Technical 1242 8v SPI Preparing Engine For Turboing

[SlinkyCinqi]

howdy again people
I have another question (i know there have been many, and probably many more to come!) The 8v pistons that are currently in the block are all B size pistons which I have been told are 71.77-71.78mm dia. But the 16v pistons that i aquired are 2 B sized pistons and 2 A size pistons which are 71.75-71.76mm dia.

The question I have is are there different rings for the A and B sized pistons? or would I be ok just getting the correct rings for the bore?

I phoned my fiat dealer today but couldn't get hold of the guy i needed, just wondering if anyone on here knew?

Thanks in advance

Lenny

 

[arc]

i don't know the answer to that, but have found these on another forum that maybe of interest;

Basic. This explains what a turbo is and how it works. Also includes roller bearing vs journal and different wastegate types...
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech101.html

Advanced. Right now we're getting there, explain's what "trims" are, A/R housing size's and how they effect performance. Fueling and Engine Knock, Compression Ratio.
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech102.html

Expert. Now we are talking. Compressor Maps explained, Boost Characteristics, Boost / Air Flow for Power Target etc etc
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html

 

[balidey]

Pistons are sized to suit the bore. They are graded to the size range. You then fit standard rings (all the same size) but you need to gap them, ie dry fit them and measure the end gaps at certain parts of the bore. Then if the gap is too small you can open it up with a file

 

[SlinkyCinqi]

Pistons are sized to suit the bore. They are graded to the size range. You then fit standard rings (all the same size) but you need to gap them, ie dry fit them and measure the end gaps at certain parts of the bore. Then if the gap is too small you can open it up with a file

So i should be ok to just get the right rings for the bore, it doesn't matter that the pistons are different sizes? i.e. there aren't A and B rings as such? I know i need to get the right rings for the bore size thats not a problem

Thanks again

Lenny

 

[fingers99]

Going back a bit -- if you are still using the stock ECU, don't use the McRich! It has substantially more ignition advance and on a forced induction engine, you really want less advance when the boost kicks in. (Or you're likely to get detonation.)

 

[arc]

he is using megasquirt like me

 

[SlinkyCinqi]

he is using megasquirt like me

:yeahthat: but i did know about the Mckritch anyways someone mentiond it in a thread i was reading through a while back.

Got some bits and bobs from work today to measure the bore on my block, should be able to use standard rings me thinks, it doesn't look like it needs honed just need to know if there are A and B rings though for the different sizes of piston, the more i think about it the more i think there won't be.

Thanks again

Lenny

 

[Tricker...]

I don't think there are A, B and C rings.
Follow Balidey's advice and you will be fine - this is what I learned to but I didn't have to do it on my new rings cause they were sized perfectly.
Keep in mind that when you fit the new pistons make sure that the gap on the two compression rings are sitting as far away from eachother as possible.

 

[SlinkyCinqi]

Keep in mind that when you fit the new pistons make sure that the gap on the two compression rings are sitting as far away from eachother as possible.

when you say as far away from each other as possible, the ring gaps are meant to be 120 degrees away from each other? is this a sufficient gap? Obviously it's 120 to keep the gaps even.

Thanks again everybody

Lenny

 

[SlinkyCinqi]

Quick question again,

If i check the gaps on the old rings in the bores and they are ok, surely this would mean i can use the old rings?

Thanks again

Lenny

PS - Have a look at this and see what you make of it, http://www.aa1car.com/library/ring_end_gap.htm where it says about a blown (turbo'd) engine opening up the gaps, if my old rings are slightly worn and the gaps have opened up would i still be ok to use them? Obvisouly not the oil ring also, what should i be looking at for piston to bore clearance? bore is 70.80-70.83 and the pistons are measuring about 70.72-70.74 (this is only with my calibrated digital caliper though. I'm thinking i should get them measured more accurately with a mic.?

Thanks again!

 

[SlinkyCinqi]

Right-o, time for some more updates me thinks..

The pistons are out of the block now:


The manifold has been welded (TIG welded using dissimilar MMA rods as filler wire, shield of 100% argon, pre and post heated):


and finally, picked this up the other day


Next step is to get new big end bearings and piston rings, and the 16v pistons will be in there then, then the temp sensor and oil return will be fitted to the sump. Then need to find out what compression ratio i'm going to have before I fit the MPi head.

As always guys, comments welcomed and appreciated.

Lenny

 

[Brooky]

The pistons are out of the block now:


As always guys, comments welcomed and appreciated.

Lenny

Nice toes




Some good work how much did you get the head+inlet for??

 

[randomizered]

TIG welded using dissimilar MMA rods as filler wire, shield of 100% argon, pre and post heated

Don't know what it is but sounds impressive.....I actually have a Haynes Automotive welding book from the library.....a bit of reading, and i'm sure i'll understand

Looking good though! Can't wait 'till you get it running!

Kristian

 

[SlinkyCinqi]

howdy everybody :wave:

some more updates,

Old piston rings have been removed, and some snapped in half and used to clean out the grooves:


New 16v rings have been fitted to the pistons:


And I have new 16v big end bearings, ready for fitting the 16v pistons in to my block:


Will update further when this is done.

Lenny.

 

[Whiley]

tbh fella you should write a guide up for the turbo conversion this way when your done would be awesome as it aint as hard as most people think tbh.

 

[SlinkyCinqi]

I will once this is done, i'll use this thread as my base for all the information. The thing is, the guide will be for a turbo car like mine (and arc's most probably when it's done) running megasquirt for fuelling, spark, controlling boost etc.

I won't be able to write a guide re:MF2, decomp plates etc. But should be a good guide where people can choose their own methods of lowering compression, fuelling etc.

Lenny

 

[SlinkyCinqi]

further update! Pistons are in now with their new rings and big end bearings, see pics attached:



Need to start sorting the head now, take it apart to get it skimmed then i can somehow work out the CR (anyone wanna help me with that one?) before putting the head on, then the manifold and turbo, then line up the oil return, and turbo inlets and outlets etc. also when the oil return is lined up, i'll get a return point fitted to the sump, and still need to fit an oil temp sensor to the sump, or might just fit a T-piece to the oil pressure switch bit and try and find an oil temp sensor to fit there. Think people have done this before? can't really remember at this moment lol.

Anyways main thing, anyone want to help me work out my CR after my head has been skimmed?

Many thanks again, comments welcomed

Lenny

 

[Tricker...]

anyone want to help me work out my CR after my head has been skimmed?

Do you know if the head has been skimmed before?
Remember to measure the hight of the head before getting it skimmed - this way you can calculate CR based on the missing material. Getting the head skimmed 0.1-0.2mm won't be catastrofic regarding the CR.
On the standart 8v head the 16v pistons make 7.8:1 CR, so every 0.1mm skimmed off the head will change the CR @ 0.1:1

 

[arc]

tricker, do you know how much material would have to be taken off a head to skim to the max skim markers?

 

[Tricker...]

tricker, do you know how much material would have to be taken off a head to skim to the max skim markers?

I'll have a look in the Fiat-bibel to see if theres any max/min. measures for the 8v head. But my experience says that you can skim the 8v head further than the max skim markers :devil: