Boost Gauge Working Backwards
02-16-2010, 04:04 PM
#21
So when a car is on the road @ WOT and is running 6000rpm and is seeing 12lbs of boost, since that what it is pullied for and then I sit in my driveway and rev the motor to 6000rpm, I will see the same 12 lbs of boost.
I have never seen it happen. Always had to be under a load @WOT.
I have never seen it happen. Always had to be under a load @WOT.
02-16-2010, 04:53 PM
#25
So when a car is on the road @ WOT and is running 6000rpm and is seeing 12lbs of boost, since that what it is pullied for and then I sit in my driveway and rev the motor to 6000rpm, I will see the same 12 lbs of boost.
I have never seen it happen. Always had to be under a load @WOT.
I have never seen it happen. Always had to be under a load @WOT.
You are turbo. We are talking about supercharged cars.
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02-16-2010, 05:12 PM
#27
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02-16-2010, 05:37 PM
#28
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BATTLE OF THE BOOSTS!!
Soooo..... which is it. I'll tell you this, I called Vortech and asked them (couldn't do this last night, sorry). They said you wont see boost on a gauge, but at a neutral trottle the boost bypass valve opens due to vacuum in the manifold opening it. This happening allows the volume of air produced by the spinning supercharger to be the same as with a load. BUUUTTT, since the boost bypass valve is open, the pressure (i.e. boost) is never collected. The only thing that increases is the vacuum that holds the bypass open, hense the reading. Vortech said get it on the road drive it, then I will see boost. Haven't done it yet but hopefully i will soon.
Hope this clears things up...
Soooo..... which is it. I'll tell you this, I called Vortech and asked them (couldn't do this last night, sorry). They said you wont see boost on a gauge, but at a neutral trottle the boost bypass valve opens due to vacuum in the manifold opening it. This happening allows the volume of air produced by the spinning supercharger to be the same as with a load. BUUUTTT, since the boost bypass valve is open, the pressure (i.e. boost) is never collected. The only thing that increases is the vacuum that holds the bypass open, hense the reading. Vortech said get it on the road drive it, then I will see boost. Haven't done it yet but hopefully i will soon.
Hope this clears things up...
02-16-2010, 05:58 PM
#32
[QUOTE=Scoggin Dickey;12903643]You must have only seen turbo cars. Explain to me how a load will affect a compressor that is only driven by RPM please? RPM = boost with a supercharger, plain and simple. It absolutely can not be related to the way a turbo builds boost
I fully understand that a supercharger is RPM related. But I promise you if you rev a motor in the driveway to 6000rpm, you will not build the same boost as if you were driving the car @WOT and at 6000rpm. My explanation has nothing to with a turbo car building boost.
I fully understand that a supercharger is RPM related. But I promise you if you rev a motor in the driveway to 6000rpm, you will not build the same boost as if you were driving the car @WOT and at 6000rpm. My explanation has nothing to with a turbo car building boost.
02-16-2010, 06:02 PM
#33
BATTLE OF THE BOOSTS!!
Soooo..... which is it. I'll tell you this, I called Vortech and asked them (couldn't do this last night, sorry). They said you wont see boost on a gauge, but at a neutral trottle the boost bypass valve opens due to vacuum in the manifold opening it. This happening allows the volume of air produced by the spinning supercharger to be the same as with a load. BUUUTTT, since the boost bypass valve is open, the pressure (i.e. boost) is never collected. The only thing that increases is the vacuum that holds the bypass open, hense the reading. Vortech said get it on the road drive it, then I will see boost. Haven't done it yet but hopefully i will soon.
Hope this clears things up...
Soooo..... which is it. I'll tell you this, I called Vortech and asked them (couldn't do this last night, sorry). They said you wont see boost on a gauge, but at a neutral trottle the boost bypass valve opens due to vacuum in the manifold opening it. This happening allows the volume of air produced by the spinning supercharger to be the same as with a load. BUUUTTT, since the boost bypass valve is open, the pressure (i.e. boost) is never collected. The only thing that increases is the vacuum that holds the bypass open, hense the reading. Vortech said get it on the road drive it, then I will see boost. Haven't done it yet but hopefully i will soon.
Hope this clears things up...
Thank you! You drive it, it produces boost,why , because of the load placed on the car from driving it. In the driveway,no load, it's vacuum, maybe 1lb of boost, but thats about it. I am not mixed up with a turbo car. LOL
02-16-2010, 06:02 PM
#34
I think people are forgetting the the bypass valve on the supercharger systems. With a good working BPV in place you can certainly rev the motor to 6k RPM and not see any boost. Load does make a difference as the Bypass valve has to close before the motor gets all the air.
That being said I can quickly stab the gas in my drive way and get a few pounds of boost for a moment, but I do not get max boost.
Cruising around town I am always under vacuum regardless of my engine RPM as I'm not pushing the motor enough to lose vacuum, thus keeping the valve open.
