GS back boxes on 4200

[Lozzer]

Tbh, fitting standard GS boxes to a standard 4200 system will be at best disappointing. You will get no real increase in sound. What you will get is an increase in bass at tick over, which gives the impression on more noise but it really isn’t. To get a noticeable increase in sound levels, you need to change 2 or 3 of the exhaust elements, these are:

1. Cats - change the standard 2 x 400 and 2 x 600 cell cats for 2 x 200 cells.
2. Centre resonator - change for an unsilenced H or X pipe.
3. Rear boxes - modify the internals to reduce the muffling effect. (Modifying GS boxes work well as you can still use the valves - if you have the pneumatic operating system fitted). Or, fit ‘straight throughs‘ which is basically a piece of pipe with 2 outlets on.

Changing only one of these elements will give a small increase, which might be enough for some, but changing 2 will give a much more noticeable increase. Do all 3 and you are looking at an ASBO if caught. That’s why I now have a 4 valve system on my back boxes in which 2 valves ‘fail’ open and 2 valves ‘fail’ closed. This set up gives a decently muffled quiet side or a barking mad fully loud side.

 

[BennyD]

No mate, it really isn’t.

 

[CatmanV2]

You don’t just put a set of valved exhausts on a 4200 and expect them to work. You need the pneumatic system of the GS installing as well. This comprises; a vacuum tank, (which sits behind the rear splash guard in the front near side wheel well), a pneumatic solenoid, about 15’ of rubber pipe, a T piece, about 15’ of wire and a switch. It took me about 2 hours to install. IIRC, to utilise the Larini remote kit, you need a vacuum source to operate the valves.

The (well a) vacuum tank is already there.

https://www.eurospares.co.uk/parts/maserati/4200-coupe/engine/secondary-air-system-20123

C

 

[rockits]

You don’t just put a set of valved exhausts on a 4200 and expect them to work. You need the pneumatic system of the GS installing as well. This comprises; a vacuum tank, (which sits behind the rear splash guard in the front near side wheel well), a pneumatic solenoid, about 15’ of rubber pipe, a T piece, about 15’ of wire and a switch. It took me about 2 hours to install. IIRC, to utilise the Larini remote kit, you need a vacuum source to operate the valves.

Thanks Ben

Yes, I did expect to need to add some form a vacuum activation of the valves even with the Larini remote kit. I was just going to get AV to help me with that though.

I might fit the back boxes myself first though to see what they sound like as default valves open. Might be good enough and what I'm looking for. The V8 Vantage stock with the remote was spot on for me. Never quite got the 4200 where I want it.

 

[rockits]

The (well a) vacuum tank is already there.

https://www.eurospares.co.uk/parts/maserati/4200-coupe/engine/secondary-air-system-20123

C

 

[BennyD]

The (well a) vacuum tank is already there.

https://www.eurospares.co.uk/parts/maserati/4200-coupe/engine/secondary-air-system-20123

C

It is but best to fit the bigger tank out of the GS.

 

[BennyD]

Thanks Ben

Yes, I did expect to need to add some form a vacuum activation of the valves even with the Larini remote kit. I was just going to get AV to help me with that though.

I might fit the back boxes myself first though to see what they sound like as default valves open. Might be good enough and what I'm looking for. The V8 Vantage stock with the remote was spot on for me. Never quite got the 4200 where I want it.

Alas, I don’t think the standard GS boxes will get you to where you want it.

 

[rockits]

Alas, I don’t think the standard GS boxes will get you to where you want it.

I think your right but got to get it where I want it. I've got secondary decat with straight through section, standard silenced centre xpipe then rear box delete with straight through pipes. It sounds good when driving briskly and at full tilt but too noisy the rest of the time.

Was thinking a Larini secondary decat race pipe section, Larini unsilenced centre X pipe the Larini rear boxes I've got already.

I'll see if the Larini rears sound better than the complete rear box delete pipes first. Not necessarily after just loud but a nice noise. I couldn't fault the stock V8 Vantage setup both valves closed and valves open. They got that spot on IMHO.

 

[Delmonte]

Tbh, fitting standard GS boxes to a standard 4200 system will be at best disappointing. You will get no real increase in sound. What you will get is an increase in bass at tick over, which gives the impression on more noise but it really isn’t. To get a noticeable increase in sound levels, you need to change 2 or 3 of the exhaust elements, these are:

1. Cats - change the standard 2 x 400 and 2 x 600 cell cats for 2 x 200 cells.
2. Centre resonator - change for an unsilenced H or X pipe.
3. Rear boxes - modify the internals to reduce the muffling effect. (Modifying GS boxes work well as you can still use the valves - if you have the pneumatic operating system fitted). Or, fit ‘straight throughs‘ which is basically a piece of pipe with 2 outlets on.

