vtc/valve noise and knock.

[aga]

hi! first of all, when the engine is cold i can hear a lot of valve noise and a friend of mine who's been around silvias all the time says its my VTC sprocket going... when it warms up it's ok. Also, when the VTC engages at 5700 rpm, the power fc shows knock. Is that real knock (pre ignition) or just the klang of the vtc engaging that ticks off the sensor?

[jr_ss]

Your VTC disengages at "5700". It is only to aid in making low-end torque. Most likely your gear needs to be replaced.

[aga]

oh i thought it was the other way around. anyway, the sprocket is like 400 bucks so i won't bother, i can get a set of cams for that money, and adjustable gears.

my real question is, what the power fc registers as knock, is real knock, or just the vtc sprocket banging around?

[jr_ss]

I suggest you retain the VTC. Your car is going to feel extremely sluggish without it. There are used VTC gears that pop up occasionally. Either way, you can buy a new one and not have to replace it for 5-10years. That's a pretty good product life in my eyes and will certainly keep the low-end torque the S14/15 motors offer.

It could be gear the knock sensor is picking up, depending on how sensitive the knock sensor is set. Are you running lean up top? Do you have a means to see it? What are your mods? Any chance you can datalog timing an fuel maps at that point?

[aga]

i'm running fairly rich up top, around 11.5:1. ignition advance is -2 degrees than the default map of the powerfc, cause i'm running 95 octane fuel. i can datalog , i do the tuning myself. cutting the power off the vtc solenoid means that i'll be running on high timing all the time? since you said it's engaged on lower rpm...

[jr_ss]

Its cam timing, not overall timing. The intake cam retards/advances 20degrees depending on load, TPA, etc. So no, you'll still be running what timing you have setup in your PFC.

[aga]

i assumed you were talking about ignition timing, since there's no way the ecu knows cam timing obviously.

[jr_ss]

Yes, I was refering to overall timing on your tune. Cutting power off on the VTC probably has an effect on your overall timing, however I cannot be certain as I'm not a tuner nor have I gotten that intimate with the timing maps of the S14 SR.

The ECU may have a log in it that prevents ignition timing from going excessive when the VTC is active, but once again I do not know. I'm sure there is a safe gaurd in there somewhere to prevent it.

[aga]

nah ecu's , especially the fc, isnt that smart.... you'll have to retune the ignition table if it knocks. i switched the vtc point to 5000 rpm now, and it knocks there now... i hope it's the sensor , and not actual knocking...

[Hoffman5982]

Hit me up if you need a new gear. I have a known good one for sale

[aga]

i don't know if it's the gear or the solenoid... i think these last few days the vtc is not engaging/disengaging. maybe the solenoid died?

[jr_ss]

Anytime you hear rattling at idle is the gear. It's needs to be replaced.