Yup, you are spot on, its definitely restrictive. What should have been done is new piping from the cats back to the stock mufflers, full twin system with a merge. But for probably $1000-$1500, i really couldn't justify it. As i mentioned Sonny had built such a system with custom mufflers, and they netted 260kw at the wheels, with no tune! So there is definitely more left in it, but im happy where i am for now.

 

Maybe one of the vendors here needs to start working on this for the rest of us

 

WOW!! Nice job . Like, really nice job

 

Thanks mate, it's pretty cool being involved in some new stuff over here, especially the little gem about widening the manifold exit. That's a great solution for those not wanting to spend huge $$ on mods.

 

Looks like the rate of return on this mod is greater than installing aftermarket headers. Boring out a whole inch on the primaries is very appealing.

 

Ditto. Thinking about going Monday to see who can fab something up like this. And NO SMELL

Edit - So I'm still learning and I have a few questions. Could an exhaust work (like borla, joe z, etc) with this set up? Also if this is done would it work with RR's tune? Or should I go the traditional route with H/E/T?

 

Yes, imagine if the cats had been gutted like a lot are in the states, would be even better results. Considering RR Racing have pretty much maximised the tune on their car for everything except for widening the primaries, it would be a perfect test bed for ascertaining the gains of widening the primaries. Do it boys :-)

Yeah the smell would kill me, i still think its not great as is, seem to always get exhaust smells in the car. Yes it would work, but you may need to modify the connection point closest to the cats, as i had to in the last few pictures. But definitely would work. If i had a massive budget, then def would have gone headers, they sound awesome.. But as RR Racing have proven, primaries with gutted cats perform just as well if not better. Otherwise they would be using headers, simple as that.

I am VERY confident though that if they wide the primaries that they will be even better..

 

Hi mate, great to see a fellow Aussie tuned ISF. I joined this forum as there is alot more activity for this car vs in Oz where many are standard.

Ive got a cat back exhaust, K&N in the stock box and Apexi throttle controller but otherwise its stock.

I wanted headers but they are very pricey here vs the states. A few went PPE but paid about 3.5k AU. I got a quote from Liverpool exhaust to do custom ones to the similar PPE specs but titanium, better cooling etc for the same price. I was hoping they'd be cheaper.

CPI have offered to tune mine but just weighing my options as this is near 2k. They showed me a dyno of another ISF tuned with a aftermarket filter. It went from 247 to 283 after the tune and showed big gains throughout the rev range at 509NM torque. He wants me to get headers and then do the tune as this would give even more to play with and surely get a better result but thats going to cost about 5.5k :-(

Just weighing up my options what the next BFYB mod will be lol. Might contact Sonny and see what he can offer

 

I'm not sure if I'm understanding you correctly, but RR racing are using headers. I have a few questions about how your tests were performed.

How many dyno pulls did you do for your base line? How long did you wait to dyno after the mods? How many dyno pulls did you do after the mods? Was this dyno at a controlled weather facility?

 

Thank you for sharing this nice mods. Is there a difference before and after the flange mods interms of smell? My muffler shop quoted $250 for the modification. Is this reasonable?

 

Yeah the cost of headers makes your eyes water, throw on a full exhaust and you are looking at $5-6k! Then tune haha! Yeah give Sonny a call, should be able to sort you out!


Oh my bad, i was sure they have been advertising the benefits of a de-catted manifold? Maybe thats someone else..
The dynos and mods were done over the course of a week, so maybe as the ECU learns a bit more it will pull harder, who knows. I dont think its a weather controlled..? Dont actually know. Bu there was a LOT of dyno pulls, some good thorough testing and retesting.


No difference in smell, none at all. That seems pretty reasonable, its a bit of work to do it properly.

 

hmmm.. should I get him to look at mine...

 

Hey Sparky the torque figure don't add up they are only 505 nm at the fly ( i said on the oz forum they seem high for a 5L ) its a pity i would love 650nm standard what do you reckon.

 

Yeah you are spot on, maybe if it was supercharged it would be! I think the main thing I was trying to iterate was that the figure aren't important, just the % increase.

They went up around 10% for power and torque, which is awesome, and extremely noticeable in both day to day driving and fun time.

But yes, if that torque was a reality, would be rather nice haha!

 

Nice write up! Good inexpensive mod for decent gains! thumbs up man!