Exhaust

Nice shiny ceramic coated 1” 7/8” headers from Australian manufacturer PaceMaker.

Part of a group buy organised by Richard Ingram…Thankyou !!!!!

So, 11^th June 2015 and I finally find time for myself, for the next 3 days it’s project exhaust.

Not much to see from above, pretty straight forward case of unbolting dipstick bracket, swing out of the

way, remove the ht leads and remove the manifold bolts, from underneath disconnect the steering column

joint, push up out of the way, remove the std manifold with cat attatched, wiggle in the new headers and bolt up !

Cable tied just for support while getting a few manifold bolts in, note how close the oe position

of the cat joint is.

Both headers bolted up. No drama’s

Looks very nicely finished off merge collector, notice the little swirl casting.

Cats next, I’d already bought 2 other sets of cats, which after some opinion decided not to use.

These came from Germany, some nice big 100cell oval units, apparently designed for up to 450ps each, the

cores seemed generous enough, almost 150mm long, most I’ve seen is 100mm, fingers crossed

these will be ok, only one way to find out !

Ends cut back and slightly expanded to remove the slight oval shape at the ends, then one end welded

to some 10mm thick stainless steel 4 bolt flanges, also o2 bosses to take the rear sensors (I know, can

be removed from the tune eventually, but easy enough job to do, so may aswell).

Temporarily bolt up (there was lots of temporary bolting up !!) the cats and make up the connecting

pipework.

I wanted a mid box with this setup, and thought I’d try a H pipe this time instead of the X kiss.

I’d bought a pre-fabricated rolled silencer box, but because of the rolled rim endplates, this effectively

made the overall oval too big, so I had to weld a box up from parts, also had to replace the metal tunnel

strap with another fabricated one as the box did hang lower than the std strap.

It’s a long bit of exhaust!

Took a few test runs to discover, I’d left a cable tie around the prop, a large washer rattling on the oe

tunnel strap (don’t know how that managed not to fall off), the rear silencer box hangers were hard

up against the mount brackets (I’d taken the opportunity to site the boxes a little further back so that the

tail pipes ended further away from the rear bumper) the exhaust grows nearly ½” when hot!. All now adjusted

including the mid box hitting the oe tunnel bracket under load, despite ensuring a 12mm gap! (cheers Phil G,

was only when you tapped the strap and the sound was just like the knocking we heard on the run out, I’d

never have believed it could have been this otherwise!)

So, how does it perform ?.......well first off, not being a great fan of loud exhausts on my own cars (love them

on others cars, just not mine) thank goodness I added the midbox, I’d understood from from other PH HSV

forum posts that long tube headers can make the exhaust louder. It’s loud on cold start up, but when warm

it’s relatively mellow. Noticeable lower level of drone, which is gone by 1.5krpm (before was 2.0krpm).

WOT to redline, it really does howl….more so than before, goes through at least 3 different tone levels,

and I have to say all of them quite pleasant. I actually think that the “v8” beat/burble is more regular and

even now, I think that must be down to the headers having equal length runs. Power wise, it would be

nice to think there is more, maybe there is, I don’t think I’ve lost any, (I’m still on a std tune)……….needs a dyno

What’s next ?…….bigger rear boxes…….eventually (oh…perhaps in between that, a little power enhancer …)

Update 23/07/2015….MOT test

Fast Idle_______Limits_________result 2014____result 2015
CO__________<= 0.20%vol__________0.04_________0.01
HC__________<= 200ppm____________15___________12
Lambda______0.970 to 1.030_______1.000________1.004

Natural Idle
CO_________<=0.30%vol____________0.02_________0.03

Only comment from tester was that the cat light up time took a little
longer, other than that all good

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