Question about 964 Intakes

[edbaus]

Hi,

I have a pair of 964 intakes. One is aluminum and one is plastic.

I have two questions. But first, let me lay out what I am doing with my 3.6L. I am putting this in my race car. My goal is to have a very flat Hp curve, which means that I am interested in low end torque as much as I am interested in Hp. The motor is getting a stock rebuild. My ultimate rwhp goal is about stock at 245 Hp.


The first question is that I see there is a difference in configurations of the throttle body of the aluminum vs the plastic. The aluminum has two butterflys. One is small and one is large. They both open mechanically with the throttle. The plastic intake has a single butterfly arrangement like I am more accustom to seeing.

Which one of these would be best for my goal. I have heard that the plastic intake flows better, but if the aluminum throttle body is better, then maybe I should use it with the plastic runners ?

The second question is that there is a second tube that runs between the left and right runners below the throttle body (on both intakes). It has a butterfly that seems to open by vacuum with a solenoid. My guess is that this butterfly is closed at idle and opens under higher rpm to create better air flow and basically to create a larger volume for the manifold.

Should I keep this. Should I remove the butterfly. I really do not have anything that can open or close the butterfly with my aftermarket setup.

I have included a few pictures of what I am talking about.

Thanks

Ed

[Bill Verburg]

The plastic is considered best

The resonance flap is normally closed but opens at ~5500rpm to fill both L/R chambers better as the intake pulse frequency in the intake rises

[edbaus]

ok, so what would be the result if

1. the resonance flap were not to open, or

2. the resonance flap were open all of the time.

Keeping in mind that this is going to be for a race application that will probably live in the range of 5000 rpm to 6500 rpm.

Thanks

Ed

[Bill Verburg]

It's sort of like tuning exhausts or church organs

The 964 intake has 2 tanks L/R that are connected by 2 pipes, the larger one is always open the smaller is controled by a flap. The area of the connection is varied by the flap. At low speeds the flap is closed the L pistons feed from the left tank and right from the right. The resonance freq is low and wants a smaller opening connecting the 2 tanks

As speed increases the resonance frequency also rises, to corrctly correlate the the 2 tanks the area of the connection must change by opening the flap.

The resonance between the tanks enhances filling the tank that is drawn from, keeping intake pressure as high as possible when it is needed

[rsscotty]

Ed,

The 964 intake works great when the resonance is functioning. What engine management are you using that won't operate the resonance solenoid? If indeed the ECU won't do the job then I have a good option for you.

[edbaus]

I am running an electromotive tec 1. It is a fairly old electromotive twin plug system, but they are actually more reliable and have a more stable spark than the tec 3 units.

Some have a spare output, but mine does not.

It would seem to me that for a race car that will see mostly high rpm work (above 5k anyway) the flap staying open would not be a big issue. I am thinking that the flap being open at idle would produce a poor idle quality.

What is it that you have.

Thanks

Ed

Now that you have me thinking, I could get one of those stand alone shift lights and wire it so that instead of the bulb, it actuates the solenoid.

[rsscotty]

Ed,

Check out this link for getting your resonance to function.

http://www.msdignition.com/pdf/FRM23778-PN%208950.pdf

I will be putting a 3.0 liter engine on the dyno late this week or early next week with individual throttle bodies and a 3.6 intake. I will test the engine with resonance inop. and with it active so you can see the graph overlay. This will give you an idea on what it does to power and torque.

[edbaus]

That is great. Really appreciate it.

What kind of signal do you provide that solenoid to open it. Just a 12v, or something else.

Thanks

Ed

[rsscotty]

With engine management, the solenoid or vacuum switch is provided with a constant 12+ and the ECU auxillary provides the ground.