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My question is on a 4bt can you run a t3 turbo off of two cylinders and then run the other turbo off the other two. I have done this on a gas inline 6 and didn't know if the turbos will spool up on a 4bt. I'm trying to put the turbos on each side of the motor.
 

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My question is on a 4bt can you run a t3 turbo off of two cylinders and then run the other turbo off the other two.
Sure, but you need to pair up cylinders 1 and 4, and then 2 & 3.

I think two GT25's from a Mazda Speed would work well.
 

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It should, but you're also cutting your CFM to each turbo by 50%. Basically twins on a diesel you need a low RPM turbo and an upper range one, similar to the new Ford Diesel setup so you've got more boost for the entire engine operating RPM. I dont see any advantages to separating the exhaust like you're wanting to do. Run both turbos off the entire exhaust.
 

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I'm doing it more for looks than performance only reason i was going to do it this way is so the headers have a little flex for the heat so they don't crack or break from shrinking i'm not wanting to run big boost numbers but i would like both turbos to spool up well so should i run a single stile header
 

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I don't see any advantages to separating the exhaust like you're wanting to do.
There is a huge advantage in spool up time, that is why six-cylinder diesels always pair up 1-2-3 in one side and 4-5-6 on the other side (with divided turbine housings, firing order 1-5-3-6-2-4). Our 4BT exhaust manifolds pair up 1 and 4, and also 2 and 3 on factory exhaust manifolds and split housings.

It would be the same concept, just with two smaller turbos. The two smaller turbos have a lighter mass and would spool faster. I would NOT recommend mounting them on separate sides - - the turbine wheel needs to be as close to the exhaust valve as you can get it!
 

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The more heat you can keep in the exhaust before the turbo the more efficient it will be. You don't want to have a long distance between turbo and exhaust ports as this is a good way to loose heat.
If all you want is looks you may not care about all that, and if that's the case just plop an extra turbo on the other side for looks, no need to make it functional...

If you want twin turbos, one on each side, a V type engine would be simplest, like this V6 in an f350:


I had considered a twin setup on my 4-53T, as I can get two 2 cylinder manifolds and they bolt on, but for now I just don't think it's worth the effort. I think the Detroit would be OK pairing cylinders 1-2 and 3-4, as they fire every time the pistons get to the top?

Grigg
 

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why do the turbine wheels need to be so close to the exhaust valve
The farther away, the less heat available to spin the turbine. It isn't just the pressure, the heat energy does a lot to move the turbine, too. If it weren't the case, all diesel manufacturers would mount the turbo in a different place.
 

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why do the turbine wheels need to be so close to the exhaust valve
While heat is a a very valid reason, capturing exhaust pulses is the main one.
The longer path your exhaust has to take, the more the pulse smooths out and loses energy.

This is also the reason for 6 cylinders splitting their exhaust into two pulses, exhaust pulses 240 deg apart seems to work the best. On a 4 cyl being 180 deg apart they get in the way of each other a little.
 

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Sure, but you need to pair up cylinders 1 and 4, and then 2 & 3.

I think two GT25's from a Mazda Speed would work well.
A GT25 will be almost too big even as a single, let alone twins.
I run a single T25 on my 3.9L Isuzu right now. With a 0.48 A/R exhaust housing it boosts whaere it should. The GT25 has more flow than the old T25 and as twins would only deliver useful boost at around 2500rpm. Too late for a 4BT.
 

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Sure, but you need to pair up cylinders 1 and 4, and then 2 & 3.

I think two GT25's from a Mazda Speed would work well.
I might have one for sale soon... The turbo that is...
 

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While heat is a a very valid reason, capturing exhaust pulses is the main one.
The longer path your exhaust has to take, the more the pulse smooths out and loses energy.
All valid points. And in the case of the OP wanting to have them on opposing sides of the 4BT block "for looks" one must also not only take into consideration heat loss, pulse wave diminishing due to distance, but also every additional curve leading up to and away from the turbo housing will also increase back pressure. Since the OP wants them on opposite sides, there is no way to prevent unnecessary distance and additional bends in the exhaust path.

I agree with DarylB, though...

 
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