Couldn’t find anyone who had done this already, so for ****s and giggles I did it myself.

The result? 2 BHP and 2 Torques less with the fuse OUT.

I’ll let the debate begin as to whether that’s statistically significant, either to physics or the seat of the pants, but to me that falls within the variability of the dyno and makes no difference.

I was going to do 2 runs each which might have narrowed the gap a little, but in all honesty hearing the engine screaming at full chat scared me a little and I bottled out of the second set. I didn’t want to see pieces of engine flying out of the bonnet.

Car is a stock 07 DB9 Volante, 22,000 miles.

Not sure what losses to apportion to the drivetrain, but the averages were 350 torques and 375BHP at the wheels.

Fuse IN - http://www.youtube.com/watch?v=1obfM1p8q4k

Fuse OUT - http://www.youtube.com/watch?v=Bge_EXXzFtI

 

Should point out that on the graph the solid line is Fuse OUT, dotted line is Fuse IN.

 

What is the deal with the fuse in/out debate? As a new member, I don't understand what the theory is or which fuse you all talk about. Is this something that affects certain Vantage model years? Please enlighten me.

Thanks

 

I’ll answer quickly before you get slammed with “do a search” from some of the others. Bu do one anyway, as there’s a lot of good info.

Fuse 22, certainly on the BD9 but I think on all current Astons, governs when the exhaust butterfly opens. With the fuse in (as stock) the butterfly opens at around 4000rpm, increasing the noise about 200%. 300%? This is the case with most Europeans cars in order to pass drive-by noise restrictions.

If you take the fuse out the butterflys remain open all the time, and you get a much throatier sound right across the rev range, crucially from low down. There has been some debate as to whether you lose a bit of power/torque, but the dyno test today says that you don’t.

Driving the car home with the fuse still in was actually quite odd as I’ve had it out for so long. The car seemed strangely silent below 4000rpm: Quiet, quiet, quiet, quiet, LOUD! Quiet, quiet, quiet, quiet, LOUD!

Took the fuse back out when I got home. It’ll stay out.

In the DB9 the fuse is in the trunk – far back left as you look at it, far front right relative to the car. Look n your owners manual to confirm for the Vantage.

Then do it and let me know what you think! I suggest apologizing to your neigbours first though.

 

Thanks for the info, and I promise to search..........

On my wife's BMW Z4, most take out the "S" section of the tube and fill both ends with a golf tee. Same idea. As soon as I get my Vantage, I will try it. Most of my neighbors are old and deaf, so it will not be an issue.

 

You can apportion about 15% loss to the drive train, so if you are measuring 375BHP at the rear wheels, the engine is putting out about 440HP.

Also, I think your conclusions are right, the small difference is due to variability. The reason I say that is that in both situations, fuse in or fuse out, the valve is fully open at Max HP.

Question: Does, "Fuse 22" control anything other than the valve in the exhaust system? I've heard some comments that some exhaust components can get very hot if the fuse is removed?

 

Actually you make a good point, in that the debate is really around low end torque, not top end.

In which case I may have just added fuel to the fire – bugger! The curves for each are identical all the way up, but the torque at 2000rpm does seem to be coming in higher with the fuse in (dotted line)....

Don’t know enough about dyno’s to comment on that.

I’ll ask them tomorrow.

 

Thanks for posting this...

Very interesting and the debate goes on.

 

Actually I'm a complete idiot, aren't I? I need to get comparisons lower down the range, say 1500 - 3000rpm. I'll go do it again...

****!

 

What we need are some comments by exhaust experts. I think there is some need for back-pressure in the exhast system at lower RPMs, and that is what this valve would provide.

 

This is definitely just dyno variance, it is not statistically significant enough of a difference. Just to put a precise number on it. 2HP/TQ comes out to .005 or 0.5% difference, which definitely in the category of inter-dyno variablity.

Keep in mind, that's on a DB9, not a V8 Vantage so the results may be more significant on a smaller displacement higher revving V8V. But I wouldn't be surprised if the results are the same. It appears the psychological effect of the noise alters the brains perception when in reality makes no real difference at all (basically its all in our heads).

The only way to really make significant difference is to alter the actual exhaust route (aka putting a new exhaust on). Even then from what I've seen, the differences aren't that big up top, but there are gains in torque to be had from 2500-4000. This is siimply because there are not two exhaust ways, but rather one better freer flowing single exhaust path. Backpressure shouldn't be an issue with those cats & etc. That's where the staggering majority of your backpressure is going to be found. Now if you deleted cats all together ... then torque loss would be a serious issue probably, but otherwise these motors don't appear to need a whole bunch to do the job quite well.

FYI, that's a mustang loading dyno so the drivetrain loss is actually higher, its probably closer to 17%-18% than 15%. those are strong numbers.

my 2 cents,
007
________
Philippine girl Cams

 

Haha, you beat me to it.

OP Also, if there was any difference it would be under 4k RPM as some others were saying. The way to really see if there were any differences would be to do 3 pulls with the fuse in and 3 with it out. I would imagine you MAY see a VERY slight loss in low end torque with the fuse out but if this were even so, it would be negligible.

 

I am curious to see 1500-3000 rpm but something tells me it won't be much .... granted you have a bigger engine so its different than V8V.

going to pull mine today to see how it sounds and if I feel any difference ... something tells me its all in our heads but I'll give it a try.
________
Pamelabigtitsx cam

 

Pulled out the fuse ....

I would start another thread but this topic has been beaten to death so I will just post my findings here.

The fuse was literally "Gone in 60 seconds" ... very easy to do. If you are too lazy to look at the fuse number just know Fuse #22 is the very last fuse towards the rear of the car inside the rear fuse box in the trunk. You can't miss it, its a yellow 20 amp fuse closest to the rear tail lights.

Initial impressions: I genuinely believe this talk about fuse 22 was in our heads prior to do this. I genuinely believe I feel more torque now not less .... Go figure. I also thought it was going to be obnoxiously loud but in reality its not. Below 2000rpm its still relatively quiet even with the fuse out. Idle is definitely deeper & meatier upon startup (also slightly quieter than I expected). Sound really picks up around 3000 and goes full at 4000 just like before when the cams really open up. To me the biggest difference isn't so much for people inside the car as it is for people outside the car, which is why Aston did it in the first place it seems (more due to noise regulation than what driver/passenger can hear). With that said it is impressive how good the sound deadening material is in these cars.

In many ways the car is far more enjoyable now now that I don't have to rev it so much higher just to get a bit of sound out. Now I am actually cruising lower in the power band and upshifting far sooner so I don't feel like I have to run the **** out of it in every gear just to get the enjoyment out of it.

Oh ... and freeway underpasses & tunnels will be your new best friend

Moral of the story .... just do it and enjoy it without worry, any torque "gains" or "losses" are probably just in your head.

007
________
Hot_Brunet1

 

Ha! Nice Job! Best bang for the buck you'll ever get on a mod.

Totally agree on the tunnels. My DB9 is a Volante. It sounds biblical in a tunnel....