Discussion
Sorry to start a new thread but am on my phone and can't do a search.
I currenty have a standard exhaust system that's been decatted.
I've been looking on the ACT website and on the exhaust section.
They sell JP sports back box for ~£350 and a full big bore system from cats for ~£750.
I was originally only after the back box but have read that this along with the decats make the sound quite raspy.
The big bore system has a deeper sound, well that's what it says on the website anyway.
The reason for this post is to ask what benefits, apart from the sound, does the full system have over the standard exhaust. Is it worth the extra over?
And finally for the big bore system to be fully efficient does the exhaust manifold need to be enlarged too?
Thanks for reading
I currenty have a standard exhaust system that's been decatted.
I've been looking on the ACT website and on the exhaust section.
They sell JP sports back box for ~£350 and a full big bore system from cats for ~£750.
I was originally only after the back box but have read that this along with the decats make the sound quite raspy.
The big bore system has a deeper sound, well that's what it says on the website anyway.
The reason for this post is to ask what benefits, apart from the sound, does the full system have over the standard exhaust. Is it worth the extra over?
And finally for the big bore system to be fully efficient does the exhaust manifold need to be enlarged too?
Thanks for reading
I have the big bore JP system on my T350 and have had it fitted for just over a year now. This system @£750 is indeed a bigger bore system from the cats back but is also the track day friendly one which was purposely designed (using my car) to be both loud and liveable with at the same time. .
It is definitely not as loud (with cats) as the standard JP but for me is a great compromise for a sports exhaust that sounds great and is not too intrusive like the standard JP can be on longer journeys. I drove my car 3000 miles to Italy and back this year and then to/from Belgium for the Grand Prix and can confirm that it is a great mix of volume above 2500rpm whilst not being boomy or drony at all. I am told that with de-cats it sounds very good indeed and is much raspier (if that's what you want).
Now that I only use my car once every few weeks (and less this time of year) I would consider selling my full JP system and going back to the standard JP or Power exhaust if you are interested in doing a deal?
It is definitely not as loud (with cats) as the standard JP but for me is a great compromise for a sports exhaust that sounds great and is not too intrusive like the standard JP can be on longer journeys. I drove my car 3000 miles to Italy and back this year and then to/from Belgium for the Grand Prix and can confirm that it is a great mix of volume above 2500rpm whilst not being boomy or drony at all. I am told that with de-cats it sounds very good indeed and is much raspier (if that's what you want).
Now that I only use my car once every few weeks (and less this time of year) I would consider selling my full JP system and going back to the standard JP or Power exhaust if you are interested in doing a deal?
you won`t get any power gains on a speed 6 by removing the cats, in fact you could be losing up to 10bhp, not that you`d notice that much when driving the car anyway.
basically its just done for the noise, and reducing the heat in the transmission tunnel, a big bore pipe will give a deeper note, I found that the speed 6 was far to noisy when decatted, to raspy compared to a nice v8 rumble so made my own back box which is a lot less restrictive than the standard version but better silencing, so a nice note, IMHO, and plenty of pops and bangs coming through on the overrun.
basically its just done for the noise, and reducing the heat in the transmission tunnel, a big bore pipe will give a deeper note, I found that the speed 6 was far to noisy when decatted, to raspy compared to a nice v8 rumble so made my own back box which is a lot less restrictive than the standard version but better silencing, so a nice note, IMHO, and plenty of pops and bangs coming through on the overrun.
Diablos-666 said:
Targarama said:
Stu - if you've still got the big bore system come February-ish I'll be interested. Do you know what the volume in decibels is at the average track day test?
Oi I've already sent a private message, get in line you! 
Not that mine is going anywhere for the next month or so
Targarama said:
Diablos-666 said:
Targarama said:
Stu - if you've still got the big bore system come February-ish I'll be interested. Do you know what the volume in decibels is at the average track day test?
Oi I've already sent a private message, get in line you! Not that mine is going anywhere for the next month or so
i'm going to a PH meet on the 28th and maybe to a TVR meet on the 2nd 
I've also booked the PH Welsh Weekender in April - Will be good to get on some decent roads for once instead of the clogged up roads in south London.
