Launch Strategy Incorporating the BOV

[Alky V6]

The Pro light strategy is to pre-stage, set the transbrake, go WOT, obtain the target launch rpm and map, creep into stage and release the TB button on the amber.

The two important items on the list will be maintaining the target launch rpm and map into final staging, and creeping into stage.

 

[Alky V6]

The controlling of the BOV will be handled by providing boost pressure from before the throttle body to the lower chamber of the BOV. It will be a straight line from the compressor housing to the lower chamber.

The upper chamber of the BOV will be connected to the new switching valve. The switching valve will normally provide map pressure from after the throttle body to the upper chamber. When the switching valve is energized by the activation of the transbrake, CO2 control pressure from the aux channel launch mode of the boost controller will be sent to the upper chamber of the BOV.

 

[Alky V6]

Here's the trick. When the transbrake is activated, the switching valve will be energized and will provide CO2 from the aux channel to the top chamber of the BOV.

Before any boost has built up, the BOV will remain shut due to atmospheric pressure in the lower chamber and CO2 pressure in the upper chamber helping the spring to keep the valve closed. The CO2 will be a relatively low pressure. Let's say 5 psi.
As boost begins to build, that same pressure will be rising in the lower chamber of the BOV. There will be a point where boost has reached 5 psi. That will be when the spring alone will be what keeps the BOV closed. The pressures in the upper and lower chambers will be equal. 5 psi of CO2 pressure in the upper chamber and 5 psi of boost in the lower chamber.
Let's say that the BOV spring is set to allow the valve to open at a point where the lower chamber pressure is 5 psi over what the pressure in the upper chamber is. That means that when 10 psi of boost has built and is providing 10 psi of pressure in the lower chamber with a constant 5 psi of CO2 pressure in the upper chamber, the valve will be on the verge of cracking open.
At any boost level above 10 psi, the BOV valve will be open, and the more boost there is, the more the BOV will open to help relieve boost pressure and keep it under control.
The important variables involved in controlling the boost level to a certain target value will be the strength of the BOV spring setting, the amount of CO2 pressure provided to the upper chamber of the BOV, how relentless the compressor is at trying to overpower the BOV control, the wastegate control setting.
The wastegate control setting would be the last variable to look at in trying to control the launch boost level target. If the launch boost level can be controlled by the BOV with a tight wastegate setting, then a higher turbine speed can be achieved so that when the BOV is shut closed at the release of the transbrake, the boost level should jump by a higher possible value sooner than would be obtained with a lower turbine speed.

 

[Alky V6]

When the switching valve is turned off with the release of the transbrake, manifold pressure will be provided to the upper chamber instead of the 5 psi of CO2 pressure. Manifold pressure will be the same as boost pressure at the compressor, so the pressures in the upper and lower chambers of the BOV will be equal. The spring pressure setting of the BOV will shut the valve.

 

[Alky V6]

I forgot to add that there will also be boost pressure acting on the BOV valve itself that will be helping the boost pressure in the lower chamber to move the valve off its seat, working against the spring pressure and the fixed upper chamber pressure.

Rack tests begin today to find a setting that will nose over the rise of the rpm and boost level to around 5500-5700 rpm and just over 182 kPa MAP. After that setting is found, the next question will be, will the car be able to handle that tuneup at the launch? That will be about a 12 psi launch at close to peak torque rpm.

 

[Alky V6]

Very, Very Cool!!! :biggrin:

 

[charlief1]

What have you done Donnie? Did everything work out right?

 

[Alky V6]

It worked exactly as planned. Rpm noses over at 5600-5700 and map settled at 178 kPa. Time to test it at the track.

 

[charlief1]

Well you had all day, didn't you get the chance today?:biggrin: Waiting on the results Donnie.

 

[GDNF2ET]

Anxiously looking forward to results also...

 

[Alky V6]

I missed the last track opportunity to test out the BOV strategy. I've been brainstorming over the last week or so on a system that will allow me to stage the car for a Pro light launch with the car under rising rpm and boost. I think I have it figured out. Just need to install the subsystem, wire it up, and dial in the programming with some tests at the shop. It will be controlled by the Electromotive TEC unit. It should allow automatic staging after pre-staging and setting the transbrake. Should be exciting. The new subsystem is surprisingly simple using basic electrical components.

