Launch Strategy Incorporating the BOV

[Alky V6]

It's time to explore launch strategies that use the blow off valve to help decrease the time to accelerate turbine shaft speed pre-launch. This is in preparation for putting together a pro light launch strategy. This should be very interesting. I've already got some ideas in my head on ways to plumb the system without having to add a bunch to the existing boost controller and spool valve CO2 plumbing. Teeing into the launch control pressure setting for the wastegate control.

The first thing to do will be to examine the Godzilla BOV for loose sealing that would waste CO2 during the pressurization of the lower section of the valve diaphragm. When I briefly played with CO2 controlling of the BOV months back, I got the impression that there was quite a bit of CO2 leakage around the valve shaft. If that truly is the case, I'll need to better the seal design, if there is even a seal there to begin with.
Once that is adequately sealed so that CO2 is not wasted. It will be fun slowly working up on the tuneup that will provide a higher turbine shaft speed by the time the transbrake is ready to be released, along with the fact that there will be less stress on the engine while staged and waiting for the lights to come down.

If anyone ever wondered how a BOV could be used to better spool the turbo in preparation for the launch, this should be an interesting thread for you.

 

[Chevota]

Use a wastegate instead of a BOV.

 

[Alky V6]

In the past, my setup was not building very much boost before the launch, so the need for a BOV strategy was not there.
Now that it seems that I can build more than enough boost for whatever launch I desire, I can see where a BOV launch control strategy could work out very well.

First, let's explain the advantages of BOV control for the launch.
The BOV is like a wastegate valve, but on the cold side. When opened, it releases boost pressure from the intake side.

How this launch strategy works is, when you are staging the car, or when the car is already staged and you're attempting to build boost, turbine shaft speed can increase quicker with the lack of boost pressure working against the compressor wheel. You have the exhaust side working to increase turbine speed and without building resistance in the form of increasing MAP on the compressor side, the turbine shaft speed can increase quicker than if the turbine had to deal with an increasing resistance from the compressor side working against it.
By the time you are ready for the boost to hit the engine, the turbine shaft speed is at a higher level and when the BOV shuts closed, a sudden increase to a higher than otherwise obtainable boost pressure is realized.
Another thing to realize is that while the car is staged and turbine speed is increasing, boost pressure is not working on the engine that would make it work harder and push on the torque converter harder, increasing thermal loading on both. In my case having a BOV control strategy will be a good way to control the launch rpm level. With the lack of boost, or with the boost level controlled to a lower level, with the benefit of a relatively higher turbine shaft speed before the launch, the engine rpm and TC stall will not be pushed to unreasonable levels. Less chance of getting burned down at the starting line.

 

[Alky V6]

Use a wastegate instead of a BOV.

Why is that? The Godzilla BOV is configured pretty much like a wastegate already.

Why haven't you brought that truck down yet!

 

[Otto J]

Using blow off valves to control launch boost is not a new idea. The Turbo pro mod guys have been doing it a while.

 

[turboc87gn]

hmmmm....

 

[TurboBob]

you will probably have to disassemble the unit and machine/modify it for a valve stem seal.

Bob

 

[Alky V6]

Using blow off valves to control launch boost is not a new idea. The Turbo pro mod guys have been doing it a while.

I'm sure it has already been used. In fact, I first learned of such a system here on this site. The thing is, it's hard to find information on how to setup and tune in such a system. I plan to go through the learning process of setting up my own BOV launch strategy and sharing it with the rest of you.

Tuning in such a system will be the important part to pay attention to.

 

[Alky V6]

you will probably have to disassemble the unit and machine/modify it for a valve stem seal.

Bob

Yes. I think you're right about that. Working on transmissions for a living, transmissions are full of different designs of seals that seal off moving shafts. I'm sure I won't have much difficulty coming up with a solution for that. My thought at this moment is that I'll end up using a small metal clad lip seal. I may have to machine the recess that I'll need to receive the lip seal.
Another option would be to machine an o-ring groove into the valve shaft if the bore in the housing is long enough to keep the o-ring against the bore through the complete range of movement. I'm guessing right now that the housing bore will not be long enough and I'll have to go with the metal clad lip seal.

 

[S2V6RACER]

Don, you will have to use the aux channel on the AMS to control pressure to the BOV. However, I do not think it will do it's job on the other side of the track so you might need to add a second. I can PM you my ideas if you are interested, but I think you can figure it out from here.

Gotta love the Aux channel on that controller.

 

[Alky V6]

Don, you will have to use the aux channel on the AMS to control pressure to the BOV. However, I do not think it will do it's job on the other side of the track so you might need to add a second. I can PM you my ideas if you are interested, but I think you can figure it out from here.

Gotta love the Aux channel on that controller.

I'm already using the aux channel to control the spool valve. I don't have to use the spool valve and could free up the channel to use on the BOV, but I think you're right about the aux channel not allowing for the proper operation of the BOV other than for the launching procedure.

My thinking is this. I would Tee into the CO2 line controlling the wastegate. That would get me my pressure feed. In the line from the Tee to the BOV would be an electrical switching 3 way valve. The 3rd leg would go to the intake manifold. The valve would switch between the wastegate feed line and the intake manifold. When the transbrake is engaged, the boost controller would go into launch mode and supply a determined amount of pressure to the wastegate and the BOV. The electrical 3-way valve would be energized by the activation of the transbrake. Normally the 3-way valve would allow flow from the intake to the BOV, blocking flow to the wastegate feed line. When energized, the 3-way valve would block flow to the intake manifold and only allow flow between the wastegate feed line and the BOV.
Timing the switching of the valve around the time of transbrake release is still to be worked out.

