[MacDaddy]

inbits wrote:

matty87 wrote:

so are ya gonna cross it over underneath to help with scavenging? or run both banks of cylinders down into one tail pipe? tuned length extractors and no bigger in diameter than 2 and a half inch id think too else you run into problems with the old backpressure vs velocity scenario.

and a couple of high flow mufflers at the back for a nice noise.

the biggest flow inhabiter in a standard exhaust system is the factory muffler.

and not exactly legal but grab a cat bash the center out and fit it like that highest flow cat you will ever get.

EDIT: power and quiet dont go together. and by upgrading the whole system and restricting it at the muffler you may as well not bother at all.

I think ill go down the path of a glass pack and a resonator and if its still to loud ill sort that out later. Whats a decent but cheapish brand of muffler

I had a " Mercury " brand muffler put on -
http://www.mercurymufflers.com.au/
I hadnt heard of that brand before, but they are Aussie made, and i like to support Aussie made, i think it was about $80 to $100 for a glass filled straight thru... hope this helps you...

[Lockie666]

Don't zook engines need a litle bit of back pressure? Therefore to much of a free flowing exaust wouldn't be a good thing in the long run?

[JrZook]

Lockie666 wrote:

Don't zook engines need a litle bit of back pressure? Therefore to much of a free flowing exaust wouldn't be a good thing in the long run?

Go do a bit more research and explain your statement

[Fatzook]

Lockie666 wrote:

Don't zook engines need a litle bit of back pressure? Therefore to much of a free flowing exaust wouldn't be a good thing in the long run?

I don't think the 'back pressure' can of worms needs re-opening again.

Here is what I know about exhausts.

There are ways to calculate the size pipes you need to achieve a certain result. So if you are chasing top end speed for example, a 2.5" pipe may be what is required. If you are wanting good midrange torque increase, then 2.25" could be what is needed. Having said this, I have no idea how to do said calculations. But if you look at the cross section flow area of a 2" pipe compared to a 2.5" pipe you will see a massive difference in potential flow rate.

The fitting of extractors, and high flow cat and non-restrictive muffler will net 90% of any gains that are to be had by changing an exhaust system, even with the standard pipe size (with mandrel bends). Pipe size would only attribute to the remaining 10% of any gains. The downside to changing the pipe diameter is increase in noise. Ofcoarse turbo charged motors are different again.

This is based my experience and readings on the subject.

So to the OP.....

If you have 2" press bent factory system now, the fitment of extractors, a 2" mandrel bent system with high flow cat and straight through sports muffler will get you most of the 5hp or so that you could hope to gain by ditching the OEM exhaust. The muffler choice will dictate noise levels.

JMO
Pete

[matty87]

^^^^ best post yet.

[chris_mac]

chris_mac wrote:

royce wrote:

Do you know the brand of muffler and approx dimensions of it?

no, i check dimension tomorrow and try to find out the brand for you

i havn't got the chance to call the shop yet, but will check the brand for you on monday. muffler dimensions: 350x220x120mm and few pictures

muffler:




cat:

[inbits]

Thanks for that info fatzook that's very helpful.
When I said using two cats i meant that only 3 cylinders will run through each one therefore giving it a higher flow rate. I don't have a shit load to spend on it that's why I want to have a go at doing it my self and saving money where I can but don't want to waste me time either.
Does that make sense?

So far I'll be using
2-2.25" pipe with mandrel bends
Glass pack muffler
Resonator
Cat I'm as this will determine how I route the exhaust
Thanks for the help guys

[Fatzook]

You certainly won't be at a disadvantage by using 2 cats. But they need to be as close to the manifolds as possible.

Also keep in mind that a second hand cat of over 2yrs of age will most likely no longer be effective. The catalysts platinum and rhodium? are almost always used up after a few years.

Beats the fuck out of me why the DOT enforce having a cat fitted to your car when over 50% of cars will have an ineffective cat convertor.

Another thing to consider is replacement costs. Buying 2 cats down the track will be dearer than buying 1.

