Benefits of GT series turbos?
Turbo Mini Forums

Okay, I got to reading up on some of the GT turbos. What's the real benefit? As far as I can tell the only real difference is the ball bearing instead of regular bearings. Did I miss read somewhere or is this the case? In a different thread it was recommended that I go with a GT15 turbo for my 850cc project. Now, I assume this is because of size of the motor, which is fine. But I was wondering, for the larger turbos, wouldn't a T3(yes I know, outdated...) from the likes of Turbonetics be just as good? They are now using ball bearings in almost all of their turbos.
Thoughts?

-James

Ball bearing cores are not really of concern to us, as they only start from the GT25 series upwards.

The main difference of the Gt turbos is the effiency of them compared to old hat T2/T3 style turbochargers. They have quicker spool times, higher pressure ratio capability and are generally much better due to improvements in design over the last 20 years. Just remember how old the standard T3 design is, things can only get better.

yep, they generally flow more for their wheel sizes, and as a result have less inertia, also they can be designed hold their efficiency at higher pressures.

ah. okay. That clears some up. Now, lets say a GT15 turbo doesn't hold enough power for the 850, theoretically, would a GT25 be best then?
-James

The GT1548 will flow enough air for 120hp.

You are going to need 15-20 psi boost to get that from an 850.

You will not benefit from using a larger turbo.

Do the air flow and pressure ratio calcs for your engine and then work with the compressor maps.

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 gt15 will,

next size up is a gt17 in a 52 trim wheel thats good for over 200hp,

then theres a 20, 22 then the gt25.

a 25 is huge, they use them on the focus RS.

have a play with this calculator,

it has some (but not all!) GT maps

set the ve to about 80% that sould be an ok starting point



http://www.motorgeek.com/index.php?page=6

Edited by Joe C on 10th Sep, 2009.

Ah. So gt17 would probably be the ticket then once I have the motor built. Now, here's the thought. I'm building the motor to the nines, everything built for turbo(crank, rods and pistons included). What would be the estimated power output would someone say of an extremely well sorted 850cc turbo with a GT17 or a GT20? I'm looking for no less than 125bhp, but I would want more.

-James

tbh i think even the gt15 might be a bit big,

depends on the wheels,

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."

Well the GT17 works very well on our racer and is good for 150+ bananas on a 998. A mate has an 875 imp engine with a GT17 on and that works well too, but it revs much more than a mini engine.

If you are building it for the ultimate 850 turbo then I think the GT17 could work well. You will need to do the maths though really, and don't expect boost much below about 4k.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

That's about what I'm figuring. I know a 850 is really not the place to start, but it's unique I think. How many people on this forum, or anywhere really, have a 850cc A-series turbo mini? When I have Crower do up my crank and rods and such I'm going to have them do the crank for high rev. I'm looking to get 8500 to 9500 rpms out of the motor, and still have it be as reliable a motor as one like this could be...

I thought long and hard about using an 850 for my turbo/mpg project. In the end, I decided to take the easy route and use the 998.

850 cranks can be workked to run at 9000rpm, according to Vizard. I've got one destined for a 980cc K100 motor.

850 rods have pinch bolts so should be thrown and use 998 rods instead. They should be a straight fit.

I'm not aware of any 850 pistons that are currently available that will be up to the job. You can get 998 Hypatecs, but it will be a big overbore and you will need to deck the block.

You will need to fit cam bearings in the block as they are not fitted as standard.

Best of luck.

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."

I plan on having crower do the whole bit up for me. Custom crank, titanium con rods and custom pistons dished for turbo use. When they have it in shop I'll have them line bore and install the cam bearings as well, because as you said they are not fitted.

Titanium con rods?

For an 850?

Is it april 1st again, or do you have bottomless pockets?

I'm just willing to pay a lot to get what I want. They're $560 a piece, so roughly 335 pounds a piece. But Crower guarantees against their failure. The whole motor is probably going to cost $6,000(3500 pounds). Granted this is without the gearbox, but it will create a much more reliable motor, and a much more powerful one because the parts will be lighter and better balanced. Like they say, you get what you pay for. However, MED's forced induction motor is 5700 pounds, or $9,500 U.S. currency, which is what I'm going to spend roughly for the whole motor and tranny as well, but have a motor that is tricked to the nines.

-James

Not to mention, it'll be one of the few 850's that can keep up with quite a few 1275cc motors...

I must say that while you will have a unique engine, you'd get at least 50% more power starting from a 1275 and would not spend more than what you will on the 850. And it would still be unique with those parts.

I just don't see the point.

Jean

http://www.jbperf.com/

I don't think this project is about the ultimate forced induction motor, it's about the ultimate 850 motor.

It'll certinally be the fastest 850 A-series on the plannet, and that will be an achievement.

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

www.twin-turbo.co.uk

Buy a 970 engine, turbo that..

Keep us updated, sounds very interesting. If these titanium rods are any good it could Id like to know

Paul

I seriously doubt it!

I like innovation and doing something different.

But a £10k 850 Turbo is unlikley to polish your ego any more than a £2k 998 Turbo.

I was questioned by a few people on here when, in 2005, I said I wanted to turbo a 998 for a road car. Up until then the majority of 998 Turbos were for racing to meet class rules.

My reason was to test a theory that I've held from the 70s that I could produce a much more economical performance Mini with a smaller engine but turboed for top end performance.

I've recently achieved the aim of running a 998 Turbo on the road.

BUT, boost is addictive

I can't keep my foot out of when I'm driving and the mpg is irrelevant. Now I want more power and I'm thinking of improving the head and fitted piston buttons so that I can get more POWER.

The point I'm trying to make is that the idea of doing something different is OK until the reality sets in.

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."

thing that gets me and no offence ment, but your in the states how many other 1275 mini's do you know of? why not build the crazyest 1275 for 1380 what ever to race against the yank cars and ricers? big power 13's or 10's on hooser tires longish diff and a k1100 head or a k100 head turbod with all the power you can get? would probably be more fun

Drives
-Ford S-max Mk2 Ecoboost
-Rover 100 VVC #2 - track project

Searching is all you need on TurboMinis

paul its clear why......
he's american....

Normally I would agree with you that it's because I'm american, but you have to give me credit where it's due, normally americans like big bore, gas sucking behemoths. Remember the muscle car era....? And thanks to those of you that can see my vision(wil_h, paul wiginton, and ben H primarily). I'm looking for the ultimate of ultimate 850's. And if I can keep up with your 1275's on the 1/4 or the street, whos to argue who has the better motor?

-James