What rpm does exhaust valve open?

Does the exhaust valve on the F355 open at a certain rpm or certain vacuum? What is the source of the vacuum?

 

bypass valve doesn't open in 2nd gear - FerrariChat.com

Cliff notes:

80 percent throttle position and above 2800 rpms in 1,3,4,5,6
80 percent throttle position and above 4000 rpms in 2

This detail is also in one of the WSM (forget which one). But the 80% throttle is not referenced...but is indeed required to open the valve.

 

Is the computer seeing throttle position by the TPS or is it by vacuum?

 

God, that is stupid.

 

Per the 355 Owners Manual:

Section C-9:

"Exhaust Bypass Valve, it is controlled by the ECU according to the engine rotation speed and depending on the engaged gear."

AND

Section C-16:

"Note: when the engine speed reaches 4,000 RPM in 3rd gear, or 2,800 RPM in 1st, 2nd, 4th, 5th or 6th gear"

The vacuum source is from the intake manifolds past two vacuum check valves (one each bank) and stored in a vacuum reservoir. See 'figure 5', reservoir is marked 'P' in Section C-15. Image is marked as: C 0132.

 

Yep, that's what both my 97 and 95 manuals say. The 95 manual says it on different page numbers but it is there.

 

This is very odd cause I have confirmed that mine opens in all gears except for 2nd at 2,800 rpm and around 80%+ power. And she opens at 4,000 rpms in 2nd gear with same amount of power. Was very easy to hear it open when I had the capristo installed. I wonder if since mine is a 99 and the manual I have is for a 98 if Ferrari changed it.

 

DOH! I messed up and forgot to change 2nd & 3rd.

Goth is correct.

My bad.

 

How much power would you loose if bypass does not open?

 

He is correct in that is what the manual reads, but I swear mine doesn't open until 4,000 rpm in 2nd gear and 2,800 in 3rd.

 

I agree. Mine opens @ 4k in 2nd gear and 2800 in all others.

 

How obvious should the volume delta be between open and closed with hyperflow cats and a Capristo? I hear the amazing wail around 4500 rpm all the way to 8500rpm but no real change under 4000 rpm in any gear.

Any idea?

Maybe I need someone else to drive it and I should listen from behind...

 

Mine is high flow cats/Capristo 2/3 but no secondary cats so that would make a difference but should still be very obvious I think.

You can hear the bypass operation here-

https://www.youtube.com/watch?v=qfrcN-IbBGU

 

Video is private...

 

Whoops, try this one-

https://m.youtube.com/watch?v=VdJ7CyZIWHE

 

And wot for comparison-

https://m.youtube.com/watch?v=1W_axP-HckQ

 

Thanks for the video. The 4000 rpm valve opening is very obvious but I couldn't really tell on the 2800 rpm one.

 

Yeah I don't have a good video of it at lower rpm. Pretty much the same change in loudness however.

 

Ok thanks. I'll drive it around some more.

 

About 10 HP

 

I'm not getting vacuum to mine. It works when I apply vacuum is applied from an outside sourse and I drove it with a vacuum gage rigged up and nothing. No idea

 

So it looks like my bypass is opening, but the sound isn't very clean when it opens. Any idea what would cause that to happen?

Also, when idle and in neutral, should the valve open when I rev it hard? Mine is closed regardless how hard I rev it.

 

There has been multiple information and some differences of opinion but I believe it needs to be in gear. It is at approximately 2800 rpm in all gears except 2nd I believe which is 4000. I tested mine and it was starting to opened at a vacuum level of a few pounds and seemed all open at 10 pounds approximately but I was using a brake bleeder so not real accurate.

 

^^Chris, you could try to lock it open and drive the car, just to see if there's a difference in sound. Pull the vacuum hose off of the valve, open it by hand and put a vacuum cap over the port.

Mine will open at WOT in neutral, not moving.

https://www.youtube.com/watch?v=_7J82wpQwOo

 

My valve also opens in N (depending on throttle position), but I have a Capristo valve and F1 transmission.