Exhaust Choice Q's

[acidreign]

Gday,

Ive had a good look around the search tools, and google, but i found too many broad articles to obtain anything useful.

I'm at the stage where i have my extractors (cheers dave) and am now selecting an exhaust for my smallport GE.
Anyone care to share the specs and bits pieces to their systems? I'm getting the job done locally in Gawler, that way i can theoritically tow the car there, and drive it away when complete. The extractors are 4-2-1 with an end diameter of 2 inch.

Here are my questions for those who have 'been there'.

1.) I want to run a 'fake' (pipe wlded) Cat, so to the eye of the 5-0 it appears legit. Is this reccomended, and should i bother? if so - Can i use the Cat from my original 4AC? Or do i need to get hold of another one? As i can not check under my 86, as it is stashed in a mates garage at the time of this post.

2.) I'm not sure whether or not to get a resonator, from my understanding they change the note of an exhaust by 'cancelling' out the 'crackles' and undesirable sounds...*shrugs* ...To buy or not to buy, this is the question? and why?

3.) Is over the diff my only option here? and does this have a dramatic effect on flow?

4.) I also have the choice of stainless muffler for $100 extra, which 'apparently' gives it a nicer tone? To buy or not to buy?
Also,I don't want a cannon like the P-Platers in their Hyundais, but i don't want to be slapped with a canary... Suggestions?

Any help or words up is greatly apprciated

Cheers. Zac

[DRFTPG]

don't do a fake cat!! there is a massive fine for not running a cat when you are ment to, invest in a metal cat and save money in the future!!

[Jonny Rochester]

1) Your 4A-C did not have a cat. But you can use any other cat if you want.
2) A resonator or hot dog type muffler is very good to have, sounds much better.
3) more of a suspension clearance issue and how low the car is. You would need short shocks for under the diff exhaust I would think.

[acidreign]

<div class='quotetop'>QUOTE (SON57A @ Feb 3 2008, 12:58 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=479261)</div>
don't do a fake cat!! there is a massive fine for not running a cat when you are ment to, invest in a metal cat and save money in the future!![/b]

Fake as in, outside, looks legit, inside, has a pipe welded through the centre. Is this worth the effort, as i have the option NOT to run a cat, but was quoted a cople of hundred frm the exhaust shop for a new one... 2nd hand maybe?


<div class='quotetop'>QUOTE (Jonny Rochester @ Feb 3 2008, 12:59 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=479262)</div>
3) more of a suspension clearance issue and how low the car is. You would need short shocks for under the diff exhaust I would think.[/b]

The car is running Kei office colies on 8kg, and KYB short strokes on 6kg at the rear. Which is lower than standard but not stupidly low. What do u mean, 'short shocks for under the diff?' The exhaust guy asked if its Fixed diff or IRS, so i have to go over the diff?

What have other people done, that is all I'm after really. Suggestions. Reccomendations etc.
Also - about the alst pint in 1st post - is a stainless muffler worth the extra $100?

Cheers guys

[Jason]

there was a big discussion not long ago about the cats. All in all, just get one.

[acidreign]

Cheers guys,

i found the articles on Cats, and i guess its a wise choice, i was going to dodgy it up and weld a pipe thrugh to make it seem i was running one. But better respect that big bitch mother nature too, and preseve some back pressure.

Which leads me to the 3rd round of questioning :P

1.) What sort of cat am i looking for? is this a univesal item at an exhaust shop, or is it wise to shop for something specific?

2.) Is there a difference in resonators, brands, types? So shold i just go for the one the guy offers me at the shop?

3.) Preferences... Suggestions.... Over or under the diff of my 86?

Thanks for putting up with my noobish gear guys

[Gunner]

with the cat go a size up so say the exhaust is 2.25 or 2" got for a 2.5" cat, i personally do this with any restriction, so the resonator and muffler.

as for brands, a resonator is a resonator, anyone will do.

the only problem with goin under the diff is one of rideheight, police will go for the lowest point on the car and u can garuntee if u have an under diff exhaust, thats what will be the lowest point on the car. apart from that there is no real difference, u wont notice the 1 antpower u will gain or lose, adding or remove the 3 or so bends to go over the diff.

[Gunner]

i don't understand what u mean in that first line.

as for the only section that counts bein the manifold/extractmores, if that was the case, a 2.5 exhaust on a 4a would work, which it doesnt u lose a fair whack of midrange torque, after the testing i did on my ae111, the exhaust can make quite a large difference, i made an extra 9-10kw just fuckin round with pipe dianmeters in different spots

[acidreign]

Sorry man, i don't quite undestand - are you saying, the 2 inch pipe into the cat, should exit at a diameter of 2.25 o 2.5 until the muffler and ot the arse end?

forgive my noobiness once more

[Gunner]

what my 4a exhaust consist of is, extractmores 4-2-1, 2.5 outlet, 2.5 cat, after the cat down to 2.25, to a 2.5 resonator/muffler (depends on what noise is wanted) then 2.25 to the diff the 2.5 to the final muffler or str8 pipe

[Mr Freeky]

I'm not sure if its been mentioned cause ive just skimmed through the thread but the cops can test the temp of the exhaust and if the cat is hollowed out or a normall pipe there no temp difference.

or a exhaust guy said to me is if the exhaust is 2 inch go for a cat that suits a 2.25 or 2.5 so theres less restrcition but it still does some thing. hope that helps a bit


and i can't remember my exhaust size atm

[acidreign]

i got 2 inch 4-2-1 extractors. So i should drop that pipe diameter down after the cat then? or keep it 2inch the whole way through?

