[Stan Weiss]

If I have an engine and 2 turbo charges of a fixed size. Will I make more HP if I do a twin turbo charger setup or if I compound them?

Thanks,

Stan

[johnta1]

I'd be interested in this as well?



Speedtalk had a good thread on this, think Panic(?) might have been in it?
edit: it was Warp speed I think

[JSPONT]

I would think separate, not compounding. The turbos will only flow so much so I think you will "peak" them when compounding. If 1 is good for 1200h.p. if you compound it it can still only flow enough for 1200 h.p.
If you use one for each bank assuming it's a v8, you could possibly get 1200 per side.
Some guys compound for spooling. I think the turbo technology is past that.

This is just my .02 no math involved just guessing.

[johnta1]

But what of the 'boost' of the first turbo going into the 2nd one?

The 1200 HP is from 1 bar being compressed (from 8 cylinders?)
If you had 2, it would be from 4 cylinders?

Like having 2 bar instead of 1 bar being compressed with the 2nd one?
1200 HP compressed going into another turbo?

[JSPONT]

I am not saying 1 bar, I am saying full potential, if you are pushing thru a choke point there is only so much you can push. You get to a point when a turbo will make no more power.
I have 2 boost gauges, one for boost one before the the turbo , when those numbers become even, or the before turbo higher than boost, it does not matter how much psi you turn it to, it hits a ceiling.
if you keep them separate, you can make more "usable" boost on each side.

Like I said just my .02

[johnta1]

Well, by Stan's question, have to figure 2 turbos.

Say 600 HP supposedly out of each one.
Total 1200 HP using one for each side of the Pontiac V8.
(for example)

Would it still be 1200 HP with one per side (4 cylinders) or one compounded by shoving 8 cylinders of boost into one turbo?



Also just wanting some expert opinions.
Not a clue really on which is better.

I personally had thought of trying the compound setup.
But the logistics of all the hardware routing probably easier just one per side.

[Tom Vaught]

Read up on inter-cooling, mass flow, density ratios, and flow restrictions thru a pipe/inter-cooler and you will know the answer.

There is always a weak link vs a time under full load. Temp is a lot bigger player than most assume. But Stan already knows this stuff.

Tom V.

[Stan Weiss]

Yes Density ratio is very important. But doesn't what the size of the turbos are come into play?

Stan

[taff2]

What I've seen of compound setups - a big primary turbo (that is sized for the power output you require-say 1200hp) then pumps into a smaller secondary turbo which increases the density and boost even further. I assume the size (hp rating) of the primary turbo would be the limiting factor as I can't see how any more mass flow could go through the primary turbo than what it is sized for.

[Tom Vaught]

1) Large turbos when run at low speeds have high leakage rates, which cause poor low speed airflow capability.

2) Large Turbos need mass flow to provide the ENERGY to drive the large turbine wheels which also drive the compressor blades at the same time. Large turbo wheels are inefficient at low speeds.

Compound Turbos have smaller turbos downstream of the larger turbos. The large Turbo is moving air mass, but doing a poor job of it at low speeds, the smaller turbo is much more efficient at those speeds, picks up the ball, runs with it, and increases the HP of the engine where the large turbo has not come on line yet.

At some point the large turbo and the smaller turbo have similar flow rates and the boost is compounded efficiently.

At even higher airflows the large turbo tries to reach its highest efficiency but the smaller turbo becomes a restriction. Now the smaller turbo is controlling the total mass flow the engine can generate unless the smaller turbo is by-passed.

Look at Pictures #1, #2, and #3

#3 is a Hot Rodders attempt to reduce the airflow thru the small turbos turbine and make the larger turbos exhaust flow more efficient.

Tom V.

[JSPONT]

So Tom and Taff agree with me. Good to know, not that I would compound turbo charge anyway.

[Tom Vaught]

JSPONT.

Boost People have for years tried to match the low speed drivability of a small roots supercharger vs a larger turbo.

The small roots supercharger (example) 90 cubic inch per revolution Eaton Supercharger (used on the 3.8L Buicks and Fords) vs the Turbocharged early Ford 2.3L engines. 2.3L stuff gave you a bit more hp on the top end but drove and transitioned poorly at low speeds.
Turbo and Belt SC Guys have fought that OEM war for years trying to sell their parts.

