Horsepower gains on 93 octane and 12psi

[aaronllewellyn]

anyone know what the expected HP gains would be on a bone stock ej22t with boost at 12psi on 93 octane. (non-inter-cooled)

maybe 20-25hp?

what do you think.

[robertpaige]

For 1, unless you install a Fuel Cut Defender, you will peak at 10psi. But if you have a FCD, even then the power increase will be very small. You should always be running 93 octane PERIOD. Bumping from 8 to 12psi on a non-intercooled VF11 car with a non-freeflowing exhaust will not warrant very many results. I'm bad a guesstimating HP. But the power increase will be very minimal, you won't notice much. But now, let's say you went TD04 turbo, top mount intercooler, 3" downpipe, and 16PSI, then you might see about a 25HP gain. 4psi increase on a bone stock motor with restricting exhaust and no intercooler, you ain't getting even a quarter of 25HP.

[aaronllewellyn]

For 1, unless you install a Fuel Cut Defender, you will peak at 10psi. But if you have a FCD, even then the power increase will be very small. You should always be running 93 octane PERIOD. Bumping from 8 to 12psi on a non-intercooled VF11 car with a non-freeflowing exhaust will not warrant very many results. I'm bad a guesstimating HP. But the power increase will be very minimal, you won't notice much. But now, let's say you went TD04 turbo, top mount intercooler, 3" downpipe, and 16PSI, then you might see about a 25HP gain. 4psi increase on a bone stock motor with restricting exhaust and no intercooler, you ain't getting even a quarter of 25HP.

Well I was asking because I had no Idea, thanks! I was Just thinking 20hp because of a quick Google search for hp per Psi (which is completely different on different cars so, my bad.) read somewhere that fuel cut was 13 so I guess that's also wrong, good to know.

do you have any preferences for 3" downpipes? I hear all the WRX 3" cheap downpipes are 3" longer than the 91 ej22t ones.

[James614]

Fuel cut is somewhere around 13-14, i was running 13psi for a while (riding on the very edge of fuel cut). But Robert is right, benefits from bumping boost with no other mods are minimal/none. I originally cranked it up to 10/11 on my car when it was stock (high as it wanted to go on the VF11/stock exhaust), and my butt dyno said it add maybe 5hp.

A TD04, intercooler, and turbo-back exhaust can be had for relatively cheaply, and they WILL add the extra power you're looking for (even without a FCD, those mods at 12-13psi really wake it up!).

[Alphius]

That's correct, stock fuel cut is at 13psi. You'll see plenty of gains with a free-flowing exhaust, snorkus delete and raising boost a little bit. The VF11 can handle 11-12 psi but an intercooler makes it safer, and if you are putting an intercooler on you might as well drop in a TD04 as well.

[Legacy777]

Minimum octane you should be running is 91. Some areas can get 92 or 93 octane, and the main benefit from higher octane fuel is that it provides a higher safety margin when raising the boost. With a stand alone or another means to control timing, you can add more timing with the higher octane fuel and get a little more power. The stock tune is conservative enough that over time the learned timing advance may increase a little bit if you drove around with 93 octane vs. 91.

[lucas]

I have a spare intercooler i can part with for cheap. Has all the plumbing, but like everyone else i would higly recommend a TD04 turbo. I did the same mods on my car but left it at stock psi levels. The first time i drove it i felt like i could achieve flight the difference was that apparent.

[robertpaige]

Sorry, 91 octane is what I meant. Been a minute since i've had my SS and used premium. And correct, fuel cut is 12+. man i'm rusty on my facts lately or something

As far as downpipes, Invidia makes the 02-07 that fir our cars, and also eBay has a brand named Godspeed. I had two of those downpipes and had no issues. Though you'll need to go to an exhaust shop and have them mate up the downpipe to the rest of an exhaust.

[Alphius]

The 02-07 WRX Helix catless downpipe in my opinion has the best fitment on the firstgen Legacy. It has an O2 bung in the perfect spot for the factory O2 sensor and is a really nice downpipe.