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jong said:
That Y-pipe is part of the ACIS system. and both sides are used all of the time. the ACIS control valve is situated in the intake manifold and just moves to change the length of the runners. removing that y-pipe and replacing it with throttle bodies would completely ruin the ACIS effect making it useless.
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The 7M-GE doesn't have a true ACIS system to begin with... it's just a butterfly valve that is open at idle (to allow the CSI to work), and then closes (yes, closes) at fuel pressure up (FPU). 86.5-88 7M-GEs use two separate VSVs for FPU and valve operation. The 89 and later 7M-GEs used the same VSV for fuel pressure up and to apply vacuum to the butterfly valve.

Replacing the Y-pipe would not render the system ineffective, as both sides of the manifold would still be fed simaltaneuosly...
 

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jong said:
sorry to disagree... but thats incorrect.

The 7m-ge does infact have a true ACIS system. The Butterfly valve in the manifold changes the effective length of the intake runners. One mode extends from immediately behind the throttle body with the ACIS control valve closed for long runners. The second mode, with the ACIS control valve open, begins in the middle of the manifold to the runners, short runners. If you would replace the Y-pipe with throttle bodies, you would eliminate the "long runners" that is utilized with the Y-pipe, making it a short runner system. the ACIS control valve would do little to nothing because the shared intake air volume is coming from primarily the same spot.

the 7m-ge has almost the same system as the 2JZ-GE.

read here...
http://www.supraforums.com/forum/showthread.php?t=227121&highlight=ACIS+jong
http://www.geocities.com/mwsupra2003/acis.html

Why do you say that the 7mge doesn't have a true acis? It changes the length of the intake runners, which is what ACIS is supposed to do. The system on the 7mge does everything that ACIS does on current toyota models with the ACIS system.


I read that, even posted in the thread. To recap (and to repeat what I posted in that thread)

The normal state of the butterfly valve is open, not closed. if it was closed, the cold start injector woud only feed cylinders 1-3.

When vaccuum is applied, the valve closes. The valve activates at 4200 RPM, thus it closes at 4200 RPM, creating the long runners, not short (same time as the fuel pressure up VSV activates, which is interesteing, becuase on later 7M-GEs, the FPU and butterfly are controlled by the SAME VSV, which means there is not multiple open/close operations of the valve as on a true ACIS system))

This is completely at odds with what you wrote about the ACIS system on the 1MZ and 2JZ (and I'll note, you have nothing on that page that shows the 7M-GE system, just the 1MZ and 2JZ)


Replacing the Y-pipe with throttle bodies would not ruin the long runner/short runner effect either. The throttle bodies simply become part of the 'long runner'. When the butterfly valve is open, you still have a short runner...
 

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No... it means that when the valve is closed, cylinders 1-3 are fed from one side of the y pipe, and 4-6 are fed from the other. The chamber in the upper manifold effectively becomes part of the runner.

When the valve is open, the chamber becomes the starting point of the runners.
 

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1. Show me a proven reference that Toyota calls the 7M-GE system an ACIS system. There is almost a decade between motor designs between a 7M-GE and a 2JZ-GE. The 7M system operates exactly opposite to what you wrote about the ACIS system. Either Toyota is wrong, or you are. They are different... period. If you call the 2JZ system an ACIS system you can't call the 7M system an ACIS system. Maybe there's a reason why there was no mention of 'ACIS' until after the 2JZ and 1MZ were introduced (93 and 94 respectively...)

A carburetor and TBI both do the same thing, provide fuel for a motor, but you don't call one the other on that basis do you?

2. Using two throttle bodies, the runners are still separated. The length of the Y-pipe now becomes the length of the throttle bodies. I see where you're getting confues though... I'm saying to attach the throttle bodies directly to the upper manifold.

3. Speaking of comparing apples to an orange...

If there were little room for improvement, and Toyota acoustically designed the 7M-GE, then there would have been no need to change the design so drastically as they did on the 2JZ-GE. Larger diameter runners, larger diameter Y-pipe, different upper manifold design, etc all affect the acoustics of the manifold.
 

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jong, if you had bothered to put any of this info here on the page you wrote, it would have made more sense.

The butterfly valve on the 7M-GE is not closed at idle. In order for the system to work as your saying, at it has to close after idle, and then open back up.

AT 4200 RPM, it either leaves the valve closed, or opens it, depending on WOT or not.

On the 7M, when the valve closes, fuel pressure up also occurs. If the valve opens up again t 4200 RPM FPU cuts off. That's what doesn't make sense to me.

Isn't anything more than 60% throttle considered WOT on a TCCS system? I seem to recall a discussion about this before...




You've shown me is that the system on the 7M is called the Intake Air Control System (IACS), which makes sense, as that is what the VSV that controls the butterfly is called.

There has to be some reason why Toyota chose to call the same system something different on the 2JZ... i.e ACIS.

To quote you...
Of COARSE, they are going to change the ACIS system "drastically" on a DIFFERENT ENGINE... I'm sure the Toyota engineers said " oh ok, well, lets take the exact ACIS system from the 7m and throw it on the 2JZ, even though the compression ratios, valves, and pretty much entire air flow through the head is different!"
Exactly my POINT... What they did was take the identical IACS system on the 7M and modified it into ACIS.



As for runner lentgh using two throttle bodies....

As long as you make the length of the runner from the dual throttle bodies to the head the same as the distance with the single throttle body, the system is not affected.

I.e, the axis of the dual throttle bodies mut be colinear with the axis of the single throttle body.

The only time 'shared air' is in effect is when the butterfly vavle is open (i.e, short runner)... when the valve is closed, the runner length is now from the throttle plate.




not to all gang up on you..but dont misinform the public w/o hard cold facts to back you up
Wu tang....

Don't post a page and link to it if you don't have all your facts there either...

I was disputing the 'facts' presented, not informing. It wasn't until this thread that any facts showed up. Had they been there to begin with...

You need to go read every thread on this forum and then post that....
 

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Getting a little long here...

Pre 89 NA's do have a FPU, and it's activated by a VSV (it's pin 10 on the 24 pin ECU connector), on post 89s, it's simply vaccuum activated. I was wrong about the post 89s, I thought that the VSV was in-line with both systems.

Note the missing identifier on pin 10 for the post 89s...




If the fuel pump crossover is at 4200 rpm, that would explain the simplification on the post 89s.




That statement led me to think you wanted to bolt the throttle bodies directly to the manifold. Which is what you said.... And now you said you don't want to do that?
I should have inserted a 'not' in that statement. I never preview what I type... I do now though.



AT 4200 RPM, it either leaves the valve closed, or opens it, depending on WOT or not.
WRONG!! At idle, the valve is always going to be open. At 4200 rpms, if the VTA ( throttle angle) is below 60% then it will close. At 4000 rpms with a VTA of 70% or higher the valve is closed, heck, at 1500 rpms with same VTA the valve is CLOSED, as it passes 4200 rpms, the valve OPENS.
How is that statement wrong? At 4200 RPM, the valve either stays closed, or opens. Did you read the sentence prior to the one you quoted? I.e...

The butterfly valve on the 7M-GE is not closed at idle. In order for the system to work as your saying, at it has to close after idle, and then open back up. AT 4200 RPM, it either leaves the valve closed, or opens it, depending on WOT or not.

The valve being open at idle was my main point of contention to begin with...


Never-the-less, we've covered it, etc... Sorry for any consternation.
 
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