How come you want to change your exhaust? Do you want a bit more volume. Jason @ str8six has said in his opinion the the full JP exhaust is probably the best on the market - so that's good.
I would like a bit more bass and fruityness, but not too much to ruin long trips or wake the track day sound monster. I'm also thinking ahead to when the car gets a 4.3/4.5 and is tuned for that engine. The larger bore system will hopefully help release a few more ponies and torques.
I really don't like the raspyness or loudness of the TVR Power and Blueflame back boxes. I am also not a fan of popping and farting all over the place, IMO it sounds chavvy.
I really don't like the raspyness or loudness of the TVR Power and Blueflame back boxes. I am also not a fan of popping and farting all over the place, IMO it sounds chavvy.
clive f said:
you won`t get any power gains on a speed 6 by removing the cats, in fact you could be losing up to 10bhp, not that you`d notice that much when driving the car anyway.
basically its just done for the noise, and reducing the heat in the transmission tunnel, a big bore pipe will give a deeper note, I found that the speed 6 was far to noisy when decatted, to raspy compared to a nice v8 rumble so made my own back box which is a lot less restrictive than the standard version but better silencing, so a nice note, IMHO, and plenty of pops and bangs coming through on the overrun.
I was under the delusion that PDQ's decats were dyno developed and showed some improvement?basically its just done for the noise, and reducing the heat in the transmission tunnel, a big bore pipe will give a deeper note, I found that the speed 6 was far to noisy when decatted, to raspy compared to a nice v8 rumble so made my own back box which is a lot less restrictive than the standard version but better silencing, so a nice note, IMHO, and plenty of pops and bangs coming through on the overrun.
Targarama said:
I would like a bit more bass and fruityness, but not too much to ruin long trips or wake the track day sound monster. I'm also thinking ahead to when the car gets a 4.3/4.5 and is tuned for that engine. The larger bore system will hopefully help release a few more ponies and torques.
I really don't like the raspyness or loudness of the TVR Power and Blueflame back boxes. I am also not a fan of popping and farting all over the place, IMO it sounds chavvy.
I'm not a fan of the raspy sound either if I'm honest, I much prefer a deeper beefier sound.I really don't like the raspyness or loudness of the TVR Power and Blueflame back boxes. I am also not a fan of popping and farting all over the place, IMO it sounds chavvy.
As for the popping and "farting" - I dont know many chavs that own such a car that cabbage those sorts or sounds. Dump valve yes but not the pops and bangs. I love giving it the beans and hearing those sounds.
It's like smashing the mrs and hearing those "noises"... Yeahhhhhhhh
I think we are on the same wave length re the 4.3/4.5 engine though, thatss def on my shopping list in the future.
willtvr said:
I was under the delusion that PDQ's decats were dyno developed and showed some improvement?
Edward Quick tried numerous variations at TVR before settling on this version, as part of their development work. Worked well on mine on the dyno.Just removing the cats leaves a 'can' that flows poorly, as I think Clive was meaning.
tail slide said:
willtvr said:
I was under the delusion that PDQ's decats were dyno developed and showed some improvement?
Edward Quick tried numerous variations at TVR before settling on this version, as part of their development work. Worked well on mine on the dyno.Just removing the cats leaves a 'can' that flows poorly, as I think Clive was meaning.
My Tamora has the full ACT/JP system plus a pair of decats. I posted sound clips on here of with and without the cats about a year ago.
The system gives a nice, deep exhaust note. It's much less raspy than the stock pipes with decats. It pops and bangs if you let it, but in my world that doesn't sound chavvy. The driver of the gorgeous GT3RS - who drove behind me with his windows down to listen to the Tamora - didn't think so either.
In my experience, the decats improve mid-range response. I very much doubt they'd lose power, but I haven't compared them on a dyno. I've heard some folk worrying about running lean with decats, but my particular TVR is always on the rich side, so for me it's never been an issue.
The system gives a nice, deep exhaust note. It's much less raspy than the stock pipes with decats. It pops and bangs if you let it, but in my world that doesn't sound chavvy. The driver of the gorgeous GT3RS - who drove behind me with his windows down to listen to the Tamora - didn't think so either.
