Full Exhaust advice. Manifold back --POST 21 UPDATE

As some of you know I'm getting a new exhaust done for my supra, its an NA so please bare that in mind with the recommendation.

So my car currently has both cats in place with a custom made cat-back exhaust. (which I love I might add) Its currently loud-ish, could be a little louder and deeper but wouldn't want it too much louder.

Now I have decided to do a full system for the car and have a few different routes/options I could do. I need some help as I want to keep the volume down, so its not stupidly loud like some NA's but equally need it to be as free flowing as possible as my ECU is mapped for this. (Mines)

Option 1- OBX manifold- 2.5" 2nd decat- Cat back exhaust

Option 2- OBX manifold- 2.5" custom mid pipe with high flow cat- Cat back exhaust

Option 3- OBX manifold- 2.5" custom mid pipe with silencer- Cat back exhaust

Which of these 3 options would provide the most free flowing system? I'm tempted by a high flow cat, but only if they will reduce emissions enough and keep the sound down enough.

Now part two to the dilemma is the cat back itself, what do I go for?

Should I stick with the current one, or get the one I want which is a HKS silent power, which unfortunately arnt that silent making the above decision critical. Or does anyone have any other recommendations (maybe twin box systems). Please bare in mind it will have to be an NA exhaust with 2.5" pipe work, plus I want the system to be an angled exist back box too, and the can cant be to big as I has a shine auto diffuser.

If you advice a high flow cat does anyone know anywhere on the south that may be able to help, and approximate costs.

Little video of how it sounds now-

[video=youtube;R8rUT-FlZ54]

PLEASE SEE POST 21

anyone?

Im running a fully decated kakimoto 3.25" exhaust to a 5" tip on my n/a, and it is seriously loud lol.

Still on the standard manifolds,but from there back its al stainless.sounds the nuts though even though it is abit too loud,I just live with it.get plenty of bangs and flames when really giving it some.

Fitting a tubular manifold and 2nd decat will be the most free flowing option but will make your current exhaust a LOT louder, the 2JZGE Fujitsubo Legalis R would help keep the noise down to a reasonable level, it's design is similar to the stock exhaust with twin mid pipes and silencers. Or perhaps look at getting a custom exhaust made with a large center and rear silencer.

http://www.fujitsubo.co.jp/prods/detail/000000000000001336/00000000000000003079/00000396

I personally wouldn't bother with a manifold. The car seemed a lot better when it was stock manifolds and 1st decat. The manifolds are so small stock so hardly anything noticable can be gained by changing them IMO save your money and don't bother.

I would also stick with the stock cast manifold with a first decat. The manifolds I've seen and fitted, are never a good fit. Also my car ran really rich with one fitted. Tried a set of new oem lambda's and two sets of screw in types with no real improvement.

If you could be arsed to fix the manifold I had from BarneyBrendan feel free. As above and due to those reasons just stick stock with the 2.5's. My friend had a supra a couple of years ago. Mine was quicker with the smaller 2.5 system than his 3" cat back.

Well basically I have been offered the Manifold for a very good price, works out the same as a 1st decat so if it doesn't have any adverse affect I wanted to put one on. However its interesting to see people saying they have had negative results from them. Any one give an explanation why.

The 3" to 2.5" comparison doesn't surprise me as an NA needs a certain amount of back pressure to perform effectively.

Thanks for the recommendation on exhaust Nic but sourcing one of those for a reasonable price would be hard I should imagine. Adding an addition silencer may be the route I take, any reason you would advice a silencer over a high flow catalytic converter.

 

The 3" to 2.5" comparison doesn't surprise me as an NA needs a certain amount of back pressure to perform effectively.

This is where people are so so wrong and I don't know where they get there information from as I have heard it a million times,an NA does not need any back pressure at all it needs to be as free flowing as possible.its not a 2stroke where it needs the scavenging effect to help drag gases away. The less back pressure the better.

Thanks for the input but just to add .5" I think is just creating another option. For the gains its just going to make it even louder which I'm trying to avoid.

This is where people are so so wrong and I don't know where they get there information from as I have heard it a million times,an NA does not need any back pressure at all it needs to be as free flowing as possible.its not a 2stroke where it needs the scavenging effect to help drag gases away. The less back pressure the better.

Thank you, saved me some typing! The stock N/A is a matched resonance system, whilst it doesn't need nor want any back pressure, changing the effective tuned balance between intake and exhaust resonance will affect the power and torque interrelationship, often adversely.

