Catts off or free flowing Cats

[AR]

I am wondering what the process is for decatting an NSX. I have not gotten the car yet, but it will be a 3.0 post 94. Are there any problems with the MOT. Any particular recommendations as to which headers to use.

Cheers AR

[Kevin]

Mine is decatted. Process is to replace cats with pipes. Getting the old cats off was a pain. My car is a J reg, so does not need cats for the MOT. Cars before K reg don't need cats, and are tested with different allowable limits for emissions.

As for headers either DC sports / Comptech / Taitec / Fujitsubo are your options for off the shelf. You could go to a company like Simpson race exhausts for a custom set in the UK. They would probably be better quality too, as Simpson exhausts are great. Just sit down when you get told the price.

[swlabhot]

Also may I add Hayward & Scott in Basildon are tops for custom exhausts. The can custom make headers, DPs, manis, mufflers etc... the whole lot.

The do alot of systems for prestige and exotics, but can do for any car. If you intend to go with them be prepared to wait for at least 1 month as thats how busy they are. I had my 3" DP back system for my turbo ITR made by them and could not praise it enough. They can tune the exhaust note to your taste. I'm actually currently considering letting them do my rear box for my NSX as opposed to an off-the-shelf unit.

[AR]

So if the car is newer than a K reg it must have Cats. Will it fail an MOT if it is decatted and later than a K ( 93 right ? )

Also will it make more sense moneywise to import the complete exhausts from America or have it done here. I can see it turning into a £ 1500.00 plus job to get an extra few Horses.

I have the type R chip on order and an ehaust system seems to be the first thing to do to get an edge in RWHP. If I can get between 25 and 30 RWHP with the chip and exhaust I will be delighted.

Is there any way of getting around the Cats if the car is newer than K reg, what will be my options ?

Cheers

AR

[jaytip]

on the NA-1 cars you will get the biggest gain with a new manifold(or so i have read) as oppossed to the back box.

i have been told there is a place in Cardiff that makes exhausts to order,but i don't know the name of the place.

[AR]

So basically the headers will bring in the most gain regardless of cat converters ? I like the look of the TAITEC GT Exhaust Headers
and the TAITEC S-TAI Racing Exhaust but that sounds like it will be a loud combo. Other than that I would like the TAITEC GT Exhaust Headers and the TAITEC Center-Exit Exhaust.

[ctrlaltdelboy]

to gain power you have to remove the gas-flow restrictions - clearly there is no real benefit in putting on a free-flowing backbox if the exhaust gases are still flow restricted by the oem manifold and cats. so the first thing to change is the manifolds for some nice free flowing headers, then the cats and finally the backbox.

the requirement for a vehicle to have a cat installed for the purposes of the MOT test is this, vehicles registered prior to 1st August 1992 do not need to have a cat test as part of the MOT. Vehicles registered after will have to have a cat test as part of the MOT IF a cat was factory fitted to the vehicle. If not, then no need. Even if your car is post 1992 and did have a cat factory fitted, the cat test is purely a measurement of certain gases taken from the exhaust of a warmed up car - the levels are by no means draconian and it is common for a vehicle to still pass even if it's cat has been removed provided there are no fuelling or timing problems with it.

I have DC sports headers and backbox and hi-flow cats measuring 98-99db at 0.5m.

I did have de-cat pipes in at one stage and it did make a significant difference to the seat-of-the-pants power rating, but the increase in noise to 102-103db prevented me from driving at several circuits so I have gone back to the hi-flow cats

parts links:

DC Sports headers
hi-flow cats
de-cat pipes
DC Sports Exhaust

[jaytip]

have you got any dyno figures since your mods Darren. I am curious as to what the BHP gains would be.

[AR]

Many thanks ctrlaltdelboy that clears it up a lot. Now to begin the hunt for parts

[ctrlaltdelboy]

AR - you're welcome
Ivor - I've only ever done one dyno with the car, and it was not too impressive - I was suffereing from a bit of a fuelling problem at the time which was giving me some bogging down in lower revs and probably affected overall power throughout the rev range, plus it was a scorchingly hot summers day too!
I do intend to get it dyno'd again once I have got the AEM EMS & Wideband UEGO installed and setup.

meanwhile here's the results from the one dyno day I did - figures are as measured at the wheels not adjusted at all.



of course, I read on the nova/saxo/maxpower forums that once you add 10% for the heat that day, 20% for drivetrain losses and 30% for the sparco seats/racing sticker/blue tint bulbs it must be about 4 million HP at the flywheel (at least) :lol: