Twin turbo
Turbo Mini Forums

Ive been looking at crazy arse 1000hp+ 1/4 mile cars on You tube. Most of them either have 1 enormous turbo or 2 small turbos.
Obviously a lot of you know my cars n/a and I dont know too much about turbo but I take it the 2 turbo option is to create as much power as 1 big turbo without the lag. Am I right? Also you old boys dont rev your engines very high it seems but these 7-8 second cars are revving very quickly and very high, whats this about?
There may be some more questions as this thread goes on.
Paul

I seriously doubt it!

Are the two turbos in series or parallel? If in parallel then they will spool quicker. If in series then they are generating much higher boost.

Very few turbos can boost higher than 25psi efficiently. If you try to go higher in pressure you get so much more heat that you do not generate any more power, because you cannot get the mass flow of air into the engine.

This is particularly a problem for small displacement engines. The T2/3 and the GT12/15/20 turbos just will not do that sort of boost efficiently.

2 stage turbocharging or super/turbocharging allows you to go much higher, say 45psi without generating excessive heat.

Edited by Paul S on 2nd Feb, 2007.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Any turbo engine could be made to rev with the right combination of cam and compressor.

It's jut that you will compromise the off-boost driveability. So much so that it would make a useless road or track car. However, this probably isn't a [problem for drag cars, they're just power hungry.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

i suppose a twin turbo setup over the clutch housing would be a decent position for it, i'm not that clued up tho :) has anyone tried to do a twin turbo setup on an A/A+ motor, may prove interesting in a mg midjet

SKYLINES ARE LIKE CLITS, EVERY FLANGE SEEMS TO HAVE ONE: see this sticker on my silvia

the Search-section on this forum is blummin superb & simple to use, unlike some other forums, without the search-section & the help of this bunch of chaps on here i'll never be able to !!!Start the day with a 998cc turbo!!! :) i'm getting closer though!

Tom Fenton says: I have it all, make me an offer

Two reasons why you'd want a twin turbo:

1) Instalation reasoning (or maybe aesthetics) eg V8 twin turbo

2) Compressor / turbine - or range of - not easilly available to meet your needs for your larger (usually) displacement engine.


If you have a 4-pot engine in the 0-4000cc range, then there is a huge choice of turbos to suit whatever need you could want - basically there is little need for a twin turbo. As you get larger, the choice is more limited.

You also start running into more restrictions and compromises.

What I haven't got my head round is high revs and turbos.

I know a good road cam is fine up to reasonably high revs, say 7000 rpm, but how do you get a turbo engine to run to 10,000rpm say?

Do long duration cams work with turbos? Do you need long duration cams to rev a turbo engine? Will a short duration cam engine keep revving as long as the compressor can feed it?

You use long duration/high overlap cams to rev a NA engine, because you are using the inertia of the air to fill the cylinder, but with boost you do not need to do that.

I can see another sleepless night coming, trying to figure this out!

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Edited by Paul S on 2nd Feb, 2007.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

AQ friend used to run a 8.2 second bike. It was 1200cc, burnt methanol and run 60psi back in the 70s. Ive contemplated doing this sort of thing with a A+ possibly with 2 smallish turbos instead of the 1 big one he used. What do you guys think?
Paul

I seriously doubt it!

3 port wouldnt make dual turbos very easy.

id say that would be brilliant, but whats the point if you cant get a clutch to cope with the power?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Isnt TurboDave sorting this out?

I seriously doubt it!

lol beat me to it!

yeah, on the other list of things to do....

Axel - 30psi (at 75% above eff) is defiantely in the realms of currently available compressors. Especially if you are willing to dick about with turbine housings. I sugggest you look harder.

Edited by turbodave16v on 2nd Feb, 2007.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

On 2nd of Feb, 2007 at 09:02pm TurboDave said:
Axel - 30psi (at 75% above eff) is defiantely in the realms of currently available compressors. Especially if you are willing to dick about with turbine housings. I sugggest you look harder.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

If you have a huge turbo then you will have lots of lag, then it comes on boost and over powers the clutch. If you had 2 smaller turbos with little or no lag would it be easier on the clutch?
Also why cant we get a larger diameter clutch plate (almost the size of the ringear) and make a flywheel to suit?
Paul

Edited by paul wiginton on 2nd Feb, 2007.

I seriously doubt it!

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

A mini engine is far too small, to make use of 2 turbochargers.


Dave has already covered the whys and why nots of a twin setup though.

Generally its all down to which is easier to package. With modern turbos, there are units that will perform pretty much equally well whether in single or twin format.

As for not efficient above 25psi ??? There are Garrett BB units, that are still pretty damn good at 4 bar !!!
One of the big GT42 units, is still something like 74% efficient at 4.5 bar !

Its only the really small oil journal units that are poor at high poost levels.

Go big

As for the big power cars..... dont forget 1 turbo is also cheaper than 2 turbos.....

Edited by stevieturbo on 2nd Feb, 2007.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

IMO all the Garrett BB turbos that can do high boost, say over 30psi, 3:1 pressure ratio, are too big for the A Series.

The air that the engine can take is the wrong side of the surge line.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Unless you rev the tits off it![/quote]

This is the idea

I seriously doubt it!

mmm yes this is a BIIGG dilemma,

i went from planned 7 port to 7 port turbo bring the rpm down to gain a more reliable engine, now i find my self looking at bigher chrgers and subsiquently higher rpm's in the search of higher bhp, and perhaps more sane torque levels, i'm still waiting for someone to do something big with either a 7 port, K head or arden and give some real results to healp me sort out in my head where i need to go next.

Cheer tpo john K and jimter for their proogress so far we have a good idea of what a NA 16v is capable of but not really yet a 16v turbo.

soo right now i'm looking at GT22V (variable vane turbine) or perhaps a GT25V in the search of a "tunable?" bottom end, and
the top end flow.

having read htis appologies for the poor spelling, but i've cracked into my new batch of home brew...

Go for a proper BB T3 ??

http://www.epsturbos.com/Turbos+Turbonetics.category

Or why not try and squeeze something like this in ?

http://www.stealth316.com/images/gt28rs-62trim-raw.gif

or this, although its an oil journal Mitsi unit
http://www.stealth316.com/images/td04h-16t-cfm.gif

Go big....

Edited by stevieturbo on 3rd Feb, 2007.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

SOme more turbo info...

http://www.900aero.com/main/tech_main_turbo.htm

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I've been thinking about this.

TD has estimated that for every 16psi of boost you get 100% more power. So N/A 90hp, 16psi 180hp, 32psi 270hp.

The additional power due to revs is proportional to the increase in revs, ie if you up your max revs from 6000rpm to 9000rpm you get 50% more power provided you can maintain the volumteric efficiency of the engine.

To up the boost and stay at 6000/7000rpm rev limit is quite straightforward. There is enough info on this site to build a usable 200hp engine that would push the clutch and gearbox to its limits.

To run an engine to 9000/10000rpm is a totally different ball game, in my opinion. You need an expensive bottom end, a high flowing head, maybe 16V and special cam(s). Would it then make any power below 4000rpm?

Great headline hp figures but what would you use it for?

Given the above, I think chaising power from revs lacks rewards.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."