In my experience, the decats improve mid-range response. I very much doubt they'd lose power, but I haven't compared them on a dyno. I've heard some folk worrying about running lean with decats, but my particular TVR is always on the rich side, so for me it's never been an issue.
Diablos-666 said:
Targarama said:
Stu - if you've still got the big bore system come February-ish I'll be interested. Do you know what the volume in decibels is at the average track day test?
Oi I've already sent a private message, get in line you! Where did we get to Stuart? I'm still up for getting it sorted!
tail slide said:
willtvr said:
I was under the delusion that PDQ's decats were dyno developed and showed some improvement?
Edward Quick tried numerous variations at TVR before settling on this version, as part of their development work. Worked well on mine on the dyno.Just removing the cats leaves a 'can' that flows poorly, as I think Clive was meaning.
I had the JP back box with a bigger bore cat-back system and found that it droned unbearably at around 70mph. I decided to get ditch the JP back box and have a custom made system which is basically straight-through except for a high flow cherry bomb pipe on either side plus it's de-catted with NTEL's de-cat pipes. No more droning at motorway speeds plus I now have a deep growl at low revs which is much nicer and the thing absolutely howls as the revs pile on. It is very very very loud but only when you want it to be - perfect.
Diablos-666 said:
Well I've got a price of ~£900 + VAT for supply and installation of a full bore JP exhaust from the cats down.
I don't have cats in so my decats will need to be modified to suit.
Is this system a lot better than standard? Just trying to justify the outlay ATM.
Your decats shouldn't need modifying for the full JP system - mine didn't, even though the JP is slightly larger bore.I don't have cats in so my decats will need to be modified to suit.
Is this system a lot better than standard? Just trying to justify the outlay ATM.
There's a lot of confusion on PH about the full system compared to just the back box. The full system (as you're considering) is quieter than the back box, which is a completely different part. The full system's only been around for a year-or-so.
I posted this when the JP was done on my Tamora:
http://www.pistonheads.com/gassing/topic.asp?h=0&a...
As for fitting, it's not a big job. I whip my exhausts off every year for the MoT.
Evening all
Well I started at standard and after a while it does not shout enough for me! So decided to resolve and I wasn't intending to or looking for any increase in power just to increase the noise and loose some tunnel heat!
Firstly I had the ACT (JP) Decats fitted and ran it with a standard back box. It was louder and sounded OK but was raspy especially around the 4k rpm mark like something in the standard box was resonating. The overall sound was like a louder E46 M3.
So I then had the JP rear box fitted. Its loud when your on it but you can drive it sensibly on long runs and its not to intrusive. It does pop and bang like good morning Bagdad out the back but you can control this if you wish (both ways more or less!) and when your on it if words could descirbe the sound its not really raspy its dirty and rude!!
A car park DB meter measured it at 130! IMO it sounds great. I was never looking for a deep exhaust note as the car is a racy loud straight 6 not a V8.
The heat removed from the tunnel by taking out the cats was the biggest bonus! Oh and the rear box is a lot lighter than standard.
Cheers. Lee.
Well I started at standard and after a while it does not shout enough for me! So decided to resolve and I wasn't intending to or looking for any increase in power just to increase the noise and loose some tunnel heat!
Firstly I had the ACT (JP) Decats fitted and ran it with a standard back box. It was louder and sounded OK but was raspy especially around the 4k rpm mark like something in the standard box was resonating. The overall sound was like a louder E46 M3.
So I then had the JP rear box fitted. Its loud when your on it but you can drive it sensibly on long runs and its not to intrusive. It does pop and bang like good morning Bagdad out the back but you can control this if you wish (both ways more or less!) and when your on it if words could descirbe the sound its not really raspy its dirty and rude!!
A car park DB meter measured it at 130! IMO it sounds great. I was never looking for a deep exhaust note as the car is a racy loud straight 6 not a V8.
The heat removed from the tunnel by taking out the cats was the biggest bonus! Oh and the rear box is a lot lighter than standard.
Cheers. Lee.
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