Compound turbo 3B (1 Viewer)

[Dougal]

Here is how i was going to fab up my next manifold. It has several bennifits:

easier to weld up
can utilize divided manifold on large turbo making it more effecient and spool faster
turbos can be changed out easily for different ones (less welding)

Drawbacks:
will add turbo lagg on small turbo during normal accelleration. during towing or really slow accellerations the small turbo will still spool at low rpms. Its boost will just be delayed.

Because the flex pipes are downstream of both of the turbos the fabing is much much easier and dosent have to be as exact. I would recomend this way (in the pic). I did it with the small turbo first and getting it to fit properly was very tedious. I 'll draw a pic later for you on how mine is currently.

View attachment 657746

That is essentially the setup Borg Warner are running with some production diesels. The advantage is your small turbo can be smaller than it could be as a single, the disadvantage is you need more valves and more control over the system.

Depending on the sizing, you may need a bypass around the compressor of the little turbo. A spring-loaded valve so if boost gets higher from the big turbo than the little, that it can bypass the smaller compressor and head straight to the intake.

Again depending on the sizing, you might need to get clever on a bypass for the small turbine. It's the switching of this bypass that normally needs computer control to avoid a valley of death.

 

[gerg]

The external wastegate in the large turbo first design sits between the two turbos and only opens at desired small turbo pressure limiting its boost. A very large wastegate will really allow for alot of exhaust to escape straight to the tail pipe bypassing the small turbo and prevent boost creep. I have found a true 60mm in and out wastegate that should breath really well. Most are 60m in with 44 out which would most likely still work.

As far as large turbo compressed air bypassing small turbo I think that as long as the small turbo is still sized for the origional engine and the compressor housing is generous to allow for good air flow, I wouldnt think that a bypass system wouldnt be needed necessisarily. That actually sounds like a real sequential system. I had always planned on utilizing small turbo for compound pressures so I actually dont want to bypass it. That would be for pressures greater than 1 turbo could feasably produce by itself (30 psi and up).

 

[gerg]

Here is a drawing of my current manifold. My main problem with this set up is the wastegate sits between the two turbos and has to fit with the main dump pipe from small to large turbo. Essentally you have to weld two solid sections of steel pipe that are different length that fight eachother. I also used v-band wastegate conection which suck for this stuff because they have to be very precisely fit in order to actually be clamped. In order to change my little turbo I have to reweld this problem section and make it all fit again, which was the hardest part of the whole manifold.

The other set up sidesteps this by allowing for the use of flex pipe due to low pressures. I guess I could have used flex pipe in between on mine, but I thought it would leak as the pressures are pretty high there.

 

[wildbj70]

Hey guys like your post on compound and sequential turbos on a 3b
Very interesting would love a set up like that
But I'm happy with my single 3b turbo

My only question I have is u talked about modifying your injection pump for the turbo set up
What has to be done or what can u do to the injection pump for a turbo system other then just turning up the fuel
Can u modify it for boost?
And if so how?
Any info on that would be a great help
I have been told if u modify the pump for boost I can get more power from the turbo system
Is this true???

 

[gerg]

The pump only delivers fuel (power). However, it cannot be burned unless there is enough air. Turbos bring more air. Intercoolers bring more air if the turbo boost is hot enough (essentially makes the turbo more efficient).
My pump has not been modified yet to deliver more than the maximum amount of fuel in stock form. It now has to be modified by an injection shop.

 

[cody c]

Hey guys like your post on compound and sequential turbos on a 3b
Very interesting would love a set up like that
But I'm happy with my single 3b turbo

My only question I have is u talked about modifying your injection pump for the turbo set up
What has to be done or what can u do to the injection pump for a turbo system other then just turning up the fuel
Can u modify it for boost?
And if so how?
Any info on that would be a great help
I have been told if u modify the pump for boost I can get more power from the turbo system
Is this true???

There was a couple options posted in another thread, one being the P pump of a cummins 4BT adapted to the toyota, the other option being a shop in vancouver that Gerg mentioned, who could modify it for around or over $1K to push more fuel than the stock cummins P pump.

 

[wildbj70]

Has anyone ever Installed a P pump of a cummins 4BT to the 3b
If so what has to be done to the pump or engine to have the P pump of a cummins 4BT intalled
And does anyone have pics of this done on the 3b

 

[cody c]

Has anyone ever Installed a P pump of a cummins 4BT to the 3b
If so what has to be done to the pump or engine to have the P pump of a cummins 4BT intalled
And does anyone have pics of this done on the 3b

Please read post #8.

Dougal is a bit of a diesel geek, so if its been done he'd probably know about it, Im guessing it hasnt been done, but it should be doable maybe with some machining.

 

[Dougal]

Has anyone ever Installed a P pump of a cummins 4BT to the 3b
If so what has to be done to the pump or engine to have the P pump of a cummins 4BT intalled
And does anyone have pics of this done on the 3b

I doubt a 3B would be strong enough to take advantage of the fuel available from a 4BT P pump. A 4BT A pump or VE pump is a more suitable upgrade if they can be made to fit and work.

