I guess it closes at idle too, perhaps your 1500rpm number is inaccurate. It would make sense that the valves are closed at all rpms below 3800rpm regardless if it's moving or not.

 

No. I'm not guessing at this. Aston's manuals are very clear in spelling out the exhaust bypass behavior: 0-1500RPM open; 1500-3000RPM closed; 3000-redline open.

 

For what model years? Because I know for a fact on the older 4.3L it does not open until 3800rpm (tested it dozens of times). The valves are shut below 1500rpm too. I wonder if they changed things on later model years?

 

Please look at the image I just added above. This is for all V8 Vantages which don't have a sport exhaust (which opens the valves sooner).

 

Hi Karl,


As you say the valve is supposed to be closed at idle, but what I've found is that if you start the car from cold the valve stay open until the engine has warmed, then they close, I’m guessing it must be something to do with the start cycle. That’s why you could hear the change in exhaust tone in my clip, I’d started the car from cold.

 

I don’t want to detract from this thread, but seeing as you’re getting high flow cats here's another clip, this one is a comparison of a friend’s car fitted with standard cats and mine fitted with 200 cell cats both with fuse22 removed.

 

Actually, quite the opposite. What I was saying is that the exhaust valves should be open at idle, because idle RPM is ~750 and the valves don't shut until 1,500. This is why I don't understand why we hear a difference in the video. Your remote switch essentially automates the process of inserting or removing the fuse. But fuse in or out, the valves should be open at idle.

But you may be onto something about the cold start. If, during the warm-up cycle, the engine speed is above 1,500 RPMs, then the valves would try to close if the fuse was in. So removing the fuse (or pressing your remote button) would open them.

 

Hmm. Maybe I'm odd this way, but I think I might actually prefer the sound with the standard cats.

 

Yes I think you must be odd to be truthful I dont think computer speakers will ever do the sound justice, in the flesh it sounds amazing.

Here's a quote from my mate after I fitted a set of cats to his car, I think it sums up how we feel about them quite well.

I gave you my Vantage for a few hours and you took out a couple of the big heavy tube thingys which contained the roaring tiger that always seemed to be chasing me when I accelerated .. and you replaced the with 2 of of the small light tubes??
Only a couple of questions .. how the fk did they replace the tiger and fit a bloody great growling snarling monster in those little tubes and how do I get the smile off my face whilst accelerating away from it?

 

"Only a couple of questions .. how the fk did they replace the tiger and fit a bloody great growling snarling monster in those little tubes and how do I get the smile off my face whilst accelerating away from it?"

Outstanding!

 

Karl,

Turns out we were both half right. I just installed the high flow cats and I can now hear the cut out and cut in much more clearly now.

The cut in point is around 1500-1800 depending on load, but the valve open threshold is exactly 3800 Rpm every single time regardless of load or gear. It is 100% 3800rpm... So technically we were both half right. This was true on both my 4.3Ls. Not sure if this was changed later in the production run, but on the 4.3L it is 3800rpm

FYI, full cat writeup coming this weekend if I have time... Results are amazing including the dynos as well

 

Did anybody answer this question? I am lucky enough to own a 2011 V12V, and I pulled fuse 22 because the owners manual said it was the fuse for the exhaust bypass valves, and it didn't do anything. The valve still opened and closed as normally. The owners manual says fuse 15 is unavailable, but I see a 5A fuse in it, is the owner manual wrong?

 

I have a V12V 2012, USA model.
I had the same frustrating problem and questioned the $16.98 relay purchased off of Amazon. Using all the cool discussions and pointers on this Fuse 22 thread, I checked the voltage and 12V was read with the switch "ON" and 0V was read with the switch turned "OFF." Still no results.

My owner's manual also says Fuse 22 is the exhaust vacuum, so, knew I was connecting everything correctly. Unable to find a schematic wiring diagram for MY2012, I was able to find one for a MY2011 and it showed the 5A Fuse 15 as the exhaust vacuum. I took the relay circuit and wiring off of 20A Fuse 22 and placed it on Fuse 15, along with a 5A inline fuse, and "Presto!" The remote relay worked like a charm, as well as, programming the switch/relay to the Homelink buttons on the rearview mirror.

So concluding, my owner's manual is incorrect. The exhaust vacuum for my V12V, Assembly date 10/12, is built with a 5A Fuse 15 circuit.

And, furthermore, the MY2011 schematic I found showed that in 2011, Fuse 15 rather than Fuse 22 was used in the exhaust vacuum circuit.

 

So what is Fuse 22 for on the newer cars?

 

Here is the V12 MY2011 circuit diagram...