Jump to content
SAU Community

Recommended Posts

Hi Guys

At the moment I'm looking at upgrading my cat because the car is a bit loud. Drones like a bitch between 80kmph and 100kmph.

Currently Producing 300rwkw and looking at the 3.0l bottom end in the near future.

Anyway, the current exhaust is 3inch off the Turbine, and another 1.5 - 2inch from the waste gate plumbing back in just before the lower bend in the front pipe. The Cat that is there has 3 inch flanges and is one of those "extreme flow through non restrictive" ones.

Anyway, I've searched and seen a few threads about a few Different cats:

Catco

Metalcat

SMB

Xforce

Does anyone have any recomendations for me? I want to retain power and get rid of this drone, and quiet the exhaust a little.

Thanks guys

Edited by The Mafia

i think you forgot a few things, what is it from cat back? as well as what it made of mild, stainless, titanium? these might help as well. the Cat itself doesnt really hinder on noise control as far as i know, its other factors usually from the cat back, IE: Resonators, inner mufflers and the likes, as well as mild steel does drone. aswell as what size is it from the Cat back.

Ive got same issues, but running the highflow metalcat heaps of drone, but running 3.5 to resonator to then 4" through from there to a cannon, its expected with that esp when in mild steel. Gotta love the drone... inner mufflers may help but may hinder on overall power through restriction tho changing from mild steel to stainless or titanium cat back usually will help as well.

Correct me if im wrong

Cheers

A

Changing from twin high flow cats to twin metalcats on our supercharged xr8 made a huge difference in noise (alot louder) so if noise restriction is what you are after id stay away from them, but 300kw is a fair bit for a street car so im guessing you do track work? maybe a straight through pipe as thats what i have on my 34 and it doesnt drone and isnt too loud...

Hi Mafia , one thing I've never gotten around to proving is the worth of putting "soft spots" along an exhaust system to beat that low frequency vibration or drone .

The story I get is that everything has a set or natrural frequency point where it will ring like a bloody bell and transmit vibration into everything around it . It seems to me that large exhaust systemys are quite rigid and capable of acting like a great long engine steady - transmitting lots of vibration to our speaker box like cabin area .

David Vizard used to say that exhaust systems should be hung not mounted to isolate unwanted noise .

I tend to think that if soft spots like those stainless mesh covered concertina things are placed along the exhaust in a few places the tailpipe loses much of its rigidity and can have its vibratioin isolated by well thought out flexible hanging mounts . I remember on occasions being in Goulburn where they have an Olden dealership and Commodes backed up on ramps , they seem to have quite a few soft points down the back and I doubt its to do with stopping the pipes cracking when the engine moves about .

By any chance would the drone occur at low revs in high gears and mysteriously correspond to 60/80/100 km/h ?

Any how I'm interested in what other peoples thoughts are , cheers A .

Could we assosiate this drone to resonance frequency? I could well associate mafia's problem to similar background to mine, as i have got the "Drone" syndrome with mine. mainly around the 80-85 it would start, and reach around full drone around 100-110 around that area, where it is quite loud. this would be assosiated with 5th gear, so around that rev range it does it, 4th gear would be similar to around the 60 mark, but no where near as loud as 5th at the above speeds.

On the theory of the flexible hanging mounts. Im not too sure if they would be greatly assisting the problem no matter how many you put in or have, as the metal itself would still have its natural RF properties, and would still occur. Changing the characteristics of the metal will help, Stainless vs Mild, Stainless having that tinny sound while Mild having the drone. The only way I can see to minimize the drone, is to either change restriction value of the system, ie: mufflers, resonators etc. and change to a better steel compound mild to stainless/titanium.

Cheeers

hey guys sorry I haven't posted yet.

Its a Stainles 3inch+1.5inchWG system to the cat, then from there 3.5inch mild steel to a 4inch cannon and a 5inch tip..haha. Its very big.

I was talking to cubes and he said the cat will need a pipe put through it, as this one is just "super high flowed" lol.

