Confirmation Of Cr Ratio

[wardy18 33 1 Cars]

Just need confirmation of my details for the CR Ratio for the latest build

 

XU10 8v head

Xu9 8v Bottom End

Mi16 Piston/Rods

 

Bore - 83mm

Stroke - 88mm

Head G Bore - 83mm

Head G Compressed Thickness - 1.2mm

Head Combustion Chamber Volume - 36cc

Piston Deck Clearence - 0.4mm down the bore

Piston Dish Volume - 2cc

 

I come out with 11.2:1 however using the search i come up with a few variations of Mi16 Dish Volume and Deck Clearence from different people.

 

Also should i take into account cleaning skims on the head, how much would these have reduced the head cc over the years?!

 

Many Thanx

 

Simon

[EdCherry 34 1 Cars]

You should take into account the skims its had but it all depends on how much is taken off, you'll need to measure it to find out.

 

If I wasn't watching the F1 id confirm your CR, but I am sorry.

[wardy18 33 1 Cars]

no worries mate, im bored of the GP which is why im thinking CR rations

 

ill measure the head when i get it back!!

 

oh and big bummer, the new head hasnt arrived in time so cant do the hillclimb monday, oh well

Edited August 30, 2009 by wardy18

[Sandy 191]

Using the numbers you've given, I make it 11.2:1 aswell

[wardy18 33 1 Cars]

thanx sandy, just need to confirm mi16 dish cc and deck clearence

[welshpug 1,657]

I'm sure its 2.8cc for the D6C pistons which are 37.12mm tall.

 

not sure if they come level with the deck though, find that then compare it to (add 37.12mm to 143mm long rod) 180.12mm

Edited August 30, 2009 by welshpug

[wardy18 33 1 Cars]

did a few measurements yesterday and its seems the mi16 pistons are sitting 1.4mm down the bore (i dont know if this would reduce at all once the head is torqued down on the liners however)

 

also the XU10 head height is 158.45mm compared to the standard figure of 158.73 so thats 0.28mm skimmed off or 11thou of an inch

 

my question is on the XU10 head with 36cc combustion chambers how much of a difference to the 36cc would 11thou make?

[Sandy 191]

About 1.6cc I reckon.

[wardy18 33 1 Cars]

About 1.6cc I reckon.

 

Thanks Sandy, do you know this from experience or do you know how to work it out properly?!

 

Would be great to know

[DrSarty 90 1 Cars]

&

 

Looking forward to hearing how this engine works out. Would be good to see some video when it runs and what difference it makes to any competitive runs.

 

Good luck with everything.

 

Incidentally, can CR be worked out by a comp test? What I mean is I'm sure it can, because if we know what a standard engine makes in PSI, because we know the standard CR then surely we can figure out backwards from a newly measured PSI? Am I being dumb?

Edited September 4, 2009 by DrSarty

[wardy18 33 1 Cars]

i have a 1/4 mile Sprint event tomorrow so fingers crossed it all goes to plan

 

i just have the carbs to re-fit and the cam timing to do then the first fire up and then run the new rings in hard

 

my 1/4 mile on the std head/block was 14.24s so ill see now what its like with the XU10 head on std block but don't want to rag it too hard on new rings straight away

[Saveit 0]

Will be very exciting to see how it acts up! Please do tell us about it when you get back!

 

I am going to be racing my XU10 conversion the 12th of september so ill post my experience with the engine in here.

[wardy18 33 1 Cars]

Yeh great, i got a hillclimb on the 12th Sept too, praying for good weather

[wardy18 33 1 Cars]

Thought you might like to see the finish engine build, it has been the hardest engine i have ever done and almost broke me into tears (i also need to fit a new cupboard door as my fist knock it off)

 

BUT

 

It revs so cleanly and smoothly and even though its std non balanced lightened bottom end its revs so easily

 

Just need to run it in the morning then go to my event and test it

 

couple more

[DrSarty 90 1 Cars]

Viddy-oh!

 

[Saveit 0]

Looks good!

 

Will be exciting to hear how it pulls.

[petert 587]

did a few measurements yesterday and its seems the mi16 pistons are sitting 1.4mm down the bore

 

That means you've got XU9J4Z (DFW) pistons. What letter is stamped in the crown? X or Z?

[wardy18 33 1 Cars]

i really cant remember what was stamped on top, sorry

 

they doin the job pretty well as it did go really well but need the carbs jettings adjusting to suit the new head

 

once this is done and the ignition timing properly set i cant wait to test her out again