Vvt

[Daox]

Impretty sure those maps take into account friction.

[Piwoslaw]

Originally Posted by Ryland

It sounds like if it's just the VVT-i then it's just the intake side.
Before VVT in Toyota's, Toyota had a set up where some of their 4 cylinder engines had 8 intake runners, one for each of the 8 intake valves, one of the intake runners on each cylinder had a butter fly valve, so that even tho the valves were all opening only one of them at lower speeds was getting fuel/air so it was more like having two intakes on the car, one for low rpm's and one for high rpm's.

Originally Posted by Arragonis

What I'm wondering though is what affect the inlet VVT system has on whether the engine is running its best at WOT vs part throttle.

I've read about something similar in GM's European engines, for example the newer 1.0 12V (Z10XE) has a so-called TwinPort version (Z10XEP) which actually has two intake paths, one much longer than the other. At idle and low load one of the intake valves remains shut and all of the air goes through the longer intake route, which is supposed to cause more turbulence and better mixing, resulting in lower fuel consumption and cleaner emissions. At higher loads the second valve opens, allowing more air in through the shorter route.

In VVT-i opening only one intake valve at low load causes the air to enter the cylinde at a higher speed, increasing turbulence.

[Arragonis]

Yep - GM have been playing with this idea for ages. The 24v version of the old Senator B had two ports which opened at different engine speeds. They needed it to get the old (circa 1960s) I6 which was already struggling to make 160hp with FI up to 200 without losing any low end torque.

Originally Posted by Wikipedia about the Opel Senator

The main feature of the new engine was a "Dual Ram" system, increasing torque at low engine speeds by means of a redirected air flow system engaged at 4,000 rpm.

Is it similar to the idea of twin choke carbs - a smaller port at lower speeds with less fuel and then a wider one ? All the old cars I muck about with have SUs

According to this

Variable length intake manifold - Wikipedia, the free encyclopedia

Toyota's version of the variable intake manifold is this

T-VIS - Wikipedia, the free encyclopedia

which looks to have been replaced by VVT in the early 1990s. But it looks like it makes the same basic advantages. Looks like quite a few people have tried it too.