My Decat questions
My Decat questions
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Discussion

Bigadz

Original Poster:

393 posts

177 months

Tuesday 31st January 2012
quotequote all
Sorry guys I know there was a recent thread on this which I have read but I didnt want to hijack it and wanted to clear up a couple of questions which I had specifically:

My car is a 97 with sports tails and I am between silenced decats and non silenced decats.

1) From what I have read decats reduce engine temps by about 10 degrees, is this about right? It can only be a good thing for hp as well...

2) I am happy with the volume of the car now with the sports tails, with silenced decats will it be much the same?

3) Is ACT the way to go?


Gazzab

21,637 posts

311 months

Tuesday 31st January 2012
quotequote all
Act is one way to go. Talk to your local indie?
I think you are comparing decat and linked decat? The latter being slightly quieter.
Decats aren't a performance improvement afaik. Certainly not without a map.
They will reduce temps under your bum and not under the hood afaik. They will make the car louder and the note raspier. The car will get fumey as a result ie they create a slight smell in the cabin that won't have been there with cats in.
They will make mot's fun.

Bigadz

Original Poster:

393 posts

177 months

Tuesday 31st January 2012
quotequote all
Thanks Gaz, didnt consider the cabin fumes. If it gets pretty severe it might not be very popular with the mrs!

Tanguero

4,535 posts

230 months

Tuesday 31st January 2012
quotequote all
Gazzab said:
Act is one way to go. Talk to your local indie?
I think you are comparing decat and linked decat? The latter being slightly quieter.
Decats aren't a performance improvement afaik. Certainly not without a map.
They will reduce temps under your bum and not under the hood afaik. They will make the car louder and the note raspier. The car will get fumey as a result ie they create a slight smell in the cabin that won't have been there with cats in.
They will make mot's fun.
While I completely agree with the rest of what you say, well fitted, linked decats have never made my car smell in the slightest.

Cooky

4,955 posts

266 months

Tuesday 31st January 2012
quotequote all

OK time to dispel a few urban myths

A decat will not increase HP or torque, what it will do is allow what is being produced to be more effective. Most exhaust systems (except specially prepared race/tuned systems) produce a loss/decrease in effective power, and a Cat is a considerable factor in 'loss' so in layman's terms removal of the cats will not make your car increase power/torque but allow what is being produced to be more functional.

A balance pipe or x (cross) pipe will normally decrease noise in a traditional V8 (two plane crank)and even help decrease power loss but in the case of a Cerbera AJPV8 due to the characteristics of its single plane crank (and the way gasses are exhausted...more akin to a twin v4 than 2 in-line 4s) it will make very little difference to losses/optimal back-pressures nor will the noise volume decrease anywhere near the levels expected with that of a traditional V8.

Whilst decat pipes may increase cabin temps mainly due to the reduced wall thickness of the pipe this can be greatly reduced by ensuring they do not rest against the heat shield and there is plenty of spacing when fitted. They shouldn't release any fumes into the cabin. I have had my non linked decats for over 6 years and have no fume ingress whatsoever.

There was a thread here on PH a while ago that referenced this article
http://www.popularhotrodding.com/enginemasters/art...
it's well worth a read

Byker28i

91,447 posts

246 months

Tuesday 31st January 2012
quotequote all
Decat pipes increase cabin temp? I found the complete opposite. By not having a huge heat source next to the gearbox/clutch/tunnel everything was cooler inside. I've certainly never had any issues about fumes.

Bigadz

Original Poster:

393 posts

177 months

Tuesday 31st January 2012
quotequote all
Interesting post Cooky thanks..

What I meant was increased efficiency (as you describe) rather than increase hp, perhaps I should have worded that better but anyway..

Byker, from reading elsewhere I know you have the slienced ACT cats and you car is a 4.2 (same colour as mine) so it sounds as though you are satisfied with your setup?

DAVEY DEE

647 posts

183 months

Tuesday 31st January 2012
quotequote all
Ok,so mines a sp6 but again the decats greatly reduced cabin heat.Much cooler.I went ACT & love em.

robsco

7,875 posts

205 months

Tuesday 31st January 2012
quotequote all
My cabin was unbearable in summer before removing the cats. The heatsoak is ridiculous. There's no downside to removing them with the exception of having to bolt them back on at every MOT - more pops and bangs, slightly more free revving, cooler cabin temps and cooler engine temps.

Bigadz

Original Poster:

393 posts

177 months

Tuesday 31st January 2012
quotequote all
Its hard to ignore the benefits of decats when you put it like that Rob.

I have yet to experiance summer in the Cerb but I know how warm the cabin gets just in winter so I can believe that.

