Single scroll vs Twin scroll

[toger13]

Now that you can get twin scroll housings down to smaller turbos GT28 etc

I have just been reading up on the twin scroll over the last few weeks and in theory it should be a win win situation but there are no real tests to back it up that i can find on the net

I have found a couple of Toyota forums who have swooped a single scroll setup for a twin scroll but all they had done is change the manifold and turbo no tinkering with cam timing or mapping there graphs showed a slight reduction it peak power but better mid range but as i say they werent even remapped

It would be nice to see the difference in graphs between an optimised single scroll setup and an optimised twin scroll setup on the same engine

I dont know what your thoughts are but surly the twin scroll set up will alow you to run wilder cams/timing?

Thanks
Si

[SWR Performance]

toger13 said:

Now that you can get twin scroll housings down to smaller turbos GT28 etc

I have just been reading up on the twin scroll over the last few weeks and in theory it should be a win win situation but there are no real tests to back it up that i can find on the net

I have found a couple of Toyota forums who have swooped a single scroll setup for a twin scroll but all they had done is change the manifold and turbo no tinkering with cam timing or mapping there graphs showed a slight reduction it peak power but better mid range but as i say they werent even remapped

It would be nice to see the difference in graphs between an optimised single scroll setup and an optimised twin scroll setup on the same engine

I dont know what your thoughts are but surly the twin scroll set up will alow you to run wilder cams/timing?

Thanks
Si

What it does is just harnessing the pulse peak pressures a tad better. But this also sometimes make the exhaust housing seem smaller than a single scroll turbo. If you want to "go crazy with cam timing" i.e. run near stock NA overlap or big cams it's a fair bit more to be considered first, especially what the exhaust manifold pressure is vs the plenum boost throughout the range..

[chuntington101]

I also hear the internal bore of the twin scroll manifolds is often smaller as they dont have such a straight forward shape of normal manifolds. This helps keep the exhaust velocity up but obviously will choke the power at higher levels.....

Chris.

[andygtt]

you spec the exhaust housing by the AR so if this is the same for single or twin scrolls means it will flow the same...

I used a twin scroll because otherwise one bank could technically start scavenging from the other bank if I had a single scroll

In reality exhaust gasses dont like changing direction so cant seeing it making a huge difference.. but on high power engine every little bit of efficiency helps

[SWR Performance]

andygtt said:

you spec the exhaust housing by the AR so if this is the same for single or twin scrolls means it will flow the same...

...A/R is just a ratio of area. .63 A/R for a T3 and a T4 housing has nothing in common. The wall friction value of the twin will nearly double and they do not flow the same even if the areas are the same..