Exhaust valve's

[JimT]

Hi

Is it possible to retro fit valves to the rear silencers of a granturismo that doesn't have them?
My car is an early one so in that respect would it even benefit in terms of volume if the silencers don't have them in the first place? If that makes any sense.
Or am I looking at replacement silencers with them already on and if so would they be londerr than the silencers I already have?

Apologies for all the questions.

Thanks

 

[CatmanV2]

You could fit some valves, but you'd have to cut and weld them in to one of the pipes and decide where to exit and blah blah

Better to find some 4.7 boxes and fit those. And yes, they'll be louder.

C

 

[Gazcw]

Hi

Is it possible to retro fit valves to the rear silencers of a granturismo that doesn't have them?
My car is an early one so in that respect would it even benefit in terms of volume if the silencers don't have them in the first place? If that makes any sense.
Or am I looking at replacement silencers with them already on and if so would they be londerr than the silencers I already have?

Apologies for all the questions.

Thanks

Get 4.7 but do not forget you will need to also add vacuum pipe, solenoid and hardwire or remote switch

 

[JimT]

Get 4.7 but do not forget you will need to also add vacuum pipe, solenoid and hardwire or remote switch

Hi

In an ideal world yes that would be great. I've done so much to this car now that it's kinda counter productive. At least at the moment.
I just figured it would really help the sound
Having a 4.2 that has had so much sorted on it.

Good point on the remote kit though.
Thankyou

 

[JimT]

You could fit some valves, but you'd have to cut and weld them in to one of the pipes and decide where to exit and blah blah

Better to find some 4.7 boxes and fit those. And yes, they'll be louder.

C

Thankyou for your reply.
Yes that's probably the best route to take if I do it.
So excuse my ignorance here.
Do the 4.7 back boxes have different silencers.
Is with the valves closed on a 4.7 the same volume as the standard non valve boxes on a 4.2?

 

[CatmanV2]

Do the 4.7 back boxes have different silencers.
Is with the valves closed on a 4.7 the same volume as the standard non valve boxes on a 4.2?

Yes. They have two paths for the gasses to exit. One goes through all the wadding. The other, normally closed off by the valve, bypasses it all, but still exits from the same tail pipes (each box has two pipes even the oval ones). Open the valve and the gasses take the easiest (loudest) path out.

Pretty much the same volume as the 4.2 IME. I fitted 4.7 boxes and a control kit to my 4.2. It was great

C

 

[Gazcw]

Hi

In an ideal world yes that would be great. I've done so much to this car now that it's kinda counter productive. At least at the moment.
I just figured it would really help the sound
Having a 4.2 that has had so much sorted on it.

Good point on the remote kit though.
Thankyou

I meant get 4.7 boxes rather than car.

 

[JimT]

Yes. They have two paths for the gasses to exit. One goes through all the wadding. The other, normally closed off by the valve, bypasses it all, but still exits from the same tail pipes (each box has two pipes even the oval ones). Open the valve and the gasses take the easiest (loudest) path out.

Pretty much the same volume as the 4.2 IME. I fitted 4.7 boxes and a control kit to my 4.2. It was great

C

Thankyou for quick reply.
So a notable difference then?
Worth the expense?

 

[JimT]

I meant get 4.7 boxes rather than car.

Sorry. Yep get that now.
Just assumed that as everyone says how much better the 4.7 is.
Hoping with 4.7 back boxes it will be comparable sound wise.

 

[Gazcw]

Sorry. Yep get that now.
Just assumed that as everyone says how much better the 4.7 is.
Hoping with 4.7 back boxes it will be comparable sound wise.

Well it will be louder.. whether the sound is the same I am not entirely sure tbh.

 

[CatmanV2]

Thankyou for quick reply.
So a notable difference then?
Worth the expense?

Oh totally IMHO. I managed to score my 4.7 boxes comparatively cheaply (you might want to sit down before you start trawling through ebay) and I'd also budget to get the valves on teh boxes cut out and replaced. They tend to fail and stick open (no bad thing but sort of pointless) or rattle (very very irritating).

Of course the other thing you can do if you don't want to be able to control things is just gut the existing boxes.

FWIW I loved the valved boxes on mine, and the ability to open and close at will. Also on the 4.7 car they don't open all the way all the time. They are gradually opened depending on revs and throttle, so it'll never quite sound the same as a 4.7 (or indeed a 4.2) but it should sound fabulous.

C

 

[ChrissGT]

The non-valved boxes are actually straight through as well if there is enough pressure to open the valve in the muffler. But they are different silencers compared to the 4.7 in design.

I didnt find 4.7 boxes to be any louder when at full throttle in high rpm. But i do like the fact that they open up at the press of a button. So at lower rpm you get a lot more noise compared to the 4.2.

Downside is that with valves closed you lose a lot of performance (back pressure), so sporty driving with valves closed isnt the best idea. This is why there is pressure valve in the 4.2 box and a valve automaticly opens up at certain rpm on the 4.7.

 

[MartyG]

I will have a set of valved back boxes up for sale soon if anyone is interested. I had them on my 4.2 and am selling it and putting the originals back on.

 

[JimT]

A lot to think about.
So in a nutshell.
At high revs the sound is comparable.
But at tickover and less sporty driving louder as you can manually open the valves.

 

[JimT]

I will have a set of valved back boxes up for sale soon if anyone is interested. I had them on my 4.2 and am selling it and putting the originals back on.

Could well be Interested dude.
Let me know when they are available just in case

 

[CatmanV2]

A lot to think about.
So in a nutshell.
At high revs the sound is comparable.
But at tickover and less sporty driving louder as you can manually open the valves.

Certainly a good summation. I'd just go for it

C