Stupid question about CO2

[sackracing]

How do the CO2 bottles help with the boost controllers and spool-up? Anyway to get a pretty decent explanation on the whole set up?
Thanks.

 

[bison]

The simple explanation would be that when you use an electronic boost controller and use compressed gas to hold the wastegate shut you can send more than manifold pressure to the top of the gate and have total control over that pressure. The controller can be set to send any specified pressure there and it can further control boost by increasing or decreasing that pressure as the car accelerates for whatever the user wants. You can set it to leave at 12psi and ramp in in a specified amount of time or you can stage it to come in in multiple hits over time. The controller relies on a MAP sensor to be able to provide a constant pressure number reading so it can control the diaphragm pressure. Keep in mind that the wastegate also has its own spring so that has to be figured in and would be a reason why one car may have to use 30psi to get a desired boost and another similar car may need 40psi to attain the same boost level. Remember the factors that will cause a wastegate to open. They are a negative pressure differential between the top and bottom of the diaphragm, spring pressure, and the exhaust pressure exerted on the valve. CO2 is great because you can counter act a high backpressure situation like in heads up racing while controlling the torque at the wheels throughout the pass. Most racers have all the boost in before the 60'.

 

[V6RACER]

Most racers have all the boost in before the 60'.

 

[Chevota]

+2 :biggrin:

 

[GNBRETT]

The simple explanation would be that when you use an electronic boost controller and use compressed gas to hold the wastegate shut you can send more than manifold pressure to the top of the gate and have total control over that pressure. The controller can be set to send any specified pressure there and it can further control boost by increasing or decreasing that pressure as the car accelerates for whatever the user wants. You can set it to leave at 12psi and ramp in in a specified amount of time or you can stage it to come in in multiple hits over time. The controller relies on a MAP sensor to be able to provide a constant pressure number reading so it can control the diaphragm pressure. Keep in mind that the wastegate also has its own spring so that has to be figured in and would be a reason why one car may have to use 30psi to get a desired boost and another similar car may need 40psi to attain the same boost level. Remember the factors that will cause a wastegate to open. They are a negative pressure differential between the top and bottom of the diaphragm, spring pressure, and the exhaust pressure exerted on the valve. CO2 is great because you can counter act a high backpressure situation like in heads up racing while controlling the torque at the wheels throughout the pass. Most racers have all the boost in before the 60'.

What he said... Bison btw who the hell is that guy in ur avitar? I could swear I use to know someone who looked just like that

 

[sackracing]

Ok, so the CO2 is plumbed into the top of the gate and the boost controller is actually bleeding off the co2 pressure to control the boost instead of the manifold pressure?

I was looking at the AMS installation instructions and it shows the controller plumbed into the top of the gate. So it would require a T and the co2 would plumb into the same line as the sensing for the controller?

What about the port on the backside of the gate?

I am gonna order an AMS from Cal and I am just trying to get familiar with this setup.

Thanks for the info.

 

[sackracing]

Another question, since you are using the co2 in lieu of the manifold pressure, you might have to set the boost controller for 40 psi to get 25 psi at the manifold?

Any pics would be great too.

 

[bison]

Another question, since you are using the co2 in lieu of the manifold pressure, you might have to set the boost controller for 40 psi to get 25 psi at the manifold?

Any pics would be great too.

You dont need the manifold pressure only the CO2. Manifold pressure would be one of the MAP sensors. You may need a 4 or 5 bar MAP sensor or even higher if the spring is too weak and you have a lot of backpressure since the CO2 pressure may be out of range of the sensor. Keep in mind the gate has a spring in it and you have exhaust backpressure working against the top of the diapragm.

 

[sackracing]

I think I kinda get it.
So, I guess that wouldn't work out too good on a car that sees street time.

 

[bison]

I think I kinda get it.
So, I guess that wouldn't work out too good on a car that sees street time.

Ill be using mine on the street. It doesnt use a lot of CO2 to work. You can have several settings on the boost controllers to control the ramp in rate and boost which will help with traction if you are making some good power.

