets messed with by the CNC program.

Thanks
-- Ed
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Old 02-12-10, 02:41 PM   #8
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Default Re: Exciting New Head Option for EJ205/EJ257 Hybrid Builds!

Oh ok sounds good. Ed, you should make a thread over on nasioc. I love it here, but I thing theres alot more hybrid engines over there since the majority of people here a sti...

Keep up the great work...
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Old 02-20-10, 04:07 PM   #9
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Default Re: Exciting New Head Option for EJ205/EJ257 Hybrid Builds!

Quote:
Originally Posted by sleepybear View Post
Oh ok sounds good. Ed, you should make a thread over on nasioc. I love it here, but I thing theres alot more hybrid engines over there since the majority of people here a sti...

Keep up the great work...
I'm in the process of becoming a vendor on nasioc. Then I'll post all our products and services there. Watch out for our upcoming twin scroll kit

-- Ed
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Old 02-27-10, 04:01 PM   #10
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Default Re: Exciting New Head Option for EJ205/EJ257 Hybrid Builds!

A little update on this... We've gone through a full break-in and full tune on a couple of these hybrid setups and I am extremely happy to see the results I was expecting.

This is an 04 WRX with an EQ Stage 1 Shortblock and EQ CNC Machined EJ205 heads. This car has a VF43, DW750cc injectors, and supporting mods:



While the power levels and curves are great all around, the really impressive part is in how the car tuned out, feels and drives. The new combustion chamber design allowed for a lot more timing advance in the mid range which really helped fill out the torque curve and also really helped with the extremely smooth drivability and response that these motors are exhibiting. I have tuned a lot of different hybrid setups in the past and I honestly have never felt any other hybrid drive as smoothly and consistently as these builds have been running.

Thanks
-- Ed
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