what turbo
Turbo Mini Forums

could someone point me in the right direction, looking for a turbo to supply me with 14-16 psi boost on my 1380 16v bmw twink engine will be 8.6:1 cr with max rpm around 7500 utilizing the 254 cams, any help would be excellent.

love that straight cut scream!!!
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let me go digging. there was a thread on here not to long ago in which Turbo's for the Twinks were talked about.

it was something like, GT1752 you wont go wrong its a good little turbo with good efficiency but i think robert concluded that a GT25 would be a good turbo for the Twinks.

EDIT: i cant find it im afraid. Maybe Robert will know which thread it was, im sure that was the general idea that robert gave though.

i think for the boost you want to run the GT1752 will be fine. and there is still more boost for it to give aswell, even if it is moving slightly out of the efficiency island....actually, where is the max efficiency for the GT1752, i have got it in my head for some reason that its between about 14-17psi? what sort of boost is acheivable with the GT1752? i imagine it tops out around 20 ish psi?

Edited by James_H on 2nd Sep, 2008.

Im running the GT17, and it goes well (Now it does anyway, lol)!!

You can get away with bigger turbos on the K heads without the worry of it not spooling up because of the amount of extra air they flow over the 5 ports.

I was tempted to go to a GT25 but thought it was worth seeing what I can get out of the GT17 first. .

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1/4mile in 13.2sec @ 111 terminal on 15psi

I got the feeling from you guys that the GT17 was a little fragile if not bought new ? Or maybe it was just the rebuild kits that where shit.....? I had a look around on the saab forums and they change from the GT17 to a TD04 variant but do say it is a little larger than the GT17 and spool up is alittle slower...What do you guys reckon ?

"So wat we gonna do tonight Brain?"
"Same thing we do evernight Pinky!"
"Try to take over the world!"

Because the GT17's rotating assembly is so much lighter and smaller in diameter I think its alot more vulenrable to being damaged from drawing something in or being out of balance, where as an old T series turbo may be a little more tolerant to being out of balance.

If you were to rebuild a T series turbo at home, you may get away with marking the rotating assembly, taking it apart, and putting it back in the same position and not getting it balanced. A GT series you would more than likely have to get professionally balanced after a rebuild to make it last.

Just my take on things! Lol

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1/4mile in 13.2sec @ 111 terminal on 15psi

Edited by Paul S on 3rd Sep, 2008.

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 reckon .... :)

bear in mind i have no maps for the 17 apart from what paul fab and i came up with on the 17 thread ,

that the 17 'should ' be good for around 265 bhp tops ,i say this because the saab chipping companies use this as the break point where you have to step up to the td04 or gt28 ,

now , bear in mind ,the saab engine is a 2 litre , so its boost to get there is prob around 5 lb to 7lbs less than the 16v 1300 mini , and looking at the 60 trim 52mm wheel ,its max flow is , i think a touch above the boost the 2 litre would run , so may be a bit more in it for higher boost areas .
this is conjecture !

but the 265bhp on the 17 on the chipped up saabs is factual on some of the saab tuning sites .

with ref the bmw head ..
its basically a matter of percentages , if a na bmw headed mini puts out around 130 to 140 bhp ,which it should ,then on 15 to 20 psi , 300 bhp should be easy , so a turbo in the 30 lbs at 20 psi is what id look at , if you look at the garret catalogue ,this runs to the gt2560r or the 28' of which there are a few types . ...
if your running a high rpm 9k engine ,and a 30 psi sort of bp ,with a good intercooler , id be looking at the 38 to 42 lb flow area ...

but bear in mind ,garrett are not the only people that make turbos ,and its worth investigating different makes to see if something will do the job and can be got for a lot less money .


with regards to the fragility of the 17 , i agree with matty , i feel that if id got my 17 balanced , it would probably have lasted a bit longer , it wasnt wrecked ,and will rebuild ,but it lost 5 thou off the compressor blades and this was simply bearing wear , it did look as if a bit of dirt had come in with the oil ,but very marginally , and i wonder about the bypass in the filter housing ,think i may block this ,
but , bear in mind , this turbo design ,does live with the master and daily panel van engines , at around 20 psi , for hours on end on the motorways with no probs ,
,and looking at the 60 trim 52mm ,and 55 trim 56mm ,maps should really work up to 30 psi , i know of a chap who runs a gt type on his bike at 30 psi ,and does 211 mph on it !

my personal experience of higher boost was at avon ,where i accidentally(sic) turned it up to 17 psi in a race ,, all i can say is that ,running 14.5 to 1 afr , it started to catch denis (with god knows what bhp) before i realized and turned it down ... so it definately works at 17 psi !:)

regards robert

Edited by robert on 3rd Sep, 2008.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Don't forget running a higher CR (which is quite acheivable with EFI) you can run lower boost and get the same sort of power as a low CR engine on high boost. I got better times on the 1/4 mile with mine on 6psi than my old 5 port did at 17psi.

I dread to think what would happen on 20psi. Will have to be done though!

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1/4mile in 13.2sec @ 111 terminal on 15psi

good insight there must think about this some more looking at the physicl dimentions there doesnt seem to be much change between the three (17/25/28) suppose it depends what sort af a/r you can get seen a gt2860rs but it seems to have a turbine a/r of 0.86 and a compressor a/r of 0.60 which seem a bit large will have to dig deeper,

love that straight cut scream!!!
______
/___|_____
_ (@)___(@)

Cheers guys. Ill carry on researching and see what i can find. A/R ratios for the GT17 ? Got inlet 0.53 and 0.43 exhaust on a piece of paper here.... sound about right ?
Sorry if im hi-jacking the thread abit...

"So wat we gonna do tonight Brain?"
"Same thing we do evernight Pinky!"
"Try to take over the world!"