 

[pacecarta]

heres another explanation of where it helps
as boost goes up so does the exhaust pressure but at a faster rate and higher pressure differential than the turbo can supply , not a big problem if you run a 20psi spring and only want to run 25 or 30psi boost
but to launch youd have to throttle to a boost level you want and consistency would be lousy , so two steps were used to hold engine at a set rpm and then launch but those had issues with wastespark ignitions

but lets say you want to run 5psi launch and be able to put your foot to the floor and hold it there without boost creep using boost control
to do that you need a 5lb spring in the gate (with this you can chose a launch boost of anything above spring pressure but not less than spring pressure)
problem with that and using turbo outlet pressure to hold the gate is that its not too hard to have twice the boost or more during an over rich spoolup where sometimes fuel is burned in the exhaust ,and with a good flowing i/c the manifold (turbo outlet) pressure is only a pound or less over the actual manifold boost pressure at low rpm (my v2 is one of the most restrictive FMIC's so ive been ok till now without co2 )
so you want to hold 5psi at the line but don't have much help to hold the gate with only 5psi pushing down on the spring and a large gate only makes it worse as the exhaust pressure can force the gate open ....there goes the spoolup ... and even after you launch until the ic starts becoming restrictive and helps hold the gate down the 60' will suffer some
co2 assist helps because now instead of having the pressure from the turbo to hold the gate closed you now have 50psi of co2 going to the top of the gate through the increase solenoid and it will stay closed during spoolup until you reach your launch boost as soon as you let off the brake which usually is tied into the launch release and sends you move to next stage your target boost the controller closes the decrease solenoid that was pulsing to maintain the launch level and opens the increase solenoid allowing 50 psi to top of gate to seal the gate hard and fast allowing you to reach the target boost as fast as possible

have to disagree with bison about not needing to use manifold (turbo outlet ) to gate

plumb manifold (turbo outlet) direct to bottom of gate and co2 to the solenoids to control top of gate . reason is bottom of gate usually dosn't seal 100% due to the valve stem and you'd run out a tank quicker as a constant leak and if you forgot to close it after a run you probably would'nt have anything left in the bottle for the next pass . the manifold source is unlimited so no wasted co2 . the top of gate is usually a near perfect sealed chamber above the diaphragm and the boost controller solenoid closes when system isn't controlling boost so bottle could stay open all day while you race and still be ready when you need it without having to worry if you forgot to open it before a run or worry about turning it off
the only loss of co2 is while your running the boost
doing it that way if you ran out the bottle the manifold (turbo outlet) would still be working and supplying air to the bottom of gate and boost will drop and be limited to the gate spring pressure.
if boost controller for some reason lost power or as i found out once when my boost controller map line blew off - controller basically turned off since it doesn't come on unless 3psi is seen at the map -the increase solenoid closed and decrease vent opened so i made the rest of run at spring pressure ..6psi

 

[sackracing]

Ok, so the boost controller is gonna try to equalize the pressure on each side of the gate if you plumb the manifold pressure to the bottom of the gate. That makes sense.

 

[sackracing]

Does the map on the controller get the manifold or the CO2 pressure plumbed to it?

 

[pacecarta]

boost controller map sensor goes on the manifold (not turbo outlet ) but the same source as you would with the boost gauge so your controller targets that you set are the same as your gauge

 

[tonka]

Something I've been wondering about, could a person extend the upper end of the boost control by putting a regulator inline between the manifold pressure tap and the bottom of the actuator, set for some lower pressure (say 15 psi) to help increase the differential across the actuator?

 

[HighPSI]

boost controller map sensor goes on the manifold (not turbo outlet ) but the same source as you would with the boost gauge so your controller targets that you set are the same as your gauge

Not true. This is only the case if you are running in "manifold mode". For best control, you should run "wastegate mode". Then the sensor needs to read wastegate psi NOT manifold psi. The AMS units ONLY run in "wastgate mode".

 

[bison]

have to disagree with bison about not needing to use manifold (turbo outlet ) to gate

You may disagree with the turbo outlet to the gate but i wasnt saying that CO2 should be plumbed to the bottom of the gate. I meant leaving it atmospheric. If you run outlet to the bottom you will need a higher CO2 pressure to get higher boost levels

 

[pacecarta]

have you tried running a gate with the bottom port to atmosphere ?

 

[bison]

have you tried running a gate with the bottom port to atmosphere ?

Yes. If no CO2 you need a really stiff spring

 

[HighPSI]

I must be in an argumentive mood :redface: I have never seen anyone run atmosphere to the bottom of the gate. If you do, your boost will be considerably HIGHER and require very little CO2. The only thing that will allow the wastgate to open is turbo back pressure. On almost all wastegates the diameter of the valve is smaller than the diameter of the diaphragm, so it won't be very proportional when you do add presure to the top.