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post #1 of 21 (permalink) Old 03-03-2009, 12:18 AM Thread Starter
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True Twin Question

Why has nobody built a set of true twins? One per bank...... Can you flow more CFM with Compounds?

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post #2 of 21 (permalink) Old 03-03-2009, 12:25 AM
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Re: True Twin Question

If you planned to have the engine ingest the mass flow of air you wanted with a manifold pressure of between 50 and 60 or so lbs (preferably less than 55) you would be fine running a single stage using parallel turbochargers.

And there's only one type of twins.
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post #3 of 21 (permalink) Old 03-03-2009, 12:34 AM Thread Starter
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Re: True Twin Question

Soooo if I ran a two 38's, each feeding its own bank, what would/could be expected performance wise?

Compounds are not considered twins correct?....... Way i thought I undrstood it was that a twin turbo system was two independent chargers feeding a bank or an equal amount of cylinders as the other

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post #4 of 21 (permalink) Old 03-03-2009, 12:44 AM
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Re: True Twin Question

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Originally Posted by Powerstroked162 View Post
Soooo if I ran a two 38's, each feeding its own bank, what would/could be expected performance wise?

Compounds are not considered twins correct?.......shrug: Way i thought I undrstood it was that a twin turbo system was two independent chargers feeding a bank or an equal amount of cylinders

Cowboy Steve

I suspect that it would work fine for a low pressure setup with excellent head/cam work making 800 - 1000hp in the 5000 to 7000 rpm range.

I hope you see how bad of a fit that would be for a 7.3 at present. At least, one running production based cast heads and Heui injectors. The 38R wouldn't be "happy" above 40 or so lbs. And even that is pushing. It's hard to make 800 - 1000hp at 40lbs of boost with a 7.3L 2v head.

And I thought "twins" was a simple as each charger being identical. Or can we have fraternal twins?

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post #5 of 21 (permalink) Old 03-03-2009, 01:01 AM
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Re: True Twin Question

Problem is you would be in the same boat as a single, there is no advantage in any way, shape or form.

Two littler chargers (like ones designed for 3.6L motors at the respective rpm) would respond the same as a 38r single would. Then you would have the problem of balancing the MAP pressure of each head, and manage two chargers instead of one. STUPID more maintenance to no advantage.

Compounds work together.......little charger to light, big one to support the top end. The true "twin" (one per bank) is overcomplexed single charging. Waste of time IMO, if sized properly, they will either be laggy on the bottom or restrictive on top just like a single, just twice the PITA.

PS this is in refrence to TRUE "twins" one per bank.

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post #6 of 21 (permalink) Old 03-03-2009, 01:25 AM
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Re: True Twin Question

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Originally Posted by moore20017.3 View Post
Problem is you would be in the same boat as a single, there is no advantage in any way, shape or form.

Two littler chargers (like ones designed for 3.6L motors at the respective rpm) would respond the same as a 38r single would. Then you would have the problem of balancing the MAP pressure of each head, and manage two chargers instead of one. STUPID more maintenance to no advantage.

Compounds work together.......little charger to light, big one to support the top end. The true "twin" (one per bank) is overcomplexed single charging. Waste of time IMO, if sized properly, they will either be laggy on the bottom or restrictive on top just like a single, just twice the PITA.

PS this is in refrence to TRUE "twins" one per bank.

Fwiw, a simpler and possibly more widely accepted term might be Parallel.
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post #7 of 21 (permalink) Old 03-03-2009, 01:34 AM
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Re: True Twin Question

I stand corrected. Parallel is "twin" and Sequential is "Compound".

What I said above still stands correct, Parallel is just like having a single, just twice the PITA.

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post #8 of 21 (permalink) Old 03-03-2009, 02:07 AM
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Re: True Twin Question

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I stand corrected. Parallel is "twin" and Sequential is "Compound".

What I said above still stands correct, Parallel is just like having a single, just twice the PITA.
Sequential is actually where you start on the small charger and a valve shifts the exhaust gas flow over to the larger charger progressively as the rpm/exhaust energy increases.

Compound literally means the pressure ratios are compounded because the outlet of the first stage is run through the inlet of the second stage, such that the second stage compounds the pressure ratio of the first.

Might as well get an even playing field while we're at it. I'm not saying that has to be the definition of each, but those seem to accurately describe them.

Your conception about a parallel setup being equally limited to the performance of a single charger is correct. No matter how many chargers you run in parallel, it's still a single stage, and is limited as such.
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post #9 of 21 (permalink) Old 03-03-2009, 03:29 AM
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Re: True Twin Question

How about Parallel Sequential's?


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post #10 of 21 (permalink) Old 03-03-2009, 04:06 AM
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Re: True Twin Question

I've heard rumors of that.
but I don't have that kind of money. as it is I"m going to be saving like mad for compounds...

Dan
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