MR2 Owners Club Forum banner

1 - 8 of 8 Posts

·
1991/2001 V6 Mr2 #8
Joined
·
2,235 Posts
Thats the vvt-i version of the 1mz. It was originally in the avalon, and later used in some of the other models i think in the 2003-2004 model year depending on model of car.

Uses a dual throttle set-up because it has the newer ACIS system. Can change from a Long to medium to short intake runner length to help aid in max tourque and horsepower curves.
 

·
Registered
Joined
·
350 Posts
I have always thought ACIS created too much turbulance in the intake & then you'd be dealing with throttle-by-wire. Ugh that is a tuning nightmare!

I wouldn't do it, but that's just me! :thumbup
 

·
Registered
Joined
·
350 Posts
Eh on our 3vz-fes & the early 1 flap 1mz-fe's, I had proven long ago that the flap being closed eleminates the power hump on the v6's. I'm sure the same is ture on the newer engines. Even more parts is even more turbulance.

Ziptie the flap closed & dyno back to back with it open. It doesn't feel any faster because it's a smoothe transition, but what you find is a totally flat torque curve on the 2500/3000 and 4400-4800rpm torque peaks.

It causes more problems than it solves airflow wise. I think they just to it do lower the airflow - to decrease gas mileage.
 

·
1991/2001 V6 Mr2 #8
Joined
·
2,235 Posts

·
Registered
Joined
·
350 Posts
Yep. That's how it works. You take manifold vacuum, run it to a one way vacuum canister to store large vacuum, which runs to a VSV controlled by the ECU. The ECU opens the VSV when the conditions are met, the vacuum pulls the diaphram, which pulls the arm, while opens the spring loaded ACIS flap.


That's cool tho. That's the updated doc.




ACIS works by the tuned runner principal. It relys on the pressure wave (Toyota calls it accoustic charging) to helps force a little bit extra charge into the engine. I calculated the runner length a long time ago (I forget all the math) But I remember I found that the intake provided said charging around 5100-5300rpm. That's right at the 3vz-fe's horsepower peak.
http://auto.howstuffworks.com/question517.htm


The reason ACIS didn't work long ago, is because the pressure wave is only helpful at a relatively high RPM, in a very narrow area of the powerband. The cost of the system, is having a turbulent & velocity decrease in the intake manifold for the rest of the RPM band when the flap is open.






Anywho, here's what I've always found true on the 1 ACIS valve engines & what would probably happen on the new ones.


The torque curve when you leave the 1 valve shut all the time picks up a lot in the mid-range from when it would normally be open.

I bet that would happen to the torque curves of the later dual TB engine's if you could figure out what combination to leave them open / closed all the time. I don't know that... but I think it would be a good bet.

Closing the big flap on early ACIS gives roughly a free 500rpm of power without the big drop-off, but like I said before - it takes a dyno to see it. It only helps a small portion of the powerband & it's smoothe power, instead of nothing, then BAM you get a good 10bhp like normal.
 

·
Registered
Joined
·
144 Posts
I've got the '01 Avalon vvti with dual throttle bodies that Brad did. I have just gotten pretty comfortable with it and will soon dyno it and get it onto a track. I can say that it has a very smooth and pretty potent torque curve, at least from the seat of my pants! I will post the dyno info as soon as I get it. Brad fabricated a dual inlet from the single line from the air filter. Don't know that he "calculated" tube lengths, but it does run great! He posted a pic of the engine showing that intake piece in December. If you can't find it, I can take more next week. I'll see if it will be possible to make dyno runs with the butterfly tied open, then closed for comparison.
 
1 - 8 of 8 Posts
Top