[TZAR]

royce wrote:

yet another thread full of ohi im jcccccccccccck the super expert, I dont know shit but fuck ill post heaps

ffs everyone that doesnt have knowledge in a subject, shut up, given a choice between participating in dumbing down society through internet bullshit and turning this place off, ill choose turning it off

I was feeling dumber until I read this post

[matty87]

the other think i just thought about is does that engine have a hot O2 sensors?if so you will need to fab some bungs into the headers to fit them again otherwise you may find that you end up with engine management lights amongst other things.


As for the enforcement of cat converters its an attempt at saying they are being sustainable while continuing to consume and pollute.

[atari4x4]

i'm pretty sure they are heated o2 sensors, well they are 4 wire heated jobbies in the SV420.

[inbits]

The o2 sensor bung won't be a problem technically the 2 cats would last longer than 1 with less gases passing through them but I'm probably wrong lol
I plan on running the drivers side along the gearbox then cross over after the transfer into a y around about where the standard muffler is then straight into a muffler, the cats will be very close To the headers this way

I'll get a pic and post it up Shortly

[MacDaddy]

Fatzook wrote:

Lockie666 wrote:

Don't zook engines need a litle bit of back pressure? Therefore to much of a free flowing exaust wouldn't be a good thing in the long run?

I don't think the 'back pressure' can of worms needs re-opening again.

There are ways to calculate the size pipes you need to achieve a certain result. So if you are chasing top end speed for example, a 2.5" pipe may be what is required. If you are wanting good midrange torque increase, then 2.25" could be what is needed. Having said this, I have no idea how to do said calculations. But if you look at the cross section flow area of a 2" pipe compared to a 2.5" pipe you will see a massive difference in potential flow rate.

The fitting of extractors, and high flow cat and non-restrictive muffler will net 90% of any gains that are to be had by changing an exhaust system, even with the standard pipe size (with mandrel bends). Pipe size would only attribute to the remaining 10% of any gains. The downside to changing the pipe diameter is increase in noise. Ofcoarse turbo charged motors are different again.

This is based my experience and readings on the subject.

So to the OP.....

If you have 2" press bent factory system now, the fitment of extractors, a 2" mandrel bent system with high flow cat and straight through sports muffler will get you most of the 5hp or so that you could hope to gain by ditching the OEM exhaust. The muffler choice will dictate noise levels.

JMO
Pete

Ha ha, Backpressure is a Myth.... its about maintaining enough restriction, to get a good scavenging effect...
For a 1.3 Sierra, i would say 2.25in is to big... i would say 2in max, maybe 1.78in if concerned...
5hp may not sound like alot, but when you consider that the alternator under load, can take 5hp away from the engine easily... some say they cant feel any difference, but i put sports sytems on 2 zooks i owned, and i could feel the difference on both of them...

Totally agree with your last statement about exhaust upgrade !

[alien]

yup - i think 1.75" is spot on for the 1.3... and 2" on the 1.6 is great... the Vit V6 i'd think would max out at 2.5", just a guess there. Mid-range performance is where its at.

[matty87]

inbits wrote:

The o2 sensor bung won't be a problem technically the 2 cats would last longer than 1 with less gases passing through them but I'm probably wrong lol
I plan on running the drivers side along the gearbox then cross over after the transfer into a y around about where the standard muffler is then straight into a muffler, the cats will be very close To the headers this way

I'll get a pic and post it up Shortly

this sounds good.

Make sure your junctions are nice and gradual and flowing too since you are doing it yourself and can spend the time on it. The less bends the better and the larger the bend radius the better.

[Fatzook]

alien wrote:

yup - i think 1.75" is spot on for the 1.3... and 2" on the 1.6 is great... the Vit V6 i'd think would max out at 2.5", just a guess there. Mid-range performance is where its at.

A 2.5" pipe will flow over 35% more than a 2". I'm not aware of any standard motor that will utilise a 35% increase in potential flow.

Just removing the restrictions from the original system will achieve the best result when noise output is a consideration.

