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Why 2 Different types of Engine Pipes on Ecotec V6 engines ?

vs-lover

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I'm still to this day trying to work out why IRS fitted cars use a different set of engine pipes from the manifolds to the exhaust flange past the Catalytic converter. IRS vehicles have a flexi joint in the RH pipe while Live axle vehicles have both pipes as solid metal without the flexi joint.

If anyone know why this is the case I'd love to know as I might have to replace my IRS Acclaim set and I do have a set of near new Live axle pipes on hand.

Thanks for any answers in advance.
 

vc commodore

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From really crappy memory, the IRS pipes at the rear are routed differently to the live axle pipes.

And by really crappy memory, I vaguely remember this, when I tried getting a job in Holden back in 95, when they were building these cars....

Was only there a week, when I got another job
 

vs-lover

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Hi VC,

Yes the IRS exhaust system goes under the axles assembly while live axle has them go above but that shouldn't affect the engine pipe set up as the flange will be in the exact same position regardless of the axle assembly fitted.
 

_R_J_K_

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the IRS exhaust system goes under the axles

This is probably the reason. I'm guessing Holden thought there was a higher chance of the rear section hitting something and moving around. Whether that would actually happen, I really doubt it.

Don't remember seeing one on mine, VS Series 2 thing or across the IRS range?
 

vs-lover

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IMG_3831.JPG



That idea probably may be the answer as the rest of the system hangs a tad lower than a Live axle unit at the rear.

The photo is looking upwards at the LH engine Pipe. This is factory and not aftermarket.
 

Harvs82

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There is a difference between series one and two exhausts, and between live rear end and IRS. Some cars ran two separate pipes merging into one, some cars just a single pipe. If you have a Gregorys workshop manual it shows a diagram in there
 

vs-lover

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Hi Harvs,

Yes I've just had a look at that particular book and it shows the early IRS exhaust system and on the following page it shows the live axle system with a flexi-joint just prior to the rear muffler, again something that was changed to removing that flexi-joint, but the vehicle I have is a November built S2 Acclaim sedan and that has the later / cheaper single front muffler system, but also has a flexi-joint in the left hand engine pipe before the O2 sensor. Not quite sure why they added that flexi-joint in the later IRS fitted systems and is it critical if that assembly has to be replaced.

I'm finding it almost impossible to locate one of these engine pipe assemblies with the flexi-joint installed as U-Pull-it cut the Catalytic Converters out before the cars go out into the yard rendering that pipe assembly in each car useless. I've been hunting on FB and Gumtree but suddenly it seems VS's are rapidly becoming rare now and prices on them is now starting to skyrocket with the low economic phase that they were in and that they are now coming out of. VT's and VX's have taken over that low market point mantle.


PS. I note you also have one of those Subaru Rocket Ships, my lad has a 2005 Manual GT (pre-face) and we've recently installed the earlier and more desirable 6 Speed gearbox that utilizes an oil pump within and it to with a few small mods around the intake is a bullet.
 

shane_3800

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Just buy some pipes and mandrel bends and build your own exhaust. This is what I do. Performance Exhaust online is a good place to buy all this stuff.
 

Not_An_Abba_Fan

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The cat is in exactly the same place on IRS and live axle so the front is the same shape. The reason for the flex in IRS vehicles is to take out harmonic vibrations induced by the exhaust. The front muffler is smaller on the IRS and it causes a harmonic vibration that can be felt through the car so the cheapest fix was to fit a flex in the engine pipe rather than build a new muffler and perform testing to eliminate it.

The same reason the live axle has a flex in the rear muffler. The position of the flex is what works best on IRS and live axle.
 

vs-lover

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Thank you very much for that detailed and conclusive explanation, this is exactly what I was wanting to know and as such it's not too detrimental to fit a non IRS engine pipe to replace a damaged flex fitted unit. Certainly Food for thought.

Again, thank you very much "NAAF".
 
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