alistairolsen

For the turbo gurus out there I was wondering if there would be anything to stop one using twin scroll technology on say a 5 cylinder engine?

Even if one could use a standard turbo, if an OEM wanted to, could they design a turbo with two different scrolls suited tot he different volumes of exhaust gas (3 cylinder against 2)

Just curious!

dojj

iTrader: (3)

merc do it with a 4 pot

Twellsie

iTrader: (1)

but he is asking about engines that have an uneven amount of cylinders

alistairolsen

So do mitsibushi, volvo...............

not seen any 3 or 5 cylinder applications yet

dojj

iTrader: (3)

i realise that

but nowadays you can use twin turbo's on 4 pot engines so the jump to a 5 pot won't be that difficult IF you work out which clinders produce the best flow lower down and which produce the best flow higher up

or design a manifold to produce these particular effects, much like the old 24V vauxhall lumps which were split to run as 2 3 pot units below a certain rpm and then as a combined unit higher up the rev range

alistairolsen

wtf are you jibbering about, twin scroll =/= two turbos

dojj

iTrader: (3)

does it not?

ok then, i'll take a "fail" then

Chip

iTrader: (3)

Very interesting question!

Sadly I havent ever seen it though so cant help.

I would imagine that the VE difference between the two and the three wouldnt be enough to cause any major problems.

Have you asked Russ if his is a twinscroll? I know mark loves them so it wouldnt surprise me.

Twellsie

iTrader: (1)

no a twin scroll turbo is when the exhaust housing is split into 2 section, so on a 6 cylinder for example you will have 3 cylinders feeding each section

Twellsie

iTrader: (1)

wouldnt you get quite an eratic frequency of pulses though due to the firing order too?

alistairolsen

I dont think it is Chip - pic from Russ thread, non divided flange

Chip

iTrader: (3)

Yes of course.

There is a pulse every 72 degrees, so you would end up with something like:

Side a: 72, 144, 288

Side b: 216, 360


But you could easily smooth those out to be fairly equally spaced at the point in the rev range that you are interested in by altering the runner lengths.

The standard Volvo manifold is unequal length in the first place bespite being fed by all 5, so the standard turbo gets an uneven pulse in the first place, doesnt stop it working well.

Chip

iTrader: (3)

Ali, are you asking because you have access to a cheap divided flange turbo (ie an EVO one or similar) and want to know if it will be "ok" or are you asking because you want to know which is optimum on a 5 banger, twin or single entry?

Cause the other option of courseon a twin scroll is to use it like a normal turbo and simply join the 5 in the collector so they all see both sides anyway.

alistairolsen

Evo 8 (or better but more expensive an evo 9 unit in the same housing) turbo on a 10.5 housing looks like a nice alternative to a GT3071R with similar spool characteristics, but if you can't use the twin scroll aspect then its only as good as any other TD05.

I can run a broadly available cast manifold from an S60R



which is proven to 420bhp and has a standard mitsi rectangular flange on it,

Pic shows my standard manifold on the left, S60R one on the right and the flange layout:



so if i use this Id b better getting a plain old td05-20g off a subaru or other (round entry) and using an adaptor plate.

Subaru flange:



If the twin scroll thing will work and is worthwhile, then I will source an evo 8 turbo and the correct housing (Tathan has one) and ask Gav if his offer to build me an experimental manifold still stands.

evo flange:

alistairolsen

For Dojj:

http://www.modified.com/tech/modp-09...ign/index.html

dojj

iTrader: (3)

aha, that makes sense now, and even more now i've seen the pictures

Chip

iTrader: (3)

Given the extra 25% more engine, I really cant see it being a problem to have the TD05 spool characteristics, will still be as if not more responsive than a standard T3 on a YB, and IME those are great.

alistairolsen

hmmm fair enough....

Might try it as an experiment, might not. I cant help thinking if it worked it would have been done!

Rod-Tarry

Asked about this yesterday it dont work.

alistairolsen

Cheers Rod, guessing you asked Mark? Any technical explanation on why it wont work (not arguing, just really curious)

Mark Shead

What I meant and my opinion is, that for the average tuner without the avalabilty of being able to cast a uneven sided exhaust housing, I feel it would not work as well in all tech aspects of a open scroll housing, based on the uneven firing split pulse.

Mark

alistairolsen

So you reckon it wouldnt just not give the advantages of a twin scroll turbo but it would actually be worse than a conventional single scroll turbo?

Mark Shead

Yes twin scroll is not as straight forward to get right.

Mark

alistairolsen

Thanks for the Gen Mark.

I guess to cope with the different volums of gas youd need a exhaust housing with different volumes and to cope with the different frequency of pulses you would need the two parts of the exhaust turbine to be doing different speeds ideally?

SiZT

Surely if you ran 1, 4 & 3 to one side and 2 & 5 to the other it would be fine? I've got something in my head saying Charade GTti's ran twin-scroll

mad russell

Hi all i did as the Shead his advise on this a while back as the twin scroll would be nice to try on the volvo thanks for thinking of me

Maybe one day if only i can keep the gearbox in one piece

Russ

foreigneRS

2 stroke is it?

Chip

iTrader: (3)

lol, for me, should have doubled all the numbers for the 720 degree cylce, but Im sure Ali new what I meant in terms of how they are distributed through the cycle.

C4llyT

You did say "something like" though Chip

So Tathan's still alive?