3.7 Header

[6pack]

I'm having a brain fart and without re-reading the whole thread, I'm not remembering what you mean by 'extractors'. Can you refresh my memory for me?

As far as the O2 extenders, I needed the one on the lower O2 sensor to stop my girl from throwing a code after a short bit of driving after I installed the header. The header removed the pre-cat, so both sensors were reading the same thing. Putting the extender on the lower sensor pulls the sensor a bit out of the exhaust flow and it reads cleaner air (I assume) which tricks the pcm into thinking the pre-cat is still there doing it's thing.

[nicetryrobin]

I'm having a brain fart and without re-reading the whole thread, I'm not remembering what you mean by 'extractors'. Can you refresh my memory for me?

Go to Page 4 of this thread........ 6 Pack has photos of the extractors at the top & also a comparison to the stock exhaust header further down the page.

[6pack]

Hmm, still not following you. Are you calling the header an extractor?

[nicetryrobin]

Yes, a "high flow" header is an extractor.

A short tube header is better for torque whereas a long tube header is better for top end HP.

Honda I believe has both variable intake & exhaust

BMW Twin Turbo models combine a short header/ small turbo for low rpm and a long header / big turbo for the top end power.

[nicetryrobin]

Here are some links that highlight they are the same (Extractors is a term from 60s & 70s typically used by Limeys/Australians)

http://www.pacemaker.com.au/faq.html

@ FAQ 1

http://en.wikipedia.org/wiki/Aftermarket_exhaust_parts

Headers section
"Switching from an exhaust manifold to exhaust headers (also known as extractors in Australia) "

[ltr450crbm]

Sorry for confusion 6pack.
As nicetryrobin wrote: headers = extractors = exhaust manifold .
At least that's how I see it

That O2 senso extender; where can I get one? or do I just solder some wires? add a resistor ?

[6pack]

Bloddy hell I was confused!

I got the O2 sensor extenders off eBay. From what I remember there were a bunch being sold on there. It's as simple as unscrewing the O2 sensor and screwing the extender in it's place, then screwing the O2 sensor into the extender. That's a lot of screwing.

And to answer one of your original questions ltr450crbm, any power mod is worth it to me. They all feed off each other. This one certainly isn't for everyone as the price is crazy for the results. But if you can spare a grand, do it.

[VrtlOfc]

6pack.

Your right, there are a bunch of these O2 Extenders on Ebay. Which one did you get? Do you have a thread count or a vendor to help us narrow down the choices?

Thanks for the help.

[6pack]

Hey Vr, I looked through my eBay history but it's been to long since I bought it. So I don't have a clue. I would think there was something in this thread about it, probably me asking someone that same question.

[Lyn-X]

Whew, Long but interesting. What did you guys decide on gutting, hacking the 1st cat ? Can we ? How ? Sounds, maybe a little more attractive than $$$.$$ of the Extractor. Thanks lynn

[6pack]

It's nice when you can read a long thread without all the crap that ends up in them on some sites. That's why I love this place. Where's that 'HummerXclub Rocks!' smilie...

[nicetryrobin]

I tried to gut the first CAT but I couldn't get the bolts undone so I left it alone.

Some great advice I got if you are going to do this........ You will break the studs & bolts getting this off so be prepared (I had replacement bolts, studs, gaskets, on hand when I tried mine).

[federicoiz]

I think I found out why the 3.7 runs like a 2.4... the stock exhaust manifold with the cold start converter... Putting the header on was like pulling the dry cleaning bag off from over the head of my 3.7... It can finally breath (or exhale, if you will). You can really tell the difference. I was thinking about getting the PCM tune so I could get the shift points re-calibrated, now I have none of the shifting (lugging) problems that I'v'e had since going to 35s. The gutless wonder all of the sudden has guts. Throttle response is the biggest part. From 1200 rpm up it finally can get out of it's own way. I have tried both the Volant and Borla cat-backs and neither made any noticeable difference, except for the unbearable drone in the cabin. I run the Volant CAI on the intake side and the stock exhaust from the header back. To be honest, I have been thinking of trading in for an Alpha. Then they announced the H3T and the fact that all will be available with front locker next model year. So, I was gonna wait and trade in. Now I am think I can keep my H3. It really is that much a difference for me. Install was a snap. I removed the CAI and washer/coolant reservoirs, and EGR to gain access. Worst part was extracting the stock monstrosity. The header slipped right down in there. I used a new exhaust to head gasket, stock manifold to head bolts, grade 8 bolts/nuts, etc. for header collector to stock exhaust pipe. The doughnut gasket from the stock manifold is re-usable and fits on the header collector pipe. I would say it took 1.5 hours to do the job. The o2 sensor port on the header puts it pretty close to the passenger shock tower. However there is no interference from Engine vibration. But, it looks like it will be a biatch to change the sensor out if I ever have to. I am wondering if there is a "low profile" o2 sensor that will work on it. The stock sensor is like 4 inches in length!!

