Compound turbo 1.8t s3 advise

[Newtoys3]

Ok guys, iv got an idea in my head which iv seen the americans do alot and one fella with a tt in uk, love the way it works, waste exhaust gas from the small turbo goes into the hotside of the big turbo, small turbo sucks air through the large turbo, so potential to have a gt42 size turbo but without the lag, or even any bigger turbo than a 28 series sized turbo, but i dont know much abt the system, what do you knowledgable people think and know abt this sort of setup, im having the engine built anyway as we speak so no worries on that front
oh and itl be going in my s3

 

[superkarl]

Have a search using the search bar. Its been discussed in small depth once before. You wont find a great deal of info on here unfortunately. Vwvortex will provide you with more info.

 

[Newtoys3]

Ok cool il have a look around the forum

 

[Scullies]

It's not easy to do and you going to pay someone a lot of money to fabricate the setup, then you have to find someone who will be happy to do the mapping.
It would be crazier to do a twin charge setup, supercharger and turbo

 

[Newtoys3]

Yep iv seen a company that do a super/turbo charged kit called senna but i just want to something cheap together using the ko4 thats already there and utilize that on a custom manifold and then add the big turbo, il be speaking to my mechanic faz at surreyside autohaus who is gna be completing my engine build soon and see what he can do, if hes willing to think about it lol, see i was thinking of buying a 3076 or gt35 so no harm if the setup doesnt work because then il uust get him to put it on as a single turbo but worth a try to see if it works if we were to use the k04 to do low end and gt35 to do top end, sit the big turbo where the battery/airbox is and put the battery in the boot maybe
just as a trial maybe just run it off the standard manifold to see if it drives down the road lol

 

[Andrew@A.L.D]

As soon as you find out how much it will cost i'm sure you will bail out of the idea

So many people on here saying that they want to go BT or compound charge, twin turbo, etc and then give up

Money Money Money

 

[jonno123]

why not buy a vnt turbo

 

[Andrew@A.L.D]

why not buy a vnt turbo

Because there crap, unreliable and they have there limitations

EFR turbo would be better

 

[<tuffty/>]

K04 manifold will no doubt melt from heat generated from this kind of setup... have discussed this before with another member..
http://www.audi-sport.net/vb/a3-s3-...audi-1-8tqs-compound-turbo-setup-options.html

While its largely irrelevant how you get air and fuel into an engine (as regardless of setup this is all you are trying to do) std management will be the biggest hurdle as it is not geared up for controlling this kind of setup and standalone ECU may be your only choice...

Flow capabilities of the supporting hardware (as is the case of anything when trying to extract over 200hp per litre) should also be considered...

<tuffty/>

 

[@udi A3]

Darkside Developements have a derv compound turbo setup on a 4motion iirc.

 

[lloydie1]

I think you need to ask yourself 'why' you want to do it ? Is it just to be different/unique ? or is it to do away with lag and have massive power?
Having just spent a load of time with Garrett i can tell you that the latest gen GTX turbos (and the Borg Warner EFR range) are light years ahead of where turbos were only 2-3 years ago. People still think that for 450bhp you need to go GT30 which you dont. They also think that you cant have 450bhp without having lag but you can ! GTX2867 is a nice turbo for our engines, loads of low down grunt, and lots of top end power. These turbos will run over 2 bar and make just shy of 500bhp when pushed, but fully spooled by 3500rpm. The GTX2860 on the Forge Mk1 makes +ve boost just off idle and 300ft/lb by 2850rpm. I wouldnt even entertain using an 'old' GT28 or GT30 as the compressor maps on the newer turbos just blow them clean out of the water.

 

[Newtoys3]

Ok thanks for the input, iv spoken to faz at surreyside and he says he doesnt recommend it for a budget of even £3000 for a turbo setup alone, he said once i start theres so many extras parts required ie management, custom mapping, 2 turbos, custom mani and basically said apart from the engine just the turbo setup and fueling mapping ecu ect will be around 5k at least off the top of his head plus lab, but i persisted and said can u try just building something with the k04 still in there, he took a big breath and had a think and earned me that he cant quote any power estimates or guarantee if its gna work properly immediatly, and made sure that i understood hes going to do this as a trial and not a project and is only going to attempt it because i the customer am pushing him to do it, naturally i said
cool lets do it
so now i am responsible for making him do it lol but i know he will manage to do something, so he had a quick look under the bonnet of my car and smiled and says hang on, went to the back of his workshop and came back with a turbo and a manifold from a audi a4 and bolted it on in 5 mins behind the engine
i was like wow!!!!!!!!
so now the exhaust side of the turbo was coming out towards the airbox side and he goes now let me think for a few days, i said are we half way there lol. He said not even 1mm to the finish line, this is just to see what parts it can be trialed with, so now im awaiting his call whenever he gets time to eork on it again
but i must say im getting excited

 

[Newtoys3]

 

[Newtoys3]

 

[Newtoys3]

 

[superkarl]

what we looking at?
what car is that? why is your turbo on the wrong way round? im confused

 

[Newtoys3]

Its a s3 210bhp, its a trial to see what can fit where in a compound turbo setup, the orig k04 downpipe comes out towards the brake fluid reserv so needed a turbo where the downpipe comes out towards the airbox, so that pic consists of a a4 exhaust mani and a4 ko3 or k03s blown turbo just to see how to begin routing pipework for this trial, we needed the downpipe to come out this side as my mechanic explained to feed the exhaust gas from small turbo into the ex inlet of the big turbo which if all goes to plan should fit somewhere in position of the airbox

 

[Newtoys3]

To all turbo gurus following this thread, apart from the usual gt28 series and 30 series usual common turbos which everyone leans towards because its the name on everyones toungue what other choices are there apart from gt series, efr and airwerks, because i dont need a ball bearing turbo i think as that can be covered by small turbo( i know the k03 will not flow enough through the housing but will be upgraded later) this is just a trial. So apart from the usual big turbos whats the cheaper big turbo option with journal bearings which wont cost the earth, need your advise please as not many people have used big journal bearing turbos on our engines but i dont know about compressor maps and all that so would be greatfull, iv seen mhi turbos, holsets, kkk what size housings and all that ar should i be aiming for, im looking for 500-550 whp with street drivability hence the compound setup, i like 500whp as i had it in my s2 20v with a k28 turbo dynamics hybrid but lag was an issue

 

[superkarl]

a holset turbo. like a hx27. or hy35. hx35 are BIG. theyre cheap as chips, very high flowing, journal bearing, and designed to run at high pressures.
Failing that, garrett 50trims are cheap-ish, and capable

then theres turbos as found on imprezas and evos, td05 - 16/18/20G.

 

[Newtoys3]

Thanks superkarl, do you what turbo will do what in my setup by looking at compressor maps because im reading stuff abt turbine housing sizing in compound turbo setups which i just cant get my head around so would appreciate if anyone or yourself has the expertise to work out sizing by doing some equations of what comes out the engine volume wise and what combo of turbos would work at what pressure ratio ect, confusing for me but i know someone on here will know exactly how to work all these things out
thanks in advance

 

[superkarl]

if you're only using a ko3 turbo for the small you may aswell not bother. they are tiny, tiny housings that are restricted as they are on their own. i cant see a ko3 being any good without cracking and melting as it is.
unless you use something relatively small-ish for the big one. Which means not hitting your 500hp target.

 

[<tuffty/>]

All I can see in the diagram is you trying to get 500hp worth of exhaust gas out through a small turbo... for a true 500hp setup I would imagine the exhaust manifold and wastegate to the small turbo needs to be able to flow this and the wastegate on the small turbo large enough to flow the excess gas as to not choke in the small turbo's hotside...

For this to work well I would imagine there needs to be an overlap in flow/'performance of the two turbos else you will max out the smaller turbo before reaching the potential of the larger one...

Its an interesting project and props for taking it on...

<tuffty/>

 

[Scullies]

To all turbo gurus following this thread, apart from the usual gt28 series and 30 series usual common turbos which everyone leans towards because its the name on everyones toungue what other choices are there apart from gt series, efr and airwerks, because i dont need a ball bearing turbo i think as that can be covered by small turbo( i know the k03 will not flow enough through the housing but will be upgraded later) this is just a trial. So apart from the usual big turbos whats the cheaper big turbo option with journal bearings which wont cost the earth, need your advise please as not many people have used big journal bearing turbos on our engines but i dont know about compressor maps and all that so would be greatfull, iv seen mhi turbos, holsets, kkk what size housings and all that ar should i be aiming for, im looking for 500-550 whp with street drivability hence the compound setup, i like 500whp as i had it in my s2 20v with a k28 turbo dynamics hybrid but lag was an issue

you should have a look on vwvortex forum. There is a section for the 1.8t 20v motor and there some Americans making crazy power on single big turbo. Also look in the mk4 golf and audi a4 (b5 b6) sections.

 

[Alex C]

That diagram you've posted shows the bigger turbo pushing charge air through the smaller turbo even for high engine rpms. Are you not going to have some sort of valve which can divert the path of the charge air? Otherwise you just have a flow restriction at high rpm?

 

[Newtoys3]

It may be a restriction and its not a restriction, the setup is all based on pressure ratios, rather than me writing it all out i have a article which is simply what everyone should resd for a understanding
the high pressure air from the low pressure turbo has to go through the high pressure turbo(small) in order for the air pressure to be multiplied.http:

Everyone should read this

www.motorsport-developments.co.uk/tech_articles/FAF307.tech.pdf

this setup blesses us with lower egt's and pressures and keeps us in compressor efficiancy,

thanks tuffty i totally understand the k03 is a restriction but its just being used as a trial and i may get faz to even weld the gate shut and put a wastgate on the manifold even, as he goes along im sure he will come up with something
but just to clear up i dont know what small turbo to use or how to set these pressure ratios so what better way then use whats available and go where not many people have been, this setup could just backfire and take me back to square one but hey i can say i tried to get it done lols.
At that point if the compound setup doesnt work my car will just get a td05 20g put on there and hope for the anything more then what a 28 series will do hopefully, if it doesnt ow well not the end of the world i just saved £500 on a turbo

 

[Alex C]

Everyone should read this

www.motorsport-developments.co.uk/tech_articles/FAF307.tech.pdf

ah got it

 

[STEALTHQUATTRO]

Ok guys, iv got an idea in my head which iv seen the americans do alot and one fella with a tt in uk, love the way it works, waste exhaust gas from the small turbo goes into the hotside of the big turbo, small turbo sucks air through the large turbo, so potential to have a gt42 size turbo but without the lag, or even any bigger turbo than a 28 series sized turbo, but i dont know much abt the system, what do you knowledgable people think and know abt this sort of setup, im having the engine built anyway as we speak so no worries on that front
oh and itl be going in my s3

Newtoys3 did you ever get much info on turbo compound? the net is very limited and it seems its all the yanks with massive motors!

 

[Samuel c5 Q]

I know this is an old post but the space behind the engine doesn't lend itself for compound turbo setup. The mate done it on a mk2 tdi golf and had to put the big turbo out past the side of the engine towards the airbox and battery tray. The downside of this is the channels between the turbines and compressor wheels needs to be short to encourage spool up otherwise you defeat the objective of trying to overcome lag issues. In the end he found that the problems associated with the compound setup didn't justify the extra 20 bhp and bottom end and midrange were no worse off with a single turbo.