Jump to content
SAU Community

RB26 exhaust sizes - what diameter is optimal?

PSIKO

By PSIKO,
in Engines & Forced Induction

 Share

Recommended Posts

Steve Grand Master

Steve

Posted
Posted

I might be able to help a bit, even if I only have an rb25

I started out fitting an N1 system, 80mm. Flowed very well, straight through design with minimal bends. Made good power but was LOUD as hell - headache material. I sound deadened the boot, not so bad inside the car

I next got an 80mm Nismo cat back. Also 90mm with a big center resonator. It had more bends than the N1, it killed power and ended up choking the top end above around 290rwkw - it also gave me around 1000rpm more lag and made the car more doughy. But it was quiet.

I tried a 90mm N1 with small resonator on the back - I am sure it actually amplified the exhaust note - it was incredibly bloody loud, so it got take off before I even took it for a test drive.

Lastly I fitted a HKS super dragger, which is 90mm, has less bends than the Nismo exhaust, but not as straight through as the N1. It has a nice burble at idle, sounds angry as hell when you nail it, but is still quiet enough that its not annoying to drive around in, and if you want to just limp around when there are plods nearby, it doesnt attract too much attention.

Bottom line is, you need to compromise. The quieter an exhaust is, the more back pressure, the less power, more lag, doughier off boost.

I dont think there is any harm in going larger rather than smaller, the HKS exhaust still has a few bends (more than the N1) but the 90mm pipe seems to make up somewhat for the bends. Just make sure you have a nice resonator on the back to give it a nice note.

Gav Mentor

Gav

Posted
Posted

HKS gear works for me - bolts up easily, isn't overly restrictive and not droney like some custom made systems I have heard.

On a GTR - you'll be amased at the difference front pipes and terb extensions make as well.

A "Jap-Spec" cat also make a notable improvement to flow and spoolup response. Mr Plod may not be impressed if he finds out, however.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • Murray_Calavera
      R33 GTR running -9 with no tune

      By Murray_Calavera · Posted

      I don't understand how this hasn't boiled down to - Upgrade the turbo when you have everything required. ECU, injectors, fuel pump, turbo, etc. Do it all at once.  If you don't have everything required, just enjoy the car as it is and keep saving up your pennies. 
    • Duncan
      R33 GTR running -9 with no tune

      By Duncan · Posted

      Sounds like you've got an interesting adventure ahead here with local support if you have trouble! My guess is that, unboosted, you will be OK with a small upgrade like -9. What will happen is that once the stock ECU sees more airflow than it expects it will add a heap of fuel and pull a heap of timing to be safe because it can't understand how it could get that much air without there being an issue. You will see clouds of black smoke and it won't pull hard through the midrange and top end. So, overall it will be a bit frustrating but should be OK. If you are still nervous set the base timing back 2o through the CAS, but it will be even more sluggish everywhere. As said above through...this is not my guarantee your engine won't be blown into a million pieces, leaving you looking for very hard to find parts A better idea is get a computer with logging ASAP, wire in a wide band O2 sensor and a use remote tuner. I've done multiple cars this way and while it is not as good as a specific tune on a dyno they can get it 90% right. I'd suggest if you can afford an R33 GTR these days you can afford an ECU and tune. And if you can't afford that you sure won't be able to afford the rebuild if it goes bad in the meantime,.  
    • Duncan
      New kid on the block

      By Duncan · Posted

      Yeah it would be nice if someone took the time to put that sort of information together, but there are a lot of variations in looms. I think you are making this way hard for yourself if you just want to get it running....sourcing an SR20 with the right wiring will be a billion times easier than matching the RB loom to an S15 chassis. If you do end up going this way, you just need to trace every wire in the loom with a multimeter, 95% of them will go to a location you can confirm at the ECU.....and then post it up for the next person who needs it  
    • Duncan
      Coolant leak?

      By Duncan · Posted

      Just top it up with water, and keep a general idea of how much you added. It is normal for water to be pushed into and pulled out of the reservoir through the cap, and it should not be more than half full or it will be likely to overflow when hot. Any decent mechanic can do a pressure test of the cooling system to confirm if you have a leak. Keep in mind if it is only leaking a little and when hot it may well evaporate before you see it hit the ground
    • GTSBoy
      Coolant leak?

      By GTSBoy · Posted

      I'd ask the shop what they used and use that. Mixing coolants is sometimes OK, sometimes not, and you have know the details of each coolant to know whether it's a good idea or not.
×
×
  • Create New...