How to throttle?
Registered User
Joined: Nov 2002
Posts: 181
From: OC, CA
Car Info: 02 WRX
FYI, i dont have MBC, but have done the restrictor mod.
when I keep it at 50-75% throttle from low rpm, around 2k rpm, there's noticeable surge that starts at around 2.8k - 3.3k rpm. i'm sure most of you have felt that switch over when riding your WRX. if the stock boost gauge is any indication, by the time the engine spins from 2k to 3k rpm the turbo should be spooled up. One thing for sure is that when i keep it over 3k rpm when cruising, the throttle becomes VERY responsive (no turbo lag) hence I mentioned 3k rpm.
this thread turned out to be very informative! thanks for contributing, everyone!
when I keep it at 50-75% throttle from low rpm, around 2k rpm, there's noticeable surge that starts at around 2.8k - 3.3k rpm. i'm sure most of you have felt that switch over when riding your WRX. if the stock boost gauge is any indication, by the time the engine spins from 2k to 3k rpm the turbo should be spooled up. One thing for sure is that when i keep it over 3k rpm when cruising, the throttle becomes VERY responsive (no turbo lag) hence I mentioned 3k rpm.
this thread turned out to be very informative! thanks for contributing, everyone!
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Posts: n/a
alright....i want to comment on the closed loop comment.
wouldn't it be VERY dangerous to run closed loop under full boost but no under WOT? seeing as how if the boost is altered or temperature, or any variance it could potentially blow the engine by running a default program? Unless it's built in to run extremely rich or retarded timing, but that'd be against the performance nature of the car. Are you sure it runs closed loop?
wouldn't it be VERY dangerous to run closed loop under full boost but no under WOT? seeing as how if the boost is altered or temperature, or any variance it could potentially blow the engine by running a default program? Unless it's built in to run extremely rich or retarded timing, but that'd be against the performance nature of the car. Are you sure it runs closed loop?
Last edited by HTM WRX; Oct 29, 2003 at 08:12 PM.
iClub Silver Vendor
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Joined: Mar 2003
Posts: 8,228
From: 631 Railroad Ave. Fairfield, CA
Car Info: A Laptop
That's the point. The stock ECU limits boost to ~7-8psi at anything under 70% throttle and also runs in closed loop up to this point. Once you're over 70%, the ECU switches to open loop fueling and makes full boost. The problem with an MBC is that it has no problem making much more than 7-8psi at <70% throttle but the ECU stays in closed loop anyway.
-- Ed
-- Ed
Registered User
Joined: Dec 2002
Posts: 242
From: Good ol oregon
Car Info: 02' WRX
It's called flow velocity. Suck air through a straw, it comes out fast, but you cant get much air through a straw. You technicly want to open the throttle only wide enough so that the engine can get the air it needs. On a turbo car this really doesnt make much difference, but I guess below boost it might make a tiny difference in felt acceleration.
If you want to actually feel this effect, ride a modern 4 cylinder crotch rocket with ITB's. If you're trucking along at mid RPM and crack the throttle wide open, the engine will bog and sputter, but use the right amount of throttle and you maintain flow velocity through the throttle body's thus achieving much better cylinder filling, motor will come back to life. ITB's really amplify this affect, but it's still a valid theory in plenum based IM's or turbo cars, even if it has a much smaller felt effect.
Electronic throttle cars automaticly regulate throttle plate position to maintain this effect, and alot of new bikes have a second set of throttle plates that adjust their position automaticly so you cant kill the flow velocity when you go throttle happy.
If you want to actually feel this effect, ride a modern 4 cylinder crotch rocket with ITB's. If you're trucking along at mid RPM and crack the throttle wide open, the engine will bog and sputter, but use the right amount of throttle and you maintain flow velocity through the throttle body's thus achieving much better cylinder filling, motor will come back to life. ITB's really amplify this affect, but it's still a valid theory in plenum based IM's or turbo cars, even if it has a much smaller felt effect.
Electronic throttle cars automaticly regulate throttle plate position to maintain this effect, and alot of new bikes have a second set of throttle plates that adjust their position automaticly so you cant kill the flow velocity when you go throttle happy.
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