In a mild setup for a centri blower it is certainly possible to not be able to make/hold any boost when sitting in the drive way, but you should definitely hear the air being released.
That being said I can quickly stab the gas in my drive way and get a few pounds of boost for a moment, but I do not get max boost.
Cruising around town I am always under vacuum regardless of my engine RPM as I'm not pushing the motor enough to lose vacuum, thus keeping the valve open.
In a mild setup for a centri blower it is certainly possible to not be able to make/hold any boost when sitting in the drive way, but you should definitely hear the air being released.
02-16-2010, 06:27 PM
#36
WOW! When you got WOT a supercharger does in fact make boost, it is mechanical! The only reason you might think it is building less boost at the same rpm free revving vs actually driving is because the gauge is slow, the supercharger has to fill the intercooler piping and the motor is revving very fast.
At 5000 rpm a supercharger does not care if it is loaded or free reving it will move the same amount of air. A two step will stop the revs of the motor and show you the boost will be there.
If you are slowly revving and not going WOT the bypass valve will not close and bypass the boost.
To the OP, lets say your gauge reads 18 inches at idle, it is common for the motor to read more vacuum if you rev the engine and let off of the throttle. If the engine is spinning more then idle rpm and the throttle is closed it will show more vacuum. If you have a low boost set-up and you are quickly going wot, you might see the needle heading towards 0 as you are giving it throttle then alot of vacuum as you let off and the motor is above idle rpm. However, if you rev the **** out of the thing and the bypass is working the thing should make boost.
At 5000 rpm a supercharger does not care if it is loaded or free reving it will move the same amount of air. A two step will stop the revs of the motor and show you the boost will be there.
If you are slowly revving and not going WOT the bypass valve will not close and bypass the boost.
To the OP, lets say your gauge reads 18 inches at idle, it is common for the motor to read more vacuum if you rev the engine and let off of the throttle. If the engine is spinning more then idle rpm and the throttle is closed it will show more vacuum. If you have a low boost set-up and you are quickly going wot, you might see the needle heading towards 0 as you are giving it throttle then alot of vacuum as you let off and the motor is above idle rpm. However, if you rev the **** out of the thing and the bypass is working the thing should make boost.
Last edited by black98ws6ta; 02-16-2010 at 11:26 PM.
Beer all around, glad I could help... once I called Vortech that is. 
02-16-2010, 07:13 PM
#38
WOW! When you got WOT a supercharger does in fact make boost, it is mechanical! The only reason you might think it is building less boost at the same rpm free revving vs actually driving is because the gauge is slow, the supercharger has to fill the intercooler piping and the motor is revving very fast.
At 5000 rpm a supercharger does not care if it is loaded or free reving it will move the same amount of air. A two step will stop the revs of the motor and show you the boost will still be there.
If you are slowly revving and not going WOT the bypass valve will not close and bypass the boost.
To the OP, lets say your gauge reads 18 inches at idle, it is common for the motor to read more vacuum if you rev the engine and let off of the throttle. If the engine is spinning more then idle rpm and the throttle is closed it will show more vacuum. If you have a low boost set-up and you are quickly going wot, you might see the needle heading towards 0 as you are giving it throttle then alot of vacuum as you let off and the motor is above idle rpm. However, if you rev the **** out of the thing and the bypass is working the thing should make boost.
At 5000 rpm a supercharger does not care if it is loaded or free reving it will move the same amount of air. A two step will stop the revs of the motor and show you the boost will still be there.
If you are slowly revving and not going WOT the bypass valve will not close and bypass the boost.
To the OP, lets say your gauge reads 18 inches at idle, it is common for the motor to read more vacuum if you rev the engine and let off of the throttle. If the engine is spinning more then idle rpm and the throttle is closed it will show more vacuum. If you have a low boost set-up and you are quickly going wot, you might see the needle heading towards 0 as you are giving it throttle then alot of vacuum as you let off and the motor is above idle rpm. However, if you rev the **** out of the thing and the bypass is working the thing should make boost.
Put a supercharged motor on a engine dyno and free rev it, no boost, then make a pull with the load on the motor and you have boost.
02-16-2010, 07:39 PM
#39
So the gauge is slower sitting in the driveway because it has to fill the pipes???LMAO!! It's not building boost because it is going thru the BPV.
Put a supercharged motor on a engine dyno and free rev it, no boost, then make a pull with the load on the motor and you have boost.
Put a supercharged motor on a engine dyno and free rev it, no boost, then make a pull with the load on the motor and you have boost.
Last edited by black98ws6ta; 02-16-2010 at 10:40 PM.
02-16-2010, 10:16 PM
#40
I fully understand that a supercharger is RPM related. But I promise you if you rev a motor in the driveway to 6000rpm, you will not build the same boost as if you were driving the car @WOT and at 6000rpm. My explanation has nothing to with a turbo car building boost.
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