silent engine knock? - Honda Prelude Forum

rentien · 02-05-2005, 11:39 PM

i wanted to know you guys' opinions to my theory, so here goes.

i was reading an article about engine knock, and the theory of it, and it was suggesting hot spots in the cylinder due to carbon deposits, etc etc. It said that there was engine knock after spark, and engine knock pre-spark... which is supposedly silent and one would not hear the "ping" now sometimes i do hear knock out of my car at idle (i have euro-r... so compression ratio is 11.0:1) this usually never happens and only happens when my idle dips really low and i put load on it (such as reversing while i'm still floating forward a little bit, happens when i'm in a rush and making quick u turns that because 3 point uturns, and when going up a hill from a stand still without raising the revs to 1.5-2k rpms before engaging the clutch) o yea, keep in mind i have hondata s100 on a p28 ecu, so no knock sensor.

if i slam the gas pedal, like say go from 0-100% throttle in under... 0.2 seconds about? i will get a wobbling, bogging sensation much like what happens when you have a clutch that doesn't hold as hard as it did when it was new so it "skips" and then grabs after a few of these skips, only thing is that this wobble due to my slamming of the gas pedal is MUCH more pronounced so that i can confidently say its not the clutch bouncing and skipping.

before i have my p28 tuned, it was so bad that the car would totally slowdown, then resume accelerating like i'm flooring it so much that it would chirp the tires, slow down, speed up chirp the tires again 2-3 times (i stopped this after two tries) so... could this wobbling that does not sound like knock be the knocking pre-spark??

thanx in advance

p.s.- if so i guess i'll have to get the ratios richened up, along with loss of more spark timing OR lessen the tip in values like spark advance due to tip-in that comes when one jabs the gas pedal like i do

p.s.s.- the previous theory was that this bogging was due to the tip-in being too rich... o and the bogging got better after the tuning, but its still there slightly as to be stil a little more then a clutch skip

damn hope this wasn't too much but this is how much thought i've put into it...

precisionelite · 02-15-2005, 05:46 PM

Knock after spark? I thought knock was the act of the gas combusting before the spark plug ignited the mixture?
-Greg P

sharkcohen · 02-15-2005, 05:54 PM

http://www.jandssafeguard.com/tech.html

paulyg · 02-15-2005, 07:41 PM

Quote:

Originally Posted by rentien

this usually never happens and only happens when my idle dips really low and i put load on it (such as reversing while i'm still floating forward a little bit, happens when i'm in a rush and making quick u turns that because 3 point uturns, and when going up a hill from a stand still without raising the revs to 1.5-2k rpms before engaging the clutch)

Well that sounds like the normal conditions in which knock would occur, low engine speed and high load. The situation is made worse by the 11.0 CR, and the fact that you only have 91 octane. Instead of playing with fuel mixture maybe you should turn down the spark advance some, since you have Hondata and have access to such things.

rentien · 02-17-2005, 07:14 AM

the people i've heard of blowing engines, knock at high rpm, under WOT load for example NIRvtec's nossing at like i forgot 70 or 85 shot on his 140k mile h22a1 and blew it... something like that, and dvsgirl's detonating a little right before vtec...