Thread: Twin turbo 4BD1-T

I would like to know which kind of gerabox have the vehicle to survive the torque of the engine?

He's stuck a TH-700R4 behind it.The adaptor kit is detailed in www.DieselSwapper.com - Accurate Technical Services, LLC.

Matt.

Originally Posted by Chucaro

I would like to know which kind of gerabox have the vehicle to survive the torque of the engine?

The gearbox didn't survive, it was a 700R4 automatic. It's since been replaced with a tremec 6 speed manual but the engine has been detuned and a large single variable vane holset turbo fitted.

Yes I went through a few transmissions thanks to the power of the twins, I also blew a head gasket after pegging the 60psi boost gauge. I dont know how much max boost was but I would guess around 80psi and power in the 450rear wheel horsepower range. I only installed a single turbo when we put the new head gasket in so I could work on getting the new T56 6 speed trans sorted out. Everything is going great so far and I am installing air conditioning in the truck right now but when its done I will be reinstalling the Twins and installing a Dual friction clutch that should hopefully hold the power of the twins.

Originally Posted by carcrafter22

Yes I went through a few transmissions thanks to the power of the twins, I also blew a head gasket after pegging the 60psi boost gauge. I dont know how much max boost was but I would guess around 80psi and power in the 450rear wheel horsepower range. I only installed a single turbo when we put the new head gasket in so I could work on getting the new T56 6 speed trans sorted out. Everything is going great so far and I am installing air conditioning in the truck right now but when its done I will be reinstalling the Twins and installing a Dual friction clutch that should hopefully hold the power of the twins.

Welcome to AULRO, enjoyed your build up thread on the 4bt forum.

Simon

Originally Posted by abaddonxi

Welcome to AULRO, enjoyed your build up thread on the 4bt forum.

Simon

x2 on both counts.

Thanks Randy for you contributions to advancing the cause for the 4BD1T.

For those that may not know:

Twin turbos is a misleading description. I don't like it for that reason, but it has entered the culture of performance diesel enthusiasts. IMHO twins should be confined to describing a pair of identical turbos, such as might be used on a V8 engine (one for each bank).

In the context of diesel performance, twins is used for describing systems with 2 different size turbos connected in series for sequential/compound/2 stage operation. The turbo that is closest to the engine operates at higher pressure (HP) than the one furthest from the engine (LP).

Exhaust gasses from the engine, first drive the HP turbine, the gasses that exit this turbine then drive the LP turbine. Because drive pressure drops across the HP turbine the exhaust gas expands, so the LP turbine must be larger. A wastgate is often used at the inlet of the HP turbine and it will divert exhaust gas to the inlet of the LP turbine.

Air from the air filter enter the inlet of the LP compressor at atmospheric pressure and is compressed before entering the inlet of the HP compressor where it is compressed further. So the HP compressor is smaller than the LP compressor.

The advantages of these turbo systems are:

Boost pressure increases sooner (at lower engine revs) because of the small HP turbo and because it is helped by the LP turbo at low engine revs.

Higher boost pressure is possible because single turbos are very inefficient at these high pressure ratios and expend much of the input energy just creating heat in the induction air (this is the nature of radial flow turbines - axial flow turbines as used in steam turbines or high performance compressors are more efficient).

Turbo technology has advanced by:

1. wastegates that allowed faster spooling by using smaller turbines through controlling turbine overspeed and excessive drive pressure rise.

2. variable geometry turbines - these have replaced wastegate controlled turbos on most diesel vehicles sold in the past few years (e.g. all Land Rover diesels since the TD5).

3. staged or compound turbos - the current "state of the art'

More manufactures are now using 2 stage turbos. Borgwarner is making these turbo systems for some of the big name vehicle manufacturers.

There are other technologies, such as using electric motors to drive compressors until engine revs increase sufficiently.

Originally Posted by Bush65

There are other technologies, such as using electric motors to drive compressors until engine revs increase sufficiently.

Many of the big EMD engines made by the Electro Motive Dision of GM have a gear train that engages to drive the turbocharger at start-up and disengages when the engine is producing enough exhaust gas to drive the turbocharger. These are two stroke engines where the turbo not only provides an amount of over-atmospheric boost, but provides an excess of inlet air to scavenge exhaust gases. EMD engines thus equipped do not have the iconic GM Roots type blower, only the turbocharger. This option has been available for many years.

Twin stage superchargers were used in the 1930's on racing cars in an effort to find more horspower by using much higher inlet pressure. It was found that twin stage blowers consumed less power to drive them than a single blower of comparable output.