My set up is stock manifolds into Whifbitzs 2.5 1st/2nd decat then into Whifbitzs 2.5 cat back twin silencer exhaust. It's loud enough now it's been run in yet not as over the top loud like most NA's. I previously had a 3" Kakimoto exhaust and the noise was retarded.

My only gripe with my current setup was it was too quiet at first and I might try heat wrapping the flexi on the first decat to stop the pssssss noise it can make. I wouldn't change a thing about it minus the previous.

the psss noise, could this be an air leak? Also can you remember how much your first cat was, I cant find it on wifbitz website. Dont want to pester Paul again until I order the bits.

the psss noise, could this be an air leak? Also can you remember how much your first cat was, I cant find it on wifbitz website. Dont want to pester Paul again until I order the bits.

I think they are about £168 iirc. I have checked for an air leak and there wasn't one, it only makes the noise depending on where in the rev range and how much throttle you are giving it. Someone said they really wrapped up the flex pipe and that cured it.

That's weird. Be interesting to know the cause. Thanks for the price guide. I have been offered the manifold for a great price so though about buying it and swapping to see which j preffer as I doubt the volume will be affected much.

Ask Paul if this is a listing mistake as I've never seen him go a 3" Na decat before http://www.pof.com/viewrespond.aspx

1st and 2nd decat is £256.

I always pm him to see if I can get a deal with him..... even if it's free postage

- - - Updated - - -

Either that or pm him and do a Supraleeturbo.."Paul will you except £200 for a full single turbo kit?"

I have checked for an air leak and there wasn't one, it only makes the noise depending on where in the rev range and how much throttle you are giving it. Someone said they really wrapped up the flex pipe and that cured it.

Something is resonating at a certain rpm, I had a similar problem with my ARC Ti exhaust when one of the brackets had broken.

Something is resonating at a certain rpm, I had a similar problem with my ARC Ti exhaust when one of the brackets had broken.

It just sounds like a psssshhhh sound at certain throttle positions... odd really.

Ask Paul if this is a listing mistake as I've never seen him go a 3" Na decat before http://www.pof.com/viewrespond.aspx

 

1st and 2nd decat is £256.

 

I always pm him to see if I can get a deal with him..... even if it's free postage

 

- - - Updated - - -

 

Either that or pm him and do a Supraleeturbo.."Paul will you except £200 for a full single turbo kit?"

I will get in touch to enquire then. Had a look on ebay and they are very cheap but unsure on quality.

Also why the link to POF ?

Ask Paul if this is a listing mistake as I've never seen him go a 3" Na decat before http://www.pof.com/viewrespond.aspx

 

1st and 2nd decat is £256.

 

I always pm him to see if I can get a deal with him..... even if it's free postage

 

- - - Updated - - -

 

Either that or pm him and do a Supraleeturbo.."Paul will you except £200 for a full single turbo kit?"

I will get in touch to enquire then. Had a look on ebay and they are very cheap but unsure on quality.

Also why the link to POF ?

Ok So This has advanced a little now, I now have a 1st decat and 2nd decat Unfitted. But now need to decide what do backbox wise. Currently I'm thinking of fitting it all and see how it sounds then get the second de-cat pip re-made with a appropriate cat or silencer added. But for this to be done correctly I need to decide on a back box.

I Love the HKS silent power and can by one at a great price but the volume is putting me off as its a fairly loud exhaust.

Any other twin box recommendations?

Also what gaskets will I need? I'm guessing 2x OEM ones for where the 1st decat meets the manifold and 2 additional aftermarket ones.

J, From today il be running a full decat on the NA, my back is an HKS Silence, and it's not that loud tbh, makes a lush sound through the tunnel or an inclosed town (petworth is a joy) plodding along on the motorway it is quiet, I know what you mean tho you don't want the corsa sound of a industrial bin sticking out

That's interesting mate. Will you be running 2.5" or 3" decats. Where are you based again would there be any chance I could come have a listen. Or maybe grab a video?

Full decat and Whifbitz twin box mate, you can't go wrong. There's an exhaust thread somewhere and Animal had that same setup complete with a video.

I got the first decat from Paul this week, 3" that one was, the second decat/box was already fitted on the car and I haven't measured it, but from what I've seen underneath I'm pretty sure it's 3" as well, the manifold is standard, I'm portsmouth way mate, hopefully the car is done today and il sort something out for you