b20 very high comp???


BuddyClubctr said:
You fill a piston when is down to dead end and count the quantity of liquid you put in my case thin oil!! Then you make a piston come to top dead end make sure you close all valves fill it again and then divide the first measurement with the second
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Fair enough, I thought you were using a pressure gauge!

12.7 is too high for 98RON really, bear in mind JDM Type Rs are around 11.5 maximum tuned on 100RON, if you up the compression and reduce the octane you really do narrow down your margin for error as you are finding.

Try a thicker gasket and see how you get on. I'd recommend 1.5mm.
 
with a gauge i tried it the gauge you do compression test and it had an output of 240 psi which i believe its really high!! tried it on other engine like this one and they are around 160-170 psi!! btw kozy and rich thanks for all your kind help!! i really appreciate it very much!!
 
BuddyClubctr said:
with a gauge i tried it the gauge you do compression test and it had an output of 240 psi which i believe its really high!! tried it on other engine like this one and they are around 160-170 psi!!
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Take it with a pinch of salt really, they are horribly inaccurate. I got 220psi on a stock B16B that was burning oil!
 
You have too much CR for road fuel.

11.5-12:1 is high enough for everyday road use on road fuel.

Anything higher and you are sacrificing longevity.
 
What's does the head measure? Have a look at the tabs on the corner, if they are not there its been skimmed to much. Why did you build a road car with such a high c.r? Also what is the dynamic c.r? Also what heat range plugs are you using and what do they look like?
 
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I didn't want to make that much cr it just happened by mistake!! They must have send me higher cr pistons and with the thin gasket and a shaved head it came very high!! Spark plugs show very good gasoline use as rhey are white and clean some greyish colour on them! For the rest I nned to make some measurements tomorrow
 
More light to my case!! Its even. Worse I found out I had some mistakes on my calculations the static cr of the engine is 13.48 :/ and it detonates with wide open throttle body above 4k rpm
 
lower your compression. 11.7 is pretty much perfectly where you want to be. cams might be a little big tho.

otherwise make sure you always have an octane booster with you for everytime you fill up. these are your options otherwise you will destroy that motor.
 
BuddyClubctr said:
More light to my case!! Its even. Worse I found out I had some mistakes on my calculations the static cr of the engine is 13.48 :/ and it detonates with wide open throttle body above 4k rpm
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That sounds more like it. You need to machine the pistons like i said. Do it properly once. The head has to come off either way
 
13.5:1 is race fuel territory.

Im surprised the motor is still running tbh.
 
You should be able to run more timing than that once the engine gets spinning at higher rpm's. I've mapped 13.2:1 cr engines on 95 octane fuel, granted they will knock at lower rpm's/high load if you push the timing too much but as said once the engine gets to higher rpm's you can start to ramp the timing up. I think changing pistons or machining them as Rich suggested is probably your best bet unless some better quality fuel is available to you.
 
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