Single vs. twin turbos ??

[Orr89rocz]

Twins have more flexibility in turbine sizing. Smaller and easier to package alot of the time but depends entirely on the package and application and power goals

Alot of big inch bbc etc type engines run twins to make the power simply because the largest available turbine isnt big enough to handle the volume. Backpressure gets high
A precision G trim 127mm turbine with a 118 mm compressor will make darn near 2800 hp but only on certain size motors. It wont make as much with a 572” motor as it would with a 450-500” motor. For the big inch big power cars, twins make sense

For a simple 800 hp small v8 turbo car like a 5.3-6.0 lsx motor, theres plenty of good small single turbos that will work fine with turbines anywhere from 75-96 mm or so. S400 frame size from borg warner is popular here

[ptuomov]

It’s easy to get back pressure less than boost with modern turbos _provided_ that you bypass a small mass fraction thru the wastegate. With wastegate fully closed, in an unrestricted system boost wants to automatically be higher than back pressure once the compressor gets on the island. Favorable cross over is more and more challenging as the mass fraction bypassed thru the wastegate goes up.

[Wolf_Tm250]

What are the advantages of twin turbos over a larger single turbo? If I have no space limitations and no rulebook to follow, at what engine horsepower should I move from a large single to a twin turbo setup on a typical V8?

On a V8 I'd say a pair of twin scroll turbos, for faster spool up and less backpressure at high rpm

[tt 383]

Twins have more flexibility in turbine sizing. Smaller and easier to package alot of the time but depends entirely on the package and application and power goals

Alot of big inch bbc etc type engines run twins to make the power simply because the largest available turbine isnt big enough to handle the volume. Backpressure gets high
A precision G trim 127mm turbine with a 118 mm compressor will make darn near 2800 hp but only on certain size motors. It wont make as much with a 572” motor as it would with a 450-500” motor. For the big inch big power cars, twins make sense

For a simple 800 hp small v8 turbo car like a 5.3-6.0 lsx motor, theres plenty of good small single turbos that will work fine with turbines anywhere from 75-96 mm or so. S400 frame size from borg warner is popular here

Agree on that s475, 476, cast 480. Their is a billet 480 knockoff I think sloppy mechanics did 1000whp with and it was under 800 at the time shipped.

[tt 383]

I guess a few questions on the build, is it purely a strip car or street? Are you planning on efi or blow thru? Are you fabricating all or any of the hotside? What is the primary performance goal?

[Turbo231]

I guess a few questions on the build, is it purely a strip car or street? Are you planning on efi or blow thru? Are you fabricating all or any of the hotside? What is the primary performance goal?

Car will be maybe 40/60 street/strip. Planning on EFI. All intake and exhaust will be fabricated. Best drag strip times are goal even if it hurts street some.

[tt 383]

Doing a stock LS1 turbo install now of course I'm limited on bottom end strength, but have read quite a few builds and pm a few guys on ls1 tech and a common theme was 7875 type medium framed turbos on 4.8/5.3/6.0 modest gear and converter will do mid 9 sec with 3500+ lbs. Move to a T6 S475/76/80 etc and usually gain a few tenths changing nothing else other than afr tune. You also have much more potential down the road. A billet S480 "shelf hotside" 96mm 1.32ar has dynoed 1289whp that I know on a "built" 6.0l, 24psi gate pinned shut.

[tt 383]

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