Turbo a mini cabriolet? you must be mad!
Turbo Mini Forums

Hello

Im Will and I drive a mini cabriolet ( the blue one! )
although i have had quite a few of them (4 Lol)
as soon as i found out they made a mini cabriolet i had to have one!
had a few after market ones until i picked up a rover one! :)

it has a 1301cc engine, modified petrol tank, boost guage, 4 pot calipers, braided hoses, metro turbo mounts and all the other tell tale signs of previously being turbo'd

now for the bad bit haha:
recently driving it on an a road when i hear a loud bang and a loud knocking noise coming from the engine
nursed it back into the garage and have started stripping the engine to locate the issue!
looks like a piston ring, but still got to get the engine out to check its nothing lower down and may aswell give it a recondition while im there..

someone has also poured brake fluid along the paintwork so needs a repaint too!

so as its going to be off the road for a while i have been tempted to add abit of forced induction :p

ive always wanted to so why not? :)

So heres the list i've bought and is currently being delivered:
A Garrett GT17
mini turbo carb with uprated dashpot spring and 8psi needle. turbo manifold
audi a4 intercooler
dump valve with kevlar diagram, also fuel regulator
a set of blue silicone hoses
and a 2 core radiator
also unrelated to the turbo build i managed to pick up some 7 x 13 deep dish mini lites with brand new tyres for £120!!
which i thought was a bargain :)

anyway, I'm 19 and have never built a forced induction engine before so it may be a case of all the gear no idea Lol
does that sound like an ok set-up?

so im here for advice and research and hopefully i'll start up a build project and someone can tell me if i do anything stupid

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Reading up on RTS Clutches

Hello and welcome.

Engine wise you need to look at your compretion ratio - mainly head and piston choice. Then an appropriate cam.

You should also look at you gearbox and diff

There are some Fecking C**T is this world, who pours brake fuild over a car.

Any Welcome, love the car always fancied one myself. hope you find the forum friendly and helpful.

Cant wait to see it finished

1972 998 TURBO SLEEPER

to my knowledge i think ive got a large valve head and dished pistons
not sure what the compression ratio is but even when all 4 cylinders were running it did seem to lack power
leading me to believe it is low compression?
(coughed when you took it over 3000rpm?)
i'll see if i can check that soon :)
cam wise i have no idea
havent got that far down yet Lol

and as the weathers nice i wouldnt mind getting on with it! haha

hoping to get it done in time for l2b :)

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i've also sold the other two cabrio minis in that pic to fund this one Lol
the black one lacked MOT and was pretty rusty
and the red one didnt have a roof and drum brakes
plus my neighbours were getting abit peeved off at having 4 minis consistently parked outside
and a 5th when my GF comes round
once had 8 out the front when i had a bbq last year!

Edited by WRLondon on 16th Mar, 2010.

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how does
11cc dish giving a 10.5:1 compression ratio with std 12g940 head sound for the turbo?

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Sounds too high

If something is worth doing, it's worth doing half of.

first turbo build and they were some pistons on ebay i was looking at :)
what sort of compression should i be looking for and cc dish?

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assuming 1293cc 11cc is a pretty decent sized dish. by my reckoning you would get a cr of around 8.7:1 with a standard 21.4cc head which is pretty good for a turbo engine.

If something is worth doing, it's worth doing half of.

Edited by Brett on 16th Mar, 2010.

Yes i moved to the darkside

Instagram @jdm_brett

The 1275 MG Metro turbo had a compression ratio of 9.4:1 & ran a boost of 7.5psi Max & produced around 90BHP.

It couldn't run any more boost because of the relatively high CR, it would suffer with detonation if the boost was any higher.

So it depends on what you would like from a turbo engine, if you want to run a higher boost you will have to lower the CR to around 8 or 8.5:1 but then then rest of the engine/gearbox/differential would all have to be uprated to cope with the increased power (depending on how much boost you run)


An easy way to lower the CR is to fit a 'decompression' head gasket, this in effect puts more space above the piston, so you can use pistons with a standard dish, but, the pistons must be uprated to cope with any boost. Standard pistons will break-up.

You'll have to do the maths when you know what finished bore you have, to see what size the dish needs to be to give the desired CR if you don't want to fit a decompression head gasket.

You'll have to know the cc of the combustion chamber (has the head been skimmed?), cc of the piston dish, the height of the piston in the bore at TDC (has the block been skimmed?), bore & stroke, thickness of headgasket to work out the CR & dish cc reqd.

"Standard pistons will break up"
At what boost do you reckon this will happen ? The standard Turbo pistons are very good & more than up to the job even at 15psi. Or are you reffering to NA pistons ?

Phil.

Edited by Turbo Phil on 16th Mar, 2010.

WWW.TURBO-MINI.COM

"modified cylinder heads" do you mean NA cylinder heads?

Utter Piffle, plenty on here have run standard pistons with decent boost, decompession plate is a bodge end of!

Do you mean standard standard pistons or standard turbo pistons?

De-comp gaskets are a BIG bodge and seriously pointless. For all the work involved in removing the head why not increase the camber size to lower compression ratio without any drawbacks, unlike the bodge plates effect on valve train geometry and double headgaskets to blow.

Standard pistons will not "break up". There are many members of this forum running a range of engine specs on many differnt standard N/A pistons. While the big boost guys will almost certainly go for expensive turbo specific pistons, there is almost no reason why on a moderate boosting engine that is well set up N/A pistons cant be used.

Swing and roundabouts if the head starts out turbo or N/A - remember there is next to no real difference bar the exhaust valves between turbo heads and others.

the pistons are +30 so thats 1301?
which is abit of a pain as it makes pistons and rings abit harder to find
I would probably only want to run it on relatively low boost as ive got an 8psi needle so a CR of 8/9 sounds about right?
but no idea whats under the pistons atm so depending on how strong the components are ie. clutch gearbox and crank
the more or less boost i'll go for

the last owner had done all the modifications, so i dont have a clue until i take it apart

if its all good and nice and strong i'll start low and build it up :p
if it can only cope with low boost then i'll just keep it low boost until i'm either craving more power/ can afford the other bits and bobs, or a mixture of both Lol

needs to be on the road for the summer though right? :)

the issue i will probably need abit of help with is cramming it all under the bonnet
as there is quite a big brake servo and a few other things in the way
may start by relocating the window washer bottle to the boot
any ideas on how to maximise room in a round nose?

Ill get some photos and a project page started when i get an engine crane and get cracking :)

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That`s had me in stitches fella.

welcome will

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

www.twin-turbo.co.uk

Lol
im going to find out the CR this weekend and im removing the engine in the next couple of days so i may be able to get some more information which would help
and thanks for the welcome
Will_H i recognise from the mini forum
aswell as the infamous 20 hour 998 turbo build

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