|
|
Post by marrcel on Oct 12, 2019 12:09:58 GMT 1
Hello guys I had two pistons with signs of detonation. There were some circumstances. The 102octane was out of stock. So i tanked the regular euro95. I was 33Celsius and moisture was high. It happend at the motorway at 120km/h about 6krpm. I noticed the temperature needle was almost out of the green zone. What can i do? Retarding ingnition now 26 deg at 6krpm. Raising barrel by thicker gasket. Modify the head volume. But how much? Yes oringed head and ss GR exhausts, vforce4. If there is someone with experience please some advice. Here some pics.       |
|
|
|
Post by Tobyjugs on Oct 12, 2019 16:06:04 GMT 1
Marrcell can you post some pictures of the piston bodies/skirts
|
|
|
|
Post by Tobyjugs on Oct 12, 2019 16:10:14 GMT 1
In the picture with the red stud the front of the piston looks like it has more heat damage than detonation. Difficult to judge can you post the other pictures you have.
|
|
|
|
Post by stusco on Oct 12, 2019 20:28:48 GMT 1
Bit late now but what compression did you have and what volume are your domes?
|
|
|
|
Post by marrcel on Oct 12, 2019 20:46:14 GMT 1
Bit late now but what compression did you have and what volume are your domes? It is a standard 31k head Y2? Dome volume is stock. Just oringed. .0,8mm base gasket. Wiseco pistons. I am going to measure the volume soon. |
|
|
|
Post by marrcel on Oct 13, 2019 8:46:56 GMT 1
|
|
|
|
Post by Tobyjugs on Oct 13, 2019 13:05:45 GMT 1
I think it looks more like overheating than detonation, i would have thought with detonation you would have more marks on the cylinder head. Is your cooling system functioning properly?
|
|
|
|
Post by tony2stroke on Oct 13, 2019 13:54:45 GMT 1
I had that happen once, overheating, the black under piston means overheating too, the fact damage is at the front means something too, but I can't remember what sorry.
|
|
|
|
Post by marrcel on Oct 13, 2019 14:29:49 GMT 1
If it was overheating, then it did at 6krpm and 1/4 open throttle. The needle of the temp gauge was high but on its last bit of the green part. This was at highway sustained 120km/h speed.
Kenny tsa also suggested overheating. I asked him were to look for.
To complicate things i did 15km to come home with that holed piston. Can the clamping marks cause the overheating?
Never did a plug chop at 6krpm and 1/4open throttle. I will check needle clip position was it 3 or 4?
|
|
|
|
Post by marrcel on Oct 13, 2019 14:30:31 GMT 1
Just measured the head volume. Some pics.    14,5/175 gives 12. So compression is at the save side i believe. |
|
|
|
Post by Tobyjugs on Oct 13, 2019 16:19:17 GMT 1
Hi Marrcel your sum is slightly wrong. The compression ratio 13.1
You have to add your swept volume and the volume measured above the piston together. You then divide the result by the volume measured above the piston.
I always fill direct to the top of the plug hole and take away 2.5cc for the spark plug.
13:1 is doable my bike runs this compression ratio. i am very interested to know about your needle height.
To solve that stutter around 5,500 - 6,000 rpm people drop the needle to make this part more lean. I don't like to do this as just above the stutter range the carburation can be come dangerously lean before richening out for more throttle.
|
|
|
|
Post by marrcel on Oct 13, 2019 18:56:02 GMT 1
Needle height was in the middle at 3rd clip. I will raise the needle at clip 2.
I am running b8es plugs. Which are yours b9?
|
|
|
|
Post by Tobyjugs on Oct 13, 2019 19:28:40 GMT 1
Im running B9's but i don't think thats the problem. If you like we can arrange a day and build it up together. Then we can measure and pressure test the engine.
|
|
|
|
Post by Tobyjugs on Oct 13, 2019 19:37:17 GMT 1
Another thing i don't like in the pictures above is the damage to the O-ring. It looks too big for the groove
|
|
|
|
Post by marrcel on Oct 13, 2019 22:19:06 GMT 1
Oring 72x1,5
Groove 1.15mm dept
1,4mm wide 73,3mmOD
|
|
|
|
Post by tsa on Oct 13, 2019 23:22:46 GMT 1
Your o-ring groove isnt wide enough for a 1.5mm o-ring it should be more like 2.2-2.4mm so your o-ring is being crushed and probably failed letting in water.
|
|
|
|
Post by Tobyjugs on Oct 14, 2019 8:31:48 GMT 1
Yes Kenny is right the O-ring needs to be squashed down into the groove. The groove has to be wide enough to let the O-ring spread out without damaging it. When i was sourcing O-rings for my cylinder head i was advised by a friend in my technical department to use an O-ring with a Shore 70 hardness rating
|
|
|
|
Post by tsa on Oct 14, 2019 9:29:53 GMT 1
Should be a viton one or similar too
|
|
|
|
Post by marrcel on Oct 14, 2019 22:13:22 GMT 1
Thanks guys. My engineer suggested to make a round groove not rectangle. I will post details soon. Another thing is the needle and emulsion tube. Will raising the needle be enough? Clip was at 3 in the middle. Or is a thinner needle or other emulsion tube the way to go? Drilled airbox  And that doubted ss exhausts by my engineer.  |
|
|
|
Post by 4l04ever on Oct 15, 2019 22:55:14 GMT 1
|
|
|
|
Post by marrcel on Nov 11, 2019 18:39:11 GMT 1
Just did some oring calculations. I am not an expert. Can one of you check the calculation? I want to use the same 0ring 72x1,5mm. I have 8 of them see pic. But it gives a caution in the calc sheet about free groove volume at min? My current groove size is 1.15mm depth and 1.4mm wide. Largest outside diameter is 73mm. So according to the sheet my oring groove has to be wider from 1,4 to 1,86mm. Is this ok?   |
|
