NA DOHC EJ Engine Build?

[Sgt.Gator]

Has anyone seen a build thread on a forum or web page where a late model 4 cyl DOHC (EJ255 or EJ257) was built as a naturally aspirated engine, or do any you have experience with one?

 

Please don't reply with "why would you do that, just slap a turbo on it!" type answers. I'm trying to figure out how much power a DOHC could make as a NA engine, if it would be enough to make a 818R competitive in NASA ST3. (10lbs/hp).

 

I've read every thread I can find on NASIOC and Legacy GT about NA engines, but they always start with the 2.5i NA SOHC engine. So that got me thinking what if I started with a DOHC?

 

I have one professional engine builder specing it out. He's built several SOHC engines that get close, but not quite, to the power level required. It involves all the usual hot rod mods you would do to any NA engine: high compression pistons/cams/porting/headers. When I get his final spec I'll share it here.

 

And the ultimate why? I think an 818R with a 4cyl NA engine would the lightest possible configuration, no turbo heat issues, no waste-gate issues, no IC airflow issues. I'm trying to reduce the complexity, failure points, and weight. I can think of several races that I DNF'd in my LGT wagon that were all related to something in the turbo system not working as it should.

 

And I ruled out the 3.0 -3.6 NA because trying to dry sump them would be a long project. Particularly the 3.6 looks dang near impossible to dry sump in an 818. I didn't realize until I dug deep into the specs on those engines that the 3.6 oil system is VERY different from the 3.0 and any of the EJ engines. I know how to dry sump an EJ and it's also lighter than a 3.0/3.6.

 

2016 NASA ST3 calculation: 2000 lbs with driver (I weigh 220 with helmet/racing suit/nomex) + 200 HP + Non Production Vehicle - 245 tires. = exactly 10lb/Hp.

 

As Colin Chapman said, "Simplify, then add lightness".

 

Thanks,

Gator

[Rhitter]

I don't know enough about this, but, is there any reason you are sticking with a Subaru engine? Why not mod the 818r to fit a K20?

 

Why did you decide against the BRZ motor? Was it the same dry sump issue?

[whitetiger]

gator, the main thing is to get a solid tuning solution figured out. I/H/E + cams and hi-comp pistons and of course the right tune should get you 200 to 220 CHP off a sohc block.

 

the higher RPM you go with the right tune and flow characterisitcs, the better chance you get your HP requirements. if you can get 8kprm out of the block, and tuned, you should be set.

[Sgt.Gator]

I don't know enough about this, but, is there any reason you are sticking with a Subaru engine? Why not mod the 818r to fit a K20?

 

Why did you decide against the BRZ motor? Was it the same dry sump issue?

 

Lower CG with an EJ; The 818 is designed for a Subaru WRX donor. All the motor and tranny, and suspension mounts are set for an EJ and 5 speed. That said, Factory Five is partnering with Ford to put in an Ecoboost. They are also considering the BRZ motor. I don't think a BRZ engine will be powerful enough in NA, and as you mentioned I'd have to develop a dry sump solution too.

 

gator, the main thing is to get a solid tuning solution figured out. I/H/E + cams and hi-comp pistons and of course the right tune should get you 200 to 220 CHP off a sohc block.

 

The higher RPM you go with the right tune and flow characteristics, the better chance you get your HP requirements. if you can get 8krpm out of the block, and tuned, you should be set.

 

CHP is not what I need. As you know ST is based on Wheel HP at a Dynojet facility. So I'm looking somewhere between 200 and 220 RWHP depending on final build weight + me in it.

 

I'm probably going Megasquirt MS3-Pro, not only because it's widely used and understood system, is tremendously powerful with lots of capabilities, has a direct plug for the Subaru EJ engine harness, but the new version has traction control built in, something the 818 needs. Maybe not so much with a NA engine, but the guys that have put 400HP EJs in them can spin the tires and go flying sideways in third gear.

 

http://www.ms3pro.com/

[Sgt.Gator]

This site was posted over in the 5th Gen forum. I can configure all kinds of Subaru crate engines. Now I just need to find someone who has run one.

 

http://www.graveyardmotorsports.com/Subaru_Engine_Category_s/756.htm

 

Edit: There's several threads on NASIOC about guys sending them a block and never getting anything back. 64 complaints filed with the Better Business Bureau in the last 3 years!

http://www.bbb.org/western-michigan/business-reviews/engines-rebuild-and-exchange/dsm-graveyard-in-kalamazoo-mi-38124681/complaints

 

I will not be doing business with Graveyard Motorsports, 1911 N Burdick St, Kalamazoo, MI 49007-1896 !

[whitetiger]

Lower CG with an EJ; The 818 is designed for a Subaru WRX donor. All the motor and tranny, and suspension mounts are set for an EJ and 5 speed. That said, Factory Five is partnering with Ford to put in an Ecoboost. They are also considering the BRZ motor. I don't think a BRZ engine will be powerful enough in NA, and as you mentioned I'd have to develop a dry sump solution too.

