Internal WG Help - Compounded 4bt

A

AcIdBuRn02ZTS

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Jun 30, 2013
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Hey guys...

Trying to slowly but surely work out the bugs in my build and at the moment, I think my current wastegate plumbing is holding me back.

Setup as follows...

120hp VE pump 4bt
6cm hx30w (high pressure)
12cm wh1c (atmosphere) wastegate disabled.

Currently, the hx30w is getting its signal from its compressor housing. As a single charger, it would run ~23psi.

Am I correct in thinking that with it setup as it is currently, after 23psi, the wh1c is doing the majority of the work?

At full boost currently, Im seeing around 35psi which is fine with me because I currently dont have head studs, however, this fall that will change and I'm shooting for ~55psi (~300whp)

What do I need to do to let the hx30w actually compound boost without risking overspeed. I've heard of guys building spring type actuators to open the gate via drive pressure... is that the only way of doing it?

I have a low pressure boost gauge on order that will be plumbed inbetween stages just to verify what I'm thinking...

What can I do here? I want the chargers to share the load and get fairly close to an equal PR. Is that possible using an internal gate?

I've done quite a bit of searching but most are running large external gates or something custom such as what I mentioned above.

Input?

Thanks guys
-Chris
 
Easiest thing you can do is put in a lot more injector to drive the turbos harder. If you close the wastegate, you might make more boost, but you'll probably make less power. That was the case on my truck anyways. Drive pressure went through the roof.
 
Hmm.. I'm somewhat concerned about overworking the wh1c if its providing the majority of the boost up top... I can drive the chargers harder easily enough but its functioning like a sequential system instead of a compound system.

I dont want to close off the gate all together on the 30, but as it stands, the truck hits a wall around ~25psi until rpm is up high enough that the wh1c can basically take over (keep in mind... 4bt)

As a single, the hx35 or wh1c really flop on the 4bt without massive overfueling and I really dont want to drive the charger that hard (50+psi)
 
If you want both turbos to run the same pressure ratio, then get dual port actuators for both.

Plumb the top side of the actuator to the pressure side of the turbo it's on and plumb the underside of the actuator to the intake side of the turbo it's on. This lets the actuator see the ratio of pressure across the turbo instead of boost referenced to the atmosphere.

For example: if each turbo had a 15psi actuator plumbed as described above, each turbo would run a pressure ratio of 2. Multiplying the two together would give you a pressure ratio of 4, or 44psi boost.

In practice, you only need a dual port actuator for the little turbo since the intake side of the big turbo should be atmospheric pressure anyway.

However, while this works in theory, I've never tried it.

Also, it might help to increase the size of the wastegate port a bit on that HX30. This would let the larger turbo see more exhaust with less backpressure. In the past, I've bored internal ports on a mill and made larger flaps out of old valves with a little lathe work. If you wanted to keep it simple, you could increase wastegate flow with your current flap size by porting with a die grinder.
 
PHP:
One more thing:

Even though you have compounds, it still takes a lot of fuel to light your WH1C. Your HX30 isn't magically creating more exhaust gasses to help spool your primary. It will, however, allow you to run the extra fuel it takes to spool the WH1C without creating excess EGTs.
 
AcIdBuRn02ZTS said:
Currently, the hx30w is getting its signal from its compressor housing. As a single charger, it would run ~23psi.

Am I correct in thinking that with it setup as it is currently, after 23psi, the wh1c is doing the majority of the work?

At full boost currently, Im seeing around 35psi which is fine with me because I currently dont have head studs, however, this fall that will change and I'm shooting for ~55psi (~300whp)

What do I need to do to let the hx30w actually compound boost without risking overspeed. I've heard of guys building spring type actuators to open the gate via drive pressure... is that the only way of doing it?

I have a low pressure boost gauge on order that will be plumbed inbetween stages just to verify what I'm thinking...

What can I do here? I want the chargers to share the load and get fairly close to an equal PR. Is that possible using an internal gate?

I've done quite a bit of searching but most are running large external gates or something custom such as what I mentioned above.

Input?

Thanks guys
-Chris
Click to expand...

first things first, get a gauge in the cold pipe so you can see what the primary is doing. You'll likely need to use a stronger gate actuator or fab a spring gate to more easily regulate the pressure ratios.
 
Got a atmosphere gauge installed.... after 23psi, the wh1c builds boost to 30 as the hx30 stops working.... basically a sequential setup at the moment.

The wh1c starts providing pressure pretty early (1500rpm or so) and doesn't seem to have an issue spooling...

I think I'm going to hold off on tinkering until I pull the head and get it o-ringed this fall... then I can really start to play.

Sent from a pay phone... using Tapatalk v2.0
 
Sounds like your secondary is being stalled out from having too much drive pressure in the hot pipe driving the primary.
Start using the wastegate on the primary, and watch the secondary start compounding the charge.
I think you said you are driving the secondary with 55psi.
Your primary is sending 30psi to the secondary.
I'm gonna guess that there is at least 35-40psi drive going to the primary when the gate on the secondary is fully open and your WOT.
This only creates a differential across the secondary of only 15-20psi, maybe less. (Actual drive pressure used to compound the charge coming into it.)

By using the primary's gate, you will drop the pressure in the hot pipe between the turbos, lose a bit of charge to your secondary, but will be able to start compounding the charge from the primary by creating a bigger differential across the secondary's turbine.
 
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