Hi there,
Im hoping someone can help me with some info I need-
Approximatly how much do I have to take out of the chambers in the head to lower the compression for a turbo application?
Or if I use a decompression plate, do I Have to use longer push rods or anything?
What would be the best way to lower the CR a tad, not a great deal because the boost is going to stay low, starting at 4-5psi, then a max of about 8-10psi way down the track.
Its an A+1275.
Also one last thing, the turbo people on here, are they using n/a dizzys or are they using metro turbo dizzys? Or something else perhaps?
Thanks in advance
Cheers

Wyan, you`ll need to "CC" the engine (That is to volumetricly measure the combustion chamber, including what`s in the block above the piston at Top dead centre)

effectively there are 3 volumes that you will want to know,, the cyl head chamber size,,, the headgasket & how much volume is in it if we pretend that it`s fitted & squashed down,,, & what`s in the block below the top deck, but above the piston with the piston at Top dead centre...

these 3 volumes are what you will need to know, before i suggest anything about modifying chambers or adding de-comp plates

i`m not one for guessing these things & these engines are so old now days that anyone could have done almost anything to change them from their factory stock standard size, so physically measuring them is the only way to go for accurate results.

once you`ve measured it all then you can do the sums & work out what you need to take out of the chamber to get your optimum compression ratio for forced induction

You will need to work out the actual engine displacement (how big the engine is) IE: 1300cc,,, or 1310cc,,, or 1360cc,,, whatever it is,,,, you will need to make sure of it to get acurate results

(SV + CV divided by CV = compression ratio ) is the formula

that is --> Swept volume --plus-- Combusted Volume--divided by Combusted Volume = the compression ratio:1

& i use twin cam 16v cyl head with an aftermarket sequential injection computer which also uses crank & cam angle sensors, so no need for the usual distributor (as such)

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

What do most people do with forced induction?
If i keep the boost low, which is what Im going to do because its my daily driver, will it suffice to leave as stock? I will be using my intercooler also.
From what i read it seems that the majority of poeple using forced induction utilise standard(ish) engines if not going on a hot ground up rebuild.
Thanks for your help Matt

PS Oh I presume my internals are still stock as its a very late motor
Cheers

Be careful, some of the late A+ 1275 motors were over 10:1 C/R stock.
Like Matt says you need to measure things up.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

If you have the nornal A+ compression of 9.4:1 (best to measure it per Matts description) and if you are only running low boost with an intercooler then keeping the standard compression will be fine. Lots of turbo guys in the UK run up to 10 psi on these engines with an intercooler. Dizzy wise not sure what people are using but you can always get that regraphed to suit.

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4efte powered Clubman
supercharged 998 race car

Oh ok cool, I thort that was the case. I will be doing abit of head work, but Im not to sure if it will be altogether at this stage. Just a few more quick ones-
If I get the compression down to say around 8-9:1 mark, and if not running FI on it straight away, will it be down alot on HP?
What are some of the recommened places that will do head work?
GR?
Cheers guys,
Oh also, who does dizzy regraphing? Is this the case for points and electronic?
cheers

GR for head work and dizzy regraph if you are in sydney Regraphing changes the advance curve in the dizzy so yes for both electronic or points types.
Sydney just had their dyno day all 'A' seires turbo were carby and made more power than the gearbox will handle comfortably so would not bother with fuel injection for power, programable ingnition on ther other hand would be a good thing to have but don't need it straight away.

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4efte powered Clubman
supercharged 998 race car

Yeah im not going injection, Ive got my turbo carb now so that will be fine.
Hey Ben with yor s/c kits, do you have to run fuel return lines and a fuel regulator?
Also, i cant remember if I asked you last tiem, but do you sell the s/c pullys as well?
Thanks mate

With the SC it is a suck through system so no regulator or return lines needed.
Yep with the kit new crankshaft and tensioner pulley supplied and uses the original pulley on the SC.

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4efte powered Clubman
supercharged 998 race car

Sorry ben, I ment do you sell or can you sell me the pulleys seperatly?
Pm me if you wana, Im off overseas tomorrow but i'll keep looking on here.
Cheers mate