Tuning turbo time!

[craigb244]

Done some piston work seeing as I have so many sets.

managed to machine out 6CC of metal dropping the C/R to 9:1


16valve engine combustion chamber dimensions i worked out for anyone thats interested

Standard compression 10.60:1... calculated at 10.5527:1 guess fiat rounded it off... close enough.


piston dish machined out to 20CC (20ml)

 

[randomizered]

That a 1242 16v compression?

Looks like the 1368cc N/A run 11 or 10.8? CR

and 1368cc turbo run 9.8 CR

Got any pictures of how much you machined? Does it look like much?

 

[whitz]

1.2 16v CR is 10.8:1
1.4 16v CR is 11.1:1

Ash

That a 1242 16v compression?

Looks like the 1368cc N/A run 11 or 10.8? CR

and 1368cc turbo run 9.8 CR

Got any pictures of how much you machined? Does it look like much?

Ash

 

[randomizered]

I think there must be a bit of variance between specific engines between cars. Probably down to the gasket. I've read a few different figures. Still whats 0.2 CR between friends....not much tbh lol

 

[Munkul]

10.6:1 and 10.2:1 are the two ive always read about for the 1.2 16v. I always put the difference down to the MLS gasket vs the composite gasket respectively.

 

[craigb244]

the piston tops are a tad over 6mm thick, and that is only about a 1cm square right in the center

I did some research and 5mm is safe on a piston. but that was on a much larger piston where the area under it is much bigger then 1cm so subject to more force. also the oil squirter keep it even safer.

I have machined 1.2mm from the top and made dish slightly wider with less of a taper.


ill get photos tomorrow after they are cleaned

 

[randomizered]

Force is all relative. greater piston area = less force be square whatever. Sure compression has a lot to do with this as well. Still, I'm sure taking reasonable amount out will have no ill effects.

 

[craigb244]

Force is all relative. greater piston area = less force be square whatever. Sure compression has a lot to do with this as well. Still, I'm sure taking reasonable amount out will have no ill effects.

took me wrong
in engine with a CR of 9:1 will have the same pressure per area what ever size the engine.
flip one of our pistons over (or look at the photos i posted of the pistons) and you will see that you can only really see a small square of the piston crown between the metal around the gudgeon pin.
Only this area is 6mm. thick and the rest tapers up to 8/9mm onto the skirts.


My reason for say I should be ok machining more then recommended (i haven't)
is that it was for much bigger pistons where leverage forces (I think) would be more...
bit like braking a pencil... anyone can do it... but try braking a half in half

 

[craigb244]

quick photo of the machined piston next to standard.

Ive been at them with a sanding disc because im going to polish the tops.

opinions? would you trust them? haha

 

[randomizered]

Certainly doesn't look like too much and worth a punt I'd say

Are you doing anything with the head?

 

[craigb244]

yeh... whats the worse that can happen... blow a hole in the piston?...fragments band a couple of valves?... fragments go into the turbine causing mass destruction? lol

head... I am just going to smooth the transaction between valve seat and head there is a large step on each.
smooth a few lumps and bumps in the casting but thats about it.
with a turbo even if i got it perfect id only gain a little and id have more chance of fecking it up. (plus im to lazy to mess about with 16ports!)

 

[Munkul]

nice work on the pistons, looking forward to seeing how this turns out

I still say you arent going to be able to reap the benefits of squish band unless you spent a few months on mapping, but meh...

 

[craigb244]

the squish band should help with det more then anything else.

update: finished building my mates 16valve head up so now started building my head up... valves ground back in, new stem seals fitted.





measured the piston crowns and they turned out to be 5.75mm on my machined pistons.

 

[craigb244]

right, not much to say as ive been working on my mates 16valve conversion, but I lobbed off the end of a 16valve manifold and found it to be impossible to use for a cheap turbo manifold (was going to weld a turbo flange onto it just to test the engine before building a proper tube manifold)

looks like ill be building a jig to make a real manifold. might as well make a few...

 

[Todger182]

I've just had some fun of my own :bang:.

Glad to see your going to be doing the manifold first, just means you have no way of testing to see what the possible gains/loss would be between the two.

Thanks

X

 

[craigb244]

yeh... personally I highly doubt the manifold would make much noticeable extra power on our cars.

at least it will look good haha (other then my horrific welding.... but thats what grinders with flapper discs are for lol)

 

[woj]

yeh... personally I highly doubt the manifold would make much noticeable extra power on our cars.

There are people that would disagree I do not have any opinion on the subject myself, but see what this guy did:

https://www.fiatforum.com/cinquecento-seicento/76248-turbocinqy1250s-new-upgrades.html

One may ask what is the sense in spending so much time on a manifold (and also limit the servicability of the car :thumbd), but oh well...

 

[craigb244]

thanks woj, been looking for that thread for a while. i plan on doing a copy of that

 

[fingers99]

Apropos power, probably not a lot, directly. Apropos when the power comes in, a great deal. You can usefully use a smaller i/d pipe than the original, smoother, larger radii on the curves, equal lengths (or volumes -- easier to check) to spool up a larger turbine(or turbo) more quickly.

These things are usually made up of 30-40 schedule mild steel gas/steam pipe. Bloody thick and pretty much indestructable. That way you also avoid the horrors of dis-welding.

 

[woj]

thanks woj, been looking for that thread for a while. i plan on doing a copy of that

And fit it under Cinq's hood together with a 16V engine, are you insane?