3inch exhaust .How to make it quieter ?

[FS5]

i have a good idea....
i take my car out to WB give it a good thrashing see what it dose as it curently stands.(with 2.5 system)
some kind person shouts me a nice new 3 inch cat back and i go back and have some more fun and see what that dose ....

[The Monty]

Ill be in that.
If you want to swap them over out there or whatever, Ill let you use mine

[StealthAu]

this test would only work if the items are in the same condtion, new would be best, same brands of cats and mufflers, and same layout. In reality ir would cost a consumer around $2k to give a difinative answer as to which is best overall, and then the condition of the car, work done to the engine, are other things to factor in.

[Stav]

Ill tell you what.I still have my 2.5 inch xorst.I will get it flanged to bolt up to the existing setup which effectively chokes the system.I will then bolt up the 3 inch and post what happens on the same night.

But then again why convince people and then they go faster than me?

[Stav]

You are all right.Dont do a 3 inch ..It will kill power and slow you down.You have to use Einsteins theories to get the exhaust right and pay megabucks to experts who run AU sixes at the track regularly. ..blah blah blah....heheh : :

[StealthAu]

This argument will never be resolved, as your not going to find an exhaust shop willing to outlay a chunk of they're profits to provide the R&D to give an overall answer. You can do as many back yard tests as you like but it wint give a true result. I need a new exhaust, and I will be getting either a 3" or 3.5" system, afterwards I could claim mass improvements, but given the condition of my current system, these claims would be crap.

[Stav]

Not trying to get religious here but Jesus said .."you can hear but do you listen? You have eyes but can you see? Remove the beam from your eyes so you can see." I suppose not much has changed on that point in 2007 years so I am not going to try.

[StealthAu]

I never said in any of my post that one option is better then the other, as the truth is I don't know, but at least I can say that unlike almost every other person that has made a post in this thread. Both sides of the argument are moronic at best, I have a 2.5" and it works so it must be the best option, I have a 3" system that works for me so IT must be the best option.

[FS5]

we realy need some hardcore proof .
i'm all for the 3 inch as in the way it sounds...ooooh yeah!!
but i'm not totaly convinced it works / dosen't.
the quickest au i6 to date acording to these forums ran a 2.5 zorst.
the quickest car running a 3 inch is stav ,his is a totaly different piece of kit compared to tripowers xr6.
monty's fairmont was the closest we got to a decent comparison ,but in all fairness he fitted headers along with the 3 inch.(josh i think we'l have to try this exhaust experiment,i can't gaurentee you'l get it back though)
the only other proof we have is me and stiddy
stiddy has run a 14.916 @ 92.27 with a stock xr6 with 3 inch intake and 3 inch cat back (3.45 diff gears) corect me if i'm wrong mate .
i have run a 14.834 @ 93.34.with....
a serise's 1 xr6 moror in au 2 runining the standard ecu with pacey 4480 headers ,3 inch cat and 2.5 zorst and 3.9 diff gears.along with the jmm cai.
again 2 completly different setups .
no one can realy argue for or against as we realy don't have a direct comparison.
maybe one of the forum sponsors (that have a bit more cash to play with than us average joe blo's)could do a comparison on a dyno before and a after results as in the same day.it would be a good way to advertise your product_2:

[The Monty]

I agree Jake. But along with a Dyno result, a quick three runs of each at the drags would be good as well.
I have no doubt that a three inch on a STOCK AU would probably be not so good.
But there arent many of us on here that have stock AU's anymore.
I did also get extractors along with the three inch, Pacie comps (4480's), I was in no way trying to trick people, I just didnt think to add it in.
We do need a comparison done, there is no doubt about it.
We cant say for sure that it is a BETTER option than a 2.5 inch (I know I was saying that it is, but thats my opinion, there is no hard proof out there), but it is no way detrimental to the Au i6.
As for the money factor, it may be a factor for most, only reason I went 3 inch was I bought it when I bought my turbo gear, but sold the turbo gear off, and though stuff it, Im still using that zorst.
Now again looking at the supercharger kit for the future, Ill need it anyway, so Im sticking with it, but it doesnt sound as good as the Lukey 2.5 incher, that thing was the nicest sound ever.

[Stav]

Originally Posted by stockoau

I never said in any of my post that one option is better then the other, as the truth is I don't know, but at least I can say that unlike almost every other person that has made a post in this thread. Both sides of the argument are moronic at best, I have a 2.5" and it works so it must be the best option, I have a 3" system that works for me so IT must be the best option.

I had both.
So what proof do you need to convince you?

[private9]

Originally Posted by Stav

I had both.
So what proof do you need to convince you?

For it to be a true comparison, you'd have to have brand new 2.5" & 3" exhausts, both with identical headers, cats and muffler designs, where the only variable is the pipe diameter. As soon as you throw in different brand of mufflers, old vs new exhaust etc., then the comparison becomes less valid.

[StealthAu]

Originally Posted by private9

For it to be a true comparison, you'd have to have brand new 2.5" & 3" exhausts, both with identical headers, cats and muffler designs, where the only variable is the pipe diameter. As soon as you throw in different brand of mufflers, old vs new exhaust etc., then the comparison becomes less valid.

What he said Stav, did you have the same brand 3" gear in the same condition as your 2.5" gear fitted? Once again I'm not leaning towards eaither side in this debate, just trying to lend a voice of logic which alot of people are missing. Waht I will do is ask what brand and model headers people with 3" systems are running, as I will out of my own pocket, pay for them to be flow tested stock, and once again with them cut back with a 3" flange fitted. I can't afford to pay to see what system is the best, but am willing to fork out to see if there is an improvment from the headers back.

[The Monty]

I think things are getting a little out of hand re, what people want in way of a comparison. How many people here know that even putting a 2.5 inch exhaust on is better than stock? Did you have the car Dyno tested and run at the track when all exhaust components were BRAND NEW, and then have it swapped to a 2.5 inch BRAND NEW exhaust, of FORD brand naming, and have it tested. Some of you people need a reality check.

[private9]

Originally Posted by The Monty

I think things are getting a little out of hand re, what people want in way of a comparison. How many people here know that even putting a 2.5 inch exhaust on is better than stock? Did you have the car Dyno tested and run at the track when all exhaust components were BRAND NEW, and then have it swapped to a 2.5 inch BRAND NEW exhaust, of FORD brand naming, and have it tested. Some of you people need a reality check.

I agree 100% with you that the sort of comparison I stated above is not realistically going to happen, however it is the only way to truly know whether there is any gain.

In your case for example, you gained 3 tenths by going from 2.5" to 3" but as you mentioned, you did Pacies at the sametime - 3 tenths could have come from them alone, that's all I'm saying.

Personally, had I not needed my AU to stay quiet, I would've done a 3", like I am shortly on my other car.

[stiddy]

Originally Posted by The Monty

I have no doubt that a three inch on a STOCK AU would probably be not so good.
.

Stock over here, like FS5 said, 3inch mandrel bent cat back, 3inch mandrel bent intake, NOTHING ELSE. ran a 14.9 @ 93mph, and 137rwkw.
Now the diff gears are in, gearbox is done, stupid cam is in, extractors and edit when i can be bothered. And when I get my licence back i'll take it down to WSID again.

[Sox]

Originally Posted by The Monty

I think things are getting a little out of hand re, what people want in way of a comparison.

Not really, it appears that people just want scientific proof that one is better than the other, or not.
Doesn't seem out of hand to me, I know if I pay more for something I want to be 100% sure that it is a better option. Non scientific examples such as ALL of the ones provided here are not valid.

The ONLY way this could be verified is with a dyno, and 2 systems designed in exactly the same way, except for pipe diameter.

Testing a car on the track for these differences is very difficult, as ambient temps, track temps, fuel type, etc, can all play a large part in ET's. These are all variables which may or may not skew the results.

Only a dyno used on the same day could verify whether there are differences between the 2 systems.

Yes it is a difficult test to set up, but the truth is, this is the only way to truly find out.

How many people here know that even putting a 2.5 inch exhaust on is better than stock? Did you have the car Dyno tested and run at the track when all exhaust components were BRAND NEW, and then have it swapped to a 2.5 inch BRAND NEW exhaust, of FORD brand naming, and have it tested. Some of you people need a reality check.

Why a reality check? This is pretty straight forward stuff, a standard Ford system has different design limitations imposed, noise control being the biggy.
Even disregarding the pipe diameter, the Ford system will always make less power than an after market system, simply because of the free-er flowing mufflers (hence, louder).

What many people seem to be unaware of is that muffler design plays a larger part than pipe diameter when talking exhausts.

My personal opinion on the whole 2.5" VS 3" (all other aspects of the system being equal) debate is that a 2.5" system is more appropriate on a street driven car as it is easier to keep noise levels under control. As far as power is concerned, my gut feeling is there is very little to no difference on any 4L I6 under say 160rwkw. Don't get me wrong, I'm not saying that a 3" is worse under these conditions, however I'm also not saying they're better.

