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Discussion Starter #1
I have a 94rs and if I'm not mistaken thats an obd1 system ,correct? My question is does my car employ a knock sensor? I advanced my timing at the track all the way till the dist. was maxed w/ out any hint of detonation, but I would like to know. thanks.
 

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You should never, I repeat NEVER go past 18 degrees BTDC, unless you have an extremely hard tuned all motor, and even then your taking a risk. Plus you won't get any realistic gains past this point, especially if you want your motor lasting more than a week. As for the knock sensor I don't know. Advance it to 18 BTDC for street and track and leave it at that.
 

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Discussion Starter #4
jonny-vtir on Sep/21/02 said:
You should never, I repeat NEVER go past 18 degrees BTDC, unless you have an extremely hard tuned all motor, and even then your taking a risk. Plus you won't get any realistic gains past this point, especially if you want your motor lasting more than a week. As for the knock sensor I don't know. Advance it to 18 BTDC for street and track and leave it at that.
Its not detonating! How is it hurting it? If you could clarify mabey I could understand what your trying to say. Its running great, and not by the ass dyno but by the dragstrip timers.
 

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Just a side note... To my understanding, the factory knok sensor included in the B18C1, B18C5 is little more than a microphone. After 4k RPMs(I think it was 4k) the knock sensor is unable to distinguish knock from normal engine sound.

BTW: I do accept paypal.
 

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Discussion Starter #8
Fentoozler45 on Sep/21/02 said:
Just a side note... To my understanding, the factory knok sensor included in the B18C1, B18C5 is little more than a microphone. After 4k RPMs(I think it was 4k) the knock sensor is unable to distinguish knock from normal engine sound.
yeh, thats what i was thinking, because even w/ the valves adjusted, I know my b18b has a fairly loud valvetrain @ 6800 .lol
 

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Discussion Starter #9
kelly on Sep/21/02 said:
Just because it's not detonating or you do not hear it detonating does not mean you are not hurting the engine. Check out this article.
Thats a good article, but if its not detonating and the engine is obviously making more power (times at track, or more importantly trap speed) then It cant be sparking too early. Right? Ive got a pretty potent ignition so the increased cylinder pressure is welcome. I feel like, running 93 octane, I should be safe no matter what the load on the engine. You imput is welcome and appretiated, and It probley needs to be discussed more for anybody else that needs to know.


When I get it on a dyno, I will fine tune it. The strip is a great place to test tuning and setups/parts ect. but A dyno is a lot more in depth, more educated way to tune. IMO.
 

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Advanced timing increases cylinder pressures which translates to premature wear of your internals.

"It's running fine" is pretty much what anyone says the second before their engine bites it from a bad case of detonation.
 

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Correct me if im wrong but almost all of the perfomance mods you do increase cylinder pressure. Does that mean we shouldnt put on c.a.i or even a supercharger because were scared of cylinder pressure. I mean thats what were working for here, right?

You are right though, my buddy has a 96 cobra. He said "its running awsome this weekend!" It took a full 30 minutes to clean the track! BTW, stock timing.
 

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Intakes don't increase cylinder pressures. In F/I cases the increased cylinder pressure is why the smart ones will upgrade internals and tune the fuel and ignition timing maps properly. You're playing with fire.
 

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it's not detonating?

if you are depending on your ears, then it is not detonating AT IDLE.

how do you know it's not detonating at say 3000 rpm or at redline? YOU CANNOT HEAR DEToNATIoN IN THE UPPER RPM'S

once again, you must look at the ENTIRE rpm range. It's the same mistake beginners make with relying on the butt dyno and how it FEELS.

A Honda knock sensor (which is NOT in the B18A/B) is a modified microphone that only has enough sensitivity to detect PRE-ignition or knock up to 4000 rpm. After this point, it can't distinguish between regular engine noise as the motor revs from knocking and so it only acts as an idle/partial throttle detector and then instructs the ECU to retard the base ignition timing map program at these rpms BEFORE it can get ugly up in the higher rpms. once detonation occurs, it is too late: the horse is out of the barn.

