Avg Peak Boost on Stock Turbo - Custom JST Tune

Hey All,

I'm curious about what peak boost numbers people are seeing who have a similar set up to mine and are tuned by JST. (see details on car below).
Upfront, the car maybe sees 24-24.5 at most in peak boost, during a 4th gear pull. This has been consistent since i got the tune nearly 4 years ago.. and boost never came up as a concern.

Here's the stats:
I'm running a custom JST tune (91 & E30)
Car is 2015, 115k on the clock.
Car basically just has panel filter, intercooler and exhaust(really no power gain here) stock dp, cooler ngk plugs— for power.


To be clear, I don't care that much about peak boost numbers, more so what i'm getting throughout the curve, HOWEVER...I tried a new flash tune recently from Dizzy and Jason said my peak boost was below (nearly 24 psi or so) what he likes to see closer to 26psi— so I'm curious about maybe a boost leak which another tuner pointed out looking at my recent datalogs. Checked boost hoses and they'are all clamed up nice.

Can’t speak to JST but I was always 26+ on Dizzy’s stage 2 and E30. You have stock BPV?

I have that tune as well, and similar peak numbers. I'm running a DV+ which i service every other oil change. I do get the occaional evap code for the cannister, I think it might be time to do a smoke test. My dry compression test came back pretty good, 180+ on all cyls. I'm still on stock boost hoses and they have 115k on them. I'm not loosing boost per se, just not hitting peak. What's funny is Dizzy never mentioned boost being a concern when I dataogged that stage 2 E30 tune.

Hey All,

I'm curious about what peak boost numbers people are seeing who have a similar set up to mine and are tuned by JST. (see details on car below).
Upfront, the car maybe sees 24-24.5 at most in peak boost, during a 4th gear pull. This has been consistent since i got the tune nearly 4 years ago.. and boost never came up as a concern.

Here's the stats:
I'm running a custom JST tune (91 & E30)
Car is 2015, 115k on the clock.
Car basically just has panel filter, intercooler and exhaust(really no power gain here) stock dp, GFB DV+, J-pipe & cooler ngk plugs— for power.


To be clear, I don't care that much about peak boost numbers, more so what i'm getting throughout the curve, HOWEVER...I tried a new flash tune recently from Dizzy and Jason said my peak boost was below (nearly 24 psi or so) what he likes to see closer to 26psi— so I'm curious about maybe a boost leak which another tuner pointed out looking at my recent datalogs. Checked boost hoses and they'are all clamed up nice.

What was the outside temperature when you took your data log? I normally see 25-26psi on Dizzy Stage 2, but I’ve noticed that some logs I took when it was cold and humid (54F), I see lower boost (24.5psi) for the same apparent vDyno power, I suspect due to the lower charge air temperatures.

I that our more modern torque based throttle mapping results in more consistent power with temperature, but more variable boost and timing than what you’d get with an old-school engine/ECU that has fixed pressure boost and static timing maps.

The throttle position is asking for torque, and the ECU dials in however much oomph needed to deliver it. At some point when the air is already cold and dense coming in, that means dialing back boost a tad.

Maybe @Jason@dizzytuning can shed some light on this, and if I’m close or just imagining things.

What was the outside temperature when you took your data log? I normally see 25-26psi on Dizzy Stage 2, but I’ve noticed that some logs I took when it was cold and humid (54F), I see lower boost (24.5psi) for the same apparent vDyno power, I suspect due to the lower charge air temperatures.

I that our more modern torque based throttle mapping results in more consistent power with temperature, but more variable boost and timing than what you’d get with an old-school engine/ECU that has fixed pressure boost and static timing maps.

The throttle position is asking for torque, and the ECU dials in however much oomph needed to deliver it. At some point when the air is already cold and dense coming in, that means dialing back boost a tad.

Maybe @Jason@dizzytuning can shed some light on this, and if I’m close or just imagining things.