turbos
Turbo Mini Forums

hi, im looking at buying the turbo for my mini at mo as i have alot of other parts,
but i dont know what turbo to use, i know alot of people on here use t2's so was just wondering what is the max boost u can run through a t2 as id like to run quite high boost but was told by a friend that they cant take that much boost.
is this true?
thanx mark

speed is the best rush i have ever had!!!

add me lanxter@hotmail.com

A T2 will deliver all the boost and more that your a series will require just look at what the R5 lads boost to!

ive seen them boosting to around 25psi mate, but sum1 told me a t2 could not handle that inda of boost is that true?

speed is the best rush i have ever had!!!

add me lanxter@hotmail.com

A R5 T2 will boost to 25psi, whether it's efficient at that kind of boost, i doubt it !

Phil.

WWW.TURBO-MINI.COM

what would you say its most efficient at phil?

speed is the best rush i have ever had!!!

add me lanxter@hotmail.com

I would have thought up to 20psi maybe, after this all you'll probably do is create a lot of extra heat and no real power gain.
Surely the Renault boys who run higher boost than this are on Hybrids ?

Phil.

WWW.TURBO-MINI.COM

i think they r swaping to t25's mate the 1's who are running higher boost.

speed is the best rush i have ever had!!!

add me lanxter@hotmail.com

From what I have read on other places on the net a standard R5 T2 begins to suffer from diminishing returns from about 17 psi onwards. This sort of ties into what Iain and Phil has mentioned.

I have a dig around me favourites to see if I can find out where I found the info

17 psi on a T2 and the temps rocket up!

Yes they will run to 25psi... but they will be moving less air than a T3 at 20 psi!!

Pressure is not air flow remember!

If your running 20+psi on a t2... think t25 or t3.

Alex

AlexF

Team Racing

I agree with you Jim.

The T2 will need to be spinning much faster than the T3 to make the pressure however.

Thus the wastegate will be less open on the T2 than the T3 meaning more heat through the turbo on the T2.

I heard that T2s would only make 12.5psi, so I asked garret. They sad that they would easy make 25 although their life expectancy would be reduced.

They offered a mod to the bearings to increase the life of a T2 running high boost.

Wil

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

I knew this would be a fun thread!

"Surley a t2 turbo, on a 1293 engine, at 6000 rpm at 20 psi would deliver the same amount of air as a t3, t4, or t5. If it could not supply enough air, then it would not give 20psi? "

nope!

Air flow and psi are not the same thing!

Alex

AlexF

WTF!!!

well I'm no expert not even got my L plates, were's fab when you need him!

Team Racing

Can you guys read compressor maps?

I'll happily explain what I'm going on about if you want :)

Alex

AlexF

I don't use maps anymore, I've got GPS

Team Racing

Hang on now i've thought about it a bit....

If the turbo is running above its efficient bit the air will get hot.

this means the air will expand.

meaning that it is less dense.

so although the boost is the same (set by wastegate)

the actual air MASS is less than a larger turbo that will be in its efficient bit!

does that make sense??

A T3 produces far more VOLUME of air at a given pressure from its HOUSING than a T2....

Think about two balloons, one has a diameter of a foot and its inflates to 15psi... now you inflate a second balloon to 15psi buts its diameter is 2 feet - the two balloons are both at 15 psi, but the amount of air in each will be different!

Alex

AlexF

close mini13..

Bacially a compressor map shows you that for a certain pressure generated but the turbo there is a specific efficency. This is related to the speed the turbo is spun at which is in turn related to the amount of air flowing through the engine (the exhaust gas drives the turbo!). So if you spin a turbo at a rate which prodives you the presuure you want but at an more efficent speed then you heat the air less.

As you know cool are is more dense. But thats only part of the story!

Alex

AlexF

I get it that the t3 will produce more flow at 15 psi than a t2 at 15psi, but if they're blowing up identical balloons (say a 1293) then surely this becomes the limiting factor meaning 15psi will always be x amount of flow no matter what is blowing because the 1293 balloon doesn't change?

Oh... I think i get it now...

Edited by Joe C on 8th Aug, 2005.

again another good point Mini13 (I can't keep calling you that, whats your real name?!).

Let’s go back right the way to basics…

An engine is just an air pump, the more air you can pump the more fuel you can add to that air the MORE POWER you make.

But Turbochargers COST you power....
Lets take an example of a std 1275 MG engine... it makes what? 74 bhp?

To make this power we are utilising the air pumping ability of our 4 x 318cc cylinders.

They are drawing in enough air and fuel at the correct ratio and importantly, expelling it again to produce this power. This is the beginning of Volumetric Efficiency!

Now with the same 1275 MG lump, remove the nice exhaust system and stick a tiny straw sized .48A/R turbine housing on it with a closed wastegate and the turbocharger actually welded tight so it can’t spin.

You'd be lucky to see 50bhp.... so whats changed?

Pumping losses! You have killed the engines volumetric efficiency.

Yes btw I am bored at work!! lol

Alex

AlexF

So what's this got to do with turbo sizing

Two example from other turbos I know the figures for...

A T3 50trim with a pressure ratio of 2.4 will be spinning at 134,000 rpm with a compressor efficiency of 70%.

A T4 60 trim with the same pressure ratio (2.4) will be spinning at only 97,000 rpm with a compressor efficiency of 82%.

Pressure ratio is simply 14.7psi inlet +20psi outlet divided by 14.7psi inlet, it takes into account the actual pressure of air around us all the time!

So there's the proof of better Air Charge Temps - but remember what spins the compressor, the turbine!

The larger the turbine the more air it can flow, but the more it takes to make it spin at all - hence the difference in lag you get. But there is less restriction in the exh... so the engine finds it easier to expel the exh gas! So the Volumetric Efficiency increases! Secondly, as the compressor doesn't need to be spun as fast it takes less exh gas to achieve the same pressure... again less restriction in the exh and again an improvement in VE.

So for the same boost you can have more power, which means in effect more air!

Alex

AlexF

Yep, the penny's dropped, or at least dropping!

I was thinking purely in terms of the compressor flow, didn't think about pumping losses and the like.

Name's Joe by the way.

wow in one thread i have learnt so much, thanx alex for being bored at work

era turbo - not even the mrs gets to drive it

Great info - but admittedly from someone who is biased towards a T3, and also never having driven a T2 mini...

I also see no T2 50 trim flow figures compared against the T3 40 trim? Last time I checked the maps, I recall the T2 50 trim ran rings around the T3 40 (assuming a non-standard engine)? Maybe I was reading them incorrectly...


I actually don't know what questions are being asked or answered here (this post got pretty confusing with questions being asked then answered 2/3 posts on )

Edited by turbodave16v on 8th Aug, 2005.