ok to knocking on low rpm?

[xtremeleo]

kweng : ping / knock may occur out of lean afr (precombustion because lean mixture combustion emits large quantity of heat, too much and ur internals may melt), and overadvance ignition timing. just imagine dis, combustion compressed mixture of air and fuel gives out a lot of energy and heat. if u overadvance (keyword : overadvance, hence advancing is safe, as long as its witin the safety limit. outta the limit, and u r OVERadvancing the ignition limit) the ignition timing, the mixture may pre-ignite and combust before the actual power stroke is supposed to be at, BUT the piston is on the way up and wit the combustion process advanced too much, it is force to go down. wit two forces applied to the piston (dynamic way up, combustiom forces it to go downwards), it cant go nowhere but force its way up, since the other pistons and crankshaft assembly is forcing dis particular piston up. dis piston will rattle on its way to balance the forces applied to it, hence u have a vibrating piston, bearing, internals which may score ur block, fark ur bearings, etc.

BUT, just imagine.. if u combust a compressed mixture and creates a whole lot of energy, how much energy can u create if u compress a combusted mixture? u get me? d 2nd process will emit even higher energy and will push the pistons down faster then the first process, which will give u higher torque output.

p/s otai2 :sumone please correct me, i think sumthing r wrong in my post ler. iam too pening to re-check, sorry ya..

 

[1298]

Ok, looks like things are getting more complicated...hahaha. Back to what the topic says, "ok to knocking on low rpm?", simple answer to it, a "NO". So, pinging or knocking won't occur if tuning is set right, doesn't matter if you are driving at low or high rpm.

Doink, to your statement, "slight knocking is usual for better performance...", that's a big no. Better head to different mech if yours is telling you that. ;)

normality78, cam position timing is to advance or retard the duration timing of air going in and out of the combustion camber. Nothing to do with ignition timing.

Cheers.

 

[kweng84]

xtremeleo: well said ;) so, what is the best solution to avoid the overadvancing ignition timing?

 

[xtremeleo]

thanx, but personally they r gonna sumbody else dat can explain those better, trust me. sumtimes iam not good at posting words, my words may be better when iam talking in person as i will try my best to show what i mean ie wit diagram, motions, etc. enuff about me, *shy* lol

solutions? hmm.. first, maybe u may not overadvance (again, keyword : OVER) and stay witin the engine limitations. 2ndly, u may wanna use a higher RON fuel such as the Vpower, as i explained earlier, RON shows how well a particular fuel avoids knock / pre igniting and since Vpower is rated to have more then 97, hence the suggestion. and 3rd, u may wanna use a colder (comparatively to factory std ie 5 to 6, ur plugs will foul if too cold a plug is used) protruded plug (the tip is a bit longer, and plugs have "P" in their code) for the same effect as advancing ur engine timing, but not mess around wit the actual timing. get me?

 

[xtremeleo]

Ok, looks like things are getting more complicated...hahaha. Back to what the topic says, "ok to knocking on low rpm?", simple answer to it, a "NO". So, pinging or knocking won't occur if tuning is set right, doesn't matter if you are driving at low or high rpm.

Doink, to your statement, "slight knocking is usual for better performance...", that's a big no. Better head to different mech if yours is telling you that. ;)
Cheers.

dat was i wanna emphasize, u shudnt tune dat slight knock / ping occurs and say its okie. but, when i asked joshua regarding dis, he said his 181 hp 4g91 iswara pings at lower revv as he set it up like dat, and he said it was okie. for me, iam not gonna do dat as i want my engine to last. wit dat being said, joshua's 4g91 hadnt any problem for about 5 years wit dat kinda tuning, and i havent seen his engine in any kinda problem except for regular maintenance and replacing wear and tear parts. dis is the part dat was puzzling me, because i can hear his engine pings slightly on lower revv, and the sound disappear on higher revv. as u can see, dat engine is making lots of power, and on dyno power came quite early and climbs to haeven fast!!

 

[Joeker]

I think alot of you guys are confuse about the meaning of knocking, Preignition, Pinging, Detonation.

I give it a shot at explaining what they mean k?

Knocking and Detonation are smiliar. When knocking or detonation happens, it creates pinging sound (as described by an old ZTH sifu, Sleepwalker, "it soulds like small pebbles rattling inside a Coke can")

It is caused by abnormal combustion. Normal combustion produces smooth pressure, the flame sweeps smoothle across the combustion chamber.

Abnormal combustion is as when the explosion flames from the spark sweeps across, before it reaches the far side, another explosion occurs.

Over a long time, detonation or knocking will also cause preignition.

Preignition on the other hand is a situation where combustion occurs before spark plug fires.

When preginition happens, it produce a "thuk" (sounds abit like when you step hard on the concrete floor with you bare heel).

 

[xtremeleo]

there u go, a complete elaboration by on of the sifu himself!!! thanx a lot joeker, it wud be ebtter if u can explain stuffs like dis to us mewbie more often. hoho..