Engine EGR technical ??

EGR technical ??

I know that on the 1ZZ-FE there is no EGR valve. Do 1998-2000 non-VVTi engines have an EGR valve? I'm under the impression that the EGR is accomplished by the VVT-i and that's why no valve is needed - am I correct?

Do our engines have an exhaust gas temperature sensor?? If so, where is it?

Late,
Trav

I'll add to Vortex's reply... it's true, no '98+ have EGR, and none of them have an EGT sensor... Even the earlier models with EGR just had a gas temperature sensor in the EGR valve itself, not in the manifold... the exhaust gasses cool significantly before they get to the EGR valve itself...

OK - well, how does the 1ZZ-FE accomplish recirculation of exhaust gas? How is it controlled? Engines with the EGR valve/modulator setup open the valve and close it based on manifold vacuum and exhaust backpresure - higher load(low vacuum) = higher EGR flow, lower load(high vacuum) = lower EGR flow and NO EGR flow in open loop (warm up or WOT). How does the 1ZZ accomplish this without a valve to control it? If the 1998-99 1ZZ-FE motors did not have an EGR valve, then apparently it has nothing to do with VVT-i. Right??

What up with this??

Late,
Trav

But EGR cools down combustion temps and allows the engine to run leaner at low loads (highway, cruising) and save fuel. So the 1ZZ-FE has no EGR at all - does not recirculate exhaust gas??

Strange - I would figure it was a necessary sort of thing to achieve that golden ULEV status and have such good highway gas mileage (40-43mpg for me on HWY). Guess I was wrong.

Late,
Trav

Well SNAP - thanks dude! I learned something new about my car.

As a side note - I was looking around on www.fueleconomy.org and noticed that the Celica/MR2 variety of the 1ZZ only have an LEV emissions rating. And the 2ZZ-GE gets an abissmal TLEV rating. Guess Toyota really needed the Corolla/Matrix, Prius, and Echo to green their emissions score up.

Trav

Exhaust-gas recirculation is achieved by internal recirculation via appropriate valve overlap...
The VVT-i system can change the intake cam timing over a 60 degree range, changing valve overlap from absolutely zero (for smooth idle, easy starting and better cold start performance), to severely overlapped for a natural EGR effect at medium load (eliminating the need for an Exhaust Gas Recirculation valve), to whatever is ideal for maximum power at any point on the powerband.

I believe you wholeheartedly b/c this is what I've heard from several sources. However, riddle me this:

The 1998 and 99 models do not have an EGR valve, either. They also do not have VVT-i. So, how does the non-VVT-i engine accomplish EGR?

Late,
Trav

HA - too friggin funny.

Are we on the same length or what?

Your name isn't Travis is it, vortex??

Trav

The non-VVTi versions were only LEV rated. Valve overlap was used before our variable valve timing technology. The 1ZZ-FE VVTi's exhaust valves always close at 2º ATDC; intake valves open between 5º and 48º BTDC, so there is always valve overlap, ranging from 7º to 50º.
Chrysler's late model Neon 2.0 SOHC engines have actually dropped the EGR valve system without opting for variable valve timing.

Thanks dominator for entertaining our endless interrogation on the finer points of EGR

I've been school'd.

Late,
Trav