new hm headers for vyll series

[cosmo vyss]

gents,
first i would like to apologise if this has been posted before. anyway hoping it hasn;t. i am not trying to start a new header thread. just after some advice and showing new header from hm.

hm header has a new header for vyll series see link
http://www.hmheaders.com.au/New%20Releases.htm

according to hm you do not need to move cat converters and this would save some beer coupons for for mods later on. i was hoping or curious has anyone fitted these or knows if someone has got them that i could speak to regarding them. i am fitting a dual catback 2 1/2 system next week (my first mod can't wait to hear the gen111 bad boy). i have been looking into headersa/extractors via many threads here. i also have two questions so please don't flame.
1. i understand the difference between 4 into i and 4-2-1 type headers. my question is does the 4-2-1 tyi y type better for low down and the 4-1 type for top end. someone tried to explain to me that longer is best for low down and shorter for top end, i think. i am not very technically minded.
i have also noted that some types og headers loose power on the dyno. however they still give great performance throught the rev range and sound tops. (got this from sureflow thread).
thanks gents :cool:

[justin74]

my vyII ute is going in the shop today, for 4-1 pacies, stainless steel catback, air filter, cai mod, and an ls1edit (maf). I look forward to seeing the results of the before and after dynos.

[VX2VESS]

Those short headers wouldn't be worth the trouble over the cast factory ones. the cast factory ones are about the same size and are also 4 into 1.

longer ones change where the power is made. but they also don't meet the cold start emissions for the VY.

[MNR-0]

I have shorty 4-1 made by CSV. They are stainless so a better quality option than the HM IMHO. I own a bolt-on A4 with stock converter. I pull in excess of 230rwkw and 108MPH in the QTR - faster than a lot of M6's. So they work well on stock cams.

[cosmo vyss]

sorry i put up he wrong part number it is hm120ss. i also just reciebed an e-mail form hn aust and they stated that i should at least gain 8kw in the mid range above standard.
is there any other types outthere that fit the vyss series ll that don't have to move the cats??
jb

[cosmo vyss]

my vyII ute is going in the shop today, for 4-1 pacies, stainless steel catback, air filter, cai mod, and an ls1edit (maf). I look forward to seeing the results of the before and after dynos.

i hope you enjoy the new found power and performance. with your headers do you need to move the cats? i am looking for best value for money. if i don;t have to move the cats i can spend that cash on something else.

[Mongy]

sorry i put up he wrong part number it is hm120ss. i also just reciebed an e-mail form hn aust and they stated that i should at least gain 8kw in the mid range above standard.
is there any other types outthere that fit the vyss series ll that don't have to move the cats??
jb
Genie have just put some on the market, and they include a new enlarged engine pipe that goes from behind the cat to the join that the catback bolts onto. Most catbacks do not include this pipe, and it is only 2" with a crush spot in both of them. If you do that you will have to get the rear of the cats opened up ti fit. Most good exhaust shops can do this, Thunder (Greg) is the best in Sydney. If you really want a good exhaust save yourself the hassle and just go and see him. He will give you a system that not only works, but sounds good.

[scat2k3]

Thunder (Greg) is the best in Sydney. If you really want a good exhaust save yourself the hassle and just go and see him. He will give you a system that not only works, but sounds good.

What he said.

Cheers,

Scott

[justin74]

i hope you enjoy the new found power and performance. with your headers do you need to move the cats? i am looking for best value for money. if i don;t have to move the cats i can spend that cash on something else.

Yeah the cats are being moved and modified to fit the new system. In terms of cost it was cheaper to get the existing ones modified than to get 2 new ones....however not all places offer this service. I'll post the before and after dyno charts later.

[VX2VESS]

can anyone explain how you would get an increase by replacing the stock headers with these when the are the same size as factory?

seems a waste of $. U can port match and port out the factory cast ones even coat them. will flow the same as any short extractor.

however enlarging the cats and the rest of the system will give some gains. those headers with nothing else will do nothing much, nothing u can measure.

i've had ported stock headers on, 2 1/2 engine pipes and enlarged cats. some time later fitted extractors and had no increase in power. still have the ported headers in storage.

so if you take off a stainless cat system a fit a mild steel one exactly the same do you also get a gain?

