Choises/calculation done right?
Turbo Mini Forums

Hi all,

I am in the proces of building my own supercharged 1293 mini engine.
At this moment I am at the point at which I need to reduce static CR by enlarging combustion chambers.
I was hoping to get a bit of advice..

Main components are:
- M45 SC
- Ford RS intercooler
- Rebuilt 1293 engeine and gearbox (sc dropgears, X-pin diff, etc)
- MG Metro cam
- Programmable ignition with MAP sensor.
Boost will be about 14,7psi (std sc pulley and Mpi crankpulley)

It will be set-up on a rolling road.

My plan concerning the head:
I want to reduce the static compressio ratio to 8-8.2:1.
I am using a MG metro head which has a combustionchamber of about 20,6cc

My calculations tell me to achieve 8.2:1 I need to enlarge the combustion chamber to 33,5cc.
-Swept volume = 323.25cc
-Ring land volume = 0.9cc
-Piston dish = 8.3cc
-deck volume = 0
-gasket = 3,2cc

I'm not looking for a top HP engine for racing, I want to use it for 'sunday drives/blasts' on the road.

Now my questions:
- Is the combination 8:1CR, 14,7psi, MG cam going to make a critical engine that will blow up in my face within hours/minutes or will it last because using IC and progr. ignition? (I'm not an extreme engine trasher)
- Have I done the CR calculations ok, 33,5cc looks a bit highish to me?

Hmm this has become a bit longer than ment :$
I hope some of you can support, forced induction is a new adventure for me.. :)

Many thanks in advance.
Han

Dazed and Confused....

not sure about the calcs, but I think you can get away woth a higher c/r than 8-1 on that boost if you are using mapped ignition and intercooler.

I run 20psi on 8-1 with no probs, maybe 8.5 would suit yours better, and be eaiser to achieve.

Others will hopefully back me up on this.

Is it possible to get that much dug out of the head?

what does 14,7psi mean?

14.7psi? 7psi? 14 or 7psi?

you need to get some extra ccs in your pistons as the head wont get 33.5 in it.

If you want that CR I'd go for 28cc head and 13 is pistons. Pistons should be easily machinable.

However, the M45 has a maximum usable psi of 10.

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

www.twin-turbo.co.uk

"However, the M45 has a maximum usable psi of 10." Very true, i spent hours looking in to all this and getting an understanding of compressor maps etc and it seems that anything above 10psi of boost with the m45 just generates heat and not a lot else.

well the '.' has been used in plenty of other places in the post.

well 14 point 7 psi is too much anyway.

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

www.twin-turbo.co.uk

On 29th Jul, 2008 Vegard said:

On 29th Jul, 2008 wil_h said:
what does 14,7psi mean?

14.7psi? 7psi? 14 or 7psi?

In other parts of the world, we write "," instead of "."before decimals.

Ignorant EX Empire people!

Also, 14,7 is quite near 1bar which makes this plausible.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

lmao

Wasn't it an ex British foreign minister that claimed the following when the Dover Calais connection was down:

"The continent is now isolated"

Fucking excellent comment

We dug the mote for a reason..

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Hmm, I like the quick replies, next day already..!

Sorry for mixing up my ","s and "."s .....
Probably to do with some 'copy-pasting'..
Or my dislektya :)

What I ment was 14.7psi (like 1ish bar)
I thought I read somewhere an M45 was used to make more than 10 psi.
Nevermind, that would mean I have to get a bigger SC pulley (or smaller crank pulley but that would affect altenator and waterpump action aswell).
On the brighter side it would mean I don't need to dig out the head that much...
How about if I rum 10psi with 9:1CR or should I go with 8,5:1?

Oh btw, anyone know an adress for bigger SC pulleys?
I have seen loads with smaller diameter but none with bigger...

Thanks again for the swift replies!
Han

Dazed and Confused....

There are people who have run way over 10 psi with the 45, but they obviously haven't looked at or understood the spec/limitations of the blower.

If you are planning using an intercooler you must be using a blowthrough system or some form if injection. If so, then 9:1 and 10psi shold be safe.

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

www.twin-turbo.co.uk

Hi Wil,

Thanks for making clear I am a newbie to forced induction...
That was the major reason for posting here.

Seriously though, from jonspeed I understood that 10-12 psi was no problem in their set-up, without intercooling, programmable ignition and MAP sensor.
So my thoughts were I thought with my setup (indeed blow-through) I could push it to about 14psi.
This way I could use the Mpi pulleys without making a custom one.

Anyway I have found a company that can supply me with a larger pulley, I only need to have to get someone to make the center ID to mate it to the SC shaft and that shouldn't be a problem.
Going to 10psi boost also means I don't have do major job in the combustion chamber I use Hepolite 8,3 dish pistons.

Thanks again for the replies!
Han

Dazed and Confused....