Leadfoot

This is just a crazy idea I have had for a while.

Would it work if a person was to place twin turbos in parallel? By building an exhaust manifold with a turbo flange from the front three cylinders then another turbo flange from the last three cylinders? After each of the turbos both of the pressurized outlets would by siamesed back together and the exhaust from both would be siamesed back together. The reason for making both outlets go back together is to maintain equal backpressures. The benefit is you gain large air flow numbers at lower pressures. By using small turbos such as HX35 or HX35 is the availability of stock turbos and the impeller speeds will much lower. Lower impeller speeds will increase longevity of the turbos. Turbo lag should be at a minimum since the impellers are small and spool up very quickly. Another benefit is the lower pressures will decrease the need for head studs and o-ringing machine costs. I'm sure someone else has tried this just wondering what you guys think.

An even better exhaust manifold would be to use cylinders 1,3,5 for one turbo and cylinders 2,4,6 for the second turbo.

Forrest Nearing

you get a lot of air flow at low pressure out of the turbos, but the ENGINE can not accept all that air flow... we're not worried about CFM (air flow), we're worried about lbs/min (air MASS)

to get more oxygen into the engine, we need to compress it furthur...

if we had an engine that was twice as large, we would need more CFM at a given pressure...

if you want an idea of how the truck would feel with a pair of HX35's on it, go get a turbo off of a 12-14 liter big rig and put it on your current engine...

it will take forever to spool, and it won't make enough boost to make any power...

Scotty

Splitting the front and rear cylinders would make it a pulsing nightmare.
Plumbing it the way you mentioned at the end of your post would work better but its still not viable. As per Forrests post.
You could have true dual exhaust though.
Scotty

Artsi_L

Dividing plumming among front/back three cylinders is more clever idea than one would initially think.

Most efficient arrangement for any 4-stroke engine using a turbocharger, is 3 cylinders per turbo. This is exactly how Cummins does it in stock form. HX35 has a split turbine housing, to keep interfering exhaust pulsations apart from another.

I know of one special high power diesel application designed for US army by a very reputable engineering company, which uses two small turbos in parallel in a 6 cylinder diesel engine. They're plummed as described above.
That engine originally comes out of the factory with one turbo.

I have no expertise to make sound evaluation on real world gains between 6B Cummins HX35 vs. two small turbos.
There are gains, but I'm afraid they're neglible with stock fuelling. Tuningchips and fuelling boxes may increase gain rates.

Mercedes Benz will use three turbos in their upcoming V6 diesel engine. That will be two-stage charged (i.e. compounded). Two small chargers on either side of the engine, plummed into one final large turbocharger.

BMW and MB have bypass valves in their turbocharging systems to prevent excessive chargepressures. I believe we're talking about less than 30psi charge pressures. Nevertheless it does employ two-stage charging in a transition phase to build up solid full boost pressures, which would be unattainable with a single charger.

More here:
http://www.seriouswheels.com/top-200...LK-320-CDI.htm

btw, that fuel consumption translates to 31MPG.


- Arto