[Munro]

I had my Munro fitted by Carline in Gosford (NSW) ......recommended to me before I found this site. I had the following installed:

Extractors HM-100SS
System ST 126 Dual 2 1/4 system with S/T muffler to single 3" t/pipe
with X-pipe (redback)
CAI007 SS Induction & Kingdragon Sports Filter (again before I found this
site)

Sounds unreal, goes much better and fuel economy has improved. Edit is next on the list and I plan to go and see Sam about it on Tuesday. One thing I know is once I had the system done I cant get the smile off my face. It sure as hell feels nice to have a V8 sound like a V8 - plus it keeps the neighbours on their toes :burnout:

I would love to know if anyone has found a real advantage between 2 1/2 and 2 1/4? Was this a mistake or doesn't really matter until you get high end hardware installed. Also, any recomended changes?

[BLACK 346]

I had my Munro fitted by Carline in Gosford (NSW) ......recommended to me before I found this site. I had the following installed:

Extractors HM-100SS
System ST 126 Dual 2 1/4 system with S/T muffler to single 3" t/pipe
with X-pipe (redback)
CAI007 SS Induction & Kingdragon Sports Filter (again before I found this
site)

Sounds unreal, goes much better and fuel economy has improved. Edit is next on the list and I plan to go and see Sam about it on Tuesday. One thing I know is once I had the system done I cant get the smile off my face. It sure as hell feels nice to have a V8 sound like a V8 - plus it keeps the neighbours on their toes :burnout:

I would love to know if anyone has found a real advantage between 2 1/2 and 2 1/4? Was this a mistake or doesn't really matter until you get high end hardware installed. Also, any recomended changes?

Yes, take the SS cai off and have a look at the size of
the hole where it actually goes into the twin horn pipe.
That is what your car is trying too breath through.

Edit: You may need to shine a torch inside the cai to
see the restrictive area I am talking about.

[Mongy]

I would love to know if anyone has found a real advantage between 2 1/2 and 2 1/4? Was this a mistake or doesn't really matter until you get high end hardware installed. Also, any recomended changes?
There is a slight advantage in going to 2 1/2", but I wanted no drone at all and did not want too much noise so went for the smaller size the same as you. You are only talking about 2 - 3rwkw difference. My rear reso is twin 2 1/4" in and twin 2 3/4" out, I don't know if the single 3" tailpipe would be hampering your system, but doubt it would. As above, ditch the SS CAI. Also fit a GTS300 maf pipe. That and a second hole in your CAI makes around an 8rwkw gain, well worth it for the price. If you use the search function for "CAI" or "second hole" you will find many threads dedicated to this subject, including instructions and photo's of how to do it.

[Munro]

Thanks Mongy. I'm just another SS victim that found out too late.

I have been wondering if keeping the SS CIA and then adding the second hole mod in the Munro box would be even better or more woftam?

My mate just did the second hole mod on his VY clubbie and we thought about doing the same to the Munro and keeping the SS CIA in place. I have searched for a thread on this but havn't seen one that hits this specifically.

I would hate to just chuck out the SS plastic fantastic $$$$$$$$ :(

MAF pipe and edit is on the wish list...santa has his orders! I'm seeing Sam on Tuesday and will talk about the essentials.

[BLACK 346]

Thanks Mongy. I'm just another SS victim that found out too late.

I have been wondering if keeping the SS CIA and then adding the second hole mod in the Munro box would be even better or more woftam?

My mate just did the second hole mod on his VY clubbie and we thought about doing the same to the Munro and keeping the SS CIA in place. I have searched for a thread on this but havn't seen one that hits this specifically.

I would hate to just chuck out the SS plastic fantastic $$$$$$$$ :(

MAF pipe and edit is on the wish list...santa has his orders! I'm seeing Sam on Tuesday and will talk about the essentials.

Don't ditch the SS Cai, do the second hole mod on
the mcai and then mate the 2 together. You get
air from over the radiator and from behind the
headlight and with the help of a bit of adhesive
foam and a bit of cutting it seals the mcai from
hot engine bay air.

[Mongy]

Don't ditch the SS Cai, do the second hole mod on
the mcai and then mate the 2 together. You get
air from over the radiator and from behind the
headlight and with the help of a bit of adhesive
foam and a bit of cutting it seals the mcai from
hot engine bay air.As above. I cannot see any reason why that would not be a really good setup. I'm surprised I have not seen anybody do it before that has a SS Inductions CAI.
Thanks Mongy. I'm just another SS victim that found out too lateSame here, I'm not really into computers and forums so I only found out about this site this year. There are a lot of LS1 owners out there getting incorrect information and doing modifications that are not cost effective. There are many ways to arrive at a destination and this forum helps guys get there the right way.

[Munro]

Cheers folks, I'll put in the second hole mod and see how she goes.

Thanks for the feedback.