| Author |
Message |
Mitch Alsup (Mitch_alsup)
Intermediate Member
Username: Mitch_alsup
Post Number: 1023
Registered: 4-2002
| | Posted on Tuesday, September 09, 2003 - 10:13 am: | |
"Once again the depth and breadth of your Ferrari knowlege amazes me! "
And all I did was to read the owners manual (several times; and also the shop manual, several times). |
Phil Hughes (Ferrarifixer)
Junior Member
Username: Ferrarifixer
Post Number: 155
Registered: 7-2003
| | Posted on Tuesday, September 09, 2003 - 6:50 am: | |
The 355 CH has no valve. It is simply removed and the void filled with a spacer.
Other than that, the system is same as road car apart from a smaller (louder) silencer.
The valve on road cars also needs a 75% throttle input to be sensed by the throttle potentiometer via the ECU, in order for it to open at 3500 rpm.
The same philosophy is applied to the cam timing variators on the 360, which retard both exhaust cams by 20 deg under same conditions, and the variable length inlet track on all current models. Obviously, exact rpm's and throttle positions vary slightly between models, and temperature is also considered by the ECU's. |
Ben Cannon (Artherd)
Member
Username: Artherd
Post Number: 848
Registered: 6-2002
| | Posted on Tuesday, September 09, 2003 - 6:05 am: | |
Mitch- Once again the depth and breadth of your Ferrari knowlege amazes me!
If I didn't know any better, I'd say you worked on the F355 design team!
Thanks again.
One more question: do 355 Challenge cars have a y-pipe withought cats, (does Tubi?) or a completely different exhaust?
Best!
Ben. |
Mitch Alsup (Mitch_alsup)
Intermediate Member
Username: Mitch_alsup
Post Number: 1018
Registered: 4-2002
| | Posted on Monday, September 08, 2003 - 9:33 am: | |
The valve is controlled by RPMs from one of the ECUs. AT (1995 F355) 3500 RPMs the valve opens by a vacuum valve in the passenger rear fenderwell. The valve is kept open by a vacuum accumulator (also in the fenderwell) and this is fed by manifold vacuum. At 3500 RPMs, the valve opens the central passage to the muffler and the exhaust gasses now have three ways to exit the combustion chamber, left and right ceramic cats and two metalic cats in the (combining) y-pipe.
There are 3 inlets to the muffler, left, right, and upper central. All three allow exhaust gasses to exit at all 4 tips. However, the natural way for gasses to pass through the muffler is to head (more or less) straight to the closest tip pair. |
Ben Cannon (Artherd)
Member
Username: Artherd
Post Number: 843
Registered: 6-2002
| | Posted on Monday, September 08, 2003 - 1:28 am: | |
I've been wondering for some time now, how exactly the F355's muffler switchover system works?
I know there's two mufflers, and a valve system that shunts between the two, but when and exactly how does it switch over? Vacumm, from manifold? From a solonoid? (keyed to a control unit to switch at a fixed RPM?) What does the activation curve look like, and how is it weighted?
Oh, and does anyone have pictures of the 355 exhaust? I'd love to see exactly where the two banks do or do not combine/crossover.
Does anyone know if the 355's 2 mufflers in 1 exit out of only 2 of the 4 tips at once?
Best!
Ben. |
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