CVVT – What They Do & Why

The CVVT job — burn off environmentally bad gasses produced in the first minute or so from a cold engine. CVVT technology superseded fussy air pumps after it matured enough to be a dependable component of passenger cars. See Wikipedia’s CVVT page. See MVS’s how to change the CVVT hub on P2 Volvos. See all the various CVVT news and DIYs on MVS.

MVS Contributor bmdubya1198, with a strange noise in his 2000 V70 R’s engine bay:

There is this whining/buzzing noise that I’ve noticed around the area of the power steering pump. It’s very electronic-sounding, and I can’t figure out what it is. When I removed the timing cover and listened, it didn’t sound like it was related to the CVVT hub or solenoid, so I think I can rule that out.

I’m going to attach a video, and you can hear it pretty clearly in the video. It’s a high-pitched whining/buzzing noise.

MVS Contributor jimmy57 explains how how CVVT is used in Volvos:

That car wouldn’t have the secondary air pump as CVVT effectively replaced it starting with 99 year model. 

The crankcase vent nipple on intake is on that end of intake manifold and the throttle can make air noises of various pitches. In gear and a/c and headlights on should make throttle open more and affect vacuum amount and throttle opening (more throttle and less vacuum). Turning everything off and putting it in Park will reduce throttle opening and increase vacuum. The evap purge valve can make noise and would not be consistent when idling as it is not always operated at idle. It is under intake but above starter further away from the power steering pump.

They may put them in somewhere in the world but in US they dropped air pumps with intro of CVVT. The air pump only worked for a minute on cold start to pump air into exhaust to afterburn fuel in the exhaust and it sped up O2 sensor warm up and catalyst warm up.

With exhaust CVVT you advance exhaust valve opening several degrees before BDC while combustion is still going and retard ignition timing to start combustion later. These two will cause active flame exiting the opening exhaust valves which will ignite tail end of the gases of the last exhausted cylinder and assure the unburned fuel that could be there is burned to reduce hydrocarbons.

The increased flame in exhaust does the sensor and catalyst heating too. Air pump systems sucked and failed a lot. CVVT is not without issues but is way more reliable than the air pumps.

The 2.9 S80 non turbo for 99-> and the 2000-> 2.4 non turbo 5 cylinder have intake CVVT only (until they went with dual CVVT) and the intake cam is retard together with retarded ignition timing to get a little bit of the same action with no air pump

See the Volvo forum discussion where these quote originated…

CVVT vs. Air Pump

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