2008 Solstice GXP's Optimized Hydraulic Boost (OHB) feature information - Pontiac Solstice Forum

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Old 06-29-2007, 07:28 AM   #1 (permalink)
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2008 Solstice GXP's Optimized Hydraulic Boost (OHB) feature information

Here is some information about a new feature of the 2008 Solstice GXP and some operating characteristics to be aware of.

Quote:
Subject: Information on Optimized Hydraulic Boost Characteristics 2008 Pontiac Solstice GXP



The Optimized Hydraulic Boost (OHB) is a standard feature, included with all 2008 vehicles equipped with the 2.0L (RPO LNF) engine) and Electronic Stability Control (ESC) or known as StabiliTrak. OHB assists / supplements brake operation under low engine / low brake booster vacuum conditions using the ABS system.


Important: Increased brake pedal effort due to low brake booster vacuum conditions may exist during;

• The initial cold engine start up and the first few brake applies.

• When the vehicle has been parked for extended periods and/or at higher altitudes and restarted.

• Any time the vehicle is started up after a brake booster has been completely bled down (no stored vacuum).



The OHB functions are controlled by the Electronic Stability Control (ESC) Module. The ESC module determines when to activate the OHB.

The following OHB characteristics are considered to be normal:

• Increased brake pedal effort under low brake booster vacuum.

• Change in brake pedal effort when OHB is active.

• Ratchet sound coming from the brake system during OHB activation.

• Frequent brake stops may result in OHB activation.

• High altitude driving may result in OHB activation.

• Brake pedal movement or pulsation when the OHB is active.

Some customers may bring their vehicle back to the dealership commenting on any or all of the above characteristics . The customer may experience brake pedal movement or pulsation accompanied by a change in brake pedal effort when the OHB is active.

Important: Do not attempt to repair or replace any parts for what is considered normal operation of the OHB.

If a condition should exist in which you might not be receiving the intended brake boost, the SVC BRAKE SYSTEM message may be displayed on the DIC.
Here is what the 2008 Solstice Owner's Manual has to say about it:
Quote:
If your vehicle has Electronic Stability Control (ESC) and the 2.0L turbocharged engine, it also has a hydraulic brake boost feature which supplements the power brake system to maintain consistent brake performance under conditions of low brake booster vacuum. Low brake booster vacuum conditions can include initial start up after the vehicle has been parked for several hours, very frequent brake stops, or high altitude driving. When hydraulic brake boost is active, you might feel minor brake pulsation or movement but this is normal. If brake pedal feel changes or the brake pedal feels hard to push, you might not be receiving the intended brake boost and the SVC BRAKE SYSTEM DIC message may be displayed.
Here is some information from the Service Manual:
Quote:
Hydraulic Brake Boost System

If your vehicle is equipped with Electronic Stability Control (ESC) and the optional 2.0L turbocharged engine, it also has a hydraulic brake boost feature which supplements the power brake system to maintain consistent brake performance under conditions of low brake booster vacuum. Low brake booster vacuum conditions can include initial start up after the vehicle has been parked for several hours, very frequent brake stops, or high altitude driving. When hydraulic brake boost is active, you might feel minor brake pulsation or movement in the pedal but this is normal.

The Hydraulic Brake Boost system activates (only) during a brake apply when the brake module detects low vacuum from the vacuum sensor mounted in the booster. The boost function in this case will be provided by the ESC system to provide metered brake pressure to the wheels. When the system activates to build pressure, the ECU will run the pump motor, opens the Electronic Shuttle Valve (ESV), and closes the Isolation Valves (NO TCS Valves) at the same time. The ECU runs the pump in pulsed cycles and builds pressure in the wheels that exceeds the TMC (with low vacuum in the booster). As the brake fluid is drained from the TMC, the brakes pedal will move accordingly (pulsing feel in pedal). Pump speed and duration are controlled by computed volume models in the ECU (information includes low vacuum sensed, TMC pressure, and pedal travel through the BAS sensor). If the pressure is reduced or vacuum restored while a Low Hydraulic Boost is required the wheel pressure can thus be continuously adjusted to the TMC pressure by selectively lowering the current on the Isolation Valve (NO TCS Valve).
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Last edited by Small Dealer; 06-29-2007 at 04:49 PM.
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Old 06-29-2007, 07:34 AM   #2 (permalink)
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Can't wait to see what this does to stopping distance and brake fade do to heat. Sounds like some is building one KickA$$ tack machine
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Old 06-29-2007, 12:05 PM   #3 (permalink)
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The question is, can it be add it to a 2007 model?.
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Old 06-29-2007, 12:45 PM   #4 (permalink)
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Originally Posted by LatinVenom View Post
The question is, can it be add it to a 2007 model?.
Anything is possible, but I doubt it would be worth the price. My guess: you'd have to replace the ABS unit, the ESC module, possibly the lines, and make sure that you have all the 'new' sensors that such a system would need. You prolly also need some sort of update in either the ECU or BCM.

