Alloytec Exhaust Fun :)

[Kung-Foo-Kamel]

After a week of messing around, cutting welding bending etc etc etc..

I have finally found a system that sounds good and produces solid torque with a increase in power through all rev ranges

Firstly, I was running a 3" Single sytem from the cat back, this lost me some torque at the bottom end but after 2500rpm it was like a power band kicked in all together it sound ok and gave good top end power

I also tried this system on a SV6, not recomended, it lost all its torque and gained nothing up top, these 190kw motors really like there back pressure

Then I thought hmm extractors, I got a set of HM Headers and put them on with no Cats, there 2.5" out into the single 3" system

All I can say is bloody noisey, horrible sound and it had a vibraty sound that kicked in at about 2500rpm, made me sick, but produced awsome power

I then thaught OK wheres this resonence coming from, so I put my stock single 2" back on and oh my god, all I could here was vibrating resonence every time you reved the engine, It was comming from the intermediate muffler

It sound like the left and right bank were arguing over who has right of way through the exhaust, so I thought OK lets try and slow the flow a little, and I installed 2x 2.5" Cats and I shortend the Extrators by about 3" and it made the world of difference, but there was still a little bit of resonence, so I tried a twin 2.5" system with intermediate and rear free flow mufflers and bingo, smooth clean pure note, very V8 ish, this setup has given me the best torque as well, I can be at 1000rpm in 6th gear and it will accelerate away, where before it was drop it back to 4th

Also we found the best cat back on a SV6 is the stock 2" twin system from a SS Gen3, just dont use the rear muffler and have straight pipes made up instead, this car prefers mufflers with restriction, if you use free flow type mufflers it appears to loose all its power

Anyway hopfully this info helps someone out, as I have just spent a small fortune on getting this Alloytec to sound good and produce good power, its not like the old buick V6, just remove the rear resonator and thats it

Cheers KFK

 

[Nordy]

Great info mate! Really explains a bit about the torque issue with these 190's
Wish u were a couple of weeks earlier with this info thi haha oh well might come to modding my exhaust slightly shortly

 

[aklame]

175

Hey mate, was just wondering if you know what the best combo is for a 175 donk?

 

[brownie82]

With this stock 2.5" gen3 system would it be the same on an auto?? How would you have a rough price on what a system like that would cost??

Post some vids of the sound that you come up with if you can, would be nice to hear what it sounds like.

Cheers,
Browine

 

[jaisvz]

i've just installed a twin 2.5" cat back system with free flow mufflers and it seems to give a good note and the power gain is pretty good. Didnt notice any loss of torque tho.

 

[Kung-Foo-Kamel]

I will take some good quality recordings of my system and the SV6 we have after easter and some pics

SV6 190KW has a stock Manifolds, 4 x Cats, 2 x 6 wire O2 sensors, 2 x 4 wire O2 sensors with Intermediate twin 2" Restricted Mufflers from a 6ltr SS with custom 2 x 2" Tail pipes, sounds nice, very little loss in torque, slight increase in topend power, very noticeable volume level, sounds quite nice

175KW Ute, 2 x HM Headers with 2.5" Collectors, 2 x FINN-EX 2.5" High Flow Euro Cats, 4 x 4 Wire O2 Sensors, 2 x Free Flow Manta Mufflers, 1 x Twin 2.5" Manta Rear Free Flow Muffler, Sounds Awsome, very V8 ish, probable better than most Gen3's with cat backs, produces fantastic torque, absolutly pisses on the SV6, had a XR6 Turbo worried for the first 3 gears , just need a better diff now

Somthing to look out for, if you vehicle has 4 O2 Sensors, which is most 06 Euro compliant VZ's, you will probably get issues if you put extractors and aftermarket cats on as the ECU monitors the flow via the O2 Sensors and will log fault codes due to to much flow, mine has been logging faults on both left and right banks, fuel econamy is still good so theres no bad to come of it apart from the "Check Power train" message that gives you the ****s

I know the Powerchip ECU remap can remove Cat detection, but I think $1000 on a software mod is a waste of money as its only about $1080 for a Haltec piggy back Box that can easily be removed (for warranty purposes) and played with Via a laptop, but I dont know what it can and can not do as yet

Also if you have a bog stock Allotec Sedan or Ute/wagon I have a couple of 3" Manta systems for sale on Fleebay, 1 for sedans and the other for Ute/Wagons both have nice Crome Tips in place as well, I will fit them for free and while you wait, these are not good for SV6's so dont even bother, they sound a lot like a rice boy 300zx or skyline only a little more racey

 

[NickVR]

Great info mate, just the other day i made a thread asking about the best exhaust for a VZ SV6. A mate of mine has one and wants an exhaust but kept getting told so many different combos and was confused.

So if i have read this right then a 6Ltr SS exhaust with straight pipes at the rear would be the best. He isn't too fussed about sound just wants more power from it. Would a single 2.5 mandrel bent be just as good, that the system he has been thinking of or a twin 2.5 mandrel bent.And he is getting diff gears done when his warranty runs out.

 

[Not_An_Abba_Fan]

Your check power train issues would be more to do with the shift points changed in the transmission. The ECU is saying change, and the tranny is going nope, I like this gear, I'll keep it for a bit longer. Then the ECU chucks a spaz and says error.

 

[Kung-Foo-Kamel]

Your check power train issues would be more to do with the shift points changed in the transmission. The ECU is saying change, and the tranny is going nope, I like this gear, I'll keep it for a bit longer. Then the ECU chucks a spaz and says error.

"Check drive train" is a standard universal message for any issue, its just a flash version of a engine light

Mines a 6sp Manual, the error mine is still brining up is "Left/Right Bank Cat Converter to efficiant" because they have before and after O2 Sensors the ecu can monitor the Cats, I can clear the fault codes but it will just come back again

It does take longer to log the fault each time so Im hopping after the cats start to block up a little the fault may dissapear

 

[Willz]

Kamel

have u tried a 2 n 1/4 twin system from a hsv on that sv6?

got that system on mine atm

car feels many times better through the mid range while topend remains preety much unchanged