G'day gents, So picked up my brand new RS 275 Cup Premium at Christmas 2016. Pearl White with sunroof. I've done about 3,000kms so far and loving it. In Australia the Cup Premium has basically every option except the Ohlins Coilovers. Mods to date; *3M Window tint *Opti-coat Pro + paint protection *Advan AD08R tyres in 235/35/19 *1,000km oil change [emoji57]because old habits Future mods for the coming months; *Custom Dyno Tune *BMC panel and foam remove *Endless Brake fluid Wishlist; *Downpipe with cat + flex pipe *Braided lines *KW Clubsports *investigation into E85 tuning Cheers guys Robbie Sent from my iPhone using Tapatalk
Hi buddy, welcome along. The dealer put a tarp over my Trophy on delivery, but I didn't think of getting a cheesy picture... Car looks great and nice plans.
Haha thanks mate, it didn't happen unless you get the cheesy photo! All I could think was, cool, now I have to drag this paint scratching sand paper tarp over my entire paint work. Sent from my iPhone using Tapatalk
You're thinking of doing the flex pipe also rather than leave it standard to have the down pipe with cat join the OEM flex pipe?
Hey mate, Correct, when I undertake the downpipe swap I'll be doing the flex pipe section as well. It would defeat the point a bit to gain better flow off the turbo but then try to jam it into the oem 1.9" flex pipe opening. I assume it's ok now because of the cat restriction so flow isn't hampered but with a bigger dump and 200 CPI cat I can see it hurting. Sent from my iPhone using Tapatalk
So the flex pipe that comes with the Akrapovic is not 2.5"? CGR can do either a 4" cat body with 200 cell (most restrictive) or a 5" cat body with 100 cell (least restrictive). Both may throw CELs but the 4" 200 less likely to.
i have a de-cat CGR on its way, will be going 2.75" straight through to stock rear box - cheap and best chance of no drone is the stock box from what i have found in the past. Will see how it goes and then it will be tuned when Paul is out in April
I'm not 100% sure any more to be honest mate. I thought it might be bigger but CGR advised from the photo only they think it's the same as a 250 flex. Would love it if some one with a akrapovic measured there flex pipe inlet haha Sent from my iPhone using Tapatalk
Looks like you may need to bite the bullet and decide what to do with the flex pipe when you fit the down pipe.
OK here is what i have learned from my de-cat/exhaust changes i wasn't going to make ! CGR de-cat - awesome piece of kit, relatively cheap, very very well made, PITA to get stock cat out - needed to take drive shaft out, disconnect hub and remove scuttle (no i didn't do it myself...) Flex pipe - this is a bugger, hard to get to unless taking downpipe out, so didn't end up getting a bigger flex so far, definitely do this when installing de-cat, which means you need an exhuast shop who can do the de-cat or get a pre-made system so you can install the de-cat and exhaust at the same time. Overall - decat is great, significantly louder,, revs faster and seems to pull better everywhere. I would definitely retain a back box, would even consider a centre res to keep down the pops as it pops pretty much non-stop and is a lot louder now. If you are going to get a de-cat, i would get the whole exhuast fitted/modified at once. From what i have seen, i would go the CGR de-cat and full system, not the cheapest but i feel it would all fit properly and work as expected.
Changing the flexi won't make any difference, I'm running a hybrid at 365bhp and still have a stock exhaust
Jamie, thanks that's good to know - there has been some debate that the flex restriction (seems to be only 47mm ID) could be an issue.
I'm assuming you're so sure about this because you've used an OEM flex and an aftermarket flex and tested on the same dyno on the same day?
No I'm so sure about this because I'm pushing 365bhp thought it. Far more than any of the others in this thread. I will be going for a custom system and shall do a before and after just to see if it is actually a restriction, if it is it will only be a handful of bhp anyway. Main restrictions the cat.
So actually changing the flex may make some difference. It may not make any difference to peak power but there's more to performance than that. It may make a difference to flow in certain parts of the rev range which will then impact EGT and torque at certain RPM. So until someone does before and after runs with a changed flex, all we can do is a best guess. Kind of like flywheel power figures taken from a chassis dyno.
Did you find any issues with the 3 inch decat joining the flex piece? All joins up ok? On the flow restriction topic - my two friends both have Evo X Final editions, both got tuned by same company, one has a hiflow cat - stock exhaust, the other same high flow cat but matching after market catback back. Looking at their dyno graphs, both 100% identical power and torque up till 5,300, then the aftermarket cat back picks up a peak of 20wkw in the top end. So around town, no difference. It's only when you're really in it that the flow is a restriction for the last 2000rpm. I wonder if in our case though the turbo may not flow as much, so we may not see as much of a restriction up top on the factory flex pipe and a hiflow cat due to the less flow restriction over a hybrid or bigger turbo requirement. Sent from my iPhone using Tapatalk
You're right Robbie, and as Jamie has said, the biggest restriction is the engine pipe off the turbo. However, even with a bigger bore decat the Megane engine pipe is still a restriction with its twists and turns. A 90 degree mandrel bend 3" pipe still doesn't flow as well as the equivalent straight pipe. But then compared to Evos and STis our turbos are tiny.