IMO 2" on a 1.6L is still over sized. I have this setup on my ute and its too loud. But its hard to get good mufflers/ cats in 1.75"

[alien]

weird you say that - my 1.6 runs lukey extractors to 2" pipe, 2" cat, then 2" muffler and 2" pipe out the back... its very quiet and goes great - far better than it did with a 1.5" cat and muffler left from the 1.3 engine.

[inbits]

ok here we go obviously i will be using steel but this gives you all the idea and i plan to take my time and make it flow nicely with minimal bends.

I will also be heat proof wrapping the drivers side of the exhaust so my feet dont get to warm

[alien]

cant you fit a single cat at the Y join? will save $$$ - perhaps a 3" cat so the Y bend isnt restrictive? i dont know much about exhausts or flow rates, just that cats do restrict the flow and theyre not cheap.

[inbits]

I think having the cat that far back wont be much good and i wont have much room for a muffler either
but im no exhaust expert either thats why im asking t

[zooky08]

Fatzook wrote:

2" on a 1.6L is still over sized. I have this setup on my ute and its too loud. But its hard to get good mufflers/ cats in 1.75"

i have to agree. i have custom 1.75 exhaust on my 1.6. has good flow and power. its quiet too

[shep]

just remember that ya cant have a good exhaust with out using
random bits of tin and lots of hose clamps.

[alien]

heres pics of mine from extractors back:


the only real bend in mine is the one that goes around the shockie, then one more at the tip to point the bugger down so it doesnt suck fumes into the cab.

[MacDaddy]

inbits wrote:

ok here we go obviously i will be using steel but this gives you all the idea and i plan to take my time and make it flow nicely with minimal bends.

I will also be heat proof wrapping the drivers side of the exhaust so my feet dont get to warm

Looking at those pics, to my thinking, i can see a potential, possible problem... an unbalanced flow... if one side has longer pipe than the other, the exhaust gases will favor the path of least resistance, and take the shorter route, and you may get 75% on the shortest pipe, and 25% on the longest pipe, i am pretty sure this will upset flow enough, to negate any power/performance gain, and may make it run worse... both sides will need to be the same length to get good balanced flow...

[gregdixon]

You will find your exhaust is the same Mac. The two collectors go into one cat. It is just that inbits has two cats but the pipe crossing over is still the same length as it was standard. It is just further back in the car.

[MacDaddy]

gregdixon wrote:

You will find your exhaust is the same Mac. The two collectors go into one cat. It is just that inbits has two cats but the pipe crossing over is still the same length as it was standard. It is just further back in the car.

Yep i understand and saw what mine does on the GV.....

Ok i just reread over this thread, i thought he was going to have 2 pipes out the back, but they are going back into a Y joint at the muffler....
I am still a bit puzzled as to why it needs to split into 2 then go back into a single, just more expense, except maybe prolong the life of the Cat's... i just think a single pipe with High Flow Cat would do the job just as good... but, i do like different and unique... if i had the opportunity to put twin pipes off the headers, without the Y joint, on my GV, and have two pipes out the back, i wouldnt hesitate to do it, ha ha, but it will be interesting to see the pics, and hear how this project goes...

[royce]

it doesnt split into 2, Mac you do understand any type of V engine has 2 exhaust manifolds dont you?

Twin lake pipes, with the pipes made into sliders, that might be the best suggestion in this thread

[MacDaddy]

royce wrote:

it doesnt split into 2, Mac you do understand any type of V engine has 2 exhaust manifolds dont you?

Twin lake pipes, with the pipes made into sliders, that might be the best suggestion in this thread

Yes i do understand, and know that... twin lake pipes, havnt heard about a lake pipe setup in quite a while, they were all the rage about 15 to 20 years ago... ha ha...

[inbits]

Twins would be cool but i dont think theres enough room under there at the back
The main aim for me was to get the exhaust up higher and to flow better at the same time doing a heat wrap should stop the floor getting to hot aswell. I think ill go with 2 cats which technically 2 standard cats would flow better than the one standard one and shouldn't be to expensive While prolonging there life.