De-cat truth

[TM.]

Wow this threads turned into a hot one lol!

I thought I would give a quick in sight information on the results we found when we were testing a de-cat on a 182 at Torque of the devil last year (dyno dynamics rr)... Sadly I have no graphs of this as there were all stored on my previous work partners lap top so its your call on if you decide to believe my findings or not, frankly couldn't care either way

Test 1. Completely standard 182 bar milltek cat-back, Rolling road showed normal power/ torque, was in the region of 170/173 bhp

Test 2. Same car but this time with the decat fitted, Peak power was near identical but lost a good chunk of torque at around 3,000rpm (this being the flat spot your feeling in the above threads) AFR in the mid-range ran very lean hence theloss

Test 3. Decat & ECU calibration (not a live, Just our generic) good solid torque curve with gains of over 10ftb's points below 5,000rpm and no flat spots at all! only showed a rise of a couple of peak bhp but it was still on standard airbox/inlets etc

Test 4. removed the de-cat and re-fitted the catalyst, and left the ECU calibration on, torque at 3,000rpm was lower than test 3, in the mid-range test 3 & 4 showed near identical power, Up top test 3 held the power much better

Now these test were carried out over a course of 2 days (due to fitting/ removal of parts) so there are variations there that couldn't be helped, but the best figure of the test was test 3.

Moral of the story is, If you wan't a de-cat, get it mapped and you should see gains, if you don't get a decent calibration your just gaining noise!


James

Wise words.

 

[Dean.]

Lol. Phil.

James out of interest was that my car you tested on? As I know you took it up to get some RR results

 

[Quid]

Best "sat on the toilet" read I've had in a long while, lol.

 

[stephen chadwick]

no blody idea were a few of you are getting £150 for a blody decat?! if you payed that you got mugged off, and 2hours to fit one? that made me LOL hard

 

[Chris205]

Funnily enough I bought Phil's 'beloved' de-cat from him for £75 second hand. I gained 4bhp and upto 6bhp peak in places with a 3 Hp gain ATW, however I have created a mild flat spot between 3250-4000RPM, then I get a nice surge of torque and power at 4000rpm onwards.

On a rough calculation the power increase cost me £20 per 1bhp

The car coupled with a btb exhaust sounds bloody amazing as well

 

[Cup_Phil]

no blody idea were a few of you are getting £150 for a blody decat?! if you payed that you got mugged off, and 2hours to fit one? that made me LOL hard

K-tec prices. And you've got a 182 so it's a 5 minute job. 172 takes fricking ages - it's bloody impossible to get to the bolts

Funnily enough I bought Phil's 'beloved' de-cat from him for £75 second hand. I gained 4bhp and upto 6bhp peak in places with a 3 Hp gain ATW, however I have created a mild flat spot between 3250-4000RPM, then I get a nice surge of torque and power at 4000rpm onwards.

On a rough calculation the power increase cost me £20 per 1bhp

The car coupled with a btb exhaust sounds bloody amazing as well

LOL I'm glad you like the noise - Now get a remap to get rid of that flat spot

 

[_Tom]

I'll throw something in the mix. Sports cat. Worth it? Discuss...

 

[Cupman29]

Cost tooooooo much for the gains you get or not as the case may be. Don't even get any more noise.

 

[Dan]

is this still goin?? its nearly as bad as that clio with an espace engine thread lol

its a piece of pipe that makes it louder and you cant tell any physical effects due them being so small :S

just helps you to get that awesome sound

 

[Dan]

I'm out.!

i also thought u gave up a bit ago trying to let people know you gained 2 secs on a track just from putting your cat back on lol

 

[Cupman29]

is this still goin?? its nearly as bad as that clio with an espace engine thread lol

its a piece of pipe that makes it louder and you cant tell any physical effects due them being so small :S

just helps you to get that awesome sound

Now onto sports cats rather decats.

The thread is evolving much like the human race its been going on so long!

