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Old 10-21-2002, 07:51 AM   #1
2000vfr800
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Default UTEC Boost Control and the ABC

Can somebody explain to me why we still need the ABC when using the UTEC to control boost?

To me, it looks likes the stock ECU is controlling the stock boost control solenoid, but when the UTEC takes over boost control, it just intercepts the signal out to the stock boost control solenoid and the ABC is now controlling boost.

So basically, the UTEC acts as a solenoid which switches between stock boost control, and the ABC...
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Old 10-21-2002, 09:54 AM   #2
RiftsWRX
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'07 Honda FIT sport (5MT)

Default Re: UTEC Boost Control and the ABC

Quote:
Originally posted by 2000vfr800
Can somebody explain to me why we still need the ABC when using the UTEC to control boost?

To me, it looks likes the stock ECU is controlling the stock boost control solenoid, but when the UTEC takes over boost control, it just intercepts the signal out to the stock boost control solenoid and the ABC is now controlling boost.

So basically, the UTEC acts as a solenoid which switches between stock boost control, and the ABC...
Specifically for those who are trying to run boost levels that the stock solenoid typically can't produce.

See.. what happens now is that you have a brass actuator which is sprung to open when a certain pressure is applied to it. For us that's around 8 PSI.

When you wanna get a higher boost pressure, you have to "bleed" off the signal coming from the pressurized side to "delay" when that spring is pushed in, opening the wastegate door.

The solenoid can only move so much air if it was wide open, thus the ABC, which will allow you to bleed off air via an auxillary fixed rate port.

If you didn't want to use an ABC, you would use the restrictor which subaru puts into the hosework for your boost control system. That restrictor will also "limit" what gets to the solenoid, affecting the overall effectiveness of the boost control system.

I don't know if that helped you, or hurt you... but I hope it was the former.

Jorge (RiftsWRX)
www.ProjectWRX.com
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Old 10-21-2002, 10:10 AM   #3
2000vfr800
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Default

OK...maybe I'm understanding a little better. LEt me see if I have this right.

I understand the role of the stock solenoid. You have a hose that runs from the outlet of the turbo, to the wastegate actuator. If this is the only connection, than when the pressure at the outlet of the turbo is high enough to overcome the spring in the wastegate (about 8 psi as you stated), the wastegate opens and the pressure no longer builds because it is dumped into the downpipe.

So, in order to getting boost pressure higher than 8 psi, we essentially have to replace that 8 psi spring in the wastegate with a stiffer spring, one set at the level of boost we want to run.

Well, we don't actually want to have to replace the spring, so we have to do it some other way. That way is to bleed the pressure in the line going from the output of the turbo to the wastegate actuator. With the stock system, it has a solenoid that connects this boost pressure to the intake until the boost pressure it desires is reached, at which time it closes the solenoid, which opens the wastegate.

So, since the UTEC now controls this stock solenoid, I was wondering why we still needed the ABC since the UTEC could open and close this solenoid to give you the boost you want. However, from what you said, I take it that at boost pressures near 20 psi, the stock solenoid can't dump enough of the exhaust actuator pressure fast enough (even if it's wide open) to keep the wastegate closed to build boost. So, the ABC is used to dump most of the exhaust actuator pressure, and the stock solenoid is used to trim the exhaust actuator pressure.

Am I close?
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Old 10-21-2002, 02:37 PM   #4
RiftsWRX
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Default

Quote:
Originally posted by 2000vfr800
OK...maybe I'm understanding a little better. LEt me see if I have this right.

I understand the role of the stock solenoid. You have a hose that runs from the outlet of the turbo, to the wastegate actuator. If this is the only connection, than when the pressure at the outlet of the turbo is high enough to overcome the spring in the wastegate (about 8 psi as you stated), the wastegate opens and the pressure no longer builds because it is dumped into the downpipe.

So, in order to getting boost pressure higher than 8 psi, we essentially have to replace that 8 psi spring in the wastegate with a stiffer spring, one set at the level of boost we want to run.

Well, we don't actually want to have to replace the spring, so we have to do it some other way. That way is to bleed the pressure in the line going from the output of the turbo to the wastegate actuator. With the stock system, it has a solenoid that connects this boost pressure to the intake until the boost pressure it desires is reached, at which time it closes the solenoid, which opens the wastegate.

So, since the UTEC now controls this stock solenoid, I was wondering why we still needed the ABC since the UTEC could open and close this solenoid to give you the boost you want. However, from what you said, I take it that at boost pressures near 20 psi, the stock solenoid can't dump enough of the exhaust actuator pressure fast enough (even if it's wide open) to keep the wastegate closed to build boost. So, the ABC is used to dump most of the exhaust actuator pressure, and the stock solenoid is used to trim the exhaust actuator pressure.

Am I close?

Spot on...

Larger turbos employing internal wastegates will be sprung to 15PSI on average. That way... if your solenoid could do 18 PSI before tapering, then that same stock solenoid could do 25PSI because it has to bleed off less signal to get higher boost levels.

Bravo!
Jorge (RiftsWRX)
www.ProjectWRX.com
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Old 10-21-2002, 03:15 PM   #5
2000vfr800
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Default

So, are there any plans to replace this stock solenoid with a larger one that the UTEC can control boost totally with the solenoid and not have to use the ABC?
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Old 10-21-2002, 11:02 PM   #6
Steppin Razor
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Default

Dear lord. This is one of the most informative threads I have read in about 6 months here at i-club. Mods, please make this sticky. I know so many people out there that want to understand our cars better and this thread explains the boost control system of the WRX in such a sharp, consice manner. Nice job fellas, you helped me out a lot.
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Old 05-06-2005, 05:56 PM   #7
KitchenerWRX
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is it true that if you use an EBC to hold the wastegate shut longer, like twice as much as its set to ( approx 17 psi) that it can pose some serious problems?
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Old 05-06-2005, 06:58 PM   #8
KitchenerWRX
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up up up
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Old 05-06-2005, 07:45 PM   #9
KitchenerWRX
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upppp
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