ACIS cleaning/Modification (5/8hp) - Club Lexus Forums

ACIS cleaning/Modification (5/8hp)

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Old 04-12-05, 10:28 PM   #1
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Default ACIS cleaning/Modification (5/10hp) *56K*

Acoustic Control Induction System
The varriable intake found on all 3vz, and first gen 1mz engine's. Here is the Upper Air Intake Chamber split open:

(Stop calling it the intake manifold... Here is the intake manifold)

Notice that the top, and bottom runners are split from each other. The top three runners curve to the rear head. The bottom three curve to the front heads. The thing hanging off the left side is the ACIS flap.

Anyone ever notice the boost in power you get between 4000 and 4100rpm?
That is the ACIS flap slamming shut. Supposidly is stays shut under that amount to "increase fuel mileage and raise low end torque". I call total BS on Toyota's part. All it does when staying open (letting air from the top and bottom mix) is reduce the air velocity. Lower air velocity means less air ramming into the cumbustion chamber = less power.

First thing is first... If have NOT cleaned the carbon that cakes up inside your entire engine intake/exhaust path, you ARE loosing at least 5 hp from stock.

You *seriously* need to take the upper air intake off (throttle body also) and clean it... This way you get back to stock power!

Everyone with a 2vz-fe, or 3vz-fe should take our their cold-start injector, and clean it periodically. It takes little time for it to carbon over, impeeding, or even 100% blocking fuel flow.

Last edited by Pheonix; 04-12-05 at 10:31 PM.
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Old 04-12-05, 10:30 PM   #2
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Wondeirng how bad the EGR - carbon buildup is?
Here's a '93 3vz-fe torn down at 96,000 miles.
(It's only this good because it had been cleaned rpeviously)

intake manifold

cylinder head

combustion chamber, after some cleaning from a pressure washer
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Old 04-12-05, 10:31 PM   #3
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front bank (ignore the oil & antifreeze spilled)

rear bank (ignore the oil & antifreeze spilled)

intake valve

Everything you're not afraid to take off the car should be cleaned. The upper intake must be cleaned by hand. (becuase it get's so bad, INCLUDING the bakc of the throttle plate) The heads will clean themselves if you use some Seafoam into your intake. (It will not clean the combustion chambers, it doesn't "live" long enough to clean that)

You should use a spray bottle with watter to clean the pistons. Rev the engine with one hand (on the throttle) and squirt a full 8oz of water into the blow-by breather comming from the front head. This alone won't do it. To distributue the water evenly, squirt another 4oz into the brake booster (top, thickest hose on the side of the ACIS plate) and spray the last 4 oz into the PCV line (same thickness hose before, but runs between the PCV valve on the rear head, to just below the ACIS)

This will leave your pistons and combustion chambers / valves (both sides) perfectly clean of carbon. It'll probably take 10m and your hands will be tired, but short of tearing the entire engine apart, you will NOT be able to clean anything.

(Water won't hurt anything. Infact water injection is the smot awsome thing on earth)

Spray the water fast enough to slow the engine down. Back off *just* a hair so it doesn't stall, and that's how fast you should be spraying. (It's very hard to stall a v6 engine. You'll run it lean/out of air before it hydrolocks. Hydrolocking an engine this size with a spray by hand would be... Simply next to impossible!)


You would think that the split that is roughly 2 1/2 to 3" behind the throttle body would bea nice sharp, high flowing split. No sire! It's a full 1/2" of flat, high turbulance/poor airflow aluminium.

By taking that flat piece, and grinding a razor sharp edge on it, you will get a few extra horsepower for nearly nothing.

Dremel works just fine with a grinding stone attached.


The ACIS flap is controlled with engine vacuum. Vacuum is routed to the vauum tank under your battery (which stores vacuum in times of low vacuum) then the vacuum runs up to the vacuum switching valve (vsv). (the red/orange/brown one is for the ACIS valve, the blue/green/teal one is for the fuel pressure regulator)

The ECU grounds the electrical connection to the VSV, which opens. That let's the vacuum travel the round vacuum flap. The flap is sucked backwards, which pulls an arm on the ACIS flap, which closes it.

It's less complicated than it sounds.
The ECU activates the ACIS valve at: 3900rpm and 50% or higher throttle. (It might not activate it without the car moving, so opening the enigne bay and pulling the throttle won't make it move)


The problem with this system is that it activates far too late. You *could* use a piggyback (or a switch) to trigger the valve whenever you want, but that's simply retardidly a waste of money. You don't even have to buy anything to modify it!

By taking the long vacuum hose off the vacuum tank, you can connect that to the ACIS's flap. (Be sure to take the tank OUT of the car... it is no longer needed and dead weight. The vacuum hose going to it should be cut off short, and plugged with a screw into the end of the line. That will form a 100% tight seal for free)

If you look on top of your throttle body, you will see four vacuum barbs. (from back to front) Is the Idle Air Control valve vacuum sorce. The next two are EGR control, the fourth doesn't matter.
Use one of the two EGR nipples to connect the new ACIS vacuum line to.

You will wonder why we use the throttlebody vacuum. That's because it's a switched vacuum line. Under 3000rpm it has little vacuum, over it has full.

In our sintuation, there is enough vacuum to slam the ACIS flap shut at *any* rpm as long as the throttle body is open. This means it will be closed between a 650-1800rpm, but sitting at 650 rpm and opening the throttle will near instantly slam the flap shut.


What does this do power wise?

At worse you'll loose some power under 2500rpm. I noticed none. From around 2500 - 4000/4100rpm you will pick up power.

Not a huge gain, but keeps the power from dropping off on a 3vz-fe between the 95% peak torque @ 2500rpm, and 100% peak torque at 4400rpm. On a 1mz-fe it'll simply add some power under the stock torque curve.


In a state that requires no emessions checks, the EGR should be taken off the intake, blocked, and the bung on the rear exhaust log should be capped with a 5/8" brass fitting (no point in buying the correct JIC fitting)

If your state requires emessions testing, you should remove and cap all vacuum lines running to the EGR valve. It will still open, but only at higher throttle.
Must be done to cut down carbon buildup.


Thanks to Sean for the ACIS - TB vacuum swap.
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Old 04-13-05, 05:16 AM   #4
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This is definitely warranted to be in the Maintenance forum

Good info!
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Old 04-13-05, 09:01 AM   #5
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i dont know what all you said there. but looks cool. good job!
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Old 04-05-14, 09:38 PM   #6
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I'm sorry for bumping this thread, but this is a very interesting topic that I found through a Google search. The only thing stopping me from doing any of the suggested modifications is scientific proof, such as Dynamometer graphs, before and after. Cleaning the carbon is one thing, but grinding your air passages and cutting off vacuum and EGR pipes is a whole different matter.
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