 

[Chris205]

LOL I'm glad you like the noise - Now get a remap to get rid of that flat spot

It already has an Rs tuner map on mate, Paul says he can get rid of the slight flat spot but tbh I'm going to hang fire as I need to decide whether I'm going to go forced induction or itb's

 

[Cup_Phil]

ITB's

 

[Dan]

It already has an Rs tuner map on mate, Paul says he can get rid of the slight flat spot but tbh I'm going to hang fire as I need to decide whether I'm going to go forced induction or itb's

ITB's!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[bennno2005]

removing the cells altogether = no internal restriction, maximizes flow even further.

On that logic why bother with an exhaust at all? I imagine there is an optimum flow rate which might be achieved with or without the cat on, although I actually know nothing about this.

I decatted my old GTI 6 an noticed that i seemed to have less torque lower down but the car really seemed to go better after 5K, wouldnt have bothered if i didnt get the decat with the exhaust.

 

[Cup_Phil]

On that logic why bother with an exhaust at all? I imagine there is an optimum flow rate which might be achieved with or without the cat on, although I actually know nothing about this.

I decatted my old GTI 6 an noticed that i seemed to have less torque lower down but the car really seemed to go better after 5K, wouldnt have bothered if i didnt get the decat with the exhaust.

You gain 20bhp if you take the manifold off and run without an exhaust - there's no restriction at all then

People concentrate loads of the cubic feet per minute flow rate of an exhaust - no-one bothers to work out what the flow rate of the exhaust ports is.
If you're exhaust flows more than your engine then you're just creating lots of stalled air that expands and cools - and anyone who knows anything about tuning knows keeping the exhaust gases hot is essential

 

[Dan]

You gain 20bhp if you take the manifold off and run without an exhaust - there's no restriction at all then

People concentrate loads of the cubic feet per minute flow rate of an exhaust - no-one bothers to work out what the flow rate of the exhaust ports is.
If you're exhaust flows more than your engine then you're just creating lots of stalled air that expands and cools - and anyone who knows anything about tuning knows keeping the exhaust gases hot is essential

i think its the spoon racing exhaust that looks tiny in diameter but gets the most gains for a N/A B16 honda engine but due to testing time and so on it costs a bomb lol

 

[B19WAW]

Ermmm clio's arent turbo'd - you're talking s**t

De-cats lose power if anything due to the lack of back pressure. Worst mod ever unless all you want is noise

the cat is about 5 and a half inch bore with restriction......the decat pipe is 2 and a half inch with no restriction.....im sure miltec did their homework and balanced flow/back pressure ect.....im no exhaust expert but im sure the boys at miltec know what they are doin..........no offence to the experts on here, but im sticking with my decat on my 182 and my boy is with his 172 simply because the cars rev beter and have more tourqe

 

[Cup_Phil]

the cat is about 5 and a half inch bore with restriction......the decat pipe is 2 and a half inch with no restriction.....im sure miltec did their homework and balanced flow/back pressure ect.....im no exhaust expert but im sure the boys at miltec know what they are doin..........no offence to the experts on here, but im sticking with my decat on my 182 and my boy is with his 172 simply because the cars rev beter and have more tourqe

Rolling road graphs?

 

[Darren S]

I agree to a certain extent when dealing with a decent flowing cat like the 1*2's have, but once you are dealing with a 100K old cat that is either breaking down or carbon'ed up, the same is not always true, and on some other cars where the car is more restrictive its more beneficial to remove it.

This is the part I'm interested in, tbh. For example, I have the factory standard CAT on mine and the car is circa 92k on the clock. I've always thought (but have never checked!) that the replacement OEM CAT would be pretty expensive to replace? I would therefore consider a de-cat purely on the basis of cost, rather than hoping to make any 'performance' changes to the way the 182 drives.

Do CATs simply fail outright? Or is it a progressive thing - taking many weeks/months to actually deteriorate?

Cheers,
D.

 

[clio ph1 Belgium]

hi , I just put my normal exhaust on for the inspection. It makes very little noise now:approve:
But is just feels sluggish now
It pulled on the dyno 184hp and 220 torque with all mods(no cat) etc
Now with cat and normal exhaust bye bye torque !! fact!

(sorry for my english)

 

[B19WAW]

Rolling road graphs?

im not quoting power.....im telling you my car drives beter, an theres plenty of hills 2 test the tourqe out in wales......lets b honest its a preference that some people take them off while others keep them on....mine pulls harder, revs beter but is noisier, ill live with it, and no its not that i think its faster coz it makes more noise.......if the boys who know everything about flow/backpressure are convinced about their claims then why dont they make a clio system that works.....as i said before, i think miltec do a little bit of research before selling exhausts:banghead:

 

[Cup_Phil]

You think Milltek spend as much on R&D to sell a few decats as RenaultSport spent on R&D to sell the 182?

 

[jesus]

Can't believe this thread is still going tbh. Decat on a Clio makes it smoother and nicer to drive. If it increases power, it isn't much.

 

[George k]

As the former owner of a 182 Trophy I went through quite a lot of these considerations before defecting to a Honda Integra DC5, as for hill climbing I needed to be able to guarantee a significant increase in power. On the DC5 a decat is virtually essential to optimise a power increase. What is significant is that it particularly affects the mid range and point at which the V tec change can be made (as this can be moved down from the standard 6,000 to in some cases as low as 3,800). A possible conclusion is that in V Tec mode the cam timing is quite extreme and that having a Cat in place dampens the pulse effects down the exhaust manifold. Working back to the Clio, on standard or 'Group N' cams the timing is quite mild and so the Cat may well not have such a signficant affect.

As far as I can remember the limiting factor on cam timing is the inability of the standard AFM system to idle properly on much more aggressive timing than standard. If using a different ECU with TPS, then longer duration/overlap cams can be used and then the Decat could well be a critical factor.

Regards

 

[B19WAW]

You think Milltek spend as much on R&D to sell a few decats as RenaultSport spent on R&D to sell the 182?

lol renault have emissions they need to meet, miltec dont........

 

[Cup_Phil]

lol renault have emissions they need to meet, miltec dont........

RenaultSport (not the same as Renault ) Also have a performance they want to meet
As you can see by the flow rates they don't restrict the engine and they make good power but still hit emissions
That takes a LOT of work to achieve - so why **** it up with a decat unless you want more noise

Anyway mines running an Omex, ITB's and will have lairy cams in the new year and after being enlightened in here I'm going to run it without an exhaust manifold or system at all - with all that free flowing it should make 320bhp

 

[B19WAW]

RenaultSport (not the same as Renault ) Also have a performance they want to meet
As you can see by the flow rates they don't restrict the engine and they make good power but still hit emissions
That takes a LOT of work to achieve - so why **** it up with a decat unless you want more noise

Anyway mines running an Omex, ITB's and will have lairy cams in the new year and after being enlightened in here I'm going to run it without an exhaust manifold or system at all - with all that free flowing it should make 320bhp

performance is also compromised by emissions......as ive already said, people make their choice and ive made mine, also the bore difference between cats and decat pipes come in to it....im not pretending to be an expert but seems you are.... ill be happy to buy an exhaust off you once you start manufacturing them as you know better than big companies :hail:

 

[Cup_Phil]

performance is also compromised by emissions......as ive already said, people make their choice and ive made mine, also the bore difference between cats and decat pipes come in to it....im not pretending to be an expert but seems you are.... ill be happy to buy an exhaust off you once you start manufacturing them as you know better than big companies :hail:

LMFAO - No I don't and that's the point - there's nothing wrong with the renaultsport cat
It's not legal, it won't pass new MOT's, mine barely passed noise tests on track and they are PROVEN on rolling roads to lose torque

There are cars on here running 13s quarter miles on standard cats, there are cars on here running 240bhp on standard cats.

 

[B19WAW]

LMFAO - No I don't and that's the point - there's nothing wrong with the renaultsport cat
It's not legal, it won't pass new MOT's, mine barely passed noise tests on track and they are PROVEN on rolling roads to lose torque

There are cars on here running 13s quarter miles on standard cats, there are cars on here running 240bhp on standard cats.

we make our own choices.....but it seems u want everyone to do what you want......some people notice a difference some dont, leave them to it.....mine is staying on regardless of your opinion, because i have my own opinion......i aint had my car on a rolling road but i feel the gain and its enough for me........the 182 has a good cat but there is one printout shown on here and that should help people make up their own minds

 

[Dan]

I'm sure you said you was out a long time ago phil lol

 

[Cup_Phil]

I keep getting drawn back like a troll to noobs LOL

 

[B19WAW]

I keep getting drawn back like a troll to noobs LOL

stay out of the mirror then, simples lol

 

[Andyman]

On that logic why bother with an exhaust at all? I imagine there is an optimum flow rate which might be achieved with or without the cat on, although I actually know nothing about this.

I decatted my old GTI 6 an noticed that i seemed to have less torque lower down but the car really seemed to go better after 5K, wouldnt have bothered if i didnt get the decat with the exhaust.

Because you need back pressure. You know what its like when you get a hole in your exhaust. You loose performance and mpg goes down

 

[Chris32uk]

Without, reading all this, it might help someone, In my own experience, I have a Janspeed cat back on, and did have a Decat, and JMS remap, ITG Filter (pops and farts crap - now removed) to put it really simply


With decat :-

Freerer revving, Petrol Smell, Less low down torque, pulls better at top end, more noise - at expense of low end torque, oh and i have been told decats eat lambda sensors (how true i dont know)


And basically the opposite with the cat on.... Oh and i never noticed any mpg difference, how much bhp .... Id reckon 3-4 at a guess performance was not changed imho

 

[KevF182]

Without, reading all this, it might help someone, In my own experience, I have a Janspeed cat back on, and did have a Decat, and JMS remap, ITG Filter (pops and farts crap - now removed) to put it really simply

With decat :-

Freerer revving, Petrol Smell, Less low down torque, pulls better at top end, more noise - at expense of low end torque, oh and i have been told decats eat lambda sensors (how true i dont know)

A noticeable performance difference then... (Decats cannot eat Lambdas on a clio. LOL.)

And basically the opposite with the cat on.... Oh and i never noticed any mpg difference, how much bhp .... Id reckon 3-4 at a guess performance was not changed imho

Ok, so no noticeable performance difference then? Which is it?

A frosty morning vs a humid afternoon makes more differece to a clio's power delivery than an exhaust mod.

This thread breaks me!:dead:

 

[Cup_Phil]

The problem is - 90% of people (yourself included looking at your reply) think BHP = Performance
Whereas more often Torque = Performance

What you gain in 2-3bhp you lose in torque. Bhp is good for bragging to your mates in the pub that your £100 de-cat gained you a few bhp but in reality probably makes your car a touch quicker high end which is useless, and a touch slower low end where you will mostly use the car

 

[B19WAW]

The problem is - 90% of people (yourself included looking at your reply) think BHP = Performance
Whereas more often Torque = Performance

What you gain in 2-3bhp you lose in torque. Bhp is good for bragging to your mates in the pub that your £100 de-cat gained you a few bhp but in reality probably makes your car a touch quicker high end which is useless, and a touch slower low end where you will mostly use the car

totally agree on this....torque=accelleration....bhp=top end power

 

[Chris32uk]

Noticeable difference - as in more performance, no, definitely not, It drove differently. - What do you want low down torque or high end action .....


Low end - Keep the cat

Top end fun - Ditch the cat

As for the actual measured power difference, Id say neglible, certainly in my case, Maybe if you had lairy cams and ITB's


Im totally in agreement with jengis, Give me a cold morning any day for more of a difference...

 

[_Tom]

Sports cat gives you a fine blend of both i guess... LOL