 

[Alky V6]

I've whiteboarded, breadboarded, desk tested, did a final packaging and assembly of the unit, and installed it in the car. Some rack testing and preliminary adjustment has been done. A simple modification to the transbrake unit of the transmission has allowed for an increased range of the adjustability of the new solenoid control unit. The transbrake mod also helped to smooth the bumping of the transbrake.
The new tool is very cool. Frequency and pulse width are both independently and finely adjustable. Next weekend is the next available track date. We'll see how all the changes work out. Shooting for a 60' into the mid to high 1.10s.

 

[Alky V6]

A couple pics of the mod I did to the BOV.

 

[Alky V6]

It Works!!!

VERY COOL!!!
The first few passes were a bust due to me getting the lines routed incorrectly to the switching valve for the BOV control. After correcting that,... next pass was amazing.
The map and rpm was controlled during staging just as advertised, and when the switching valve changed BOV control, the rpm and map jumped almost straight up to an unexpected level for the launch. HOW COOL!!!
The tires held and the time slip stated a 60' of,

ONE point ZERO NINE !!!

 

[Alky V6]

A car rolled on the track and ended the day before I could try to backup that 60', so I'm not going to change my sig until I can confirm that the 1.09 wasn't some sort of electronic timing quirk.

The electronic control box I put together for the transbrake control also worked very well. Still some adjusting to do with it to get it to a preferred shallow stage. Most of the stages were deep enough to flicker the top bulb.

Yes. Deep staged, and still a 1.09.

 

[charlief1]

Waiting for you to back it up Donnie. If you get this time on the 60' then you really can make her serious on the track. Here you come Pinks.:biggrin:

 

[BRAD D]

How about a vacuum accumulator on a 3 port solenoid valve, you feed manifold pressure to the BOV like normal. but have the solenoid valve switch when you want and feed the vacume to the BOV just like how it normaly works... and bam your BOV opens up... and your car idling will charge the vacuum accumulator.

just a idea.

i have this same problem but with a 600whp 4cly nissan with a ford C4.. i was using a small spool up shot on the t-break.

 

[WarWagon]

Awesome stuff Donnie!
Very nice work

 

[Alky V6]

How about a vacuum accumulator on a 3 port solenoid valve, you feed manifold pressure to the BOV like normal. but have the solenoid valve switch when you want and feed the vacume to the BOV just like how it normaly works... and bam your BOV opens up... and your car idling will charge the vacuum accumulator.

just a idea.

i have this same problem but with a 600whp 4cly nissan with a ford C4.. i was using a small spool up shot on the t-break.

That sounds like a good idea if you really need the BOV to open that far.
In my case, I need a certain level of boost to build to push the stall on a tight torque converter. Controlling how much the BOV opens allows some control of the amount of boost that is building during staging.

On the last pass of the recent track testing session, during the new staging routine, the rpm rose to 4550-4650 rpm after going WOT and on the nitrous, and leveled out at that rpm range while the map rose to 165 kPa. The map level was still on a climb when I released the transbrake and in doing so also switched the BOV control to manifold. The aux channel of the boost controller that was feeding CO2 to the BOV during staging was set at a control pressure target of 2 psi.
I'm performing some testing in the shop tomorrow in an effort to adjust the map level during staging to 175 kPa. The nitrous is set to shut off at 175 kPa, so the nitrous system may be the control factor that keeps the map at 175 during staging. If the map drops below 175 kPa before the launch can occur, the nitrous will come back on and push the map back up above 175 kPa. Kinda like a 2 step, but instead of timing being retarded, or cylinders being dropped, the nitrous cycles on and off.

At this point in the tuning involving the 91mm turbo, this is the highest amount of boost I've been able to build at 4,600 rpm. 165 kPa MAP and still rising.
With the best previous tune, at 4,600 rpm, I was only able to build around 110 kPa.

 

[Alky V6]

I've tried to figure out how I'm seeing so much boost at 4,600 rpm while the BOV is partially open. The idea behind cracking the BOV open during staging is to allow the turbine speed to increase so that more airflow/boost is available to the engine when the BOV is suddenly shut closed at launch. I would think that with the BOV cracked open the map should fall to a lower level, not rise to a level that I would have previously thought was completely impossible for this engine/turbo combination. Very interesting stuff. We'll see how the testing today goes. Maybe it will shed more light onto this strange finding.

I'm not complaining, I just would like to understand this.