The Hondata guys will tell you that it's better just to get a second knock sensor and use a J&S Safeguard to protect you. The J&S is no picnic to setup either. You have to enter the sensitivity range and how much you want the base ignition timing map to retard by. The unit "intercepts the firing signal going to the leading plugs and delays it in proportion to any knock that is sensed. The unit is very sophisticated, and can identify which rotor face is associated with the detonation. It then retards the spark to that face only. If more than one face is involved each face is treated independently."

Here is an example of the amount of timing retard to program in (Y-axis) versus rpm (X-axis) in a boosted CRX. Notice the 2 different curves for each manifold vacuum pressure and when they are activated by a certain amount of vacuum. This is applicable to FI setups:



You'll want to avoid buying the older "classic" version of the J&S Safeguard if you have VTEC, since the knock sensor seems to think that VTEC switchover is a form of detonation (by the sound) and retards timing substantially, as Gvtec can tell you. The newer version apparently does not have this problem...debugged it.


You really also should get a datalogger if you are seriously thinking about tuning (tuning means to adjust the air:fuel ratio, ignition timing, and cam timing so that you get a broad, flat torque curve). There are several available which hook up to a standard palm pilot for under $200. It will tell you your engine temps as you advance the ignition. You will see with your own eyes how much advancing jacks up the engine temps. High engine temps are one sign of high cylinder pressures.

When you advance, the cylinder pressures spike quite abruptly. High cylinder pressures with high cylinder tempatures are great conditions for detonation. If you have never seen a piston pin or piston melted by detonation, it is quite horrendous. A lot of damage. It's as if someone took a sledge hammer and wacked the piston down hard with 100x the force that it was generating when it was coming up on the compression stroke.
 

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SOME TERMS THAT GET MIXED UP AND THROWN AROUND TOO LOOSELY WITHOUT KNOWING THE PRECISE DEFINITIoN: KNOCK, PING, PRE-IGNITIoN, DEToNATIoN

Detonation; Knock; Ping; Pre-igintion. You hear these terms mentioned all the time, so we might as well straighten them out.

Let's get pre-ignition out of the way first. Nothing mysterious about it. The A/F mixture (intake charge) explodes before the spark plug fires. You would figure the intake charge would have to get pretty hot to do that, and you would be right. The pressure from a high compression engine is enough to generate that kind of heat. (In fact, diesel engines are designed to fire on the heat from compression alone.) Higher octane fuel is the antidote, so in general, a higher compression engine will need higher octane fuel.

Cramming more intake charge into the combustion chamber has the same effect as raising compression, so in general, the higher your boost, the higher the octane requirement to avoid pre-ignition. Finally, premature inflagration occurs more easily if the intake charge is hot when it enters the engine. This is why larger intercoolers add a margin of safety in forced induction engines--at least until you turn up the boost.

Another cause of pre-ignition is a hot spot in the engine. Maybe some of those carbon deposits are glowing red hot. Maybe the spark plug itself is hot enough to ignite the mixture before firing. This is almost certainly the case if you have ever experienced a car that kept trying to run after you turned the key off.

The more tricky term is "knock." Although most of us prefer to talk about "detonation," it turns out that "knock" is the correct term as used in automotive texts.

"Detonation" is actually slang, and "ping" is not a well defined term at all. That having been said, I will stick with the term "detonation" for this discussion.

"Detonation" differs from pre-ignition in that it occurs AFTER the mixture starts to burn. Normal burning involves a flame front--a relatively slow, controlled explosion--which marches along in a calculated fashion. As you would expect, normal burning raises the pressure in the combustion chamber. Sometimes this is enough to get the last bit of intake charge (called the "end gas") so excited it explodes before it is supposed to. It is a very hot explosion, on the order of ten times the heat of controlled combustion.

But there is more to it than that.

If you graph the amount of pressure in a combustion chamber during normal burning, it shows a relatively smooth event. The occurrence of detonation shows up as a sharp spike on the graph--a sudden shock wave if you will, with pressures on the order of several thousand psi. The duration and strength of the explosion is too fast to contribute to the rotational output of the engine. Like a slap in the face, the full impact must be absorbed within the combustion chamber itself. Damage is most likely to occur at the weakest points--namely the piston pin and piston crown. Piston engines designed for high stress situations can have the piston rings further away from the crown of the piston. The shock of repeated detonation will eventually weaken anything it can, and the heat generated will take care of the rest.
 
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