 

[Alky V6]

I took the Godzilla apart today. There was a seal for the shaft. It was a hard plastic type of seal. I machined out the receiver cavity to install a metal clad rubber lip seal. I also surface block sanded the mating surfaces that clamp the diaphragm, and countersunk the fastener threads away from the mating surface. If I remember right, most of the leakage was around the diaphragm mating surface. One of the surfaces, the one that also has the threads for the fasteners, needed quite a bit of sanding to get a nice flat surface going.
After I finished with it, I could push down on the valve, block the lower cavity of the diaphragm, and release the valve and have it hold a rock steady position until I released the block on the lower diaphragm cavity. The BOV is back on the car and it's now time to figure out the control lines configuration. I guess I'll see if there is a 3 way control valve available.

 

[Alky V6]

What I'll be searching for is a 3 port solenoid that will block off flow to the one unused leg while allowing flow between the other two legs. When the two legs are switched, the leg that now becomes the leg that is not being used will, again, need to be blocked, no flow allowed. Sounds like a simple device. It would have to operate on 12V. I wonder if that would be similar to the type of solenoids that are used by the boost controller?

 

[S2V6RACER]

Don, you might be able to incorporate this device to control the BOV on launch with 1 stage and the second stage will allow the BOV to work at the end of the track.

I believe it may be able to modulate a solenoid(s) to work... Just a quick thought.


Nitrous Express NXD5000 Nitrous Express Boost Reference Progressive Nitrous Controller

 

[Alky V6]

Don, you might be able to incorporate this device to control the BOV on launch with 1 stage and the second stage will allow the BOV to work at the end of the track.

I believe it may be able to modulate a solenoid(s) to work... Just a quick thought.


Nitrous Express NXD5000 Nitrous Express Boost Reference Progressive Nitrous Controller

I was thinking of a much simpler electrical control of the 3 way solenoid.

When the transbrake button is pressed to set the transbrake, the boost controller would go into launch mode. The pressure setting for the launch mode would be set to a level that would move the BOV to a position that would give the desired amount of boost control, whether that level is zero or whatever.
As described earlier, one leg of the 3 way valve would tee into the wastegate control pressure line. When the transbrake button is pressed, that signal would not only signal the boost controller, but would also energize a relay that would energize the 3 way solenoid of the BOV. As long as the transbrake button is pressed, the relay and the 3 way solenoid will direct the wastegate control pressure (launch mode) to the BOV.
On the release of the transbrake button, the relay would de-energize and the 3 way solenoid would switch to its normal mode. That normal mode would be to supply intake manifold pressure through the one leg that is left.

 

[Alky V6]

The solenoid is on order. It's similar to the type that is used to control the wastegate.

 

[Chevota]

Why is that? The Godzilla BOV is configured pretty much like a wastegate already.

Why haven't you brought that truck down yet!

I didn't realize the the Godzilla BOV had a top and bottom port. Precise control is what I was getting at. Getting the truck ready for the SCSN radial class (Street Car Super Nationals) I'll make it down eventually!

 

[Alky V6]

Good luck at the event.

 

[Alky V6]

[Thinking out loud]
How would a pro light launch routine go?
I would pre-stage. Bring the rpm up as high as the brakes will allow me to get away with. Roll into stage, then set the transbrake and go WOT.
I would need to have the nitrous activate with the setting of the transbrake and going WOT.
The BOV would also open getting its signal from the wastegate control pressure line (teed into) via the 3-way valve. The 3-way valve would be activated to allow flow from the wastegate line to the BOV when the transbrake button is pressed. When the transbrake button is released, the 3-way valve will switch to flow from the intake plenum to the BOV. That way the BOV can act as it normally would for the rest of the run.
The BOV should only be allowed to open enough to maintain a certain rpm and launch boost level. Launch rpm and boost level could be finely tuned by how the BOV is set, adjuster screw and control pressure wise.
A turbine speed sensor might become useful for the tuning and monitoring of this launch routine.
The nitrous system would need to time out at some point, or leave it on until the release of the transbrake? Or, leave it on threw the first part of the launch and shut it down at 176 kPa. That would depend on how controllable the rpm and boost level becomes at the target launch values. The AB level could be adjusted to help with this, maybe.
A problem is, I've found a good launch boost level that is right in the middle of my aux fueling activation transition point. Not really a point. It's more of a MAP range. How to make that work. Move the transition range higher? That would be the best way to handle it, if I have enough range left in the VE table to allow it.

 

[cdsttype]

launching bov style

The way mine works is like this. I do the burn out and two foot
the car in two the stage lamp.Then i set the trans brake the
rpm trigger switch which is activated by the t brake turns on the
no2 at 3000rpm and off where i want usually 4000 rpm then the
two step takes over to control rpm while the gate controls boost
my problem is i cant dump enough boost due to waste gate size
now if i could bleed a little through the bov that would very nice.
A bigger waste gate is the solution but that means fabrication and more money.
i have the bov on the car already why not try to make it multi funtional.
controlling the bov will be the trick if i stray far from the proper spring size
it wont function as intended for initial purpose.