Header1.jpg

Header2.jpg

Mt Index Hummer.jpg

The header eliminates the 1st catalytic converter (incorporated into the stock exhaust manifold) and the 1st o2 sensor which sits about the stock manifold converter. This causes the computer to throw a code for the o2 sensor... as if the o2 sensor needs to be replaced. Keep in mind that I have been running it for a day without the 1st o2 sensor attached. This has caused no discernible problems other than the "check engine" light being illuminated. I am researching what voltage the computer is looking for from the 1st o2 sensor under normal operating conditions to eliminate the code. This could take the form of installing a resistor or tying the 1st o2 harness into the 2nd 02 sensor (which sits below the stock manifold converter). It is my understanding that the converter incorporated into the stock exhaust manifold is there for cold start conditions only and it's absence will not cause a bad sniff reading for emissions testing.

So there you have it. I will update as things progress. But, so far, so good. Also, my H3 is 2007 3.7 adventure with 7k miles, BFG 35s on 16x8 wheels. For the record; messing with my H3 - I have money to throw at it and it is more of a hobby for me. Maybe I can be the guinea pig here and we will see what happens. I have the stock manifold in a box if I need to revert. But, so far... I am sold! I am wondering what a PCM tune will do now! Here is a picture of the header installed (it's down there somewhere) and a picture of my rig when I drove it up the mountain today. If anybody has any input, chime in. From my searches on the internet I found no info about somebody actually installing this thing!!

Anyway, I would like to buy it but the sensor problem makes me insecure. One guy also told me "it has the correct bungs to bolt in your exhaust sensors so you should not have any problems".

What do you suggest? Thanks

[6pack]

I've run it successfully without codes by using the extender on the second sensor, but after swapping in the supercharger and seeing the gunk that was inside the intake manifold, I think the 'fix' let the engine run just rich enough to be under the radar for the computer, and allowed all the buildup. I'm not sure I would do it this way a second time. I think the correct way to go is to have a tuner adjust for the change after you do it.

[ltr450crbm]

I have done the mod. The part looks like a quality item.
OEM exhaust manifold cracked for the second time, this time out of warranty.
There were also 2 leaks between the head and the manifold through the metal gaskets.
The whole job was easy. I got an electronic torque wrench to make sure I don't overdo this tiny 20Nm torque setting.
There are 2 oxygen sensor sockets. Unfortunately the lower one was pointing too much to the side and the sensor was abutting on the chassis even without putting on the extender. So I took it to my motorcycle exhaust guy and he drilled and welded in a new socket. The old one I just plugged off.
The exhaust manifold turned a sexy blue colour after the first drive.
But, honestly, I don't see any hike in power, still using the same gears to climb fast freeway inclines.
The reason could be in a new code that sprung up last night P0171 = engine running too lean, but that happened about 5000km post installation.
When doing the installation the emissions canister hoses were moved a lot , ? maybe some cracks I haven't found yet.
You guys talk about 2 catalytic converters.
I have the Australian spec car and definitely there is just one, the one inside the original exhaust manifold. The second swelling after the joint is a resonator only. It does look a bit like a catalytic converter, but is it only a resonator. Maybe US spec cars have 2 cats, but I doubt it.
Now: .... the sound ! Wow, wow!!, ouch! ouch !
When modifying all my cars in the past I was trying to get just that sound.
It turns out that to get a racing car sound , you have to remove ..... the catalytic converter.I removed the rear silencer long time ago to make room for an extra fuel tank, so there is just one tiny resonator , no cat , no silencer
Idle is pleasant, quiet.
Up to 2700rpm a nice masculine burble.
Over 2900rpm a roar, loud roar, ease the throttle when you see da Police roar
Driving the freeway has become easier, scared sedans move out of the way in anticipation of thunder passing by.
In essence, too much.
I will let you know if and when I solve my lean condition.