I'd have to talk to someone from one of the companies that do vehicle stability controls work, but you need very good control over line pressures, meaning a new ESC module. And a bunch of software. Rarely are these 'backward compatible' for the shade tree mechanic.
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Old 06-29-2007, 12:52 PM   #5 (permalink)
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Sounds like the new 'cure' is going to cause weird behavior...enough that the bulletin expects folks to bring their cars in for repairs.
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Old 06-29-2007, 01:04 PM   #6 (permalink)
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Originally Posted by JustMike View Post
Can't wait to see what this does to stopping distance and brake fade do to heat. Sounds like some is building one KickA$$ tack machine
J'M', unless you change the tires, stopping distance won't change.


So, Small Dealer, IIRC there is a vaccuum pump on the GXP/RedLines now. Is it still there in 08, or does this OHB replace the vaccuum pump?
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Old 06-29-2007, 04:48 PM   #7 (permalink)
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Originally Posted by SolsticeMan
So, Small Dealer, IIRC there is a vaccuum pump on the GXP/RedLines now. Is it still there in 08, or does this OHB replace the vaccuum pump?
Probably replaces it, as there is no Power Brake Booster Auxiliary Pump replacement instructions in the 2008 Service Manual.


Added some additional information to the opening post.
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Old 06-29-2007, 06:59 PM   #8 (permalink)
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if I'm reading the part description right all this feature does is give your brakes boost when you otherwise wouldn't have it...there's stored brake pressure and that can get exhausted in rare situtaions like when you first start your car

if you turn off your engine and use the brake like four times or so you'll see what types of situations this addresses

I personally don't see the need for the device in any situation other then an engine malfunction while you're driving...even then you get about 4 good braking episodes before pressure is exhausted and you won't even loose brkae pressure if you don't keep the engine in gear .

in other words I don't think too many people will ever need this new feature, it's a safety feature and nothing else, it's not a performance feature, it doesn't help your car stop in a shorter distance and I think I prefer the car without it.

whenever I get a car I test the brakes without engine running to see what's needed on my part in the case of engine or pump failure, this car brakes (relatively) easy without the boost but really I suggest everyone make sure they know how the car will react incase you're ever faced with that kind of emergency

in a parking lot or a long empty road turn your engine off and throw your car (if manual) into neutral, hit your brakes about four times and youll see what they feel like when the boost is no longer there

Last edited by perris; 06-30-2007 at 04:58 AM.
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Old 06-29-2007, 09:05 PM   #9 (permalink)
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I wonder if this is something they designed after having worked on the Setup/T2 cars to help assist braking in certain circumstances?
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Old 06-30-2007, 05:04 AM   #10 (permalink)
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I wonder if this is something they designed after having worked on the Setup/T2 cars to help assist braking in certain circumstances?
I think you nailed it brentil

this is specualtion on my part but here's what I think you're talking about

people have complained about brake fade in hard braking and it now occurs to me that might not be because of overheating but brake boost exhaustion

that would make this feature for the track more then anything else

if they made the boost replensh faster that would be at the expense of engine performance right at the time you need it...the twisties when you're braking hard and often

Last edited by perris; 06-30-2007 at 05:26 AM.
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Old 06-30-2007, 10:40 AM   #11 (permalink)
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isn't fade when you press the pedal normally but the brakes just don't brake as hard?

isn't brake boost exhaustion when you run low on boost and get a hard pedal meaning you have to push harder to get the brakes to work?

if autoxers were just getting a hard pedal would they describe it as fade? i would think they'd push harder.
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Old 07-01-2007, 12:04 PM   #12 (permalink)
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Quote:
Originally Posted by perris View Post
I think you nailed it brentil

this is specualtion on my part but here's what I think you're talking about

people have complained about brake fade in hard braking and it now occurs to me that might not be because of overheating but brake boost exhaustion

that would make this feature for the track more then anything else

if they made the boost replensh faster that would be at the expense of engine performance right at the time you need it...the twisties when you're braking hard and often
Nope - having now experienced it firsthand, it is a THERMAL brake fade, and goes away with the heavy duty brake pads.

This OHB is addressing something different... situations where there is low assist. Maybe they just wanted to save the cost and weight of the vaccuum assist pump - it looks like this systems operates under the same situations as a vaccuum pump would.


Small Dealer - the base solstice does not have a vaccuum assist pump, does it? Does this OHB apply only to the turbos, or is it also on the base car. Reading your post, I would infer that they only apply to the cars with turbo engines.
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Old 07-01-2007, 01:03 PM   #13 (permalink)
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The information available all points to only Turbo / StabiliTrak cars having the Optimized Hydraulic Boost sytem.

Also it appears just the 2007 Solstice GXP had a vaccuum assist pump or Power Brake Booster Auxiliary Pump.
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Last edited by Small Dealer; 07-01-2007 at 01:06 PM.
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