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Intercoolers Open At 4k Rpm : False


Matt64341
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We are all under the assumption that the intercoolers open at 4k rpm and above. After all, if you pop the hood and watch the actuator while revving the engine, as soon as you hit 4k rpm, the actuator switches position. But this is not true.

 

Sorry this is such a long post, if you want to skip the whole story behind it, the conclusion is at the bottom.

 

I went out this morning to try to find out if tapping the bypass actuator into the intake manifold vacuum line would be a good idea. And to clarify, the numbers on my gauge are not accurate, if it reads 10 and drops to 8, pressure DID drop, but it is not in PSI just unknown units. It will correctly say when there is vacuum and when there is pressure.

 

There are only 2 things when it comes to the operation of the actuator

1) There IS vacuum - intercoolers ARE NOT being used

2) There IS NOT vacuum - intercoolers ARE being used

To simplify things for this, I will say the intercoolers are closed and the intercoolers are open.

 

It is also important to note that when the engine is off, the intercoolers are open, but as soon as the engine is started they close. And if you pull the vac line off the back of the actuator and cap it off, the intercoolers are always open.

 

 

What I did:

 

I wanted to find a place to tap in the Bypass actuator that would close the intercoolers at idle, no load, and cruise, but have them be open any time the car is accelerating.

 

1) Found out how much vacuum it takes to fully open the actuator [close the intercoolers] (about 5 units)

 

2) Made sure that the actuator was sealed and would not "leak" off the pressure/vacuum given to it

 

3) Tapped the vacuum/pressure gauge to the intake manifold. Then I used tape to attatch the gauge to the windshield so I could see it while I drove.

IPB Image

 

4) I monitored when there was vacuum and when there was pressure. There was pressure in first gear when you accelerated moderately hard, and the other gears pretty much any time you were accelerating. The rest of the time, the gauge read vacuum. http://www.youtube.com/watch?v=hAbJOkLF9XU

At this time, I had driven around for a while. I felt the CAC piping and it was hot, and the ABV and pipes around were still cool.

 

5) It then attatched the bypass actuator to the intake manifold. I was sure that this would be better than the stock 4k rpm opening. I drove around for a while and everything felt good. When I stopped I felt the abv piping and the cac piping and this time they were BOTH hot.

 

I was concerned that when the intercoolers were modified to remain always open, the ABV was not actually being used. See this diagram:

http://i28.photobucket.com/albums/c234/Fuj...Ctrl/img055.jpg

I believe the ABV vents off excessive boost, which would be a good thing at idle and very light loads. When the intercoolers are made to remain always open, it might prevent the ABV from doing its job. So it was something to think about.

 

Now, I thought my new configuration would be better than stock, but what WAS stock? I wasn't exactly sure since I had never actually monitored the control that it originally had when it was connected to the CAC Bypass Solenoid, I had just assumed 4k rpm was what opened the intercoolers.

 

6) I returned everything to the stock position including the bypass actuator, then I tapped the vacuum/pressure gauge between the solenoid and the actuator. I knew from before that anything more than 5 units vacuum would move the actuator so the intercoolers would be closed, and at 0 units and above the intercoolers were open.

 

7) When I went for a drive I was shocked.

The guage read 0 ANYTIME I was accelerating from idle to 6k rpm. When I kept a constant speed, it dropped to vacuum. At 4k rpm NOTHING CHANGED. Very small changes in throttle did not switch the intercoolers back to open, but if you try to accelerate at all, they will open again. Once you stop accelerating, after a couple of seconds, the intercoolers close again.

 

 

Conclusion:

The intercoolers opening at 4k rpm is only true when there is no engine load. During actual driving the intercoolers are open EVERYTIME you are accelerating, and it does not matter what RPM you are at. The only time the intercoolers close are at engine idle and constant cruise speeds. They will open anytime you start to accelerate again. This way is the most ideal way to have the intercoolers controlled, so no modifications are needed to the stock configuration. In the end, the results that I was aiming for were correct, but since I did not test the original set up I didn't realize that Mazda had it right the entire time.

 

If anything I wrote doesn't make sense, I can clarify.

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:hmm: I find this most interesting, and confirms the seat of your pants experiance is more mental. Perhaps when cruising and then shifting the intercoolers are "charged" so to speak so you get slightly better acceration but not much, interesting indeed.

 

so would you leave it all stock, or disc the switch

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:hmm: I find this most interesting, and confirms the seat of your pants experiance is more mental. Perhaps when cruising and then shifting the intercoolers are "charged" so to speak so you get slightly better acceration but not much, interesting indeed.

 

so would you leave it all stock, or disc the switch

 

Leave it all stock, that is how mine is now.

 

The mod was based on the fact that the intercoolers open only at 4k rpm, and if it were true, the mod would be very effective. But since this is false, it is better left stock. The bypass solenoid has excellent control over the intercoolers already.

 

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Wow that is cool, so all of you with the CAC bypass mod should put it back to stock conditions. So mazda had a god reason for implementing that system in.

 

Yea, mine is back to stock. The funny thing about it all is that we knew that 4k rpm seemed too high, and we were right about that. But it turns out we were all wrong about how it works in the first place.

 

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Well done Matt! This kind of research and writeup deserves honour :thumbup1:

 

Thanks :D There should be more things to come in the future, I am determined to get this vacuum system completely figured out. I am also in the process of another project right now and have a couple of things planned for a later time. I will post important things as I find them out.

 

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Sticky sticky!! You spent a lot of time and it deserves a bravo.

 

For years I keep saying mazda engineers are not idiot and they should have calculated the CAC actuation way before you heard about millenia. And eventually someone proved my claim. I had this mod, when my solenoid was bad and after i fixed it there was no difference. For those who feels better acceleration with the mod, explain now how you can feel it!

 

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