 

 

 

CHP is not what I need. As you know ST is based on Wheel HP at a Dynojet facility. So I'm looking somewhere between 200 and 220 RWHP depending on final build weight + me in it.

 

I'm probably going Megasquirt MS3-Pro, not only because it's widely used and understood system, is tremendously powerful with lots of capabilities, has a direct plug for the Subaru EJ engine harness, but the new version has traction control built in, something the 818 needs. Maybe not so much with a NA engine, but the guys that have put 400HP EJs in them can spin the tires and go flying sideways in third gear.

 

http://www.ms3pro.com/

 

220whp is gonna be tough without FI on these motors. that about what a stage 1 lgt puts down. Maybe look in to ITBs, an agressive cam setup. whats available for high comp pistons?

 

you may be better of with a FI setup while focusing on low CG for the power you are looking to get.

[Sgt.Gator]

220whp is gonna be tough without FI on these motors. that about what a stage 1 lgt puts down. Maybe look in to ITBs, an agressive cam setup. whats available for high comp pistons?

 

you may be better of with a FI setup while focusing on low CG for the power you are looking to get.

 

Yep, that's why no one has done it! There isn't a direct relationship on the dyno HP because LGTs and WRX-STI are AWHP, and this would be RWHP, so there won't be as much drivetrain loss. And another bonus is NASA penalizes dynos run on anything other than a Dynojet by 10%. So an AWD Mustang dyno like Cobb uses has to add an extra 10% to the HP when running the Wt/Hp ratio.

 

The whole point is not to go FI. If it can't be done, it just can't. The other solution for an 818 is to go AWIC because so far no one has gotten enough airflow thru a TMIC or Side Vent scoop to work.

 

As far as high comp pistons, there are some made for the NA EJ25. Example, JE 314346 set of 4, 11.5 CR, in Std, .25 and .5 overbore.

 

I'm sure I've seen others as high as 12.5 CR. Not sure I want to push it that hard though.

There are also stroker cranks to take it to 2.7L.

[whitetiger]

definitely gonna be tough. maybe youd rather do a DOHC 2.5 or 2.2 and aim for 9k rpm with the cams and intake mani or ITBs to support the airflow needed. gonna have to engineer the valvetrain and rotating assembly like a boss though and you will probably sacrifice some tq.

[Underdog]

Personally I would destroke it with long rods and custom high CR pistons. Paired with pnp'd DAVCS heads, intake & exhaust manifolds, etc. I've been looking for a project to build one for.

[Sgt.Gator]

Personally I would destroke it with long rods and custom high CR pistons. Paired with pnp'd DAVCS heads, intake & exhaust manifolds, etc. I've been looking for a project to build one for.

 

I've got the project. I can also buy many of the parts at wholesale on the aftermarket stuff and I get a good price on my OEM parts thru my sponsor. If you're interested shoot me a PM and we can talk!

[Underdog]

PM sent. What fuel/octane are you restricted to? What type of gearing are you dealing with? The 5MT gear spacing would not be ideal for a high-RPM N/A powerband.

[whitetiger]

ralispec sells short ratio gears for the 5mt.

 

here's a thought. ever consider doing supercharger like something from raptor? the weight can be kept lower than a turbo system and the build will be cheaper and simpler conceptually than a N/a build. OEM gears will work better too.

[Sgt.Gator]

PM sent. What fuel/octane are you restricted to? What type of gearing are you dealing with? The 5MT gear spacing would not be ideal for a high-RPM N/A powerband.

 

No restriction other than WT/HP ratio. 103 octane is no problem, that's what I run in my LGT race car now. I don't want to go higher than 103, it gets very expensive to do that.

 

I have a 2005 LGT tranny to use now (4.11). For an 818 a little surgery is required to convert to what would be FWD in regular car, but RWD in an 818. I also need to put an LSD in it, so swapping in a 3.90 or 3.70 should be no problem while doing that. Or I could buy an 06-07 USDM WRX 5 speed with the 3.70.

 

It's possible to use a STI 6 speed, they have a kit for that. But it adds 75lbs, more length, and the idea is to Simplify and add Lightness.

 

ralispec sells short ratio gears for the 5mt.

 

here's a thought. ever consider doing supercharger like something from raptor? the weight can be kept lower than a turbo system and the build will be cheaper and simpler conceptually than a N/a build. OEM gears will work better too.

 

The PPG gearsets are super expensive. It would be cheaper to carry a second spare oem tranny to the track with me!

 

Raptor Supercharger. I like your thinking, 4-5 psi is probably all it would take to get 220 HP with a higher compression well built NA engine. I've looked at it, both for our EJ and the H6 EZ30-36. The problem is the Raptor hangs too far off the side of the engine to fit the 818 frame. At least I *think* it does. Everytime I look at pics of Raptor installations and 818 pics, I just don't see how it would work.