So the VW Compound SC/Turbo deal was one of the first successful STAGED sequential boost systems. Roots at low speeds and Turbo at higher speeds. (They used a A/C type Clutch to turn off the Supercharger at higher speeds when the Turbo was doing its thing). Not compounded, STAGED.

I drove one of the 1st Staged VW systems in the USA (Borg Warner was doing the Turbo side of the design and the Borg Warner Head Engineer brought me the car (for my evaluation). It was a nice system. Only draw back was the A/C type clutch could not energize (at speed) to bring that SC device back on line without a noticeable dip in the power. You get the "clutch slip" right and the parts wore out quickly. Bad for warranty.

But the VW was impressive to drive except for that issue.
People (including Ford) tried Magnetic Particle Clutches vs the A/C type clutch with limited success, MP Clutch did not wear out but the unit was large and hard to package in the typical vehicle.

Tom V.

[Stan Weiss]

Wish I could remember how long ago it was that Chase Knight (Worked at Crane Cams) ran this combination.

Stan

[johnta1]

I found the link for the compounding, it was Warpspeed but in Eng-Tips forum

Twincharging

Lots of ideas info there.



From the SpeedTalk thread that led to the Eng-Tips thread

Compounding

[Tom Vaught]

Originally Posted by Stan Weiss

Wish I could remember how long ago it was that Chase Knight (Worked at Crane Cams) ran this combination.

Stan

That was before he moved the turbos higher and ran 3 smaller Turbos for better off line response on the "Golden Gator"
The 3 small turbos were not compounded, they were sharing the volume of the engine exhaust. The system WAS Compounded because the turbos (2 or 3) fed into the Roots Supercharger.

Dan Parker in Kalamazoo Michigan ran a similar Compounded Turbo/Supercharger system (just like your picture) for 3 years on his Dragster at US-131 and other tracks. I worked for Dan Parker and his partner for 3 years in the evenings (after my college classes) building race engines. I helped one of his employees build a turbocharged 351 windsor Ford van (similar to a few other mid engine drag cars at the time).
The employee kicked the driveshaft out of the vehicle (after the driveshaft was twisted 7 turns and pulled out of the transmission in a few seconds).
This was 1974.

The Picture should be before 1976 for the system you are posting about. Macinnis had a picture in one of his turbo books over the years of publishing that showed the 3 turbo system.

Chase Knight got a lot of his technical info from Don Hubbard who worked for Crane. Don.wrote a small pamphlet about Turbochargers for Harvey.
Hubbard was a Turbo Expert as well as a Camshaft Expert.
His "Everyday Driver" was a turboed/ triple webered 65 Jaguar.
Don H is mentioned in Macinnis books if you read the book carefully.

Tom V.

[Tom Vaught]

Here is a Picture of Dan Parker's altered before he built the Turbo/Supercharged Dragster. Heck of a racer.

Tom V.

[Tom Vaught]

Originally Posted by johnta1

I found the link for the compounding, it was Warpspeed but in Eng-Tips forum

Twincharging

Lots of ideas info there.



From the SpeedTalk thread that led to the Eng-Tips thread

Compounding

Did not read the compounding thread but the Twin-charging thread in Eng-Tips had some pretty accurate information.

Tom V.

[charlie66]

So you're turbocharging a turbo! lol!

[johnta1]

Bsically, yes.



This would be good for your 4 cyl.

[Tom Vaught]

You are correct Charlie.

WW-II aircraft did a lot of Turbocharger into Centrifugal Supercharger engines.

It basically allowed them to fly higher altitudes and get "ABOVE" the bad guys and attack them.
Also to fly at a higher average speed.

We have already had this discussion about cutting back on the boost, raising the compression ratio for the lower boost level, improving the driveability of your engine/vehicle, so why would you want to follow John's suggestion and run 60+ psi of boost with 6 to 1 compression ratio.
Lol! John is a bit behind the times on your 4 cylinder engine strategy Charlie.

Keep after the twin stuff, when you can, for your V-8 project.

Tom V.