Ian928

I cc'd my 1980 Euro S combustion chambers and pistons today (see links to pictures furher down). I did one piston three times and head cahmabers and got consistent numbers. Here are the results:

Piston cut-outs: 8,7ccm
Combustion chamber: 53,5ccm

This is Tony's numbers (for S4 but I could not find any other info):

Deck height = 0,076mm: 0,6ccm
Compressed headgasket = 0,9mm: 6,7ccm

Using 583ccm for bore*stroke calculates to a compression of 9,4:1!!

Of course, deck height might be wrong, but can it really be lower?
Of course, gasket thickness might be wrong, a compressed thickness of 0,3mm give the expected 10:1 compression ratio.

The cc-ing process:
http://www.flickr.com/photos/21967367@N00/

Ian928

There is good news here for you US-drivers. If you use Euro pistons in your US 4,7 your compresson will be higher than for Euro S! According to Mark Kibort the US 4,7 head volume is 48ccm, and using the same numbers for deck height and gasket thickness gives a compression ratio of 10,8:1!

mark kibort

you just verified my euro piston numbers for the 80-83 euro pistons, but the combustion chamber should be 48cc, not 53. that sounds like a US 4.7 head!
quick check is the valve size. 40-45mm in diameter
we built up scotty's euro 82 and it came right out to 10.2-3 :1 with deck hight being shaved a few thou, but even without it shaved, it was very close to 10.0:1
gasket is 7-7.8ccs. based on a sub 1mm gasket thickness.

http://kb-silvolite.com/calc.php?action=comp


MK

mark kibort

Its been a while, but i think i had calculated the US pistons with cuts, on a euro head. I think ive said the heads were always in the 48cc range, but pistons are all over the map. euro pistons at 8cc, while euro 84-85 is only 2cc, and the US with those little flycuts, but little trouth too, is somewhere inbetween. I think the combination of the US pistons, euro heads and shaved block was going to get us over 10:1 on a US piston being used.
MK

Ian928

I found one of your first posts about this, and there you said the Euro heads were 52ccm as opposed to the 48ccm US heads! My valves are 40 and 45mm. I guess this proves it is a Euro "S" head?

I am not sure what's going on. I am quite sure I am using the correct way to measure volume. Could there have been a design change in the heads between 80 and 82? Have you looked at my pictures? Do they look exactly the same as the ones you have been dealing with?

One thought: "cc" - is that cubic centimters or has it something to do with inches? I use cubic centimeters (= ml)

Skunk Workz

CC is cubic centimeters,Ian...

Herr-Kuhn

I don't think this is out of line. The marketed 9:1 of the 4.5 liter is actually like 8.1:1. I beleive that you might have the full 10:1 after the heads are shaved to the min for resurfacing. As with everything there are tolerances and I beleive there is a +0/-0.6 tolerance on the CR.

Ian928

Yes, this is probably correct. It is the same situation with the S4, as others have proved, so it makes sense that the same principles were utilzed for the early cars.

Ok, If the compression is 9.4:1, is this Ok for turbo/compressor or should I reduce it to 9:1 or even lower just to be sure?

GlenL

Are there part numbers on the heads? The chamber shape isn't like the way I recall mine looking.

Ian928

Part number: 928.104.348.3R. Do you have a possibilty to check it?

m21sniper

"the first big lie?"

IMO the HP ratings for the Euros are either A) a blatant lie, or B) BHP ratings vs the US models SAE ratings(i suspect B to be the truth.

There's no way a car with 76 more HP such as the 84 Euro suppesedly has over the 84 US model only results in a .3 sec 0-60/1/4 mile edge as is claimed.

No way.

Look at any 300hp car in the 3300lb range such as the 84 Euro is, and they're all high 13 second cars.

STI, Lancer EVO, 05 Mustang GT, etc, etc.

IMO the Euro numbers are BHP, not the SAE net the US cars are rated at.

Vilhuer

928.104.348.3R is casting number of the head. It can tell actual part number only if said head is only one that was done from this casting.

300 BHP is around 296 SAE NET. I believe many stock ROW S models have given that out in dyno.

m21sniper

300bhp is WAY less than 296sae net.

BHP is HP measured at the flywheel with no accessories installed.

SAE net is defined as "HP reading at tailshaft of transmission with all accessories installed and operating".

Vilhuer

True, my mistake. I meant DIN hp. Factory has used DIN outside USA for decades. That's source of 320 DIN vs. 316 SAE NET hp numbers for S4, 330 vs. 326 for GT and 350 vs. 345 for GTS. All of these numbers are from crank but accessories included. Same measuring point, same equipment is on, slightly different way of measuring.

m21sniper

Ok, gotcha.

I suspect that the HP rating for the 83 Euro if converted to SAE net is more like 265hp, vs the US models 234.

If the sae net HP spread was any bigger the performance numbers between the 2 models would be much bigger too.

300sae net HP would mean that the 84 Euro should be fully .75 seconds faster both 0-60 and 1/4 mile vs the US model, but the difference is only about .3 seconds, which would lead to the conclusion that the actual SAE net HP figure for the 84 Euro is actually about 265.

It's the only way to explain how a car in the Euro 928s weight range with 300hp can turn an anemic mid 15 second 1/4 mile. In fact, because the euro is a bit lighter(about 100lbs) then the US model, it's highly likely that the actual SAE net figure for the 83 Euro is really more like 255(and 265 for the 84 Euro).