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Home > Beginners Tech > Lowering compression ratio

minimauritius

69 Posts
Member #: 10545
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MAURITIUS

Hi all,
I can't make a decision on what to do with my compression ratio for my turbo engine.
What would you choose between fitting a cometic gasket (I know it is not ideal) and going for round chambers ?
Engine is fresh 1360 with Hypatec pistons actually running 10.3/1 comp ratio with 24.5 chambers ( cost me two weeks of work and two dremels).
I would need another 5cc somewhere to make it closer to a compression of 9/1 (not looking for a lot of boost).
Thanks for help I can sleep at night lol


Joe C

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12307 Posts
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Carlos Fandango

Burnham-on-Crouch, Essex

is it skimmed at all,

if not man up and get som metal out of those chambers, or pay somone to do it for you, its not exacty expensive around 80 quid?

also ftop boloxing around with dremels, get somthing with a bit moire go, maybe a cheap router?

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

https://joe1977.imgbb.com/



minimauritius

69 Posts
Member #: 10545
Advanced Member

MAURITIUS

Where I am I can only make the job myself... Router could be faster than a dremel I admit what are your thoughts on the round chambers ? Don't see how to get 30cc keeping the beak


Joe C

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Carlos Fandango

Burnham-on-Crouch, Essex

28cc is common with the beak still in, on an unskimmed head though.

problem is the pistons.



On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

https://joe1977.imgbb.com/



minimauritius

69 Posts
Member #: 10545
Advanced Member

MAURITIUS

Pistons ? For the use in turbocharged or to get the cr low enough because of their dish ?


Joe C

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Carlos Fandango

Burnham-on-Crouch, Essex

Yep, with 24cc in the head i was at about 8.2:1 on a 1380 with 18cc pistons.

It's possible to get some taken out the pistons, but obviously that's an engine out job.

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

https://joe1977.imgbb.com/



minimauritius

69 Posts
Member #: 10545
Advanced Member

MAURITIUS

Yes they are said to be 7cc but when I measured the dish with a syringe it was more like 5/6.
Don't really want to touch the lower part of the engine...


Turbo Phil

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4619 Posts
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My sister is so fit I won't show anyone her picture

Lake District

Round chambers are far from ideal as they'll produce no mixture motion or squish, but it doesn't sound like you have much option.

Phil.

WWW.TURBO-MINI.COM


minimauritius

69 Posts
Member #: 10545
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MAURITIUS

Cometic gasket is really not an option?


jamestar

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489 Posts
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Devon

Whereabouts are you? I have a head I'm putting up or sale shortly and the chambers are 28cc


minimauritius

69 Posts
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MAURITIUS

If you don't mind shipping to Mauritius i'll take it !


PhilR

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Birmingham

On 1st Dec, 2016 minimauritius said:
...I would need another 5cc somewhere to make it closer to a compression of 9/1 (not looking for a lot of boost)...


Factory engines ran 9.4:1 CR for 7psi with old technology ignition, safety margin for low octane fuel, no intercooler, poor servicing, unmonitored AFR, unmonitored knock, generic profile SU needle etc etc etc.

Dependent on whether you can improve on some of these, you may not need a CR as low as 9:1. Exactly how much boost do you want to run?


minimauritius

69 Posts
Member #: 10545
Advanced Member

MAURITIUS

Really not much, standard will be fine 7psi would be the max. I'm not looking for huge power but good torque.


minimauritius

69 Posts
Member #: 10545
Advanced Member

MAURITIUS

At the beginning it would be no intercooler, standard timing from my 123 distributor (metro turbo curve), I did some needles filing already so should be able to improve the fueling a bit ( I have an AFR gauge).
Problem is that it is quite hot here...
Would standard specs on a 1360 could reach a little over 100 hp? Gearbox is standard but all new bearings and cross pin diff


minimauritius

69 Posts
Member #: 10545
Advanced Member

MAURITIUS

28 cc in the chambers would bring me to 9.4:1


jamestar

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Devon

Had a quick look at postage and your looking at £250+ just for postage costs... sheeeeeit!!!


jonny f

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Dorking

Why no intercooler to start with? Take the time, do it once, do it right.


minimauritius

69 Posts
Member #: 10545
Advanced Member

MAURITIUS




On 1st Dec, 2016 jamestar said:
Had a quick look at postage and your looking at £250+ just for postage costs... sheeeeeit!!!


Anyway the customs would block it as it is a used part.
I can only receive new parts so they can get the VAT on it..


minimauritius

69 Posts
Member #: 10545
Advanced Member

MAURITIUS




On 1st Dec, 2016 jonny f said:
Why no intercooler to start with? Take the time, do it once, do it right.

I'm after a standard look in the engine bay and don't want the big intercooler hoses unless I can make them pass in the wings


stevecoolerking

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You'd have to run a silicone hose from the turbo to your inlet so you might as well pop an intercooler cooler on , a nice slim but long one .. ? About 60 bucks ..


D4VE

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lowestoft suffolk

In the space of a few inches?

On 24th Oct, 2015 jonny f said:
Nothing gets past Dave lol

NOTHING GETS PAST ME!! *tongue*

1/4 mile 14.7 @ 96mph 12psi boost
Showdown class A 2nd place 18.6 @ 69mph


Rammie2000

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1750 Posts
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belgium

I do it with a dremel. Only 7 hours per chamber

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018


Turbo Phil

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4619 Posts
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My sister is so fit I won't show anyone her picture

Lake District

On 11th Dec, 2016 Rammie2000 said:
I do it with a dremel. Only 7 hours per chamber


7 hours !!!!!! Jeez. Do you have a compressor ? If you why not invest in a cheap die grinder ?

Phil.

WWW.TURBO-MINI.COM


minimauritius

69 Posts
Member #: 10545
Advanced Member

MAURITIUS

I burned two dremels just to get 3cc from each chambers.
Think I'll try a cometic gasket.
Bk 450 overhang my bores a bit, had no problems while N/A but the cometic being 74mm diameter should fit better.
Does people experienced problems with cometic on A series ?


Joe C

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Carlos Fandango

Burnham-on-Crouch, Essex

Theres 2 cometics listed, think one is under sprite, or something in-line mounted, they are a good gasket, but you need a block and head that's been surface ground rather than just milled.

Another cheap option is the copper gasket (aeg470?) that's got a larger did fire ring.

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

https://joe1977.imgbb.com/


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