I've also looked at the BRZ superchargers, some of which are screw type and sit on top of the engine. Most of them all include an AWIC, the results I've seen on the BRZ forum are not good, the engines don't seem to last long.

And any type of supercharger complicates the dry sump pump installation. A DS is absolutely a requirement in a car that generates 1.9 gs in road race for long term life.

 

Good Stuff, Ya'll keep thinking!

[whitetiger]

for the SC, you can fab up a different mount point to where the A/C comp would normally go on a road car. then its just a matter of getting the right belts

 

how would an SC hinder the DS?

[Sgt.Gator]

for the SC, you can fab up a different mount point to where the A/C comp would normally go on a road car. then its just a matter of getting the right belts

 

how would an SC hinder the DS?

 

1) The raptor is too long to fit there, it would run into the intake mani.

2) The DS pump kits from Aviaid and Cosworth both sit where the A/C used to be.

 

The P/S pump is deleted on an 818 so there is space there, but I think the length issue is still there, plus the intake pathway.

 

And then when you get down to the crank pulley and S/C mandrel it adds a bit more complication. Some DS pumps run off a mandrel attached to the crank pulley, (Cosworth), some off what used to be the A/C belt grooves on the crank pulley ( Element Tuning- Avaiad).

 

There is another DS pump built into the DS oil pan, the Dailey engineering pump/pan combo. Very elegant and expensive. But it uses a large mandrel off the crank, not sure how a supercharger belt would work with it.

 

http://www.daileyengineering.com/20-02-0623%20photo%203.jpg

 

http://www.daileyengineering.com/subaru_ej_4_cylinder.htm

 

I've done the Cosworth- Avaiad style and know how to do it. I could spend a lot of time and $$ trying to make the Dailey work with a Raptor since as far as I know it's never been done before.

[whitetiger]

then id do what UD said in post#9

 

you want 13:1 pistons de-stroked(short crank, long rods) on a DOHC build with one hell of a valve train and rotating assembly spinning at 9krpm. it will be one peaky build, but it will scream. have you found a tuner who will do the mapping for a N/A build? if so, what was his input?

[Underdog]

Yes, 75mm stroke and +4 rods/pistons will make the engine much more rev-happy by way of reducing secondary acceleration component of the rotating assembly. Regarding heads, I'm not sure there is an off-the-shelf cam profile for this type of application so a custom grind may be required if DAVCS is a design parameter. In the interest of simplicity/lightness a pair of well ported SOHC heads might be preferred over the DOHC/DAVCS heads. Paired with a large plenum short runner intake manifold, an equal length header, and a solid 103-octane tune should get you where you need to be.

[whitetiger]

yeah, and super big valves for which ever head is chosen.

[Sgt.Gator]

It makes no difference if it's DOHC or SOHC. I was thinking the DOHC with DAVCS could potentially have better breathing.

I ws thinking along the lines of the Honda S2000 F20C.

 

Tuning would be breaking new ground, especially with DAVCS. Aftermarket ECUs I'm considering are Megasquirt MS3-Pro, Haltech, and Electromotive TEC-s.

[whitetiger]

what about the person to do the tune? have you talked to anyone who will do the mapping?

[Underdog]

DAVCS will certainly provide some benefit over static timing assuming the grind is designed for the goals. Stock cams are designed to keep low-end response acceptable with the low compression motor and let the turbo pick up the slack in the midrange. That being said the SOHC large valve heads have more meat for porting (at least on the last set of S20 cross-sections I saw).

[Sgt.Gator]

what about the person to do the tune? have you talked to anyone who will do the mapping?

 

One Subaru tuner/builder is thinking about the project. I'm waiting for their response. I wouldn't blame them if they decline because they would be risking their reputation if it fails to meet the HP goal.

 

A Honda S2000 tuner might be better.

[whitetiger]

gator just realized you said that FF may adapt for an ecoboost? is so, it should be the same as a MZR 3rd gen miata mount setup. the 2.L duratec/MZR has loads of support along with a working DS solution and can make 220whp allt he way up to the 2.5L mzr full race build for over 300whp in N/A form.

[Sgt.Gator]

gator just realized you said that FF may adapt for an ecoboost? is so, it should be the same as a MZR 3rd gen miata mount setup. the 2.L duratec/MZR has loads of support along with a working DS solution and can make 220whp allt he way up to the 2.5L mzr full race build for over 300whp in N/A form.

 

What transaxle? Links? Duratec or Ecoboost?

[whitetiger]

maybe a trans adapter for the Subaru transaxle. MZR=duratec. if FF is partnering with ford to put an ecoboost in, then a NA duratec/MZRmay fit. i wonter what FF/Ford will use for the transaxle/links.