single or twin turbo best?

I have been watching american and jap car dvd's and have found a lot of tuners are replacing thier twin turbos with single turbo conversions. In the back of my mind, i was thinking of fitting 2 turbos to a 2.0 16v just to be different using a custom manifold. is it worth it tho, what are the pros and cons of using either 2 smaller turbos or one large one?!
cheers, James

 

from what I know... twin turbos are good for high top end boost... single turbos are good for quicker spool up... for example.. if you take a garden hose, and add a splitter the water flows out, and if it there is no splitter just a single hose if flows a litter stronger.. I am not a tech but this is what I have been hering..

 

Read the part at the bottom of this page.

Link

 

what u really mean is that they are replace theyre sequential turbos with one turbo.

 

yeah sequential tubos are good when there is a higher volume of exhaust gas, the first tubo spools quickly as chicago gti was saying, then, the second turbo kicks in, it is a larger turbo and can produce much more boost. usually, the best applications of such turbos are on the japanese straight sixes, and the rotary of the RX-7. on those types of engines with those setups and a few mods, 450+ hp is a pretty common number to create ie: supra, RX-7, Skyline, S2000, etc.
a friend of mine has a 92 RX-7 TT running the sequential setup, it has a few mods and is making a little over 400 hp i believe, with plenty of room to improve.

the RX-7 is the exception as far as the increased dispalcement goes, and this is because it's a damn sewing machine that can hit rpms of around 10,000 or more if u want it to.

if u want to try out the twin turbo setup, i think it can be done, and i tihnk it can work reasonably well, but u better get someone who is damn good at that sort of thing to et it up, or else you will spend 5 grand more than u needed to. of course that's a $ figure for around here.

-the con of using one big turbo is lag, and the possible inability of the engine to spool it well enough to get the boost you are looking for. the diameter of the inlets has to be appropriate, to ccreate the right balance of boost, with backpressure, and flow.
ie: a diesel bus turbo is too big for the exhaust created by our engines.

 

twin turbos on a 4 cylinder isnt a good idea

 

Twin turbos on a 2.0 16v - gay, and a waste of money.

 

TSC, could you please stop beating around the bush...

 

gay eh!? i dont want a gay engine! I guess theres not gunna be enough power/ flow involved to get the most out of a twin turbo setup on a 2.0 16v, jus wanted to be different really though thanks for the explanations!

 

Agree with Smokesho and 800g.
If you want to be different run a supercharger for low down, as well as a big turbo for up high rpm. It'd probably be easier to fit in the engine bay aswell, as there's not much room for twin turbo's at the back of the engine.
The only twin turbo four I can think of is the Subaru B4 Liberty(WRX motor with sequential turbos), and the only reason it works is that the motor can flow a lot of exhaust gas, and has really good low down torque even without boost.

 

watch this space

tt

 

Gay

 

if you dont like lag, dont lift off

 

Firstly people hows it going?
Jimbob I have been reading all the posts and its plain to see some people have the attitude of " thats just stupid" . I feel this is because they have no idea on this subject which to me makes their posts pointless.
Also I see some replies give advice which isnt entirely accurate but this comes down to what type of twin turbo setup they are actually describing.
There are 2 ways to setup twin turbos.
1. Constant twin turbo ( Both turbos run at the same time all the time)
2. Sequential twin turbo ( Lower rpm one turbo works then at designated boost level the second turbo starts to work.

Now how they compare;
1. Constant twin turbo - If take these 2 turbos and match them to an equivilant single turbo ( meaning 1 turbo thats exhaust turbine's flow rate is that of the 2 turbos compined) you will have no difference in the end.
By this I mean ( depending on sizing of exhaust turbine's flow rate and the desired engine) You will still only have top end power ( larger exhaust turbine flow rate) or you will have lower end power ( smaller exhaust turbine flow rate).
So in the end whether its a single turbo or constant twin turbo you will still only have top end or bottom end power ( all depending on turbo sizing)

Now #2. Sequential twin turbo.
This setup is the overall best performer as you get both bottom end and top end power. This setup is however harder to setup a smooth activation point for the second turbo to start working.
Lets call then turbo 1 and turbo 2.( both the same size)
Turbo 1 has a wastegate and turbo 2 has what looks like a wastegate but it is actually an exhaust block off valve
to stop the exhaust getting to the turbine( its doesnt bypass the turbine like a wastegate, it only blocks it off)
At low rpm turbo 1 gets all the exhaust gases from all cylinders (turbo 2 is blocked off by the valve)
Since turbo 1 gets all the exhaust gases it spools up early in the rpm range. As boost levels increase the block off valve on turbo 2 starts to open, Now turbo 2 is also receiving exhaust gases and it too spools up(ie sequential operation).
Since the 2 turbos are operating at the 1 time it is like the engine is running one big single turbo (This is how you get the top end power as there is no restriction like on a single smaller turbo.)

