Seriously Exhausting 33

[RaseR]

Hmmm, sounds like he's using a philosphy which relates to cars with naturally aspirated motors (ie. non turbo), where a certain amount of back-pressure will be beneficial to midrange torque and overall power gain.

The general consensus, at least in my experience with 6 cylinder turbo motors is that back-pressure is your enemy and the more easily exhaust gas can escape the turbine housing the better.

I'm sure it's possible to go an exhaust diameter that's too large and not optimum, but think about it - a turbocharger is essentially an air-pump that's driven by exhaust gas and needs to expel that gas at a fairly rapid rate so as to keep the impeller spinning at the optimum rate for boost/power generation.

50Nm sounds like a pretty big claim for torque increase on a more restrictive exhaust, I'd ask him to show you the proof (in way of a dyno chart or something) on a turbo motor.

My 2c....actually more like 10c, but whatever.

[J_Red33]

I was going to say something similar to that...... before the stupid kettle threw the saftey switch. But yeah I agree totally.

It's worth noting that the standard R33 exhaust is 2.5 inch, maybe not the most free flowing, but I doub't that even with a high flow muffler or cat that you would get any where near the gain you would by going to a 3 inch system. Bigger piping means more air flow & therefore more power capability too.

It's also worth noting that there are a lot of strict regulations when it comes to rally cars & many classes have things like inlet restrictors in which case they don't need the exhaust flow as the inlet flow is not that great anyway. It's also a matter of how a car is tuned as to how it will go exactly. A 3 inch system that only gains 3 kw extra over a 2.5 is probably a really crap too.

[J_Red33]

Well just add a bit of info as far as the power debate goes on this thread. I had my car dyno'd a couple of weeks ago with the South Australia group dyno day.

1 guy with an R33 S2 & just a cat back system got 151KW & was bitterly dissapointed (He was hoping rather optimistically for 165).

My system with the split dump & metal cat & stock boost? A whopping 177KW!

Admittedly it could only do this once with the stock intercooler as it dropped to a still impressive 170KW on the second run purely from the heat buildup. Everyone with a frontmount got far more consistent readings.

The real surprise was the torque curve which was strong from 2500rpm & barely changed until it hit high boost mode. It slowly died off throughout the rev range & once again I think mainly due to the intercooler.

All in all very pleased with the result

Edited October 21, 2006 by JazzaR33

[RaseR]

Hey Jared,

177rwkw?! Awesome result mate...I must admit I completely forgot about this thread! My cat-back section turned up from Japan late July in almost as-new condition...bought a 3" Catco big-body and 3" stainless split front/dump (old style) through BATMBL, had it all installed at Casey Exhausts in Berwick (they do excellent work, but you pay for it).

My thoughts - car is way more responsive, heaps of torque everywhere! Scary in the wet, awesome in the dry...feels way faster overall.

My review of the components purchased:

.3" BATMBL Split front/dump pipe (stainless): Amazing piece of gear, almost looked too good to install, it's the older style with smooth bends and a semi circular wastegate/turbine divider as opposed to full circle turbine wheel enclosing style of the newer type, I much prefer the design I got as it means I can go high-flow without any mods to the pipe. Spool-up of the standard turbo sounds insane with this pipe, I have std airbox with apexi panel, so literally no other induction 'sucking' noises, with this pipe you can hear the turbo whizzing away nicely without the huge 'whoosh' noise of a pod (I'm over that now...)

.3" Trust MX cat-back: Beautifully constructed exhaust, mild steel pipes with highly polished stainless rear muffler that looks the goods and also pretty damn quiet..but still has a meaty idle!

.3" Catco big-body catalytic converter: This is the second one I've bought...1st time, no troubles at all - fit onto my R32 perfect, bolted straight on...Not so on the R33, it was around 1.5" too short which meant the exhaust shop had to extend my cat back to compensate , the temp sensor bung was incorrectly positioned and caused the sensor to hit the cars underbody, fixed with a slight bend to the sensor body...not very happy with this components construction, flows well though.

Overall - awesome result...I'll take some pics soon.

[J_Red33]

Yes well I did have some issues with my dump setup too.

The original one I got cracked & BATMBL replaced it no problems, however they didn't fit the same (turns out the original was made wrong after making some checks against the stocker) so I had to get some dodgy mods done for it to fit on, so now my stainless custom cat back no longer lines up right . Not real happy about that bit since my car is otherwise nearly showroom condition.

Edited October 31, 2006 by JazzaR33

[leetom]

had ces fit full s/s 3'' system with split front pipe to my s1 stagea dec 05 [queried pos of o/sensor] have to say am very happy with quality and performance,max stnd boost now 10lb feels like a different car and sounds like ripping silk [86db].