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06-12-2022, 09:19 AM | #1 |
Scooby Newbie
Member#: 530321
Join Date: Jun 2022
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Boost taper why?
To my logic an engine is most likely to get det/knock at peak torque and lower RPM, less likely at RPM higher than peak torque, correct?
What’s the point of all this boost taper then? Is their a reason this is done so much on Subarus? An excuse for the poor boost control of internal waste gates and boost reference bleeding boost control method? (Crap boost control method imo) Or is it usually because people are running too small of turbos that will overspeed if they try to hold boost to redline? Like stock turbos, so you can max the turbo out all the way from down low to up top, but have to taper the boost down up top to not go over the turbos limits? What’s up with this? I just spent a lot of time experimenting and set up a new MBC boost control setup and I’m coming right up to about 14-15 psi at spool and tapering UP to about 18 psi by redline.. No spike at first boost at all.. No boost creep.. No FLUTTER! Solid steady hard boost like boost should be.. In ALL GEARS! “Not enough load in low gears to blah blah blah” nope.. Less load in low gears, and faster rate of change, so your fancy EBC has different effects in different gears, I imagine unless you want to tune boost for every gear, which would take hours.. Yes I do want Part Throttle Full Boost.. I’m used to it, it’s what I like, it’s how a turbo should feel (to me).. I DO NOT want some computer trying to give me half boost if my TPS is only at 50% or whatever.. Because it feels unnatural, it takes time for it to up the boost again when increasing TPS, and is just another tuning variable that could mess up with way too much variable to account for.. VF48 turbo on an EJ205.. This should not be over the turbos limits I do not believe.. 18psi at redline.. Am I missing something?
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06-12-2022, 11:01 AM | #2 |
Scooby Specialist
Member#: 515308
Join Date: Jun 2020
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Cause the turbo won’t flow enough air as the rpm go up.
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06-12-2022, 07:24 PM | #3 |
Scooby Specialist
Member#: 508105
Join Date: Nov 2019
Chapter/Region:
NWIC
Location: Greater Seattle Area
Vehicle:Link G4X flex tuned 02' EJ205 20G 6MT wagon |
It's mostly because the turbos that come on the WRX/STi are so small. Even the vf48 is a pretty small turbo despite it being pretty sluggish on a 2.0L - it just isn't efficient at 6.5K RPM @ 20 psi.
My 20G-XTR carries 24 psi to redline on my stock USDM 205 using a 3 port. And part throttle full boost is objectively dumb Last edited by K3rm1tth3fr0g; 06-13-2022 at 09:00 PM. |
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