Cats vs. linked de-cat - some driving impressions

[edhorne]

Hi folks

As you all know I have a long private road on which I can test my car without cats on......and I thought some of you might be interested in my back to back observations.

Having recently had the MOT I put some miles on the car with a new pair of cats from www.bmcatalysts.co.uk. The cats seem well made and they passed the MOT but the 2000rpm flat spot that I remembered from the old blocked cats was still there.

I made sure that the adaptives had been reset and re-learnt and that they were well balanced (-5% on both sides) before the MOT so I knew that the engine was in a reasonable state of tune but there it was.

Anyhow, I finally got around to putting my Trackcar Solutions linked de-cat on and what a difference. After an adaptive map reset and some good full throttle pulls up the steep hill on my private road to re-learn the adaptive maps, the throttle response was instant and power delivery very smooth.

The best bit however, in comparison to the catted exhaust is the part throttle cruising. There is very little drivetrain shunting and the road manners in 4th or 5th gear at light throttle settings are excellent. It improves as the engine warms up (due to expansion of the throttle link rod on the 4.2 engine) and it's almost nice to drive now. Just need to sort out those squealling brakes!

Happy driving

[clive f]

Joolz magic still impressive

[scotty_d]

Have you got any pictures of it? I am going to have a silenced Version made up i think.

[spongy]

joolz majic mine has this.mine drove the same with cats in,car felt totally different when my decats went back on.there is a step at 2000 revs with them pesky cats in

[PoleDriver]

I have a linked decat pipe on mine. I always wondered what the rationale was behind the design of these? Linked pipes I've seen on big (Yank) Fords and LS engines have always had larger diameter pipes in an 'X' style (two pipes linking instead of one straight across)
Any thoughts?

[purpleliability]

I can't seem to find these linked de-cat's listed anywhere, I'm particularly interested as it will help to reduce the noise to make it easier when going for noise tests on the track...

Thanks for the review!

[jaydom]

As purpleliability, if sbdy is abble to help me sourcing those link decats...
I searched for some and never succeed!
Thanks all

[scotty_d]

I am going to have a custom one made up but silenced as my car is a bit much with the sports Exhaust. I could ask the chap who made the rest of System if he could make a few Un-silenced and get a price?

He did make Colin Mcrae's Systems for some of his rally cars and his work is nice.

[PoleDriver]

scotty_d said:

I am going to have a custom one made up but silenced as my car is a bit much with the sports Exhaust. I could ask the chap who made the rest of System if he could make a few Un-silenced and get a price?

He did make Colin Mcrae's Systems for some of his rally cars and his work is nice.

I want a 3 inch straight-through system (no silencers) with no cats and linked-decat. I'd be interested to get a price!

[scotty_d]

After Chatsworth i need to go back up to his work shop so he can finish mine off as it is clamped in 3 sections ( i want it as one piece) and it needs new hangers made. He was not too keen to do it this way as he did not have the car due to my winter re-furb. I can confirm it sounds Awesome But more than i want hence the silenced de-cats.

If you look at my Project thread there are a few pictures of what has been done on my Exhaust so far. He made me a full 316 marine grade stainless system for my old Jaguar xj6 a few years ago and all i can say is wow it was stunning.

He works in 306 now as he is finding it hard to compete with local company's but it is still nice workmanship. But he can do Titanium or 316 if requested he is a engineer not just a welder so know how to get Ponies from exhaust systems

If a few people are interested i will run it past him. I know he makes systems for a company that sell Nissan GTR tuning upgrades and they are massive and works of art. So i think he will be keen to make a few set for a Cerb.

[spitfire4v8]

Sounds like I should get another batch of linked decats made up then! or he can just pay me a commission?

[scotty_d]

spitfire4v8 said:

Sounds like I should get another batch of linked decats made up then! or he can just pay me a commission?

Can you PM me a price and what do you make yours from i want to stay Stainless if possible (fussy git)and can you do a silenced version as well?
What is the main reason for linking the 2 systems up over keeping them separate.

Cheers Scott

Edited by scotty_d on Wednesday 11th April 21:25

[greenracing]

Just been given a set of 4.2 decats, but need to mod the length as mines a 4.5, thinking about adding the link pipe at the same time. Has anyone got some pics of the linked decats?

[Cyclone1]

scotty_d said:

Can you PM me a price and what do you make yours from i want to stay Stainless if possible (fussy git)and can you do a silenced version as well?
What is the main reason for linking the 2 systems up over keeping them separate.

Cheers Scott

Edited by scotty_d on Wednesday 11th April 21:25

Pulse balancing.

[edhorne]

Sorry guys. I don't have a picture.

I have listened to many people tell me that you shouldn't link the 2 banks of a flat plane crank V8 but I seem to remember them being good for around 8 bhp - they were all the rage back in '06-'07!

I'm sure spitfire4v8 can confirm how they compared to a standard de-cat.

Ed

[scotty_d]

With the standard Cerb exhaust system they are linked at that big back box i guess, Not as Far up the system but still linked at some point.

[tejr]

This article is a nice read with regards to linking/not linking the AJP exhausts

http://2009.tvrspeedchampionship.co.uk/index.php?o...

[scotty_d]

Good read and all is clear now thanks for posting.

[purpleliability]

The standard back box is actually two separate chambers with a divider in the middle so they are not linked (Or at least mine was).

[greenracing]

tejr said:

This article is a nice read with regards to linking/not linking the AJP exhausts

http://2009.tvrspeedchampionship.co.uk/index.php?o...

I was trying to find that article yesterday, its one of the reasons I want to fit a linked pipe. At the end of the day, if the performance does suffer, I can always swap back!