Changing only one of these elements will give a small increase, which might be enough for some, but changing 2 will give a much more noticeable increase. Do all 3 and you are looking at an ASBO if caught. That’s why I now have a 4 valve system on my back boxes in which 2 valves ‘fail’ open and 2 valves ‘fail’ closed. This set up gives a decently muffled quiet side or a barking mad fully loud side.

Cheers. I'm aware of some of that and already have a X pipe.

Surprised though that open valves on GS exhaust is no louder than standard 4200? Makes me wonder why they bothered? Like they thought the 4200 was too noisy, and on the GS the valves are only there to quieten it down, I was thinking / hoping that valves closed would be like standard 4200, valves open would give something more .. Weird thought process they seem to have used with the valved exhaust then...
Anyway the plan before I put it on is to get Jason at Jaren metalwork to refurb & modify the boxes, removing the wadding but leaving the baffles in, I don't want empty cans like a Larini cos I don't want it mad loud all the time.
I may then add the valve fob remote thing at a later date, if I think there would ever be a time I'd want it quieter...

 

[FIFTY]

This is the kit I used: https://www.ebay.co.uk/itm/203036016409

Only snagging points are: not enough silicon tube to run from the vacuum tank in the front LH wheel arch to the back boxes so you will need to order a few extra metres on Amazon or eBay

There is no 12V switched circuit in the boot... This is more of a problem... I have been keeping my car on a trickle charger and on road trips simply unhooking it if the car is parked up longer than a few days. I am intending to run a new switched cable from the passenger footwell fuses box to the boot when I have some time off in next week

I did a post on my project thread with some photos which may be useful https://www.sportsmaserati.com/index.php?threads/fiftys-manual-4200-build.28073/post-679874

Here is the wiring diagram for the kit

 

[CatmanV2]

You can mount all the electronics under the bonnet where there are ample switched 12v....

C

 

[FIFTY]

You can mount all the electronics under the bonnet where there are ample switched 12v....

C

We dicussed this when you were trying to help me with my car. There isn't a fuse box with switched 12V fused circuits under the bonnet there are only relays. What you are thinking of doesnt apply to the 4200 tipo cars only GranTurismo and QPV

If you look at the fuse box diagram for the GS you will find that the fuse is behind the kickplate in the passenger footwell....so even the Maserati factory had to run a switched cable through the car to the rear

 

[CatmanV2]

What you are thinking of doesnt apply to the 4200 tipo cars only GranTurismo and QPV

****, of course. Sorry

C

 

[Delmonte]

This is the kit I used: https://www.ebay.co.uk/itm/203036016409

Only snagging points are: not enough silicon tube to run from the vacuum tank in the front LH wheel arch to the back boxes so you will need to order a few extra metres on Amazon or eBay

There is no 12V switched circuit in the boot... This is more of a problem... I have been keeping my car on a trickle charger and on road trips simply unhooking it if the car is parked up longer than a few days. I am intending to run a new switched cable from the passenger footwell fuses box to the boot when I have some time off in next week

I did a post on my project thread with some photos which may be useful https://www.sportsmaserati.com/index.php?threads/fiftys-manual-4200-build.28073/post-679874

Here is the wiring diagram for the kit

View attachment 73408

Thanks Fifty. That thread could be mega useful to me.
What throws me here though, is you saying the GS boxes with permanent open valves on your 4200 were extremely loud and droney.... But Benny here saying standard GS boxes / open valves I'll hardly notice the difference to standard 4200...
Im confused... Personal tastes I suppose? Or is there some way different cars / exhausts could react differently with the same setups...
Anyway Fifty, how did you find the valve closed sound compared to standard 4200?
And anyone else got opinion on standard GS exhaust sound compared to standard 4200?

 

[CatmanV2]

Personal tastes I suppose?

Something like that

C

 

[FIFTY]

Thanks Fifty. That thread could be mega useful to me.
What throws me here though, is you saying the GS boxes with permanent open valves on your 4200 were extremely loud and droney.... But Benny here saying standard GS boxes / open valves I'll hardly notice the difference to standard 4200...
Im confused... Personal tastes I suppose? Or is there some way different cars / exhausts could react differently with the same setups...
Anyway Fifty, how did you find the valve closed sound compared to standard 4200?
And anyone else got opinion on standard GS exhaust sound compared to standard 4200?

Personal taste and it depends on what Benny's set up was when he fitted the GS boxes.

I had 2x 100 cell cats and unrestricted x pipe. Once the GS boxes went on with valves stuck open for me it was an acceptable hooligan mode but I would have liked something a little more restrained for long journeys, early morning/late night, etc.

I have since changed the cats to 2x 200 cell cats with 5 inch diameter and it has got even throatier

Drone with valves open is present at 1500 - 2000 rpm which is roughly 50mph in 6th. I find it quite loud but i have heard much louder droning exhaust.

