Well, I might have to buy new pistons. I made a mistake when doing calculations about compression ratio.
First of all, I dont know my current deck height. Internet says it is 191mm, but Wiseco uses 192mm. That one millimeter is going to make a huge difference. We’re talking here something above 12:1 compression ratio if the deck height is 191mm.
Also, Wiseco pistons have compression height of 30.68mm and as far as I can tell, stock pistons have 30,5mm. With a small end pin, I set a stock piston next to Wiseco piston to show the slight 0.18mm height difference. Hope the photo is clear enough:
I have to find a good source for either deck height or deck clearance.
Edit: New calculation
- Bore: 81.5mm
- Stroke: 77mm
- HG thickness: 1mm
- HG bore: 82mm
- Deck clearance: 0mm
- (this is a rough guesstimate. Many sites give a 0.38mm deck clearance. Wiseco pistons are 0.18mm taller than stock, which means 0.2mm deck clearance. Also, my block is shaved slightly (guessing 0.2mm) so total will be 0mm)
- Piston volume: 5.9cc (domed)
- Combustion chamber: 36cc (not measured yet)
With these values my static compression ratio is 12.3:1, which is slightly high 😀
If I change the head gasket to 2mm thick, CR goes down to 10.8:1. Only problem then is the squish cap, which is way more than optimum.
- 1mm headgasket – 12.3:1 CR
- 1.2mm headgasket – 12:1 CR
- 1.4mm headgasket – 11.7:1 CR
- 1.6mm headgasket – 11.4:1 CR
- 1.8mm headgasket – 11.1:1 CR
- 2mm headgasket – 10.8:1 CR