stevecivic

Thanks for the reply. Some twin turbo setups on dodges use the stock HX35 with max efficientcy by 34psi and a larger turbo with max efficientcy at around 80-100psi. So you are telling me that the hx35 will only last a few days? Some of these cummins are rumming close to 5000rpms and 100psi of boost. If you saw the pic i am not talking about sequential turbos like on the rx7's.

lonestarion

there is a difference between compound & twin tubo set up.
here it is.

twin turbos use exhaust to drive both turbo at the same time.

compound set up uses exhaust to drive a primary turbo, then uses the
cold side to drive the secondary turbo which feed the engine.

as far as anyone trying this, i havent heard of it yet. most people just blurt out
the same answer as above, not actualy knowing the difference or not
knowing there is a difference in set up. and to answer your question as to,
can it be done? sure it could be done. whould ther be a better gain over a TT setup?
or even a single turbo? dont know, but it might be possible. you just have
to get the combination dead on.

WTF

PoweredT3A6

The pictured setup is not one compressor side driving another exhaust side! Same manifold is driving both turbos.

PoweredT3A6

If you look...the compressor out of the lower turbo is plumbed in to the intake side of the top one...that doesn't increase flow in the second really, it just needs to be linked through the same charge pipe so it goes through the larger turbo. Exhaust STILL drives both turbos...and...on the cummins, the first turbo would lose compression and bypass through a valve/flapper setup thats why it wouldn't spin to 5 gillion rpm and die in 2 days.

PoweredT3A6

And...efficiency would need to meet in the middle...like small turbo would need to lose eff at a certain boost/RPM that is closer to redline, but it would be okay for it to start to taper off sooner.

aero

In the compound setups the turbo is not "bypassed". Air is compressed by the first stage, then compressed again by the second stage, then typically intercooled. The first turbo is the "low" pressure turbo and the larger of the two. The second turbo is the smaller or (high pressure) turbo, then flows through the intercooler.

The compound setups allow the use of pressure ratios far above what a single centrifugal compressor of practical size can reach, and also allow very good response.

There is no flapper that bypasses the smaller turbo.

PoweredT3A6

Depends on how the unit was setup, like I said if you are using similar trim turbines then you would be fine...BUT if there was a drastic difference in trim, you would overrun the maximum rpm of the smaller wheel. I've worked on many-a-cummins.

0b00st0

100% wrong. Both turbos are exhaust driven. The difference is that the smaller of the two is driven first. Then the output of that turbos exhaust drives the second larger turbo.

Now the secondary larger turbo's compressor feeds the primary smaller turbo. This is so that the first turbo is always working with out intake loss.

Now the way compounding works is that both turbos are set to have a pressure ratio of 2.5 or so. IT IS COMPOUNDING, meaning that you multiply them together to get the amount of boost going to the engine, so you have a pressure ratio of 6.25 (2.5 * 2.5). Boost seen by the engine will be (6.25 - 1) * 14.7 = 77psi.

Compressors are pressure multipliers, thats all.

The is the same effect as increasing the exducer size of the compressor wheel (lowering the trim). It moves the combined efficiency graph up and a little to the right giving you a slight increase in flow and retained efficiency at massive boost levels.

This technique is simply used to counteract the fact the turbos compressor is not very efficient at high pressure ratios.

PoweredT3A6

Also, AERO you must be new and quoted that from another site...because you stated the obvious with most of your paragraph: "The first turbo is the "low" pressure turbo and the larger of the two. The second turbo is the smaller or (high pressure) turbo, then flows through the intercooler. [/color]

The compound setups allow the use of pressure ratios far above what a single centrifugal compressor of practical size can reach, and also allow very good response. "


LOL