What amount of boost can our engines handle stock?

Posts specific to the 2.0 litre Turbo engine

Re: What amount of boost can our engines handle stock?

Postby dr20t » Mon Dec 22, 2014 7:44 am

Nope no messages
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Re: What amount of boost can our engines handle stock?

Postby JMlegacy » Fri Dec 26, 2014 4:23 pm

Dr20t can tell you more, but
The bottom end is basically the same rods and crank as an ej205.
The piston dish (or lack thereof) and head cc raises the compression to 9.5:1.
If you have good gas you can run 20psi fading to 18. That's as far as i'd put it.

Guys out here (Jamaica) run 23 psi fading to 17 on the EJ20Y, 90 AKI octane e10

http://www.socojforum.org/forum/index.php?PHPSESSID=dcf3cf96d831946a16c17ba39c6fd50b&topic=393.msg3993#msg3993

I'm running 18 peak fading to 16.5psi @ 7200rpm VF34
timing at redline is 16.5 degrees
11 actual AFR
i have no knock after doing a 1-2-3 pull to redline.

My car is still slow though, lol
https://www.youtube.com/watch?v=Jy7Udmn ... e=youtu.be




I use to see knock even at 16.5 degrees before my intercooler mister and my radiator hose fix.

Almost one year in this configuration, driven spiritedly daily.
My best quartermile is 14.6 at 97mph (brake tq 5EAT, can't launch as manual guys)
Last edited by JMlegacy on Sun Dec 28, 2014 12:55 am, edited 1 time in total.
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Re: What amount of boost can our engines handle stock?

Postby JMlegacy » Sat Dec 27, 2014 4:47 am

After thinking a bit, I'm wondering if big turbo, low boost is the way to go with these engines?
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Re: What amount of boost can our engines handle stock?

Postby alexeiwoody » Sat Dec 27, 2014 4:35 pm

JMlegacy wrote:My best quartermile is 14.6 (brake tq 5EAT, can't launch as manual guys)


5eat will launch fine and the time is usually better compared to a similar manual setup.

JMlegacy wrote:After thinking a bit, I'm wondering if big turbo, low boost is the way to go with these engines?


In short - no.

In "long":
- for a street car - twinscroll/BB + E85 and if possible more cubic inches (2.5, 3.0-3.3L engine instead of a 2.0L) would give maximum gains with the least lag. Also best setup for the 5eat.
- for a track car - big turbo + high boost + high revs etc etc JUST DO EEEET!! (would be shiite on the street. Needs high revs/lots of lag etc Especially on your 5eat)

The "life-story":

Turbos need exhaust gas flow (volume/velocity) to spin.

The bigger the turbo - the more gas flow it needs to spin up. A smaller turbo as a rule spins up earlier than a larger one - less mass to move. Larger turbo therefore has more lag.

A 2.5L engine has more exhaust gas - will spin a turbo earlier than 2.0. Hence 2.0 has more lag on the same turbo.

A 5eat needs revs to lockup transmission fluid. This adds lag from pedal application compared to a manual (unless you manually drop down a gear before applying pedal).

Essentially - you've just combined the three "laggiest" options for a subaru with - a big turbo 2.0L 5eat (and no e85?).

You've probably noticed that Mick (dr0t) has downsized his turbo twice now (iirc - the rear housing? correct me if wrong Mick :)) as he didn't like the bigger turbo lag on a street car and the drag strip.
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Re: What amount of boost can our engines handle stock?

Postby dr20t » Sun Dec 28, 2014 12:16 am

Downsized housing once on my gtx3076 from 0.82 to 0.63

Not so much for drag strip but more for the street, as on the drag strip it wouldve been better with a 0.82 (provided I could get it to spool off the line).

But yes i agree with almost everything alexei said - with one thing ill clarify

(Volumetric efficiency x capacity) overlaid with exhaust gas volume is what should be compared when asking what would spool a turbo faster (ie which engine spools which engine faster). Exhaust gas volume here referring to exhaust gas mass and density. If one engine combo flows exact same as another, but the first one has higher exhaust gas temps (egt). The first will spool quicker.

Same as taking two engines with exact same capacity, turbo, bolt ons etc - only difference being one has higher static comp. Assuming you're able to run mbt on both motors on spool up, then the engine with higher static comp will spool faster due to 1 greater ve and 2 hotter egt's from higher static comp.

A 2.0 litre will *generally* be generating less exhaust flow at lower revs than a 2.5 or 3.0 litre, and thus spool up slower. In saying that, some 2.0 litres can achieve greater ve and flow at lower revs than higher capacity engines due to head design and flow potential, plus features such as dual avcs etc.

In turbo Subaru speak though, generally under 2500rpm the ej25 of any kind will flow more than a 2.0 litre, and thus will generally spool a turbo faster assuming capacity is the ONLY difference.
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Re: What amount of boost can our engines handle stock?

Postby JMlegacy » Sun Dec 28, 2014 12:51 am

Hmm. Thanks for your response,alexei . I wasn't thinking for the 5EAT, Wasn't even considering street or rally cross, but all out power of the 9.5:1 compression ratio itself.

What you have posted is true for all engines, but the higher compression ratio of this particular engine + the AVCS means the turbo can be a little different than those of lower compression due to thermodynamics.
Also, a bigger turbo's backend will have less exhaust restriction, so it's possible to recover energy from that location as well. Or even better, A big compressor a, small backend for spoolup and an external wastegate

The honda guys run big turbo small displacement and make gobs of power, at lower PSI.

What's missing in the equation to apply the same to our 9.5:1 engines?
At the end of the day it's down to airflow and combustion efficiency (BSFC)

:dance:
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Re: What amount of boost can our engines handle stock?

Postby KiDo_Tuning » Sun Dec 28, 2014 12:18 pm

dr20t wrote:
A 2.0 litre will *generally* be generating less exhaust flow at lower revs than a 2.5 or 3.0 litre, and thus spool up slower. In saying that, some 2.0 litres can achieve greater ve and flow at lower revs than higher capacity engines due to head design and flow potential, plus features such as dual avcs etc.

In turbo Subaru speak though, generally under 2500rpm the ej25 of any kind will flow more than a 2.0 litre, and thus will generally spool a turbo faster assuming capacity is the ONLY difference.


Look at your old engines setup though considering it was 16psi on 98 fuel though. EJ25 beating torque and power levels at 2500rpm on 16psi boost.
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Re: What amount of boost can our engines handle stock?

Postby dr20t » Sun Dec 28, 2014 1:40 pm

Well I never really drove it on the 98 tune only e85, although yes the twin scroll 2871 was nice
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