j9chan

Hi guys,

I just spent a little time tonight adjusting the timing of my car (without a timing gun though). It was running well before, but I wanted to advance it a little so I could get a bit more kick out of my engine.

Now to make sure I didn't advance it too much, I was suppose to look out for knocks or pings from the engine, with the AC on in 5th gear trying to accelerate (basically try to put as much load on the engine as possible). I did that, but I didn't really hear any loud knocking sound.

My question is, how is an engine knock or ping supposed to sound like? How loud is it supposed to be? Also, if the knock sensor detects a knock, would it cause the CEL to light up? I've got a 98 Si coupe, pretty much everything stock.

Thanks a lot guys.

imported_GoldBadge

It wont sound normal, thats for sure. It can sound a bit different, but to me it sounds like a piece of metal is bounding around in my engine...if that makes any sense...like a penny in a jar

Cynikal.Mindset

sounds like a diesel...which is why some people call its "diesleing"

scott newman

It sounds like there is somthing loose in the engine. Dieseling is when the engine will run without spark. Sometimes when carbon gets so built up on the top of the piston, it will get red hot causing the fuel air mixture to burn without spark, now on a fuel injected engine, that wont happen because when the key is in the off position, there is no fuel coming from the injectiors. You will notice dieseling on a two stroke engine when it isnt under load and it revs high, it will keep going because the combustion chamber temps are so high, it will ignite the fuel charge, that is really what diesels do. Anyways, when you advance your timing, and it knocks, it is pre igniting, when the spark happens, the piston isnt all the way up to the top of the stroke, then it ignites, trying to force the piston back to where it came from, the knock comes because the inertia of the whole engine will force the piston up into the combustion while it should be going down. There is no need to advance your timing more than stock. There isnt much gain in detonating a piston. And the knock sensor just retards timing when it pings or knocks, it acutally senses the shaking of the engine, That is why advancing your timing is counterproductive. Just my two cents.

j9chan

Thanks guys. So would the knock sensor trigger the CEL if it senses a knock?

Also, how loud should I expect the knock to be? I know this is hard to describe, but perhaps somebody could try? Thanks.

imported_Cablerat

knock senser does not trigger a CEL unless it senses an obsurd value, at which point the ecu believes the knock to be faulty and goes into limp mode.

j9chan

Thanks for the info Cablerat, but what does it mean by "an obsurd value"? Isn't the knock sensor a 1-wire device, such that it generates either an ON or OFF signal?

And how loud is a ping or knock usually?

bbarbulo

iTrader: (2)

volume varies by intensity, but you can hear ones that won't kill your engine... prolongued pinging or severe pinging will kill an engine. With the radio off, you should be able to hear a sound similar to someone knocking a hammer against a waterpipe in the basement? I guess that's how I'd describe it.

j9chan

Thanks a lot everyone, I got all the answers I was looking for. You guys are awsome!

imported_Cablerat

The knock sensor is a Pizzo (sp?) crystal that generates a voltage based on vibrations.. So if the knock sensor returns a voltage that the ecu feels is beyond it's known limits it assumes the knock sensor is bad. That or your engine is about to explode or just exploded! heheh

The sound.. well think PINGING, what does a PING sound like? to me sounds like it's pronounced..

imported_BoOsTd

some cars have ticking valves, like most sunfires and old Chrysler Lebarons... And allot of other cars just when they are cold... even heard some hondas tick when they are cold...


How do you tell the difference between valves and knock?

imported_Cablerat

ticking is different to PINGING.. you'll actually hear a PINGING sounds coming from the engine.. it's noticable.

imported_GoldBadge

It's pretty simple...You'll get the pinging under high load, low rpm. And it sounds like Cablerat said..."PING"...the tick is like a baseball card in bike spokes, only metal on metal; it will increase/decrease with rpms where as pinging is kind of random.


Mine ticks when its cold (like a crappy old lebaron) and it was pinging before i got my timing adjusted.

Also, if you put in high octane fuel instead of 87, the pinging should go away because the fuel won't pre-ignite under the compression. It will be able to withstand the compression until spark hits it, forcing the piston back down in normal fashion.

Experts: Correct me if i'm wrong...

imported_trackhack

Pinging also referred to as detonation occurs due to advanced ignition timing because the spark in the cylinder occurs before the piston reaches TDC (top dead center).

It is true that higher octane fuels resist dentonation better than lower octane fuels. Octane, which is essentially an alcohol slows the burn of a combustable fuel. Ie. Greater amount of octane=slower burning fuel=reduced chance of detonation.

For a stock unmodified street driven engine on pump gasoline, IMO it is not worth it to advance the timing to get those few extra horsepower for a D series engine, which will most likely then require premium fuel.

Anybody else have thoughts?

j9chan

I rotated the distributor of my D16Y8 last night... I didn't have a timing gun, but I made a mark on the top of the distributor and rotated it towards the firewall such that the original mark is now about 5mm off from where it was.

As far as I know I couldn't hear any pings... and the engine feels a bit more torquey now. I'm a little worried that the ping might be too quiet to be heard though. My car is pretty quiet so should I be able to tell?

Thanks.

imported_trackhack

That's probably 3 or 4 degrees advanced...

ANY detonation in an engine is detrimental to both it's performance and reliability. Prolonged detonation can be just as bad for an engine as well. Even if your not hearing it, it could still be happening.

I had a d16z6 with a Y8 head on it and with advancing the ignition it made it torquier(relatively anyhow haha) in the bottom end as well. It made the top end feel a little bit weaker and I had to run premium fuel. I then timed it to the stock settings and it ran much better overall. For your reference, I always used premium fuel.

Just my $0.02