Experimental Exhaust System

[Spillzee]

Thanks for the update.

What is happening up near your headers? looks like a stock pipe disappears into a 2.25 or 2.5" pipe?

I am wondering about this as well. You are referring to the part where the two headers join inot a single exhaust pipe right? The picture looks like it joins them smoothly. Really nice!

Outside of the header, piping sizes, cats and resonators, the only thing that may be worth changing is the mufflers themselves. If you remove the stock one, take a look at how the exhaust flows through it. If it appears that the exhaust flow is not a straight/direct flow, then change it out for a muffler that has a straight through flow. Just make sure the muffler itself is a decent size so that it actually does some muffling rather than making a lot of noise.

I actually went from a staight through to triple flow sports muffler, give a better note than the straight through ones and give a nice rumble at revs. In reference to the front header yes the stock pipe does go into a larger diameter piece, and the rear one is that size right up to the manifold down to the merge. As dicussed in earlier threads these "pressed cone" collectors are thinner than stock pipe, due to their shaping therefore prone to sound leakage (buzzing) this is why Im thinking of either getting another manifold to cat and start again or measure up spacing for 2 oval cats and twin pipes from there.

Hey mate. bit slack at work today. ripped the rear mufflers off an put 2.25 pipes out. sound great when your up it,(real crisp) but bad drone in auto. ok if you stay in sport mode and dont go over 4th when cruisin round town, but dont want to waste the money on expensive cans that do the same thing. value your tests.

[SCOOTA44]

Hey mate. bit slack at work today. ripped the rear mufflers off an put 2.25 pipes out. sound great when your up it,(real crisp) but bad drone in auto. ok if you stay in sport mode and dont go over 4th when cruisin round town, but dont want to waste the money on expensive cans that do the same thing. value your tests.

That answers a question I had about removing mufflers and having just pipe, I still think a sporty muffler where the original resonator was and small resonators where the mufflers went, dont know but just a thought.

[Adamsy]

Random question, i looked but couldn’t find the answer but I’m sure it must of been discussed or somebody would of done it already lol. had the Sportivo around at one of customers places today which is the newest and by far the best dyno motorsport prep place in the state, seriously no expense was spared. A properly good Mainline 4wd dyno that can’t be cheated. Engine test bed which the Targa Tas winners white hot lambo's engine has been on and a onsite fabrication centre. So anyway i was saying just how tough it was to do any real beneficial power mods to the Aurion and was saying what monkey wrench racing had done in the Lotus so in the end the wacked her up on the hoist for a quick look at the exhaust system and said to me why try and fix the weird as y bend? Why not have separate pipes and join then again just prior to the cat? Surely if this was that simple somebody would have done it by now though yeah? Only problem they could see with it on their quick look is those bloody o2 sensors that make carry on because obviously it wouldn’t get as hot down there? Anyway they also thought it might be worth a crack to put straight through pipes on it without the pre cats and put a properly good high flow cat in the exhaust. So go on then break my heart and ruin my dreams, what would be wrong with this quickly thought up fix lol? Also at later date i will throw the Aurion on their dyno and see what sort of result this type of dyno spits

[DJKOR]

You're idea can be done. It actually surprises me that no one has done it as well. The reason why I didn't do it is because of the following:

1) I wasn't going to bother spending the money required to do it neatly and properly. This was in relation to my last car.

2) Doing so will most definitely affect the clearance between the pipes and the ground, especially if you were going to keep the two cats on the headers which I would do if I did it to my car.

The O2 sensors may just need some slight repositioning which can easily be done if you can get your hands on some O2 sensor connectors/extensions.

[Adamsy]

mmmm perhaps a proper look might just be in order and some further investigation lol. Yes one of the reason they could come up with for the weird **** design was so that it was tucked up nice and neat out of the way. keen to look into it a bit further now. Not sure i want to touch the pre cats though, i know there a restriction and would help make more power with out them but i think it would cause more dramas than the extra power it worth.

[SCOOTA44]

mmmm perhaps a proper look might just be in order and some further investigation lol. Yes one of the reason they could come up with for the weird **** design was so that it was tucked up nice and neat out of the way. keen to look into it a bit further now. Not sure i want to touch the pre cats though, i know there a restriction and would help make more power with out them but i think it would cause more dramas than the extra power it worth.

I too wish you could remove both the pre cats, but it would send an error, that is why I could only remove the pre cat on the rear bank and put its o2 sensor next to the 02 sensor on the front bank. on a side note Im replacing the collector tomorrow with a solid one Im sick of the buzz from the pressed cone collector,. Will let you know how that goes. I am going to look also if there was room to run the pipes seperate with sise by side hi flow cats,and twin all the way from there. maybe a, pardon the pun, but a pipedream.

[Jap]

Have you tried a spacer in the secondary O2 sensors to stop the ECU throwing a code?

I'm using a pair in the hilux and they work well.

[SCOOTA44]

After explaining to the exhaust mech's, I went in to get it fixed and guess what ,they were going to replace it with another pressed cone collector BUGGER! anyway went to another one and they had 1 welded collector in stock and booked in monday arvo to get it in.

[SCOOTA44]

Here are the before and after Y pipe refit. much smoother and less noise from the middle of the exhaust.

