Lowering compression ratio
Turbo Mini Forums

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

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?

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

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

problem is the pistons.

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

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.

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...

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

Cometic gasket is really not an option?

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

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

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

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

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

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

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

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 ..

In the space of a few inches?

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

WWW.TURBO-MINI.COM

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 ?

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.