 

[cody c]

Hey Dougal, was/is there any alternatives to the subaru STI turbos for the smaller sizing, Ive been following ebay on and off for a bit and ive only seen the non STI turbo's on at decent pricing ($175 or so-used)?

Thanks.

 

[Dougal]

Hey Dougal, was/is there any alternatives to the subaru STI turbos for the smaller sizing, Ive been following ebay on and off for a bit and ive only seen the non STI turbo's on at decent pricing ($175 or so-used)?

Thanks.

I know very little about subaru turbos. But I do know the STI's got large singles, the twin turbo Legacy (liberty in Aus) has two turbos which are smaller and run sequentially. One of them could be a better bet.

 

[cody c]

Ive been looking for a decent priced sti turbo and the bigger housing.

Sill no luck, does anyone know of a similar sized turbo that would fit the bill in order to expand my options/availibility?

 

[slowandsteady BJ]

I know very little about subaru turbos. But I do know the STI's got large singles, the twin turbo Legacy (liberty in Aus) has two turbos which are smaller and run sequentially. One of them could be a better bet.

Those Legacy compound turbos are sweet! We dont get them here, all our cars are de tuned. Parts are often smaller (like turbos) or in the case of the Legacy missing all together. My S4 even came with smaller turbos than one would see in your neck of the woods, I suppose its an importation thing as we tend to have a lot of rules....about everything.

Anyway.... hijack off.
Keep the idea alive Cody because it will be great. Perhaps an inspirational video.... anyone know who made this?

http://www.youtube.com/watch?v=so6F-Wn5qBo

 

[gerg]

Actually I thought I removed that video. Compared to other compounds its pretty lame, but it was fun to make. I have learned enough to know that I don't know much. This fall im hoping to get a bit of work done on it.

 

[slowandsteady BJ]

Actually I thought I removed that video. Compared to other compounds its pretty lame, but it was fun to make. I have learned enough to know that I don't know much. This fall im hoping to get a bit of work done on it.

So that was you Gerg...... i did kind of wonder. Cool stuf. Do you have a build link with some pics? Why did I think your compound setup was in a 40 series? I might just be out to lunch, wouldn't be the first time.

 

[ForealBoreal]

Those GTB legacy rip. They are fast.
I imported my buddy an STI but I would say it is quicker. Yet again that is comparing a fast family car to a rally car.

Simon Liew put a sti turbo I believe on a 1hz.
I would think it would work pretty good.
though i don't know if it would do good in a sequential set up.

 

[cody c]

Well, i talked to my friend who is into the STI's (subaru's not VD) and has owned a couple of them and now has a mitsu evo.

Anyway, it sounds like the WRX turbo is a little bit smaller and boosts quicker than the STI turbo. The STI turbo boosts a bit later but makes more power, and is a popular swap for the (non-STI) WRX guys, they also like the oversized BOV from the STI turbo.

Point is, the WRX turbo is apparently a pinch smaller and boosts quicker, but is easier to find and cheaper had, and is what I am going to see if i can find. Im still not sure about finding the larger housing for the merkur turbo but Ill leave that for next week.

 

[gerg]

Here is my build thread:
https://forum.ih8mud.com/diesel-tech-24-volts-systems/407381-3b-compound-turbo-25psi-boost.html

.63 turbine housing. For a standard t3 (merkur) you would be looking at the 49mm exducer
http://www.designengineering.com/ca...usa/turbine-housings/t3-turbine-housing-ar-63


When you say WRX turbo, that includes many different types. VF28, VF 52, TD04L... the list is a long one. Here is a link.
http://www.wrx.com.au/forum/viewtopic.php?f=56&t=53416

 

[cody c]

Here is my build thread:
https://forum.ih8mud.com/diesel-tech-24-volts-systems/407381-3b-compound-turbo-25psi-boost.html

.63 turbine housing. For a standard t3 (merkur) you would be looking at the 49mm exducer
http://www.designengineering.com/ca...usa/turbine-housings/t3-turbine-housing-ar-63


When you say WRX turbo, that includes many different types. VF28, VF 52, TD04L... the list is a long one. Here is a link.
http://www.wrx.com.au/forum/viewtopic.php?f=56&t=53416

Im refering to the TD04L wrx turbo. Hope it will work, just got one off of ebay.

The shipping on that exhaust housing is a bit much ($50) on a $130 item, maybe Ill call them and see if they will ship it snail speed, or order it to MSO.

 

[gerg]

I have a couple of those td04L wrx turbos on my shelf as well. Mainlander ran one with good results for low end boost. He felt it ran out of steam around 2700rpm. It is on the smaller side, but is a good fit for the 3B in my opinion. Would work well for normal driving rpms. The compressor maps really well for it for higher boost, but you would definately need to upgade to a 360 thrust bearing.
The .63 housing is more common on older t3 turbos rather than the .48 as far as I have seen in the junk yards. I have a .63 but im running it as the large on my comounds. I also have a couple .48s but they are only really good for singles.