I have a 6 psi @6000 rpm psi centrifugal supercharged water-to-air intercooled Subaru EJ253 (2.5i) motor. It only makes 180whp and I'd like to dial it up to about 10 or 11 psi (max this supercharger can do efficiently). I've read about sandrail folks running this engine stock (like mine) on 100 octane with a 10 psi turbo, so I think an 11 psi supercharger will be close to as safe, since we'll only hit that 11 psi at max rpm ("low" engine load) and no hot supercharger oil mixing with the engine oil to boot. (It may actually only go 10 psi, I am not really sure... Not a lot of people have done this with this particular blower).

I'd like to increase octane with Torco accelerator to the tune of about 100 octane (1 can per 3/4 tank).

My plan was to get it tuned on 99 octane then bring it up to 101 octane after tuning just as an added safety buffer. Since the dyno can't account for all conditions.

I don't know if this info helps, which I found on NASIOC:
Static compression ratio of 10:1.
Effective stroke is 2.59 inches.
Your dynamic compression ratio is 8.38:1 .
Your dynamic cranking pressure is 168.81 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 8.38 :1.
V/P (Volume to Pressure Index) is 63

The question is less of the piston/rod strength to handle this power, more about whether I can safely avoid detonation/pre-ignition with 100 octane and 11 psi @ 6000 rpm.

Any thoughts or input?

 

Depends a lot on the tune. But as you say, the Centri blowers build boost slowly with RPM in general. You should be fine pouring on the power after peak torque with that octane/setup IMO. Use low timing around peak torque to limit the power/cyl pressure in that area. That’s where the detonation is most likely

 

All in the tune. I assume you have a tuner on the car? Just make sure your timing is safe and let er rip. I wouldn't even bother with the fuel additives, i'd just back down the timing to a safe level.

 

Thanks... on this car the factory tune is able to be modified fairly easily. Basically there is a table for fuel and a table for timing based on load at RPM, the load basically being how much air the MAF measures.

I originally had the vehicle tuned by a pro tuner on a dyno. I Really am not experienced enough to do it myself. I would want to do the same for the new pulley but I think the tuner would be worried this amount of boost will blow up the engine. They were hesitant to do the 6 psi tune.
I know that people do it with higher octane on sand rails all the time, so it's not a factor of rod/piston strength but keeping clear of detonation.

I am not sure if you'd have to pull so much timing that you're throwing away the gains.

 

Is this in a subaru crosstrek? My brother has one and was looking into doing a turbo and a local su bee guy didn't want to touch it without changing engines.

 

It is an Outback, similar but different engine.

They can all be boosted, just depends on how much. On my car, 8 psi and 200awhp is easy power (stock is 120whp), beyond that definitely possibly but people get start getting worried, I think we can go up to 220-230awhp without too much worry with a good tune ( I know pretty weak in the grand scheme of things but would move around pretty nicely for a daily driver). The Crosstrek 2.0 would yield a little less HP.

This outfit sells a supercharger kit for Crosstreks, although he is a generation or 2 behind, made for 2012-early 2015 vehicles.
http://raptorsc.com.au/
Also facebook:
https://www.facebook.com/Raptor-Superchargers-for-Subarus-151791564911239/?ref=br_rs

If his fits that realm of years, that could be a good choice (keep in mind his prices are in AUD, USD would be less).

The newest 2018 Crosstreks are direct injected and I bet will take a bit more boost - nobody has done it yet I don't think.