Turbo engine setup/questions

[seijo]

Hey all, so as of today I'm in the process of finalizing my engine build + turbo setup so that I'll have it all assembled and installed in the next 1-2 weeks or so, just wanted to get some feedback from those with more experience.

*The fuel I will be using is 91 octane (thats the highest octane rating available readily, 94 and E85 are far too difficult to get, and I am dead-set on using pump gas for this)

The Engine:

M50 block (bored out to 84.5mm)
M52 Crank
Eagle rods (135mm)
Wiseco low compression piston (8:1 ratio)
Cut ring head gasket, no spacer
M50 head/valvetrain
All new bearings (main/rods)
ARP studs everything (Mains, piston caps, cylinder head)

Precision 6262 jb turbo with .82 ar
SPA manifold
Tial wastegate with 1 bar spring (is this too high? I will be using eboost controller, but I figured since my compression is pretty low I could turn the boost up to compensate)

OBD1 harness, will be using Link g4x standalone

My concern/questions at this point is, how much boost level should I aim for when breaking in, as well as what would be the safety margin as I'm using pump gas and with it I've heard many stories on detonation problems/misfires on high boost/pump gas combo.

I would also appreciate any other comments regarding the current setup, as in what would you change and what would you keep?

Thanks!

[dominator293]

I can't confirm exactly as I don't have the same setup exactly. But with that low compression, start at 12psi. Get it professionally dyno tuned and listen out for knock during tuning.

[seijo]

What are you currently running? build specs? I've been meaning to find a reputable tuner near my area but can't seem to find one that's also willing to tune on dyno. Any particular reason(s) on why I should start from 12 psi+?

[dominator293]

What are you currently running? build specs? I've been meaning to find a reputable tuner near my area but can't seem to find one that's also willing to tune on dyno. Any particular reason(s) on why I should start from 12 psi+?

I'm currently at 12-14psi, about 290whp on a reasonably stock M50B25Tu. Lower compression with Copper spacer and Cutring HG, ARP head studs. The rest of the engine is stock. The rest of the car is highly modified, and a full fuel surge setup - AN lines, Nuke fuel rail, 1100cc injectors, Link G4 ECU etc. You can check out my build on my YouTube channel linked in my sig block.

The reason for the 12psi is because that should be somewhat safe on 91 Octane. Here is Aus, we can easily get 98 Octane at any petrol station, and my tuner didn't want to up the boost past 14psi when tuning it remotely because he couldn't remotely listen to knock when running 98 Octane....had I have been running E85 he would've happily upped to 17-20psi remotely without fear of knock. That's why I'm saying 12 psi is probably a good starting point, but you'll want a tuner to listen for knock, particularly because you said you were keen to run 91 octane.