Which downpipe works te best?

[RyanSteel]

Hey guys, which downpipe works te best on a stock Jap Supra TT? I know of a guy who has a custom made 95mm diammeter downpipe bolted to a T88 turbo. I can get the HKS, JDM or Blitz, but its only 76mm in diammeter. Isn't that a little bit to small? Even if you run stock turbos? I was thinking of running a 85mm downpipe with 85mm right through to the back......including some resonators and a box at the back. Any suggestions?

[aman00123]

Well 76mm is 3" which is what most people will run (at max) on stock tubbies, I'll be running a 3" system on my single build aswell. Could go for the bigger one is suppose but what good it'll do I don't know

[Branners]

3" downpipe is generally the best. I had a Rod Millen on my first import and that seemed to be the free-est flowing one around, so much so that the car would hit 1.5bar on stock turbos at full load.

 

You generally dont want to go above 3" as the boost will runaway and you cannot control is back down even with a boost controller.

[Homer]

If you have ceramic turbo's you're going to be adding a HUGE restriction into the mix with the restrictor ring (to hold back the boost levels), so decat size is not going to make any real difference.

 

76mm is more than enough while using stock turbos. It's not even a restriction when moving to mid sized single turbo installations. Most decat pipes are 70mm, you do not need more than this unless you plan on going for big power later (which will replace the 1st decat anyway, so a bit of a non-issue). Also keep in mind that the collector exit isn't going to change, it's tiny.

 

If you've not already seen it have a read here: bpu

[RyanSteel]

Ok I do understand now. And what thickness pipe do you need to run after the downpipe to the rear? The reason why I am asking is that I bought the car from Japan with stock downpipe, stock pipe after the downpipe aswell, but an 85mm OD pipe joining after the mid pipe running through 2 x small resonators into 1 x box at the rear with an HKS Priest tip. So all I need to do is, get myself a decent downpipe followed by mid pipe.........but should the mid pipe be 76mm or 85mm as it should join to the 85mm rear there after?

[Nic]

The reason why I am asking is that I bought the car from Japan with stock downpipe, stock pipe after the downpipe aswell

 

The Supra has 2 catalytic convertors as standard, are you saying the car has these fitting or already has decat pipes fitted?

 

Pic of stock 1st cat (nearest the engine) and 2nd cat (connects to exhaust).

 

[RyanSteel]

Hey Nic, I'm sorry for the late reply! Was a hectic day for me. My car still have the 2 x cats on like shown in the picture! But after the 2nd cat, it joins with a flange bolted to a 85mm OD stainless pipe with 2 x small resonators there after, followed into a Jasma silencer box with HKS Priest tail piece. So if I fully decate my car, what would the best apropriate downpipe be to buy with the mid pipe? Hks, Jdm, Blitz? I really need sounddddddd......and loud noise....!!! Hehe

 

After I decat my car, I would be taking it for a Unichip, by one of the best oaks around in South Africa with tuning.

Thanks for the info and the pic Nic.........

[Nic]

Hey Nic, I'm sorry for the late reply! Was a hectic day for me. My car still have the 2 x cats on like shown in the picture! But after the 2nd cat, it joins with a flange bolted to a 85mm OD stainless pipe with 2 x small resonators there after, followed into a Jasma silencer box with HKS Priest tail piece. So if I fully decate my car, what would the best apropriate downpipe be to buy with the mid pipe? Hks, Jdm, Blitz? I really need sounddddddd......and loud noise....!!! Hehe

 

After I decat my car, I would be taking it for a Unichip, by one of the best oaks around in South Africa with tuning.

Thanks for the info and the pic Nic.........

 

Okay let me first talk you through the stock exhaust.

 

You have the 1st and 2nd catalytic convertors (see pic on my other post) the 2nd cat then connects with the stock exhaust which is made up of the mid pipes and the back box.

 

 

You say you still have the catalytic convertors fitted and then an HKS Priest cat back (everything from the catalytic convertors backwards) exhaust, are you saying you want to remove the resonators in the mid pipe of the exhaust? If so getting an exhaust company to cut out the resonators and replace with straight through pipe would probably be the cheapest and easiest way. Alternatively you could buy a complete new cat back exhaust.

 

This is a pic of a 1st (short) and 2nd (long) decat pipes next to the stock turbos. Contact the traders on here they will be able to supply decat pipes. Is yours a Japanese Supra? If yours is a J-spec Supra you will also need to fit a restrictor ring in the exhaust to regulated the boost to a safe level, to find out more click -. BPU

 

Edited March 28, 2011 by Nic (see edit history)

[RyanSteel]

Yes it is a Jspec Supra. In otheR words, I still have. The 2 x cats. The only thing that's been replaced or changed is pipe joining after the 2nd cat, in others words it joins at te 2nd cat's flange, 85mm OD 1 piece pipe running in to 2 x small resonators directly series after each other then running into a Jasma muffler box, fitted with a HKS Priest tail piece. So what would the best thing be to do? To remove the complete system from front to rear and buy a complete cat back system, or just replacing the downpipe followed by the mid pipe (in other words just replacing both cats with an after market exhaust) and still running the aftermarket piping after the 2nd cat to the rear? And then somewhere I have to fit a restrictor ring. And what would the best exhaust sizing be from the downpipe right through?