Drive pressure
01-31-2006 | 06:25 AM
#32
Muted User
Joined: Jan 2005
Posts: 640
Likes: 0
Chris, very nice work. However, I fear you may encounter a slight problem. Its not an insurmountable problem at all, but I mention it, so you check for it.
You have made the area of the valve disk, which is exposed to exhaust manifold pressure substantially larger, and also, you have moved the actuator's pivot point on the valve's lever arm further in. The increased area of the valve will cause any given exhaust manifold pressure to greatly increase the force trying to open the valve. Combined with this, the actuator now has less leverage on the valve shaft due to the pivot point move in. I am concerned that the valve will overcome the actuator, and you will be wasting prior to the intended boost.
You may have to go with a more aggressive actuator, that’s all. I mention this so that if you test it, and experience a substantial boost drop, check this first, before you fret that the valve is leaking.
KP
You have made the area of the valve disk, which is exposed to exhaust manifold pressure substantially larger, and also, you have moved the actuator's pivot point on the valve's lever arm further in. The increased area of the valve will cause any given exhaust manifold pressure to greatly increase the force trying to open the valve. Combined with this, the actuator now has less leverage on the valve shaft due to the pivot point move in. I am concerned that the valve will overcome the actuator, and you will be wasting prior to the intended boost.
You may have to go with a more aggressive actuator, that’s all. I mention this so that if you test it, and experience a substantial boost drop, check this first, before you fret that the valve is leaking.
KP
01-31-2006 | 10:44 AM
#33
Banned
Joined: Jan 2005
Posts: 492
Likes: 0
Originally Posted by 600 Megawatts
Chris, very nice work. However, I fear you may encounter a slight problem. Its not an insurmountable problem at all, but I mention it, so you check for it.
You have made the area of the valve disk, which is exposed to exhaust manifold pressure substantially larger, and also, you have moved the actuator's pivot point on the valve's lever arm further in. The increased area of the valve will cause any given exhaust manifold pressure to greatly increase the force trying to open the valve. Combined with this, the actuator now has less leverage on the valve shaft due to the pivot point move in. I am concerned that the valve will overcome the actuator, and you will be wasting prior to the intended boost.
You may have to go with a more aggressive actuator, that’s all. I mention this so that if you test it, and experience a substantial boost drop, check this first, before you fret that the valve is leaking.
KP
You have made the area of the valve disk, which is exposed to exhaust manifold pressure substantially larger, and also, you have moved the actuator's pivot point on the valve's lever arm further in. The increased area of the valve will cause any given exhaust manifold pressure to greatly increase the force trying to open the valve. Combined with this, the actuator now has less leverage on the valve shaft due to the pivot point move in. I am concerned that the valve will overcome the actuator, and you will be wasting prior to the intended boost.
You may have to go with a more aggressive actuator, that’s all. I mention this so that if you test it, and experience a substantial boost drop, check this first, before you fret that the valve is leaking.
KP
01-31-2006 | 04:45 PM
#34
Thread Starter
Banned
Joined: Jul 2004
Posts: 394
Likes: 0
From: Juneau, ALASKA
yeah...as both of you have stated, extra "sail" area and a reduced mechanical advantage crept into my thoughts early on. There's two ways this can turn out....
1. Though the big head has a heavier spring, it may allow the valve to crack early even so, the outcome will either be:
A. with the higher drive energy present, the loss may not be noticeable
B. It will either slow the spool-up alot, or at best cause some fluttering.
2. Because the Big Head has a heavier spring, it will keep the valve seated anyway which will:
A. still cause quite a flutter when it does open or...
B. Work just dandy
In either case, I fully expect some snags. To test the gate's ability to hold back against pressure, I intend to seal off oulet with an expansion plug and make a plate with an air fitting to mount to the inlet. I will pressure up the scroll and see just where the actuator loses it's ability to hold back the valve. When I find that out I will come up with a solution. It will be much easier to test this on the bench before everything else is fabbed up on the truck...and find problems.
Thanks for the input guys.
Chris
1. Though the big head has a heavier spring, it may allow the valve to crack early even so, the outcome will either be:
A. with the higher drive energy present, the loss may not be noticeable
B. It will either slow the spool-up alot, or at best cause some fluttering.
2. Because the Big Head has a heavier spring, it will keep the valve seated anyway which will:
A. still cause quite a flutter when it does open or...
B. Work just dandy
In either case, I fully expect some snags. To test the gate's ability to hold back against pressure, I intend to seal off oulet with an expansion plug and make a plate with an air fitting to mount to the inlet. I will pressure up the scroll and see just where the actuator loses it's ability to hold back the valve. When I find that out I will come up with a solution. It will be much easier to test this on the bench before everything else is fabbed up on the truck...and find problems.
Thanks for the input guys.
Chris
02-11-2006 | 10:06 PM
#36
Thread Starter
Banned
Joined: Jul 2004
Posts: 394
Likes: 0
From: Juneau, ALASKA
a few more updates images....
The first one is the new back plate ready for welding on a merge collector. The merge collector is to unshroud the bigger wastegate, much like the megamouth.
The second one is the turbine housing with the big head gate actuator mounted, adjusted and fully operational.
Tested the actuator's ability to withstand drive pressure with the reduced mechanical advantage from the relocated fulcrum point, as well as the more than double valve surface area....held 60 psi without opening on the bench, so it should be okay in the truck.
The first one is the new back plate ready for welding on a merge collector. The merge collector is to unshroud the bigger wastegate, much like the megamouth.
The second one is the turbine housing with the big head gate actuator mounted, adjusted and fully operational.
Tested the actuator's ability to withstand drive pressure with the reduced mechanical advantage from the relocated fulcrum point, as well as the more than double valve surface area....held 60 psi without opening on the bench, so it should be okay in the truck.
02-15-2006 | 09:16 PM
#41
Registered User
Joined: Mar 2003
Posts: 923
Likes: 0
From: TX
Big Head??
A little off topic.. but since it was mentioned.. I"m going to ask...
Is the Banks Big head Actuator Adjustable?? Can you turn the shaft in and out to increase or decrease the spring tension??? Just a question for a friend that has one...
I was always curious as to why Banks sold this.. but I under stand the thinking behind it with the increased drive pressures.. adjustabliity would be key.. (and not having to use boost regulator/controller.)
Thanks,
Bryan
Is the Banks Big head Actuator Adjustable?? Can you turn the shaft in and out to increase or decrease the spring tension??? Just a question for a friend that has one...
I was always curious as to why Banks sold this.. but I under stand the thinking behind it with the increased drive pressures.. adjustabliity would be key.. (and not having to use boost regulator/controller.)
Thanks,
Bryan
02-15-2006 | 09:32 PM
#42
Thread Starter
Banned
Joined: Jul 2004
Posts: 394
Likes: 0
From: Juneau, ALASKA
1. it's adjustable, but only the same way as the factory one is. Ther adjustment is critical to get enough pre-load on the valve so drive pressure doesn't open it, but if you adjust it too much, then it won't open as far. You still have to use a boost controller if your boost levels aren't where you want them.
2. No I didn't buy it, I started from scratch.
3. It'll get bolted on later this week or early next week....the rest of the hot/cold piping parts are showing up, then it's fab time.
2. No I didn't buy it, I started from scratch.
3. It'll get bolted on later this week or early next week....the rest of the hot/cold piping parts are showing up, then it's fab time.
02-27-2006 | 01:54 AM
#43
Registered User
Joined: Feb 2005
Posts: 47
Likes: 0
From: Peoria, IL
Since you fabbed the collecter backing plate, do you also plan on welding two pipes onto the plate just like a homemade megamouth and then connecting it to the downpipe. Nice writeup, its helping me figure out what I was trying to accomplish in another thread.
02-27-2006 | 02:36 AM
#44
Registered User
Joined: Dec 2005
Posts: 74
Likes: 0
From: Europe - Finland
Mystique of drive pressure.
I've been trying to comprehend, how in the earth is it possible, that drivepressure can actually be lower than boost pressure?
I know of two separate reliable sources that have this phenomena going on. First we have these people: http://tractorpulling.valtra.com/frameset.htm
Their mechanic told me the drive pressure is about 30% less than boost pressure.
Another set of people are the hobbyists (from that part of my country where that above pulling tractor is from) tinkering with 3.0 liter swirl chamber IDI Mercedes Benz passenger cars. They're using HX40's. They have reported similar results after careful pressure measurements.
BTW those MB's can haul butt. Seriously. A few attempts on a quarter mile track have resulted in just under 13 sec times, topped off with great traction difficulties.
I do not doubt these drivepressure findings.
I merely have trouble understanding how in the earth is this possible? In my books a turbocharger will have more drivepressure than boost.
Can anyone on this board offer a technical insight into this phenomena?
I've been trying to comprehend, how in the earth is it possible, that drivepressure can actually be lower than boost pressure?
I know of two separate reliable sources that have this phenomena going on. First we have these people: http://tractorpulling.valtra.com/frameset.htm
Their mechanic told me the drive pressure is about 30% less than boost pressure.
Another set of people are the hobbyists (from that part of my country where that above pulling tractor is from) tinkering with 3.0 liter swirl chamber IDI Mercedes Benz passenger cars. They're using HX40's. They have reported similar results after careful pressure measurements.
BTW those MB's can haul butt. Seriously. A few attempts on a quarter mile track have resulted in just under 13 sec times, topped off with great traction difficulties.
I do not doubt these drivepressure findings.
I merely have trouble understanding how in the earth is this possible? In my books a turbocharger will have more drivepressure than boost.
Can anyone on this board offer a technical insight into this phenomena?
02-27-2006 | 11:12 AM
#45
Muted User
Joined: Jan 2005
Posts: 640
Likes: 0
It is totally possible, and actually quite common when things are sized right. The reason is straight out of thermodynamics. The exhaust gasses are hot, very hot. So they have a great deal of internal energy. The turbine (all turbines actually) expand and cool the hot gasses, extracting that energy to create the power to drive the compressor. Think in terms of energy, not just pressure. If the temperature of the exhaust was only as hot as the temperature of the air in the compressor section, then yes, you would be correct, it would be impossible for there to be less drive pressure than discharge pressure. BUt those exhaust gasses are very hot and contain lots more energy, (even while at much lower pressures), than cooler air.
Remember what the turbocharger is.... it is an exhaust-heat driven gas turbine driving a centrifugal compressor. Its really two machines closely coupled. The gas turbine is by all definitions a HEAT engine.
KP
Remember what the turbocharger is.... it is an exhaust-heat driven gas turbine driving a centrifugal compressor. Its really two machines closely coupled. The gas turbine is by all definitions a HEAT engine.
KP