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


  • Similar Content

  • Latest Posts

    • Update 3: Hi all It's been a while. Quite a lot of things happened in the meantime, among other things the car is (almost) back together and ready to be started again. Things that I fixed or changed: Full turbo removal, fitting back the OEM turbo oil hardlines. Had to do quite a bit of research and parts shopping to get every last piece that I need and make it work with the GT2860 turbos, but it does work and is not hard to do. Proves that the previous owner(s) just did not want to. While I was there I set the preload for the wastegates to 0,9bar to hopefully make it easier for the tuner to hit the 370hp I need for the legal inspections that will follow later on. Boost can always go up if necessary. Fitted a AN10 line from the catch can to the intake hose to make the catchcan and hopefully the cam covers a slight vacuum to have less restrictive oil returns from the head and not have mud build up as harshly in the lines and catch can. Removed the entire front interior just shy of the dashboard itself to clean up some of the absolutely horrendous wiring, (hopefully) fix the bumpy tacho and put in LED bulbs while I was there. Also put in bulbs where there was none before, like the airbag one. I also used that chance to remove the LED rpm gauge on the steering column, which was also wired in absolute horror show fashion. Moved the 4in1 Prosport gauge from sitting in front of the OEM oil pressure gauge to the center console vents, I used a 3D printed vent piece to hold that gauge there. The HKB steering wheel boss was likely on incorrectly as I sometimes noticed the indicator reset being uneven for left vs. right. In the meantime also installed an airbag delete resistor, as one should. Installed Cube Speed premium short shifter. Feels pretty nice, hope it'll work great too when I actually get to drive. Also put on a fancy Dragon Ball shift knob, cause why not. My buddy was kind enough to weld the rust hole in the back, it was basically rusted through in the lowermost corner of the passenger side trunk area where the wheel arch, trunk panel and rear quarter all meet. Obviously there is still a lot of crustiness in various areas but as long as it's not rusted out I'll just treat and isolate the corrosion and pretend it's not there. Also had to put down a new ground wire for the rear subframe as the original one was BARELY there. Probably a bit controversial depending on who you ask about this... but I ended up just covering the crack in the side of the engine block, the one above the oil feed, with JB Weld. I used a generous amount and roughed up the whole area with a Dremel before, so I hope this will hold the coolant where it should be for the foreseeable future. Did a cam cover gasket job as the half moons were a bit leaky, and there too one could see the people who worked on this car before me were absolute tools. The same half moons were probably used like 3 times without even cleaning the old RTV off. Dremeled out the inside of the flange where the turbine housing mates onto the exhaust manifolds so the diameter matches, as the OEM exhaust manifolds are even narrower than the turbine housings as we all know. Even if this doesn't do much, I had them out anyways, so can't harm. Ideally one would port-match both the turbo and the manifold to the gasket size but I really didn't feel up to disassembling the turbine housings. Wrapped turbo outlet dumps in heat wrap band. Will do the frontpipe again as well as now the oil leak which promted me to tear apart half the engine in the first place is hopefully fixed. Fitted an ATI super damper to get rid of the worn old harmonic balancer. Surely one of the easiest and most worth to do mods. But torquing that ARP bolt to spec was a bitch without being able to lock the flywheel. Did some minor adjustments in the ECU tables to change some things I didn't like, like the launch control that was ALWAYS active. Treated rusty spots and surface corrosion on places I could get to and on many spots under the car, not pretty or ideal but good enough for now. Removed the N1 rear spats and the carbon surrounding for the tailpipe to put them back on with new adhesive as the old one was lifting in many spots, not pretty. Took out the passenger rear lamp housing... what do you know. Amateur work screwed me again here as they were glued in hard and removing it took a lot of force, so I broke one of the housing bolts off. And when removing the adhesive from the chassis the paint came right off too. Thankfully all the damaged area won't be visible later, but whoever did the very limited bodywork on this car needs to have their limbs chopped off piece by piece.   Quite a list if I do say so myself, but a lot of time was spent just discovering new shit that is wrong with the car and finding a solution or parts to fix it. My last problem that I now have the headache of dealing with is that the exhaust studs on the turbo outlets are M10x1.25 threaded, but the previous owner already put on regular M10 nuts so the threads are... weird. I only found this out the hard way. So now I will just try if I can in any way fit the front pipe regardless, if not I'll have to redo the studs with the turbos installed. Lesson learned for the future: Redo ALL studs you put your hands on, especially if they are old and the previous owners were inept maniacs. Thanks for reading if you did, will update when the engine runs again. Hope nothing breaks or leaks and I can do a test drive.
    • No those pads are DBA too  but they have colors too. I look at the and imo the green "street" are the best.
    • I’m not sure what happened I told them about sonic tunes free OTS tune and the next the I know .. I was booted..   To funny 
    • Yea - I mean I've seen my fuel pump which is decades old and uh, while I'm not saying this with real knowledge... but I sure get the ick at using anything in the fuel system that produced the state of that pump. Many years ago I went through multiple pumps (and strainers) before I dropped the tank to clean it out with extreme violence. I'm talking the car would do maybe 50km before coming to a halt, which resulted in me cleaning out the filter with some brake cleaner and going on my way. None of my stuff ever looked like what came out of your fuel tank. I don't think I'd be happy with it unless every single component was replaced (or at least checked/cleaned/confirmed to be clean here).
    • I'm not going to recommend an EBC pad. I don't like them. Just about anything else would suit me better. I've been using Intima pads for a while now.
×
×
  • Create New...