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. SOHC doesn't get to the 200-210 RWHP on a dyno reliably. A couple of guys have made it there, at least they claim, but I don't see many, if at all, dyno sheets on them. 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.

I guess the other question is can a 818R be built to 1780lbs wet? If not the NA engine would need to come in slightly higher at 205-210-220 Hp.

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

Thanks,
Gator

[redfogo]

You can try the rs25 forum there are a few NA builds on there. Good amount though are the older 2.5 or 2.2 motors. Or look in some of the rally forums I know I have seen some decent NA power builds out there in some of the Rally spec cars.

[305mouse]

The newer 2.5 engines are dohc. I believe it was 2013 model year on the outback. Worth looking into.

[ssssly]

If you want power in an N/A boxer, I would suggest an FA engine over an EJ. They are far happier running higher compression pistons and the direct injection gives you a massive air fuel benefit over the EJs.

A built N/A FA can reliably exceed 200hp, especially on e85.

[metalmaker12]

I have seen a custom 2.75l EJ Na build. It used big port heads, huge valves and aggressive cams, completely blueprinted and built motor, with lots of timing advance make 228whp on race gas. But this was an expensive build.

[Sgt.Gator]

I have seen a custom 2.75l EJ Na build. It used big port heads, huge valves and aggressive cams, completely blueprinted and built motor, with lots of timing advance make 228whp on race gas. But this was an expensive build.

Who and where can I see more about this engine and builder? Thanks.

[JRach]

I've built a few custom subaru engines myself and am just wrapping up a DOHC NA 2.5 build now.

Being a tech in the subie industry in years past I've build a good amount of motors with great success.

This particular motor I built to fit into the Open Light class for stage rally, but will also run the car in Rally-X and Rally sprints. Initially I built the motor a few years ago, then it sat for a couple years while I worked on other projects, now i'm pulling it back out of the car to put in new cams and check everything before firing it up.

The motor came out of a 98' Forester (that I did a full 06' STI swap on) and had blown headgaskets.

Specs
Custom 10.8:1 Weisco pistons (having decked the block/heads, should be a touch higher compression than that)
Hand ported/polished/port matched heads
Delta camshafts
EJ257 Rods
ACL race main/rod bearings
10mm shimmed oil pump, de-burred/smoothed radius on all oil passages
Fully balanced rotating assembly
Equal length headers

Will be running megasquirt for engine management.

I'll keep you posted with results as it should be up and running in the next 4 weeks or so.

[Sgt.Gator]

Thanks JRach. You're close by too. I hope you can come out to Pacific Raceways and The Ridge when Retro, Tony, and I are racing in the ICSCC races!

[Desertrunner]

removed

[3000gttom]

if cars in this league are allowed to have turbos then you should go with one too.

area under the horsepower curve is what will determine how fast the car accelerates.

if the rules allow them, turbo cars will have a significant advantage just due to the shape of the power curve

for this particular scenario you want the flat hp curve of a turbo car

[JRach]

Thanks JRach. You're close by too. I hope you can come out to Pacific Raceways and The Ridge when Retro, Tony, and I are racing in the ICSCC races!

Absolutely, what are the dates?

[Sgt.Gator]

Absolutely, what are the dates?

The Ridge April 17 Enduro, I may or may not be there.
Pacific, May 14-15. Test&Tune May 13.
Pacific, July 23-24, test & tube July 22
The Ridge, Sept 17-18, Test & Tune Sept 16

I may or may not be at the Test & Tunes the day before the racing. Hope to see you there.
Gator

[Kurk818]

If im available, Ill try to make it to at least one location. Depending on weather, ill drive my 818.

[Sgt.Gator]

JRach how's the engine build coming?
Barring unforeseen drama, I will definitely be at Pacific Raceways Fri-Sat-Sun May 13-15.