Intake Plenum Valve Removal
(Double Throttle Disablement)

Last updated: April 26, 2000

Date: Sat, 11 Dec 1999 12:08:25 -0500
From: "Sandy Linthicum" (

Doing this removes the small restriction when they are open and simplfies the intake. This is NOT a minor mod and they are not easy to get out. You need to remove it from the car and have a parts washer and air to clean it up when you are through. While you are at it you can go non-seq and remove and drill/tap & plug all the little vac/pressure openings that are no longer needed (a good days work).

It DOES remove a lot of stuff from the intake (emmissions stuff gone, as is warmup protection) but doubt it has any performance impact on anything but a race engine where 1 or 2 hp might matter.

I did all this to my car but left the throttle body coolant alone. If you get icing on the throttle plates you get stuck in an open throttle condition - no fun. Even in my part of NC with its mild winters, early morning ambient temps in the 20's and a big intercooler, give me air temp at the throttle body below 32F.


Date: Tue, 8 Jun 1999 14:36:24 -0500
From: "Westbrook, Chuck E." (

> From: Chris Davis []
> Sent: Tuesday, June 08, 1999 09:17
> I have my intake plenum off for polishing and have a question about the
> two valve inside it.  I believe they are for restricting the boost while
> the car is cold.  I have already disabled the double throttle and I know
> not to floor the car while it is cold.  My question is, can I remove the
> two valves without negative effects to performance?  What are the
> benefits?  I was also wondering if someone could give me instructions on
> how to remove them.  If it is too difficult or not worth it, I will not
> even bother with them.  Thanks.

You only remove the second set which is operated by the vacuum unit. You have to drill out the set screws that hold the valves in their shaft. Pull out the valves. Then make sure that the shaft has no burs so that you can pull it out. The side where the vacuum unit was attached has to be plugged. I just filled in the complete hole with silicon glue and place an aluminum cover plate over it. Some people first drive in a short stud into the shaft hole, then fill it up.

What's also good about this is that you can now remove all associated plumbing for the vacuum controlled secondary throttle. This removes one hose from the throttle body area. Must leave the solenoid attached so that the ECU does not give an error code unless you want to replace it with a resistor. The second benefit is less air flow turbulence after the first double throttle which does not open up 100%. The first (mechanical) is at an angle to the second (vacuum)one. This should give a wee bit more hp, but how much has not been qualified. At least it makes the system simpler and frees up space. I have had mine off for over two years with no problems.


Date: Tue, 08 Jun 1999 17:04:52 -0500
From: "Kevin T. Wyum" (

Why are you drilling the screws out? I don't recall ever doing that. Use a screwdriver or one of those impact drivers you hit with a hammer.


See the Intake plenum removal instructions. for directions on how to remove it. --Steve


Date: Thu, 15 Apr 1999 18:24:19 -0500
From: "Kevin T. Wyum" (

> wrote:

> I noticed on Rob R site he mentions to disable the Double throttle all you
> have to do is plug off the vacuum line to the actuator. Anyone have ill
> effects disabling it? any major difference?

Its function is primarily to protect against the idiot factor. The valves stay shut until the car is warmed up. This doesn't allow too much air into the cold motor. When I say idiot factor I am talking about people that would start the car up cold and immediately floor it.


From: Rob Robinette (
Sent: Thursday, December 09, 1999 8:02 PM

A couple of days ago I removed my double throttle butterflies and did a How-To with pictures, it's at:

I'm actually seeing a little more boost after this mod, I think it really does help the intake flow.


Date: Fri, 10 Dec 1999 11:21:31 -0500
From: "Ryan Schlagheck" (

One thing I noticed about the removal of my secondary butterfly plates was that the screws that you chose to remove with an impact screwdriver were mushroomed on the other side on my intake plenum, thereby making backing out of the screws impossible. Your model may vary but people pondering this mod should be aware that they may have to drill through the plates at the screws if the head is mushroomed. I speculate that the screws are mushroomed to prevent the constant heating and cooling action from slowly backing out the screws and falling into the intake tract. My vehicle is a '94 Touring, so the '93's may have had a different secondary plate setup.

I chose a drill bit slightly larger than the shaft of the screw (the head is larger so you'll end up drilling that out like you would a sheared bolt) and then I slid the plates out from the center of the rod, pulled out the rod and replaced the hole in the plenum with an aluminum hex bolt (basically the same as you did).

I also recommend that you remove the intake plenum altogether, to prevent bits and pieces of metal filings from falling into the lower intake plenum.


Date: Tue, 25 Apr 2000 21:07:02 EDT

Subject: (rx7) [3] Double Throttle Control - Prevents Detonation?

According to the Shop Manual (Page F-137):

"The response delay of the pressure sensor following rapid acceleration 
temporarily causes a lean fuel mixture.   The double throttle control system 
prevents this hesitation caused by the lean fuel mixture...."

Although I am only theorizing here, could the "lean fuel mixture" on acceleration in the absence of a functioning double-throttle control system cause detonation and destruction of the engine?

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