Sorry guys to bring subject up again, so have a drink or 3 on me :duffer: cheers!

 

Hopefully now your all sutably intoxicated -ish i can hit you with my question:

 

Do you think removing the cats and replacing them with down pipes with mini silencers as like the ones luke sells will reduce or illiminate turbo seals blowing, and will these still give a signifcant increase in power? Going for this option seems the most viable to me as i want to de-cat but am unsure as to totally de-cat due to the on going split decissions. Car is '91 J reg UK manual TT Turbos are stock second hand units so dont know true history of them but seem strong. cheers.

 

carl

Some people on here and taken their cats out and put restrictors in to create back pressure for the turbo seals.

 

Not sure on what they've said on power etc..

Thats what I'm going to do. Adding small stainless boxes and maybe small restrcitors into my phnw pipes when they turn up. Gotta be a power increase over the 15 year old cats!

Thats interesting to know. Would be interested to know the out come when you done yours, can you keep me posted? cheers

 

carl

im in for a full system tomoz, i was going to de-cat, the exhaust people ascar say they have done loads of zeds and no probs, they recon you will always get some black smoke when you de-cat as the cats hide the smoke, ill ask him about mini silencers and bhp increase and let you know, i may go for that option myself as it seems to cover all bases.

Nice one leg nose, that would be appreciated m8, seems to me to be the safest option. cheers

 

carl

so let me see, we're going to remove the restiction of the cats to increase gas flow by reducing back pressure in the exhaust system.........then we'll add a restrictor to increase the back pressure to save the turbos?!

 

seems a bit pointelss to me

Well this is the whole point of the post to discover wheather there is any benifit to removing the cats and adding the small silencers in their place. wheather there is any increase in hp and at the same time try protecting any damage that could happen to the tubs. I dont fancy another 2 grand bill thanks. If for example the car produced an extra 20hp with the cats removed, but only produced an extra 15hp with the small silencers in their place, i could live without that extra 5hp i might gain, plus i can live without wacking out 2 grand again, the extra 2 grand can be spent on other bits to gain the other 5+hp

 

HP figures are only an example.

but by the time u find out what this magic restriction diameter is, ul have popped your turbos. ur still taking a gamble, as some people get 10k with the de-cats, some get 10miles, so ur as well just running straight pipes.

you may possibly be right, but way i see it, reading through the posts the main reason ppl's seals go is through lack of back pressure? All be it there being no concret evidence this is the main reason. Or maybe that it just high lights a problem that may already there?

 

Therefore, if the engine has some back pressure, which it is proberbly designed to have due to having the cats and causes no problems to the tub seals when there is back pressure. Putting a less restrictive system on than the cats provide has to still give some benifits in hp gains but still provide some back pressure to help preserve the tub seals.

 

Thats my theory, which brings me back to my question.

 

Has anyone with these fitted found them to be of any benifit?

Decated, big bore ,didnt notice the difference except smokes like a !!!! im putting cats back on and then will probally have to rebuild turbos !

Just thought i would let you know !

Thanks for that Yamabuki, but did you completly de-cat with no mini silencers in their place to maintain some back pressure?

My experence on de catting is the rest of the exhaust system being a performance exhaust is to free flowing already ,remove the cats and get a even bigger drop in back pressure causing turbo seals to go.Just wondered has anyone de catted a standard zed exhaust and had problems.I know it not a vg engine but on the ca18det engine de catting with a hks hyper exhaust which has a massive bore and very free flowing de catting can cause more smoke problems .But put a mongoose exhaust on x2 tailpipe on which is slightly more restrictive but still a performance exhaust and not so many smoke problems .I think the turbo seals [age]have a lot to do with this problem but making it to free flowing does as well .Id like to know if anyone has de catted a standard system and had problems thanks taff.

now i dont know what to do, i have a hole in 1 back box and i might just leave the exhaust as it is and just change the back box and tips, im not all that bothered about an extra 15 as i have only just bought the zed and it feels like a rocket......seems like too big a risk for a bit more bhp.....although ascar say decatting cant cause a problem, so does a racing guy i know who builds turbos. :headvswal :headvswal

i have the money for a full stainless so i should do it all now whilst i have the cash.

..........on the other hand i could stainless the back boxes and buy an auto box cooler.......neetmare,

De-cated mine about 2 months ago and went for a Mongoose cat back and downpipes with the mini silencers from Luke. I chose this option not because of any back pressure consideration, but because I wanted the system to be on the quieter side.

 

The system replaced the Jap one, so removed the restrictors as well and it made a hell of a difference to the response from the car. Not sure if it added any BHP but the difference was very noticeable.

 

Fingers crossed, running 0.9 bar and still no smoke after about 1500 miles (cars done about 75K).

 

Gaz

ive got a full 5zigen fire de-cat exhuast system which was on the car when i got it from japan over 3 year ago and ive never had any probs.

De-cated mine about 2 months ago and went for a Mongoose cat back and downpipes with the mini silencers from Luke. I chose this option not because of any back pressure consideration, but because I wanted the system to be on the quieter side.

 

The system replaced the Jap one, so removed the restrictors as well and it made a hell of a difference to the response from the car. Not sure if it added any BHP but the difference was very noticeable.

 

Fingers crossed, running 0.9 bar and still no smoke after about 1500 miles (cars done about 75K).

 

Gaz

 

what does a cat back and downpipes mean? doesnt that mean you havent de-catted?

BOTTLE WENT!!!!

last minute, after reading one million posts on this website, im having a full stainless but leaving the cats in, he says he will do me a de-cat if i want it at a later date for £75. im happy with theat, he recons that going straight through after the cats will increase power a bit. well see, ive gone oval by the way.

just had it done with the cats left on, feels quicker although i have only driven it home a couple of miles in traffic, might be phsycho sematic. out for a quick spin in a bit so ill let you know if the power has increased.....sounds nice tho.

its faster