With an engine producing more than 160rwkw, there may be small differences above 5000rpm, and IIRC, there was some proof of a 4kw difference at around the 170rwkw mark going from 2.5" to 3" on a BA I6.
Now 4kw is hardly felt on the road, and IME you need around a 10kw increase for it to be easily noticeable, and then if it's above 5000rpm (which it will be), then it can be argued that it is not used a great deal on the road.

Anyway, some thoughts to ponder, I can honestly say I haven't had any real world experience with a 3" system, and I am most certainly sceptical of any real world merits it may have, however that's my right to be sceptical until proven with some scientific evidence.
Like it or lump it.

Rick.

[stiddy]

Everyones entitled to their own opinion, which is fair enough.

Thing I dont understand though, people assume that if you have bigger than a 2.5inch exhaust system that you will only gain power up high, ie above 5000rpm. This isnt the case however, it pulls harder from 2500rpm at any speed in any gear. My car is no exception, everyone with a 3inch exhaust will vouch for it. You gain all throughout the rev range.
You maybe right in saying that you wont need a 3inch exhaust up until and over 160rwkw. But wouldnt you think that a 3inch exhaust would help you get to that 160rwkw easier than a 2.5inch would?
A long time ago, a calculator was posted up online. Calculates the ideal exhaust diameter as per your engine stats, I did all the 4L I6 stats in this calculator and came back with 3.1 inch and in my gut I knew that 3inch would be better suited.

Between myself and the few people on here with 3inch systems, and I will speak for them aswell, when I say that the 3inch is proven, it works, its makes power all through the rev range any speed any gear, it soudns better, it simply is.. just better. (to us)
Many people wont agree but as I said in the start, everyone has their own idea an opinion.

I will always give a +1 vote for a 3inch exhaust.

[OED666]

i had my car dynoed the morning after i fitted an 2 1/2" redback exhaust. It made 211RWHP. After I had my 3" system fitted, I probably drove an extra 100k's with the 3" before it was tuned. Now tuned, it has 226RWHP. Plus I also fitted an BBM, and I was told by many people that I would lost around 5RWHP up top.

[Mark351]

Originally Posted by FS5

the quickest au i6 to date acording to these forums ran a 2.5 zorst.

This car had a stock XR6 cam, stock head, Difillipo headers and exhaust. A 2.5" exhaust for this setup, when tuned properly, is the better combination.

My XR6 was also stock cam, stock head, but also stock gearing with a manual and still the only 3" faster than me is Stav.

It's not about 2.5" v 3" alone, it's more about which pipe suits which application. Boosted engines or those with headwork will benefit from 3", no one doubts that. Otherwise, 2.5" works on these engines and there is proof.

When an XR6 engine sedan runs faster times that Tripowers car with stock head/cam and a 3" exhaust, I'll consider the 3" option proven. Until then, it's clearly not.

As for sound, I've got a single 3" on the '83 351C which has had a rebuild with decent bits, and no six sounds nearly as good.

[Sox]

Originally Posted by OED666

i had my car dynoed the morning after i fitted an 2 1/2" redback exhaust. It made 211RWHP. After I had my 3" system fitted, I probably drove an extra 100k's with the 3" before it was tuned. Now tuned, it has 226RWHP. Plus I also fitted an BBM, and I was told by many people that I would lost around 5RWHP up top.

I understand your enthusiasm, from your findings, at least on the surface, there certainly appears to be some improvements.
However if we analyse this further, there may be more to it.

Firstly, looking back on my own dyno sheets, I actually found between 3-4kw more power from 4400 upwards when I fitted my BBM. So that lowers your perceived improvements due to exhaust down to around 8-9hp.

Secondly, depending on the time of year, time of day, dyno operator, and a whole pile of other variables, 8-9hp can not be taken with any accuracy simply because it could be attributed any one of those other variables pointed out.
Dyno runs need to be taken on the same day, in lots of 3 to have any kind of consistency and credibility.
Talk to any experienced dyno operator about this.

Thirdly, the quality differences between the mufflers on your original Redback system and your new 3" system are unknown.

Really is, the testing is highly flawed and invalid - As are all of the tests that I've seen throughout this thread.

Rick.

[Sox]

Another point I just thought of is the generally accepted inlet to exhaust valve ratio size.
Meaning - What is typically accepted as a normal exhaust valve size compared to the inlet valve size.
This magic figure is 70%.
(This figure of course does vary a little depending on the state of tune of any engine, but this number is pretty close to what our mildly modified I6's will like).

Now, most of the smarter people here will agree that that a 75mm (3") inlet piping is more than sufficient for a very heavily modified I6.
Agreed?

