Pre-Lift Lift?

[DavidPIL]

Ok, this isn't a complaint or problem unless someone tells me otherwise but I was wondering if this happens to anyone else. When accelerating, usually in 3rd gear, I notice a slight boost in HP around the 4k rpm mark. I'm sure this happens in other gears but I tend to notice it more there. It's not like hitting lift at 6k, more like maybe 1/3rd of the same boost.I was wondering if this could be the effect of the little door opening up in the Air Filter box. Letting more air through the intake. I ask for 2 reasons... 1 is the oddity of such a boost at that point since I hadn't read about anyone else having that and... 2. If it's the flap on the Filter box, then would a short air intake give me similar results?Just wondering...DaveP.S. Got an '03 GT

[dmitri]

mine does that too in every gear its not a consistant acceleration if i keep my foot at about half throttle. if its not bad i wouldnt worry

[goodvibe]

You'll also hear the intake growl a bit more. You got it right. the butterfly flap at the firewall side of the the gt air filter box opens to increase air flow above 4k rpm. There is also a nice torque bump at 4.2k. It's closed and more restrictive below this to aid torque and driveability at lower rpms and opens to allow the airflow needed at higher rpms. CAIs make more power and are the most cost effective power upgrade but are not as good off idle in GTs for this reason.

[savedbyzero]

I'm pretty sure that's the VVT intelligence (Variable Valve Timing). The guys with the VVTi motors experience this. Us with the GT's/XRS have it but then have the lift kick in!

[NovaResource]

OK, here's the info. VVT-i stands for Variable Valve Timing - intelligent. VVTL-i stands for Variable Valve Timing and Lift – intelligent. The base 1ZZ engine has VVT-i, the GT 2ZZ engine has VVTL-i. That means both engines have variable valve timing but only the GT 2ZZ engine has lift. Variable valve timing is the computer advancing the cams to create advanced valve timing and creating more power. This happens above approx 3000-rpm. Again, both engines have this. The Lift of the 2ZZ engine happens around 6000-rpm and creates higher valve lift and again, more power.

[ragingfish]

I've noticed when the VVT-i kicks in...all of a sudden the car just rockets forward...when I manually go through the gears on the auto, you just feel it kick in, especially in 1st and 2nd...I LOVE IT!!!!!

[goodvibe]

You guys might be right about the vvti but that door opens right at 4k on the Gt. They may work together but the vvti will operates at lower rpms also. If you've got a stock GT just keep it quiet inside and you can hear the difference when that door opens at 4k. I suspect it could open at a bit lower rpm and be more effective. Toyota probably kept it this high to keep the extra noise down during cruising.

[savedbyzero]

I have no airbox, and the sound of my motor and acceleration change at about 4G. I put money on the timing, not the little door. Before my intake, I removed the butterfly and it still felt and sounded the same.

[goodvibe]

I'm really surprised it didn't make more noise below 4k with the intake open towards the cabin. Can't argue as I haven't tried it.

[goodvibe]

I just got back from a drive. It seems, though I'm not sure that the flap needs some throttle to open. At part throttle it's probably all vvti and gets some extra and is louder when your foots down.

[kunigj]

It's a device called a cam phaser which is located at the end of the intake camshaft, that's what changes the valve timing to eliminate overlap between the intake and exhaust valves, kicks in between 3-4k, cutting down on overlap mean more performance and better economy.