Launch Strategy Incorporating the BOV

[forcefed86]

Wish there was a way to know how fast you were turning the turbo. Some sort of laser pick-up as used on a turbine engine would sure be a nice addition to all that data your collecting. Are you worried about overspeeding the turbo?

Can't wait to hear the results!

 

[Darkcyde]

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.

shouldn't the map rise, with a cracked bov more air is entering the tb under pressurized flow. I don't know the specifics but isn't pressurized air flow in volume increased with the bov open, thus freeing the energy required to spin the turbine. And because it frees the energy required to spin the turbine boost increases and thus increase in the total volume of pressurized air going into the motor also increases? But its just a guess.

Wish there was a way to know how fast you were turning the turbo. Some sort of laser pick-up as used on a turbine engine would sure be a nice addition to all that data your collecting. Are you worried about overspeeding the turbo?

Can't wait to hear the results!

just drill and tap your compressor housing and paint a single turbine blade reflective, then use the port for a tach signal pick up and enjoy!

 

[Alky V6]

Wish there was a way to know how fast you were turning the turbo. Some sort of laser pick-up as used on a turbine engine would sure be a nice addition to all that data your collecting. Are you worried about overspeeding the turbo?

Can't wait to hear the results!

I'm far from overspeeding this monster. According to the compressor map, I'm at least 30,000 rpm from reaching the speed limit of this turbo.

I couldn't repeat the 160+ kPa at only 4600 rpm. I think that result was due to a low nitrous bottle. It caused a rich condition which kept the rpm low, but still allowed the map to increase to an amazing level.

The testing today showed that the BOV is very affective at controlling a launch RPM/MAP target. Once I found the right level of control pressure that would work with my BOV combination, I found that it is close to a 1:1 ratio, control pressure to boost pressure in adjusting the target launch map level up or down. Very predictable adjustments.

2 psi control pressure resulted in 5791/173.5 kPa MAP.
3.3 psi control pressure resulted in 5782/183 kPa MAP. The rpm lower in this test due to the mixture being set to richen past 175 kPa.