Need some help deciding on which twin set up.

[YoungGun]

hey guys i need some help choosing a setup for twins, i have a 66mm id like to run up top and was thinkin of an s475 or s480 to go down below?? want a fun streetable DD with little to no lag. and good response thanks. p.s anyone got anything for sale. dual pumps or turbos please let me know.

[strokin02]

97 twin turbo on here has a set of 64/71/14 on top an a s480 for sell. Might even have a 66 for top also..

[ahale2772]

66/480 is far from no lag.

Yes, people do it all the time, but there are better options

[whitelightnin]

i run a 66/480 and you are definately going to have some lag

[YoungGun]

i know there is gonna be some lag but im also lookin for cooler temps and so i can tow somewhat if i ever have to.

[crazyrunner33]

How much power are you looking to make? A 62/65/13 over an S480 would be fun and tow extremely well.

[estrada5.9]

Originally Posted by YoungGun

i know there is gonna be some lag but im also lookin for cooler temps and so i can tow somewhat if i ever have to.

Your logic about towing and the turbo/s to do it seems flawed a bit.

Bigger and hugher is not always better. Especially when it comes to towing unless you are talking small stuff like atv/snowmobile trailers.

A mid sized S362 over a S480 tows good on a CR and has plenty of go.

[Smokem]

88/96mm turbine with a 1.32AR supports 1000whp, so if you don't plan to use that much, get something smaller, especially if towing is a concern. Everyone seems to be concerned about the compressor wheel size, but care little about the side of the turbocharger that is doing the work.

[oldestof11]

Originally Posted by Smokem

Everyone seems to be concerned about the compressor wheel size, but care little about the side of the turbocharger that is doing the work.

You've said this a few times. How do you determine the right turbine?

[Smokem]

Power goal. Why would someone recommend the same turbine section for 500hp as they would for 1000hp? But it is commonly done on the forums, I guess the jump from a 75mm to 80mm compressor wheel makes the difference in their opinion.

[BRE]

63/475 is my dream setup...

[murphy41]

Smokem-, when does the switch from the 83x74mm wheel, to the 96x88mm wheel come into play? 700hp and more? Or only at 900-1000hp? Or are you suggesting more along the lines of housing options vs wheel size? Im just curious, you always have good insight.

[Smokem]

A turbo builder who is a friend of mine told me long ago what I believe to be a pretty good way to size twin turbochargers.

The secondary cannot spool faster in a compound setup than when run as a single, so choose the manifold charger based on this fact. It needs to be able to handle the load produced by the primary compressor, but not so small that it bottlenecks the system on the turbine side.

The primary should be sized as ~ 80% of what it is capable of as a single. For example; if an S475 with the 74/83mm turbine and 1.10AR T6 housing can produce 850hp as a single, it should produce ~ 700hp as a primary. The power potential can be swayed up or down depending on the secondary size, but it is a very good method to make an assessment.

In the end game it is the consumer's responsibility to research and become familiar with their options, or just buy something that is being sold to everyone else. I see no reason to jump from the 83mm to the 96mm as you have left out the 87mm and 92mm wheels.

[murphy41]

I forgot about the other wheels, Ive always been more of a single person myself but never hurts to learn about compound setups. I like theory your friend noted you with, its a logical, yet an uncommon way to match chargers nowadays. Hense the reason I wanted to ask you. Thanks for the info sir!

[meatball]

Smokem
How much will a large external gate dumped back into the primary aid in reducing the bottle neck of a smaller secondary turbine ? When used in a set up like I'm about to run he351 over a 475 ... I know the 351's hot side is tight , is this an effective way of bridging the gap for a quicker spool time and still driving the primary hard without excessive drive pressures .
Sorry for the derail , same topic though

[Smokem]

It has been proven to work, although in my opinion the large gate is a crutch and not an ideal alternative to a properly sized secondary. Slowing the shaft speed by wastegating around the small turbine also decreases the air mass the secondary compressor can handle, thus also creating a bottleneck on the cold side.

[estrada5.9]

Originally Posted by YoungGun

i know there is gonna be some lag but im also lookin for cooler temps and so i can tow somewhat if i ever have to.

How about..........

A Borg Warner turbo with a 62/88 compressor, 71/80 turbine, T3 flange and a .85 exhaust housing as a secondary and another Borg Warner turbo with a 80/116 compressor 82/87 turbine with a 1.10ar exhaust housing as a primary will tow good and be lots of fun.

That is ridiculous ha^^^^^

This is what I run and it spools fast and tows good.

[Smokem]

T4 or T6 on the primary?

[estrada5.9]

T6.

Is T6 80/87?

Generalities are so much easier.

[Smokem]

The older aero wheel was 80/87mm, the newer J-type turbine with the MFS compressor wheels are 81/87mm. Either way that set is an example of a better sized combination, I believe the compressor should be maximized in a twin set since compounds are less prone to surge. What I mean by this is the compressor inducer can be run much closer in size to the turbine exducer.