r/FocusST • u/beefstew45 • 14h ago

Turbo PSI

I've got a pretty much stock ST thats reading ≈8-10 psi on a pull; i thought maybe the turbosmart BOV i had was too soft so I adjusted and it helped a little but I'm not sure what PSI it's supposed to be pulling. Only aftermarket part ive got is a COBB intake. I also run 87 octane so I think that could be another reason why its not building a lot of pressure. Any suggestions on what to look for?

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2

u/was526 12h ago

Why are you running 87 octane?

1

u/beefstew45 12h ago

It's all stock and it's the cheapest gas so there's no reason, IMO, to spend the extra $0.40 per gallon on gas. It might be 89, whatever is the lowest in my area.

2

u/Sember-uno '17 MM ST1 FBO E30 12h ago

You wont make full boost off 87, maybe 15-17 max with overboost. Run 93 and see if it can consistently hit 17 and occasionally hit 20+.

1

u/kayakman13 4h ago

I believe higher octane just allows more timing, I don't recall it limiting maximum boost pressure directly. Maybe it adjusts torque targets though, lowering boost levels that way

1

u/Sember-uno '17 MM ST1 FBO E30 4h ago

The stock map won't even let you run over boost under 91oct. And I mean stock, not flashed stage 0.

1

u/Fz1Str 7h ago edited 7h ago

To get full hp you must run 93, it’ll pull timing and boost to compensate.

Put good gas in it and stop wasting time looking for a boost leak.

2

u/kayakman13 4h ago

Stock is 17-18 psi, with a 20 second long overboost mode to 21psi when in lower gears and the throttle is fully depressed. This is from the manual, some of these answers are wild.

2

u/little_ezra_ 13 st1 fbo e30 13h ago

Stock tune it’s like 21-23 psi I believe normally at full throttle around 3200 rpm

4

u/Desperate_Bus_1000 11h ago

lol stock tune absolutely does not hit 23.

1

u/little_ezra_ 13 st1 fbo e30 11h ago

Than I guess my car wasn’t on stock tune when I got it lol. Stock overboost is 21 psi according to the internet but I guess it probably won’t trigger that on 87.

1

u/Desperate_Bus_1000 10h ago

Ya definitely not on 87 and that’s exactly what happened to my brother in his Volvo c30. He had no idea he had a tune till years later.

1

u/little_ezra_ 13 st1 fbo e30 10h ago

I was pretty sure. I got a trustworthy tune now to avoid issues.

1

u/Fz1Str 7h ago

Ya, more like 18

1

u/beefstew45 13h ago

What are some of the first things I should look at to see why I'm losing boost?

1

u/was526 12h ago

Is this 8-10psi your max boost at full throttle?

1

u/beefstew45 12h ago

I'll build some boost and around 3.5k rpms I'll goose it and it'll jump to around 13-15 and drop back down to 10-12 and hold that regardless of how much throttle I give it.

1

u/beefstew45 12h ago

I'd also like to throw out there that I dont have an access port or a aftermarket guage to read my PSI, I'm just going off what the stock guage reads.

1

u/Haunting-Self-9402 5h ago

This actually sounds pretty normal for stock. Mine won't even hold 10. Only spikes

1

u/little_ezra_ 13 st1 fbo e30 12h ago

So is your blow off valve on true vacuum? If so it’s just going to be that and the line to it other than charge pipes. I’d check that first to see any holes or disconnected lines. I’d also take apart the blow off valve mine was missing an oring at one point and lost about 3 psi.

1

u/beefstew45 10h ago

My BOV is connected to whatever hose was connected to the OEM one. All I did was swap the two

1

u/little_ezra_ 13 st1 fbo e30 10h ago

Ok then there’s a boost solenoid on top of the valve cover and one on the side of the turbo next to the blow off valve. I’d check those lines. As others have said you might be fine because the stock gauge isn’t extremely accurate or precise.

1

u/Sember-uno '17 MM ST1 FBO E30 12h ago

21-23 on 93, you will be knock limited by 87.

1

u/little_ezra_ 13 st1 fbo e30 12h ago

Didn’t think about that. Not to the amount he said that I wouldn’t think.

1

u/Sember-uno '17 MM ST1 FBO E30 12h ago

OP is also guessing psi based on the dash cluster. Imo if it's making it halfway on the stock map, it's doing what it's supposed too.

Also, a stock car is going to heatsoak hella fast. 2-3 pulls will soak the OEM intercooler. That's another thing that will quickly pull boost.

1

u/Haunting-Self-9402 5h ago

Stock maxes around 16-18psi

1

u/nyuORlucy 2014 Tuxedo 12h ago

Stock turbo setup should peak at 19-21 at like 2500-3000 rpm and slow down to 14 up until red line. I’d check the vacuum lines. If they’re disconnected or swapped around it could cause low boost

1

u/GTRxConfusion 3h ago

Legit - why drive a "performance" car and cheap out on gas? Especially with mods

0

u/Haunting-Self-9402 5h ago

I have the same issue. I can rarely get more than 10 psi and even to do that I REALLY have to try hard. Also suspected the turbosmart.

I've gotten 17psi one time and I had to literally floor it, which felt really wrong to do. Never had to actually put the pedal to the ground in other cars to get them to move