TrueGS300

This is just more to figure out how this system works if anyone has knowledge of it on the 2jz. I came upon a disconnected vacuum line while doing a regular check over. I'll try to explain it best I can. In the dead center of the intake where the two large passages come together, looking from the top, there is a valve that opens and closes a flap inside the intake. The vacuum line for this was disconnected and I assume has been this way since someone removed the intake to do valve covers or whatever in the past. I am wondering what was being hindered with this being disconnected? Surely the valve was either open when it wants it closed, or closed when it wants it open as certain conditions. I don't want to trip myself out, but I feel like the car has better throttle response and higher end power now. But that may just be wishful thinking. Anyone know how exactly this system works? It makes sense that it would open the valve when high demand like WOT is present. So in theory I was lacking power. However, I've felt like that car picks up and goes very well. Haven't done any real testing yet, but a couple peddle mashes. It feels really good. I'm thinking I should see a performance difference. But crazy that I've had no codes or anything making me think there was an issue.

accrdpusha

Can you post a pic?

KTGS300

There are several hoses going that area, which one are you referring to?

FrankT

I believe you are referring to the Acoustic Control Induction System or ACIS.
Toyota has been using this setup for a few decades on several different motors.
It basically shortens the intake runners to optimize power.

Truegs300, good catch on that vacuum line, you will enjoy your car that much more.
Here is an explanation video from TOYOTA

TrueGS300

I've had a few days with it fixed now. I can't believe what I've been missing. Haven't experienced the 2jz like it was meant to be until now. All this time it has felt good, but was very sluggish with it's throttle response, and now I can tell how chocked it had been when at wot. Say at 50mph I mash the peddle, it was pretty gradual that it get's to 60. Now it has great response and you can feel the pull a very noticeable amount. Even at very low speeds I've noticed a change for the better. I was use to slowing down to take a turn then give a great deal of pedal because my car would take literally seconds to respond to lower pedal input to start gaining speed (this was all subtle in a way that was hard to tell anything was wrong). But now it is crisp and doesn't take a lot of pedal to get up and go. I am happy this is fixed but just can't believe it's been dysfunctional this whole time. It's a hard vacuum line to see and even harder to tell it isn't right. I've been chasing ways to increase fuel economy and performance, but just getting this intake flap working right is more noticeable than my intake and full header back exhaust mods! The car is far quicker than I've ever had it now!

Seriously, if you've never felt it how it should be before, you'd never know something was wrong. I picked up my GS with plugged cats for a cheap price. Once replaced, the car was so much more powerful. You'd just think, that's how it is. Then plus all my tuning up, plugs, pcv, maf and throttle clean etc. The car felt better and better. I've done intake and exhaust. Weight reduction. I've been getting good fuel economy as far as these engines go and my performance has felt great. There have been no codes, and I have even watched live data for fuel trims and the general state of things. This isn't a valve that always receives vacuum. So it won't register as a leak on a scan tool and will never throw a code. It's almost impossible to know this system isn't working and will go like that for the life of the vehicle without you ever knowing. I'm very lucky to have found this.

shwalker07

My old 87 Non turbo Supra with the inline 6 that I sold awhile back had the same ACIS system. You could hear it kick in and feel it in the mid to upper RPM range which was a very nice feature for some naturally aspirated motors and Toyota put this feature on quite a few of their motors.