Donations towards server fund so far this month.

 
£0.00 / £100.00 per month
Page:
Home > 998cc > Which pistons for 998 turbo?

Paul S

User Avatar

8604 Posts
Member #: 573
Formerly Axel

Podland

Update,

According to Des Hammill's book on 998 tuning, the gudgeon pins are a different diameter between the A and A Plus engines.

So I'm going to need some 998 A Series rods if I want to use the 20773 pistons.

Can anyone confirm this?

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."


Tom Fenton
Site Admin

User Avatar

15300 Posts
Member #: 337
Fearless Tom Fenton, Avon Park 2007 & 2008 class D winner

&

TM legend.

Rotherham South Yorkshire

Yes, the A and A+ pistons only fit the correct rods. So A rods for A pistons, A+ rods for A+ pistons.

If you use the A pistons, be sure to invest in a set of PTFE buttons to retain the circlips. I once had one get out and wreck an engine.


On 29th Nov, 2016 madmk1 said:


On 28th Nov, 2016 Rob Gavin said:
I refuse to pay for anything else


Like fuel 😂😂


wil_h

User Avatar

9258 Posts
Member #: 123
Post Whore

Betwix Harrogate and York

Interestingly, I use the 20773 pistons on rods that came from an A+ engine which had 20600 flat top, circlip fitted pistons.

So, A+ 998s were fitted with these pistons. I've never checked, but I would assume that the gudgon pin diameters are still different though.

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

www.twin-turbo.co.uk

On 2nd Jan, 2013 fastcarl said:

the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.


Paul S

User Avatar

8604 Posts
Member #: 573
Formerly Axel

Podland

Apparently, the 998 A Plus pistons changed from circlip to press fit in the late 80s.

So, logically, as long as the engine is not late 80s it should be possible to use the 20773.

Sods law is that the 998 A Plus engine I have just aquired is late 80s. It has a 99HE20 number which is the same as the engine fitted to my lads Mini 30 (1989)

I'm starting to think that for now I should stick with flap top slipper pistons and limit the boost.

I've also aquired an unleaded standard 12G295 head (megabucks but worth it) This should give me a compression ratio of approx 8.8:1 with flat top pistons.

I'm looking for about 120 bananas and 100 ft lbs which should be achievable with 10 psi boost.

But will it be possible to run 10 psi on an 8.8:1 compression ratio and a low overlap cam such as the SW5?

Problem is, I can see that I will soon want to up the boost but with limited piston options this will not be possible.

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."


Paul S

User Avatar

8604 Posts
Member #: 573
Formerly Axel

Podland

This is the latest spiel from the Minispares website for the new Mega pistons for the 998:

"This modern piston from Hypatech are flat top with oil holes rather than slots behind the rings and are suitable for up to 12-1cr. The flat top design will yield a compression of about 9.6:1 when used with a Cooper cylinder head. This pistons replaces the original Hepolite pistons 18516KR and P20950 used on the original Coopers. Owing to non availability of 998cc pistons these have been re-introduced in Mega type material for use in any engine whether road or race at a very competitive price. non slipper type and you only use 2 of the 3 rings from the ring set. On later press fit con rods you just discard the use of circlips or alternatively hone out the small end of the con rods"

I'm thinking of using these in my 998 turbo with an original 12g295 head which should give me about 8.7:1 static compression ratio.

My engine is currently fitted with the press fit slipper pistons.

Anyone like to comment on the last sentence of the above?? Do you think that you can you just discard the circlips and use these pistons as press fit?

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."


wil_h

User Avatar

9258 Posts
Member #: 123
Post Whore

Betwix Harrogate and York

On 21/04/2006 14:52:11 Axel said:

Anyone like to comment on the last sentence of the above?? Do you think that you can you just discard the circlips and use these pistons as press fit?


That's how it reads to me.

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

www.twin-turbo.co.uk

On 2nd Jan, 2013 fastcarl said:

the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.


Paul S

User Avatar

8604 Posts
Member #: 573
Formerly Axel

Podland

Yeh, but we know how the suppliers will tell us anything to get a sale!

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."


joeybaby83

User Avatar

6274 Posts
Member #: 509
Post Whore

Isle of Man

indeed, Im gonna stick with the std flat tops now and use head similar to yours to get the compression down on the first 998 build, after that ill use the +20 dished pistons that minispares sell (same as what wil_h is running i think).

With the flat tops and 28.3cc head, the 8.8(ish):1 cr well get will (according to the graphs benross posted up a while back)...

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=7872

...we should be able to get away with around 10psi if we use decent pump fuel.

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

"did you know you can toast potato waffles?"



hansvdb

6 Posts
Member #: 946
Junior Member

Netherlands

the 12G295 head is from a 998 Cooper and a MG1100, if I understand well.
On which models was this head and does it fit straigth to the cilinderblock off the mini??


