Question about DECAT pipe (advice appreciated)

[mcgon1979]

hi all,

I had a decat pipe on my last car (N/A 2 litre) and it gave great torque and power returns. Torque was actually very high for a non turbo 2 litre (156ft lbs).

I am reading on a couple of sites though that a decat box for the FTO actually causes a worse torque figure? I read Kace's comments that this had been proven to him on a dyno? Is this really the case. Disappointing if its true as I was thinking of doing this, but I would never sacrifice even 1ft/lb of torque for 5bhp. no way.

I have a 5zigen pro racer system cat back. not too loud and sounds great. was thinking of getting that milltek decat box as I don't want to make it louder and the decat box is meant to be good at keeping it quiet. anyone got one? anyone been on a rolling road day and know for sure that a decat is not worth the effort torque wise?

thanks alot guys

Neil

[mcgon1979]

deffo seems to be two schools of thought on this guys? pro and con for the decat. I know it gave massive torque gains on my previous car. here is someone who seems to be pro for it on the FTO.

from another forum....

For reference my FTO GPX did the following:
164bhp at the wheels (196.summat at the fly) at 7792rpm
134lb/ft at the wheels (dunno fly)

This is with only a Mongoose decat pipe and a K&N filter in the original airbox. BUT its vastly better than last year on a dynapack (when it was completely standard):

148bhp at the wheels,
100lb/ft at the wheels.

My power graph now looks a lot smoother and with my decat I have a lot of torque lower down the revs - I'm now getting just over 120lb/ft at 3000rpm. -_-
I know thats not a lot for you turbo boys, but please consider this is a 2.0 NA V6 engine and I dont have that much money to mod it.

[Myfeckin FTO]

Rolling road stats from last FTO Ireland rolling road day in Westward Engineering - my GPX had a 145Ib/ft of torque and it had an ITG and Decat exhaust fitted at that stage - http://www.fto-ireland.com/forum/phpBB2 ... lling+road
My peak torque came on at 4900rpm which was ideal for my Mivec as it helped with the lull of power between 2nd and 3rd gear while waiting for the mivec to come back in at 5400rpm - I do believe this also helped considerably towards my FTO getting 14.7 sec 1/4 mile times and a 6.4 sec 0-60 figure.

You may have a point re loss of torque with a decat but its not likely to be much - I believe you will find a gain in bhp though which will more than make up for the slight loss in torque - if any such loss exists - I'd say it really depends on your exhaust type and the amount of backpressure present. You may also find that the peak torque figure will move up the rev range which may make the car feel slower at lower revs.

BHP is a figure that relates to the amount of work an engine can do. Torque relates to how quickly it can do it. While its nice to have a high torque figure for real world driving - for ultimate performance I would say that the BHP figure is much more important.

[mcgon1979]

excellent detail in your reply there MFfto. I've ordered the milltek cat replacement box anyway so I'll give it a go. IF the torque loss is so slight that its not notcable in normal driving, it won't bother me. I'll see how it feels anyways and let you all know. I agree with you 100% though that I think the backpressure is unique to each car. ie. a cone filter, a panal filter, a mongoose exhaust, a 5zigen exhaust will all be affected differently by a decat pipe or a cat replacement box. I'll see how it goes. thanks for the excellent detail in your feedback.

[mcgon1979]

oh and btw lads... I'm deffo up for the next RR trip... hope you can all do one sometime this summer maybe...

[johnny]

...for ultimate performance I would say that the BHP figure is much more important.

BHP sells cars...Torque wins races

[Myfeckin FTO]

...for ultimate performance I would say that the BHP figure is much more important.

BHP sells cars...Torque wins races

Only if the cars have similar BHP to begin with.

A turbo diesel family saloon could have over 200Ib/ft of torque - so are you saying that it will be quicker than an FTO with only 145Ib/ft torque?

[johnny]

so are you saying that it will be quicker than an FTO with only 145Ib/ft torque?

Eh...suppose not...

You win this battle myfeckin...... but you will not win the war

[mcgon1979]

haha... classic. good points lads..

I had an Alfa Romeo Cloverleaf (2litre Twin Spark 145) before my FTO. It had full supersprint system including decat. I had a cone on it too. anyway it had 157bhp and 156ft lbs of torque. The thing is 90% of the torque was there at 2000rpm and the car went like a rocket.... Martin in westward said it was very very healthy torque for a N/A car.

Getting to grips with the FTO is a big change. It feels less drivable in the sense that you need to really commit the foot to the floor to get a rip out of it. I find it lacks a bit below 3000 or 3500rpm. I'd say this is lack of torque. no denying its a damn fast car once you get up over 4500rpm - 8000rpm.
My old car though you could zip around quicker because the powerband is so much shorter. so for town driving etc its impossible to kick in the mivec as you don't have enough distance in front of you to build up to 5500rpm. The power delivery is very linear too as the the engine is so well tuned so you don't notice it as much. One of the great things though is the 1190kg weight which is undoubtedly at least 100kg lighter than my alfa was.

Still.. all things said, I love the FTO. styling, reliability, V6 sound... hard to pass that up. I'm looking forward to getting the gecat box on and seeing if theres any difference in perceived torque. I'll let you all know anyways.

[mcgon1979]

57 sterling from Camskill... I'll throw her on tomorrow.

[Myfeckin FTO]

Thats a very good quality decat - it will be louder though not as loud as a straight through.

Let us know how it effects the FTO.

[mcgon1979]

Don't mind if its a bit louder outside. Once its still fairly quite cruising at motorway speeds. Mind you I think that sort of loudness is all about the back box, and thankfully the 5Zigen is just how I want it. you can pull off quietly or if you give her a bit of the right foot it sounds like a race car. cruising however its fairly silent.

I had a decat on my alfa for years, and I put back on the cat for the NCT, and it was actually louder at cruising speeds cause the exhaust was basically blocked. ah well... I'll give you a full report when shes up and running anyways. If it was stupid loud, I'd put the cat back on and sell the Milltek here. but I'm hoping the box will take alot of the bite out of the exhaust.

[mcgon1979]

Inside the decat...

[mcgon1979]

fitted...

[mcgon1979]

Ok, so I fitted this earlier today. It's fcuking awesome. Here is why.
Firstly the car is QUIETER inside the cabin. You cannot even here the exhaust note when cruising which is just how I like it. The exhaust outside sounds identical as it did, but it revs quicker now.
It also feels like it has noticeably more torque. I know though from experience that this is not likely, but I reckon the torque band is coming in earlier. It pulls strongly in 2nd and 3rd at low rpm now where before there was no torque below 4000 really. Didn't rolling road it or anything, but I know by driving over familiar roads. There is a remote 500 metre long 30 degree incline I know very well and its great for opening the car out in 2nd and 3rd. The car deffo pulls better from low rpm in 2nd up this hill.
all in all I am delighted with this mod. Car is revvier, pulls better, and sounds quieter than it did inside. I recommend if your considering a decat, get the Milltek one that is a box with silencer. super job.

[CJ]

Nice one mgon, a decat free's things up nicely, definetely one of the better mods you can undertake on the FTO in conjuction with a catback exhaust and induction kit.

CJ