Jimbob hopefully this will give you and the others a better understanding of how twin turbos work and the differences between constant and sequential.

If you decide to go constant twin turbo I think it will look cool and when you tell people it twin turbo it will also sound cool but ultimatley it is no different to and equivilent single turbo.
If you go sequential Please plan to experiment will the boost level of activation of turbo 2. I say this because as the block off valve starts to open the exhaust gases delivered to turbo 1 will be reduced and the boost level will drop off and this will create a surging feeling in the cars power delivery.

One other thing when running either twin turbo setup is dont forget about oil pump's delivery volume ( not pressure) If this volume isnt enough some part of the engine or the turbos themselves will not be supplied enough oil.

Hope I helped, Cheers Doc

 

I like golfs. Turbos are fun.
Edited by: ausgolfer

 

Ausgolfer is it not true that some have the attitude "this is stupid"?
Is it also not true that these posts are not useful in anyway except in being negative?
How is this being a smartarse?
How is this putting others down?
Isnt this forum meant to be for discussion and learning as it is useful information?
Do you care to dicuss why you state my information is only theoretical and not practical?
I am not sure what Hot4s has to do with my post on the diferences between constant twin turbo and sequential twin turbo.
Its good to know you knew all of this information and also that you took your time in your pevious post to think of pointing these misconceptions out.
From your previous post;
Quote;
Subaru B4 Liberty(WRX motor with sequential turbos), and the only reason it works is that the motor can flow a lot of exhaust gas, and has really good low down torque even without boost.
Uquote.
Is it not true that any engine can with cam work and head work be made to have the same charactoristics as you stated above?
Surely and engineering student would know this!
And like I stated in my previous post, turbo sizing is an important factor.

Helpful? Theoretical? Not Practical?
Its all good to say this but do you give reasons?
As to my post;
I cant say I was helpful as I dont know yet.
Theoretical, Its a theory so yes it is theoretical.
Practical, I gave reasons in my post as to why it is practical.

Am I here to make friends? Yeah I suppose.
But mostly I am here to give my information so I can be helpful, and Others can learn from me and I can learn from them. Isnt that what the forum is for?

Cheers Doc
Edited by: Dock

 

Ausgolfer from your private message to me;
"Quote;
You can think others are stupid as much as you want. But is it not rude to say it??
These people, while might being a tad negative/naive are thinking along a practical line(ie could you fit a twin turbo set-up behind a golf engine ) and as being on my way to being an engineer I know anything is possibleso don't make the subject any broader than it is right now lol.
I would not have pointed out these misconceptions if only you had not added your comments about the stupidity of others.
Yes both practical and theoretical help is needed.
The Hot4's part was a lame excuse for a joke.
As for the suby not all cars are boxer fours with twin cams per bank and 4 valves per cylinder(which have better balance characteristics than straight fours).
Last thing I generally edit or delet my posts after I have gotten a point across.
Cheers mate, hope I didn't hurt ur feelings.
Unquote"
Ausgolfer did I call anyone stupid? No
I said their thoughts are" this is stupid"
Did I say this about anyone who gave information whether I felt it was correct or not? No
Did I single anyone out? No
But it its plain to see which posts gave information whether correct or not and which posts were just pointless negativity. Can you say these posts were practical? No
How did I make the subject broader?
You say you pointed out the misconceptions but in your post you say nothing of whats the difference between the twin turbo setups.
Engine configuration and balance has nothing to do with gas flow!
And can you not put bigger valves, port the head and regrind the camshaft? I am sure you can.
And you generally edit or delete your posts. Is this because your posts are generally Lame and fail to get a point across?
Did you hurt my feelings? No, but you made me think twice about ever offering a bit of advive for yourself if the time ever comes and you need it, as too did the negative posts.

Sorry to all the others in this forum that have to read this. I am abviously new here and it has already saddened me in this forum to be attacked for giving advice, especially from someone who stated in their edited post they new this same information but yet failed to share it.
Once again isnt this forum here so we can share information so we can learn from each other and enjoy our vehicles? If it isnt please let me know!

Cheers Doc

 

For everyone's information I did not attack this person for offering advice, infact I comended him/her on his/her info, I attacked him/her for being rude in saying quote: Jimbob I have been reading all the posts and its plain to see some people have the attitude of " thats just stupid" . I feel this is because they have no idea on this subject which to me makes their posts pointless.

 

Go the doc........


I would have thought that going with a twin turbo setup on anything less than 3.0 ltr would be a more bother than it worth.....

Go drive a supra.....

Or even a HPA 2T R32 and I am sure you will make your minds on this one...

 

Welcome to the forum Doc,

yes this forum is all about getting help/advise from others with a better understanding of things that we are not so clued up on.

Were all here for the same reason, we love our cars and love getting the most from them.

Keep up the helpful posts mate, if i see or read something i dont like i just forget about it, not worth entertaining in my opinion.

Take it easy!
Mark