View Single Post
Undutched Undutched is offline
Registered User
Undutched's Avatar
Join Date: Jun 2014
Location: Germany
Posts: 38
Originally Posted by Raceboy View Post
45mm is good and no need for bigger than exhaust port.
You will want them as short as possible. For the power goals you aim I would go with twins, you get much shorter exhaust and lighter impellers etc making spoolup better which is important for a car that could be called even remotely a streetable.

With big single twin-scroll is also good but exhaust manifold volume will be much bigger than needed.

FWIW I am doing 2.5liter short stroke (66x90) 911 engine and it gets twin IHI ball bearing turbos capable of 300 hp each. Lighting fast spool.
It may be easier and I agree to an extent on using twins, but on my last engine the smaller Turbos didn't perform as well as the BW EFR. Turbos have gone a long way and I like the idea of one large turbo. In general I would agree though!

Originally Posted by RarlyL8 View Post
That's a lot of engine with a turbocharger!
Key to turbo header design is velocity. Counter intuitive to normally aspirated builds, the flow must restrict as it makes its way to the turbine which increases its speed. The exhaust ports you site at 44.5mm are huge. Piping with this ID would be 1 7/8"OD. Decision on primary and secondary size depends on projected HP output at X000rpm at x.xbar boost. That is the first question that needs to be answered. How the car will be used, where the powerband is preferred, and specifics on the turbo specifications also will be needed information.
My starting point would be 5th harmonic equal length 1.75"OD bumped primaries and equal length 2.25" secondaries (the secondaries on the set you have pictured are too long) to improve off boost performance and torque. Split volute T4 flange with twin waste gates.

Brian, thank you for the input.
Power: As you may know we need "Autobahn-proof" engines, so it should be capable of roughly 800, but won't see that power 95% of the time hoping to have an easily drivable car with low to midrange torque with less than 1 Bar, with seldom use of higher boost, so basically 600ish HP. The plan used to be to use E85, but it all but vanished here in Germany.

Using 1.75" to 2.25" was our idea as well (had to check in Inches). The primaries were measured to be around 65cm (25in) Thank you on the note with the regards to the length of secondaries. I have looked at your site maybe a thousand times over the last years and didn't notice this.
It seems some use equal length secondaries and others don't (like turbokraft or BB).
Old 02-12-2019, 11:59 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)