The area of a 75mm pipe is 17671mm SQ.
The area of a 65mm (2.5") pipe is 13273mm SQ.

If we use the golden rule of 70% of the inlet, then the 'correct' area is actually 12369mm SQ.

So it can be seen from the above math, that we actually have more than enough flow with a 2.5" system, if we are to work by the generally accepted golden rule of inlet/exhaust ratio.

None of this of course takes into account muffler restriction, etc, hence the mention and importance of muffler selection my other post.

Some more food for thought, I think I have too much time on my hands today......

Rick.

[OED666]

Originally Posted by Sox

Thirdly, the quality differences between the mufflers on your original Redback system and your new 3" system are unknown.

I did forget to add that my old and new exhaust have Redback mufflers. Both old and new exhaust have a straight through muffler before the diff, and resinator in the tailpipe.

I spoke to Chiptorque before fitting the BBM to seek their opinion, and they said from their experience in tuning cars before and after, they generally lose top end, but the mid range more than makes up for the top end loss.

[Sox]

Originally Posted by OED666

I did forget to add that my old and new exhaust have Redback mufflers. Both old and new exhaust have a straight through muffler before the diff, and resinator in the tailpipe.

What about the cat?

I spoke to Chiptorque before fitting the BBM to seek their opinion, and they said from their experience in tuning cars before and after, they generally lose top end, but the mid range more than makes up for the top end loss.

I've heard the same, but my graphs show otherwise.
Between 3000-3500 it picked up almost 20kw, and above 5000 around 3-4kw.

In any case, the tests weren't done on the same day, so aren't really valid.
I'm sure you know yourself the idiosyncrasies with dynos and their operators.

BTW, are you using a Chiptorque product?

Rick.

[OED666]

damn, I also had a new highflow cat each time as well...

I definitely agree about dyno's and inconsistant readings.

Yea, I have a re-programmable ChipTorque chip. Still using the original computer, and using a frequency switch the control the runners in the manifold.

[Sox]

Originally Posted by OED666

Yea, I have a re-programmable ChipTorque chip. Still using the original computer, and using a frequency switch the control the runners in the manifold.

How do you find the Chiptorque, any improvements, and where?

Do you need a ECU, I have a standard EL XR6 ECU which I had in my XH ute, it produced 175rwkw.

Rick.

[Stav]

Gidday Rick .Good to see you back mate.

The maths fromula is pretty spot on for valve inllet exhaust ratios but we have darn catalytic converters which really stuff the flow. Calculating clean cross sectional flow is a matter of counting the area of the spaces in the cats comb.Not going to happen.

[OED666]

Originally Posted by Sox

How do you find the Chiptorque, any improvements, and where?

Do you need a ECU, I have a standard EL XR6 ECU which I had in my XH ute, it produced 175rwkw.

Rick.

Not sure if I could be bothered wiring it up (even though its not that hard). I will prolly go a Haltech in the future, when there's a turbo bolted on the exhaust side.

My car wouldnt go without the chip. I think my car goes quite well, all the way to 6000rpm.

[Sox]

Originally Posted by Stav

Gidday Rick .Good to see you back mate.

Thanks, it's been a while.....

The maths fromula is pretty spot on for valve inllet exhaust ratios but we have darn catalytic converters which really stuff the flow. Calculating clean cross sectional flow is a matter of counting the area of the spaces in the cats comb.Not going to happen.

Of course, and the answer to that is to fit a high flow cat, naturally.
Why fit the entire exhaust system if you feel the cat is the major restriction?

Rick.

[Stav]

Originally Posted by Sox

Thanks, it's been a while.....

Of course, and the answer to that is to fit a high flow cat, naturally.
Why fit the entire exhaust system if you feel the cat is the major restriction?

Rick.

My 2.5 inch exhaust was press bent down to 2/1/4 inch so had it replaced and while I was at it went 3 inch mandrel bent. The 14.5 time was with the 2/1/4 inch squash. I am hoping to go a bit quicker with the 3 inch at the track and I am taking a gamble. When I ported my head If I saw any restriction it was taken out. I see the headers as an extension of the port and where they meet hopefully scavenging occuring as each pulse pulls the other out and to the collector/catalyitc converter.This is where I believe that the bigger cat can flow A BIT more like a true no cat old school setup.It is a step in the right direction.The truth for each person is if they perceive a gain.Whether it be 1/4 mile or dyno.

I have a failing auto box at the moment so If it is a simple solenoid then the car will have another crack at wsid in slightly cooler weather.