DJR 7

1,413 posts

286 months

Tuesday 31st January 2012
quotequote all
DAVEY DEE said:
Ok,so mines a sp6 but again the decats greatly reduced cabin heat.Much cooler.I went ACT & love em.
Totally agree, cabin is cooler as is the tunnel itself, I can hold the palm of my hand where once the cats would have been and the difference is considerable.
Never had and fumes in the cabin and the new enjoyable noise is fantastic ..........
D

Green Fly

819 posts

259 months

Tuesday 31st January 2012
quotequote all
DJR 7 said:
Totally agree, cabin is cooler as is the tunnel itself, I can hold the palm of my hand where once the cats would have been and the difference is considerable.
Never had and fumes in the cabin and the new enjoyable noise is fantastic ..........
D
Darren, you will have to show me the cerb after all your work especially if de catted. Is that so you dont hear me. biglaugh

Jcerb

344 posts

187 months

Tuesday 31st January 2012
quotequote all
I'm sorry i must disagree with a couple of comments about not gaining any power. I also have a 97 4.2, when i took the cats out it gained huge power! They were blocked full of carbon. I have also heard a story of a tuscan that was robbed of 200bhp from blocked cats! I was reconing on 100 bhp+. Before the cats were removed the car was running fine, but didn't seem as fast as i expected it should be, it was a huge shock. It was the first cerb i had driven so had nothing to go by. ACT silenced decats sound brilliant

robsco

7,875 posts

205 months

Tuesday 31st January 2012
quotequote all
Jcerb, did I see your car over at Track V Road recently?

In relation to the extra power, well its not really "extra" is it? In your case, it was just recovering power that should have been there initially. Forgive my pedancy. smile

Bigadz

Original Poster:

393 posts

177 months

Tuesday 31st January 2012
quotequote all
Well that's quite extreme! I think the cats on mine are quite old so may have some build up but like you I don't have another Cerb to compare to. Looks like I will need to make a purchase soon....

Jcerb

344 posts

187 months

Tuesday 31st January 2012
quotequote all
It was extreme, a certain piece of road i was hitting 108mph with cats red line, without cats to 4-5k 115mph, i couldn't give it any more as the geometry was out as it started getting hairy! I would say 125, will find out when it warms up! Too dodgy on these cold roads

DJR 7

1,413 posts

286 months

Wednesday 1st February 2012
quotequote all
Green Fly said:
Darren, you will have to show me the cerb after all your work especially if de catted. Is that so you dont hear me. biglaugh
Ian you were my inspiration! Following your Tuscan made me realise how subdued my car was.
Spiders are fitted, new cam cover, braided brake hoses all round, de-cat and a general overhaul by the boys at Str8six.
Now a totally different car to drive.
A spin out is on the cards, Pm me and we'll arrange, trust your well?

DAVEY DEE

647 posts

183 months

Wednesday 1st February 2012
quotequote all
DJR 7 said:
Ian you were my inspiration! Following your Tuscan made me realise how subdued my car was.
Spiders are fitted, new cam cover, braided brake hoses all round, de-cat and a general overhaul by the boys at Str8six.
Now a totally different car to drive.
A spin out is on the cards, Pm me and we'll arrange, trust your well?
Looked good when I saw it at the Bull Z Daz a few months back.Look forward to Seeing it now.Chatsworth I guess.Did you notice much difference in the ride/drive when you got rid of the 19's?

DJR 7

1,413 posts

286 months

Thursday 2nd February 2012
quotequote all
DAVEY DEE said:
Looked good when I saw it at the Bull Z Daz a few months back.Look forward to Seeing it now.Chatsworth I guess.Did you notice much difference in the ride/drive when you got rid of the 19's?
Feels more planted, no tram lining and certainly a little softer under the bum!
Had all four wheels aligned too this seems to have sorted the steering it now centres and makes roundabouts a little easier and quicker.
I still have the 19" which I'll use for the longer trips to preserve the spiders (given their reputation for softness)
Are you all ready for Chatsworth? I've got a few more things I'd like to sort.
D

DAVEY DEE

647 posts

183 months

Thursday 2nd February 2012
quotequote all
DJR 7 said:
Feels more planted, no tram lining and certainly a little softer under the bum!
Had all four wheels aligned too this seems to have sorted the steering it now centres and makes roundabouts a little easier and quicker.
I still have the 19" which I'll use for the longer trips to preserve the spiders (given their reputation for softness)
Are you all ready for Chatsworth? I've got a few more things I'd like to sort.
D
Nearly there......just a little issue of an engine rebuild to sort! I'll have to wait till I save the rest of the funds,but Chatsworth should give me chance to chat to some people & look under some bonnets.....& make a very long & expensive list!