Valves closed there is no drone at all and it still sounds pretty nice. Volume is much more restrained but not muted... It takes it out of that "**** off your neighbours and onlookers zone"

The GS boxes change the tone to a higher pitch than the standard 4200 boxes and seem a little more raspy

I have had the car measured with valves open at 99.9db on the current exhaust layout so if I want to can get on noise restricted circuits no problem


What set up do you have on your car... Euro or US spec cats, are they modified and have you changed your centre section x pipe?

 

[Delmonte]

Personal taste and it depends on what Benny's set up was when he fitted the GS boxes.

I had 2x 100 cell cats and unrestricted x pipe. Once the GS boxes went on with valves stuck open for me it was an acceptable hooligan mode but I would have liked something a little more restrained for long journeys, early morning/late night, etc.

I have since changed the cats to 2x 200 cell cats with 5 inch diameter and it has got even throatier

Drone with valves open is present at 1500 - 2000 rpm which is roughly 50mph in 6th. I find it quite loud but i have heard much louder droning exhaust.

Valves closed there is no drone at all and it still sounds pretty nice. Volume is much more restrained but not muted... It takes it out of that "**** off your neighbours and onlookers zone"

The GS boxes change the tone to a higher pitch than the standard 4200 boxes and seem a little more raspy

I have had the car measured with valves open at 99.9db on the current exhaust layout so if I want to can get on noise restricted circuits no problem


What set up do you have on your car... Euro or US spec cats, are they modified and have you changed your centre section x pipe?

Ta for that. I think you're after the same effect as me... I have a Larini unsilenced x pipe already on, is the only mod. Cats I don't know which I have. I'd like to change to sports cats though.... Mainly to stop worrying about unseen engine destruction.
Larini and super sprint sports cats both a bit rich for me though at what 2 grand?
And I've heard horror stories about custom cats (on here).
Whose cats have you got?

 

[FIFTY]

I have the horror story custom cats lol

I have had them rebuilt last year by someone who can actually weld and they are now less horrific.

With an unsilenced x pipe and stock cats you will likely be happy with the sound of the GS boxes with the valves left open. You may not want to bother with the valve control kit until you unleash more noise by modifying the cats

The other option to get more noise by not messing with the cats is modifying the GS boxes to make them straight through... I have heard these on conaero's old black GS and for me it was way too loud with the valves open

 

[Delmonte]

I have the horror story custom cats lol

I have had them rebuilt last year by someone who can actually weld and they are now less horrific.

With an unsilenced x pipe and stock cats you will likely be happy with the sound of the GS boxes with the valves left open. You may not want to bother with the valve control kit until you unleash more noise by modifying the cats

The other option to get more noise by not messing with the cats is modifying the GS boxes to make them straight through... I have heard these on conaero's old black GS and for me it was way too loud with the valves open

Thx again. Glad you got cats sorted in the end. Wish you could get sports cats for something like a grand but probs not happening....
Don’t want to go the straight thru route... I think too loud / drony. Going to do the Jaren wadding removal / refurb job, see how that goes.. Few weeks to wait though, Jason is busy... can’t wait lol

 

[BennyD]

Personal taste and it depends on what Benny's set up was when he fitted the GS boxes.

I had 2x 100 cell cats and unrestricted x pipe. Once the GS boxes went on with valves stuck open for me it was an acceptable hooligan mode but I would have liked something a little more restrained for long journeys, early morning/late night, etc.

I have since changed the cats to 2x 200 cell cats with 5 inch diameter and it has got even throatier

Drone with valves open is present at 1500 - 2000 rpm which is roughly 50mph in 6th. I find it quite loud but i have heard much louder droning exhaust.

Valves closed there is no drone at all and it still sounds pretty nice. Volume is much more restrained but not muted... It takes it out of that "**** off your neighbours and onlookers zone"

The GS boxes change the tone to a higher pitch than the standard 4200 boxes and seem a little more raspy

I have had the car measured with valves open at 99.9db on the current exhaust layout so if I want to can get on noise restricted circuits no problem


What set up do you have on your car... Euro or US spec cats, are they modified and have you changed your centre section x pipe?

Like I said; if you change 2 out of the 3 elements you will get a noticeable increase in sound levels. Standard cats, unsilenced X/H-pipe and Standard GS boxes has only changed 1 element and will, most probably lead to disappointment. The standard GS boxes give more bass and perhaps that is why they were droney. On mine, I e got Larini Sports cats, unsilenced H-pipe and heavily modified GS boxes; all 3 elements have been changed and that‘s why it’s pretty loud. I have a set of modified GS rear boxes coming so if anybody wants to buy a set, pm me.