[SCOOTA44]

I noted while under the car fixing last mod it would be difficult to do a full twin system, the only problem is doing a twin hi flow side by side secondary cat setup. Other than that it would be easy down to the mufflers.

[Steven]

Just had a look at the standard join on the factory headers... Is there any reason I can't just cut away the inside "pinched" parts of the join, and just join the 2 pieces together? I've attached a quick paintshop muckup that sort of demonstrates what I mean.

Really wouldn't take very long to do at all.

[Steven]

anyone?

[DJKOR]

I think the idea is quite good. Because you are then essentially creating a cleaner merge in the same small space you are given.

I'm no expert on the matter though, but the only potential issue I could imagine would be to do with turbulence and potentially creating more back pressure than normal. With the pipe 'firing' from the side, because it is essentially directed perpendicular to the flow of the other pipe, there may be more back pressure on that side... if you get what I'm trying to say.

Looks quite similar to what Andrew (apg39) and Rowan said on the first page of this thread

wouldnt the 90 degree angle make too much turbulance?

....but not so much a right angle, preferably smaller angle so the exhaust is still flowing in the same direction.

- but Ill be able to see what kind of angle is possible once I can get under the car instead of taking pictures as reference.

Your pictures are the right idea, but cos the 2 pipes are already squashed, you'd need a new straight section from the front header to the cat, then cut a scallop in the side for the rear header to be welded into.

Another dodgey Paint illustration.... (angles aren't correct)

[Steven]

Right, I want to try and get the exhaust headers off this weekend... anyone have some ramps they can lend me? By the looks of things, they're going to be an absolute **** to remove

[Steven]

Scratch that last post, looks like I can just remove the Y piece straight after the CATs - Joy.

Still need some ramps or stands if anyone has some?

[Steven]

Got the piece off and only snapped a single bolt! Pics can be found here

Already got it cut, should have the welding done tomorrow.

[Adamsy]

Got the piece off and only snapped a single bolt! Pics can be found here

Already got it cut, should have the welding done tomorrow.

If that works like we all hope it does then you are a champion lol :)

[SCOOTA44]

Hi everyone back from holidays. I am reasonably happy with the new merge mod, I still have a little bit of buzzing up front, not sure if there is a pin hole somewhere or if its the mixing at the collector, I only hear it under load.

[Steven]

Exhaust has been welded back together and about to go back on the car. Pictures here

Final result is absolutely no restriction inside the pipe. However due to how I've gone about fixing the merge, the inside walls are probably fairly rough now - can't say how that will affect the exhaust flow.

[Adamsy]

Exhaust has been welded back together and about to go back on the car. Pictures here

Final result is absolutely no restriction inside the pipe. However due to how I've gone about fixing the merge, the inside walls are probably fairly rough now - can't say how that will affect the exhaust flow.

This is awesome as, you'd have to be happy with how its come up yeah? does it feel any different to drive?

[Steven]

Exhaust has been welded back together and about to go back on the car. Pictures here

Final result is absolutely no restriction inside the pipe. However due to how I've gone about fixing the merge, the inside walls are probably fairly rough now - can't say how that will affect the exhaust flow.

This is awesome as, you'd have to be happy with how its come up yeah? does it feel any different to drive?

As per my other thread, the exhaust isn't back on completely yet, and even though I'll be able to start it I won't be able to test it until around April next year... Bit of a teaser eh?

[robie]

abit of a teaser you recon

why so long

hope it makes a noticable difference

[Tofuboi]

Exhaust has been welded back together and about to go back on the car. Pictures here

Final result is absolutely no restriction inside the pipe. However due to how I've gone about fixing the merge, the inside walls are probably fairly rough now - can't say how that will affect the exhaust flow.

This is awesome as, you'd have to be happy with how its come up yeah? does it feel any different to drive?

As per my other thread, the exhaust isn't back on completely yet, and even though I'll be able to start it I won't be able to test it until around April next year... Bit of a teaser eh?

It's annoying that it's off the road, I understand why tho. I just want to know how effective your work is. If it actually is good then i'd be trying the same thing definately.

[Steven]

Well the exhaust is back on and seems to be running well. No error codes or exhaust leaks. Slightly deeper note when revved.

Unfortunately without doing a road test there's no telling as to whether it's increased performance at all - I suspect that by the time I CAN get back into the saddle I won't be able to fully remember the stock performance.

Of interest is the exhaust bolts at the header flanges - The nuts are designed to destroy the bolts thread as they're tightened, making them a one use only item (and also, likely to snap taking them off!). Least I know they'll never come loose by themselves.

[450HP/tonne]

I'm building my own car, a 2-seat mid-engine spaceframe chassis, which is similar in concept to an Ariel Atom. I purchased an Aurion and removed the engine as shown.

Before photo (= unhappy wife) testing my unnecessary wire removing skills:

After photo (= not unhappy wife ...) testing my skills at leaving in wires required to run the engine:

Setup for engine testing:

Result ... if only this were road legal:

Just thought you might all like the sound!

I may have the unique exhaust problem, in that the back of the engine is the back of the car. I need my exhaust to be modified so that the final cat and any mufflers are much further forward.

I'll go see what the guys doing MR2 conversions have been up to ...