Tom Fenton
Site Admin

User Avatar

15300 Posts
Member #: 337
Fearless Tom Fenton, Avon Park 2007 & 2008 class D winner

&

TM legend.

Rotherham South Yorkshire

Just to add, it fits straight on 850/998/1098cc engines (small bore)

It won't fit onto 1275 large bore engines.


On 29th Nov, 2016 madmk1 said:


On 28th Nov, 2016 Rob Gavin said:
I refuse to pay for anything else


Like fuel 😂😂


miniminor63

User Avatar

1849 Posts
Member #: 672
The oversills police

Oslo, Norway

it will fit, but will not work:)


mcalvert39

388 Posts
Member #: 442
Senior Member

Manchester

hi all. I know this is an old thread but their are many unanswered questions!

i was looking at the dates on the posts and most are from 2005! So any updates on the P20773 piston? has it worked? survived?
Reason im asking is that my blocks now at the machine shop and they want to know what im puttin in it.
best regards
matt.


wil_h

User Avatar

9258 Posts
Member #: 123
Post Whore

Betwix Harrogate and York

The 20773s appear to be an ok piston. But I went through two sets last season. Mainly I think because of high inlet temps.

This year I am trying the Mega pistons, so we'll se how it goes.

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

www.twin-turbo.co.uk

On 2nd Jan, 2013 fastcarl said:

the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.


mcalvert39

388 Posts
Member #: 442
Senior Member

Manchester




On 6th of Mar, 2007 at 03:50pm wil_h said:
The 20773s appear to be an ok piston. But I went through two sets last season. Mainly I think because of high inlet temps.

This year I am trying the Mega pistons, so we'll se how it goes.


Are you using an intercooler? If so have you thought about water injection or aid inlet temp cooling?


wil_h

User Avatar

9258 Posts
Member #: 123
Post Whore

Betwix Harrogate and York

Water injection is for use when you have the wrong turbo. turning the boost down is easier and has the same effect.

Yes we have an intercooler see www.twin-turbo.co.uk

A new turbo is the answer.

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

www.twin-turbo.co.uk

On 2nd Jan, 2013 fastcarl said:

the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.


weewheels

User Avatar

157 Posts
Member #: 1508
Advanced Member

n ireland killyleagh

PISTON SINGLE MINI 1000cc +020 P20773-20 how much can be milled out of these any idea? thanks


I'm stupid Ive A fiesta with most of the bits to make my megajolt thingy. Thick or what!!!! OHHHHH and ive got a metro for free !!!!! Metros have become rare over here!!!!!!!!!
http://s216.photobucket.com/albums/cc273/weewheels_2007/


wil_h

User Avatar

9258 Posts
Member #: 123
Post Whore

Betwix Harrogate and York

Not sure how much you'd need milled out. they have a 6cc dish as standard.

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

www.twin-turbo.co.uk

On 2nd Jan, 2013 fastcarl said:

the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.


Richie

User Avatar

3184 Posts
Member #: 628
Post Whore

a LIL fishing village on the coast - Newcastle Upon Tyne

just read this thread, and it has helped me with my future build, which alas will be 850 or 998 turbo pending on what needs to be done :)

Yet again TM provides answers to the many Turbo realted questions......and other shit too !

Edited by Richie on 10th May, 2007.



______________________________________________________
TRADER HALL OF FAME
BENROSS...MINIMARK..WOLFIE (comic genius).....CARL....MARTPAUL.......AXEL
______________________________________________________
TRADERS OF SHAME
1 user....pm me 4 details

LEGENDS
MikeRace, Mini13

On 17th Aug, 2009 Jay#2 said:
I doubt I'll be dipping into the 13's like you did though!






BENROSS

User Avatar

9812 Posts
Member #: 332
Resident Cylinder Head Modifier

Mitsi Evo 7, 911, Cossie. & all the chavs ...... won no problem


mcalvert39
water injection is a band aid for not doing the job right in the first place buddy (nothing else)
quote:- CORK Bell

how true! *wink*

On 6th of Mar, 2007 at 06:27pm mcalvert39 said:



On 6th of Mar, 2007 at 03:50pm wil_h said:
The 20773s appear to be an ok piston. But I went through two sets last season. Mainly I think because of high inlet temps.

This year I am trying the Mega pistons, so we'll se how it goes.


Are you using an intercooler? If so have you thought about water injection or aid inlet temp cooling?






clubminiflip

User Avatar

1840 Posts
Member #: 54
Post Whore

nr coventry

what would happen with a 295 head & 20773s+20's i think the C/R is getting very low?

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

Home > 998cc > Which pistons for 998 turbo?
Users viewing this thread: none. (+ 1 Guests) <- Prev  
To post messages you must be logged in!
Username: Password:
Page: