F355 exhaust valve opening sound

[Mario149]

Somewhat of a specific question:

Are there any owners of 2.7 Motronic 355s with standard exhausts who've noticed that when the bypass valve on their exhaust opens, it doesn't make a great deal of difference to the volume? I've been worried that mine isn't opening when it should, but tonight I've been doing some testing and I've had a mate manually actuating the valve while I rev the car and the difference is really not that big.

Is the difference in 5.2 more pronounced? FWIW, a couple of weeks ago at the HR Owen clinic, it seemed that 2.7s were louder at idle than 5.2s.

As always, any info much appreciated.

[Mario149]

It's getting ridiculous trying to nail this down!

http://www.fcars.co.uk/forum/showthread.php?t=3774...

Is there anyone in/near the London SW6 area with a 355 and a standard exhaust that would let me pop round to do a noise comparison test to work out what's going on? It would be much appreciated!

[132]

I had a 355 some years back and don't recall a massive difference in volume (standard exhaust) when the valve opened. The pitch certainly got higher. Also, I don't think doing a static test will give you the answer as the characteristics are quite different when the engine is under load...Good luck.

[ferrari spider]

132 said:

I had a 355 some years back and don't recall a massive difference in volume (standard exhaust) when the valve opened. The pitch certainly got higher. Also, I don't think doing a static test will give you the answer as the characteristics are quite different when the engine is under load...Good luck.

There was one mod that alot of owners used who had standard exhausts,who wanted to make the car louder at tickover and low revs. They used to wire the by-pass valve open. There is a noticeable difference even at stand still..
Though yes you are right, at full load there is an even more distinctive sound change. Heres a vid of mine on a run last week with hazy, the thumb camera is located right next to my rear number plate so. You can clearly hear the sound change as the valve opens and closes to make two completely different noises. http://www.youtube.com/watch?v=OQN50Q91qBo

Edited by ferrari spider on Tuesday 27th April 13:25

[Lagerlout]

I couldn't hear any change with mine either with the original bypass valve. I had it tested three times by Ferrari and they swore blue in the face it was operating properly except I could hear bugger all change in the volume. When I wired it open for a short while it was much, much louder. In the end my Larini failed so I replace the muffler with a Capristo, a Capristo reverse operating bypass valve (defaults open not closed), Capristo 200 cel cats, new cat ECU's and a Capristo valve ECU with key fob.

So the valve is either closed all the time or wide open all the time controlled via the key fob. The car sounds simply incredible now. Pure 80's F1. Worth every penny of the admittedly ridiculous £6k. I had no choice though on the cats as they were starting to let go. Being switchable the car is completely quiet at cruise on the motorway until you open the valve. Also much, much louder all through the rev range and there is a sweet spot where it just howls! This is in a GTB and there is no way you could ever want for volume. It would sound mind bending in a spider.