[Gunner]

from the extractmores flair to 2.5 then cat then 2.25 for the pipe with 2.5 resonator and muffler, and i always go up in diameter the further down the car

so once i get to the diff where the gas has cooled down i go from 2.25 to 2.5 just to help with flow. Hot air flows alot quicker than cold air

if u don't get it ill draw it or somethin

[Jason]

i call bs lewwy, my cat has a stone shield, therefore significantly reducing it's temp. Or are you talking about the final exhaust temp? Still seems like bs, so many different variables to make a std temp. test.

[86adz]

<div class='quotetop'>QUOTE (4agteketo @ Feb 3 2008, 07:44 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=479447)</div>
<div class='quotetop'>QUOTE (gunbz-r @ Feb 3 2008, 04:32 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=479402)
with the cat go a size up so say the exhaust is 2.25 or 2" got for a 2.5" cat, i personally do this with any restriction, so the resonator and muffler.

as for brands, a resonator is a resonator, anyone will do.

the only problem with goin under the diff is one of rideheight, police will go for the lowest point on the car and u can garuntee if u have an under diff exhaust, thats what will be the lowest point on the car. apart from that there is no real difference, u wont notice the 1 antpower u will gain or lose, adding or remove the 3 or so bends to go over the diff.[/b]

exhaust doesnt count as a point for measuring as it can move "freely"....the lowest point measurement needs to be from a "Structural Point"....ie...crossmembers, chasis etc...

the only section of the exhaust that is counted is the manifold/extractors.....

hope that clears up some further questions
[/b][/quote]

can anyone confirm that the exhaust doesnt count as a point when ur lowest point of car is checked?

[Gunner]

it doesnt matter if its a bolt, exhaust or a gremlin that got wedge under the car, anything attached to the bottom of the car, whether it be the exhaust or sump or gbox, it has to be higher than 10mm from the road.

some po po will let it slide, but thats the way the law has been structured if its a part of the car that sits under 10mm from the road its defectable and therefore illegal

[riojin]

<div class='quotetop'>QUOTE (gunbz-r @ Feb 4 2008, 03:39 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=479925)</div>
it doesnt matter if its a bolt, exhaust or a gremlin that got wedge under the car, anything attached to the bottom of the car, whether it be the exhaust or sump or gbox, it has to be higher than 10mm from the road.

some po po will let it slide, but thats the way the law has been structured if its a part of the car that sits under 10mm from the road its defectable and therefore illegal[/b]

i believe he means 10cm or 100mm ;)

[Javal]

<div class='quotetop'>QUOTE (riojin @ Feb 4 2008, 03:37 PM) <{POST_SNAPBACK}> (index.php?act=findpost&pid=479946)</div>
i believe he means 10cm or 100mm ;)[/b]

I believe you're right there.

10mm is, well, cutting it a bit fine :lol:

[Gunner]

lol nah driftspec 10mm, yeh i mean 100mm, only had 30mins sleep last night, sorry for any confusin

[Gunner]

[attachment=21998:HiLine_4..._exhaust.jpg]

[attachment=21999:dyno_1_ae111_001.jpg]
power before exhaust, running a bit rich tho

[attachment=22000:dyno_2_ae111_001.jpg]
power after exhaust, a bit leaner

well thats my theory, thats my proof of it working.
obviously the more ideal afr does add some power. but the system works

[Gunner]

i should make them smaller

[Mr Freeky]

<div class='quotetop'>QUOTE </div>
i call bs lewwy, my cat has a stone shield, therefore significantly reducing it's temp. Or are you talking about the final exhaust temp? Still seems like bs, so many different variables to make a std temp. test.[/b]

i was just goin off from what i have been told. and even if it increases or drecrease the temp it means it doin something, unlike a hollowed out cat.

[Gunner]

actually from memory, when they we're doin the defect stations a la pa and in the city, they were actually testin cat temps, but that was done by the EPA, they were looking at the front of the cat housing as this is the most restricted therefore hottest part of the exhaust, so it is not bullshit.

[Paw-DK]

hey gunbz-r
are 'dynamic racing concepts' any good on the dyno for N/A 20v
should be looking for a dyno shop in sydney soonish
but yea SORRY to get off topic people!

does anyone know how big a standard R33 cat is??
i heard they are a pretty decent hi-flow cat and good in price

[Gunner]

r33 cat is 2.5" and they flow well on a 4a

As for DRC, being an old employee i have to be careful what i say, but i can say Brett macdonald, the only qualified mechanic there, is extremely good and taught me a shitload, as for his tuning, he's at the top of my list

just becareful bout the owners ay, brett isnt one, he's actually building a 1j ke70, thats who pointed me to the 1j

its on toymods ill find the post and link the sucker, very big spam thread tho

[Gunner]

hehe 1j ke

http://www.toymods.net/forums/showthread.p...hlight=ke70+1jz (http://www.toymods.net/forums/showthread.php?t=30098&highlight=ke70+1jz)