hey guys, i'm mostly a rotary guy so this issue has me stumped.
-when at low rpm, below 2500 like around 2200 and lower, if i hit the gas a bit heavy, i hear what sounds like knock untill the engine reaches higher rpm(3000) and then it goes away. the engine is a semi-built gsr with arias pistons(81.5mm/10.1:1), 3 angle valve job, skunk2 mani,aem tru times,block guard,CTR tranny,rc330s, and hondata s200 with very slight tuning job(probly not the best). it seems like its too low of octane, but i always run 93. it sounds like when you stall out the car and you hear like a pinging-knock as the motor stops. is it just because the engine isn't ready to make power that low in the rpm or should the valves be adjusted again? any advise helps and allows me to sleep better. i really want to get this figured out before i put the turbo setup on. i think its just too lean at that rpm and load from the guy leaning it out durring the street tune, OH, and its really noticable if the a/c is on. THANKS, -Nathan

 

Are you sure its not a rod knock ?
Do you have an oil pressure guage ?

Who did you have tune the car ?

 

a small shop in orlando tuned it, guy named brian lee. tuning time maybe lasted for 7 pulls down the street and 15-20 mins of driving. it was 75$. i don't know what rod knock is? it doesn't do it at idle or above 3000 just low in the rpm with a big dump of the throttle. rod knock sounds like a very bad thing. ALSO, John Vega- after i put the turbo kit on, i'm coming straight to you. you did a friend of mine's car and it has run flawlessly since the day you tuned it.

 

ok. the knock is prevelant in lower rpm with heavy throttle and gets more noticable as i get to 4th and 5th. it sounds like pinging like if you were low in a rpm and high in a gear(4th or 5th) and are heading for a hill and just floor it instead of downshifting, and the engine can't make much power and kinda bogs but it pings and ticks while doing so untill reaching about 3K rpm. i think the the retard who tuned the s200 mad it too lean or advanced my timing too much. John- whats your advise here, besides coming to see you?

 

my aem tru time cam gears are set at +4 degrees. and they say that each notch on the cam gear is equal to 2 degrees at the crank. what does all that mean? i'm coming from building rotaries so i'm new to this whole piston motor thing.

 

the camshafts rotate at half the speed of the crankshaft, allowing the crank to make two full spins for one spin of the camshaft.

the moniker 'suck, squish, bang, blow' is used to describe the 4 cycle engine. each of those steps takes 1/2 a rotation of the crank, and hence, you will get a full 4 step cycle ( or 2 full spins) for one cam rotation.

look on howstuffworks.com if you are a visual learner like me, or just go buy a d-series and play with it till it works

 

so is 4 degrees of andvance too much? yes or no?

 

depends on the tune and how aggressive your setup is. you have lower than stock compression and bigger injectors, but list no cams? and possibly a bad tune? id say if you have a stock or less c/r, and nothing more than stock on the top end, then you need stockish cam timing.

the pinging that you hear, from what i can tell, is the same noise you said you thought was spark knock from low octane. all spark knock is, is your air/fuel mixture combusting before the spark plug ignites, usually from overly hot weather or inadequately low octane. in your case, for the time being, set your cam timing back to 0, rotate the wheels a few times, very gently, to make sure you dont have any internal engine contact, and start it up to see what happens. worst case scenario it knocks more. just remember where it was in case you have to put it back.

GL

 

with the timing light at idle, the crank pully showed 15-16 degrees. and continued past 40 under free rev. the tru times show +4 themselves and each mark on the cam is equal to 2 on the crank so i'm technically advanced like 20 degrees at idle right? how do i turn the tru times back to 0 without taking off the timing belt? and do i have to zero the crank timing before i do so? thanks for all the help guys!!!

 

its a rod knock. The starting of a spun bearing.....it will get worse. Time for a rebuild.