yo. still fixing up my newly acquired ve 5-speed. have a couple more questions.

does anybody know if the vtcs and the VI works off each other. i know that the VI is wired to the injectors. wasn't sure about the vtc though. i've been reading and i'm trying to see if the "heat soak" is caused by bad vtcs. there were a number of people here who fixed thier vtcs and the heat soak problem was gone.

 

No I don't believe they are directly related. From what I can tell, the VI is rpm dependant only. Not related to the injectors either. The VTCs have 4-5 different engine parameters that control their function. Also heat soak is not really related to VTC function perse. Although the ecu might take a Temp sensor reading in account for maybe some VTC activation parameters, it's not really directly related to the VTC function themselves.

 

Jeff speaks the truth. The VI is purely rpm/vacuum related. The suction of the engine vacuum as it accelerates cause the VI to open.

I have replaced my VTCs and noticed, more apparantly than low end power, was that I gained a bunch of high-end power. Busted (ticking) VTCs cause the intake cam timing to slide back and forth the few degrees it is able to adjust. This is the ticking you hear. At high rpms, the engine is turning so fast that this 'sloppyness' causes losses of power. New VTCs fixed that (I felt a bit more power over the entire rev range too)

The bottom end hesitation is, in my theory, an ignition timing issue. Replace your oxygen and knock sensors, and bump up the ignition timing a few degrees for a quick fix. Also, check for corrosion on your water temp sensors (red one by the throttle body) and your VTC solenoid connectors. BE careful removing these connections as they can be fragile and break.

 

how does the knock sensor work? does it use the vtc to retard timing?

 

Nope. There is more than one "timing" to an engine. There is mechanical timing and ignition timing. Mechanical timing has to do with keeping the pistons and valves apart from each other. Every mechanical bit that turns in the engine (crankshaft, pistons, camshafts, timing gears, crank pulley, timing belt/chain) is part of the mechanical timing. It has mostly to do with sucking the air into, compressing, and expelling the air out of the engine.

Ignition timing has to do with the spark plugs and coils. It correlates the spark plugs to fire at the exact moment in each cylinder right before the piston comes up on the compression stroke. You see terms like 10 or 15 degrees BTDC, Before Top Dead Center, which means it's just before the pistons is all the way up. Spark plugs are usually fired right BTDC because the fuel/air mixture takes a millisecond to ignite.

Anyway, VTC's control the intake cam timing and can advance/retard the intake cams a few degrees. Most other engines can't do this. So when the VTCs start to click, cam timing goes all awry.

Knock sensors help with the ignition timing. If pinging (detonation) is heard in the engine, the KS will retard the ignition timing and the engine will lose power. And if a KS is bad, it will most likely automatically retard the timing for "safe mode" operation.