Unichip + new exhaust = retune?

RG · 09-10-2006, 02:48 PM

Just wondering if I was to get a new catback system, either a better flowing 2.5" or 3" single system would I need a retune? The current 2.5" single system I have atm is very restrictive as it has a dodgy muffler and a hotdod that is smaller than the rest of the system.

james22 · 09-10-2006, 03:33 PM

my mate done it the other day. His car runs fine

RG · 09-10-2006, 03:35 PM

Quote:

Originally Posted by james22

my mate done it the other day. His car runs fine

Thank you, I think I might be off to the exhaust shop.

james22 · 09-10-2006, 04:20 PM

Sounds good lol. No pun intended hahaha

RG · 09-10-2006, 04:27 PM

I just had a chat to Herrod's too and they said it won't cause any problems and that I should go the 2.5", so i think I had better book it in.

james22 · 09-10-2006, 04:28 PM

how much dude? I got identical car to u remember. Your quote is my quote lol

**Stav** · 09-10-2006, 04:29 PM

If your going to a bigger exhaust the existing tune will not be optimal

JC · 09-10-2006, 04:29 PM

Quote:

Originally Posted by RedXR8220

I just had a chat to Herrod's too and they said it won't cause any problems and that I should go the 2.5", so i think I had better book it in.

If you're going from single 2.5" to twin 2.5", does that mean they can use your existing system, and just modify up near the cats where it would go 2 into 1, and run another section of 2.5" parallel to the existing one?

Should go, and sound, great with twin 2.5".

JC · 09-10-2006, 04:31 PM

Quote:

Originally Posted by james22

how much dude? I got identical car to u remember. Your quote is my quote lol

Are you also running single 2.5" at the moment? If so, see my post above. They may be able to use the current single for one side, and just add another 2.5" single to make the twin system, so it may be cheaper than a full replacement.

RG · 09-10-2006, 04:32 PM

Quote:

Originally Posted by useless

If your going to a bigger exhaust the existing tune will not be optimal

Same 2.5" but without the 2" and 2.25" restrictions (one being the muffler which is a baffled type and the other the hot dog at the back) in it. Do you reckon i'd be better of going a brand name mild steel system or getting a herrod stainless system as I can get a good price on one.

james22 · 09-10-2006, 04:33 PM

Nah, its got twin 2 - 1/4 i think. Its just too quiet makes no noise unles you jump on the pedal. Even then half the noise is induction roar

RG · 09-10-2006, 04:34 PM

This is a single system i'm talking about too.

JC · 09-10-2006, 04:57 PM

Quote:

Originally Posted by james22

Nah, its got twin 2 - 1/4 i think. Its just too quiet makes no noise unles you jump on the pedal. Even then half the noise is induction roar

Keep the twin 2.25". and just replace the rear muffler with twin 2.5" or 3" pipe.

JC · 09-10-2006, 04:58 PM

Quote:

Originally Posted by RedXR8220

This is a single system i'm talking about too.

So keeping the single and just removing the restrictions? I'd go 3" single all the way back from the first restriction point then.

RG · 09-10-2006, 05:08 PM

Quote:

Originally Posted by JC

So keeping the single and just removing the restrictions? I'd go 3" single all the way back from the first restriction point then.

First restriction is the first muffler. I also don't want it to drone at all and I can get a pretty good price from Herrod's on a full 2.5" stainless sytem.

RG · 09-10-2006, 05:08 PM

Quote:

Originally Posted by JC

So keeping the single and just removing the restrictions? I'd go 3" single all the way back from the first restriction point then.

And what would be the cons of going just normal bends instead of mandrel?

xr8ute · 09-10-2006, 05:42 PM

Quote:

Originally Posted by useless

If your going to a bigger exhaust the existing tune will not be optimal

V8's are very different to the I6, because we are MAF based.

As long as a change like that is in the range of the MAF, then the existing tune will not be affected at all...

In a MAP based I6, it would affect the volumetric efficiency of the engine (which the MAP cant account for), and would need to be retuned for optimal results.

bodes-sh · 09-10-2006, 06:23 PM

Quote:

Originally Posted by RedXR8220

And what would be the cons of going just normal bends instead of mandrel?

the difference between normal bends and mandrel is that mandrel has the same diameter as the rest of the pipe at the bend, whereas press bends compress the pipe where they bend it, losing diameter, so a 2.5" can quickly become a 2.25 or 2" at the turns in the pipe with a press bent system

personally if you can get a good deal on a stainless system i'd probably go for that, but it's your money so its totally up to you

RG · 09-10-2006, 06:26 PM

Quote:

Originally Posted by bodes-sh

the difference between normal bends and mandrel is that mandrel has the same diameter as the rest of the pipe at the bend, whereas press bends compress the pipe where they bend it, losing diameter, so a 2.5" can quickly become a 2.25 or 2" at the turns in the pipe with a press bent system

personally if you can get a good deal on a stainless system i'd probably go for that, but it's your money so its totally up to you

So mandrel it is and stainless steel for a crisper note and overall longevity. Looks like i'll be heading off to Herrod tommorow, they say they use the same system on cars with 400rwhp so it should be more than good enough for me. And I can get it for smack bang on $1000 supply and fit.

james22 · 10-10-2006, 09:00 AM

Quote:

Originally Posted by JC

Keep the twin 2.25". and just replace the rear muffler with twin 2.5" or 3" pipe.

If I replace it with 3'' pipe, will it be too noisy?

RG · 10-10-2006, 10:27 AM

Quote:

Originally Posted by james22

If I replace it with 3'' pipe, will it be too noisy?

From what i've been told by Herrod all you need is a single 2.5", that's what they've been using on cars with 400+rwhp so I reckon they would probably know.

james22 · 10-10-2006, 10:40 AM

yeah but i've already got twins on it, so why would i go backwards to a single.
I was just thinking that removing the rear muffler and replacing the pipes from there with 2 3'' pipes, it might be a bit on the loud side.

Did your car come std with a single system on it?
It's the same as mine, I would have thought you had twins as well...

RG · 10-10-2006, 11:13 AM

Quote:

Originally Posted by james22

yeah but i've already got twins on it, so why would i go backwards to a single.
I was just thinking that removing the rear muffler and replacing the pipes from there with 2 3'' pipes, it might be a bit on the loud side.

Did your car come std with a single system on it?
It's the same as mine, I would have thought you had twins as well...

Stock it had a twin 2.25", when I bought it it had a dodgy single 2.5" system which before it was mangled with other bits and pieces was a Herrod s/s system. If it were me i'd just ditch the rear resonator and replace with twin 2.5" pipes, replace the standard mufflers with hi-flow jobs and be done with it.

bodes-sh · 10-10-2006, 06:45 PM

from what i understand on the xr8s the best bet is to either run a single 3" or a twin 2.5", which i think is what the herrod one would be, twin 2.5s

RG · 10-10-2006, 07:42 PM

Quote:

Originally Posted by bodes-sh

from what i understand on the xr8s the best bet is to either run a single 3" or a twin 2.5", which i think is what the herrod one would be, twin 2.5s

Herrod one is single 2.5" with twin after the rear resonator. Just got back from getting it fitted and it sounds awesome, bit more poke too.

bodes-sh · 10-10-2006, 08:16 PM

fair enough, seems a bit strange for a single 2.5 on an eight, but i guess if it's herrod's design then it must work pretty well, esp for 400+hp cars and being stainless should last practically forever

AUTickford · 11-10-2006, 12:11 AM

1ooo bucks seems alot for a single system. i just replaced the muffler and deleted the hotdog and my car sounds good and goes better with the factory pipework in place. Im pretty sure stainless doesnt make your exhaust sound crisper it just lasts longer. Mandrel bending wouldnt make much difference unless your car makes bulk hp, when u consider the price.did u get a before and after dyno????????????????? u deserve 1 for 1000 bucks

**Chris** · 11-10-2006, 09:13 AM

Anything that lessens the restriction on an engine will require some further attention to the tune in order to function correctly.

RG · 11-10-2006, 10:41 PM

Quote:

Originally Posted by AUTickford

1ooo bucks seems alot for a single system. i just replaced the muffler and deleted the hotdog and my car sounds good and goes better with the factory pipework in place. Im pretty sure stainless doesnt make your exhaust sound crisper it just lasts longer. Mandrel bending wouldnt make much difference unless your car makes bulk hp, when u consider the price.did u get a before and after dyno????????????????? u deserve 1 for 1000 bucks

$1000 for that system is actually very cheap, all other quality brands like Difilipo are around the $1400-1500 mark. Stainless does give a crisper note and mandrel bending makes a fair amount of difference.