I spoke to 2 tuner-retailers today. For purposes of fairness and anonymity, I will say that both tuners were people who not only manufacture their own branded items, but also carry other brands. Neither seemed particularly pushy with their own items, but they each had opposing opinions on the best way to tune the R56.

One tuner who seems to specialize in no B.S., top-notch quality items explained that a 2.5" exhaust, including downpipe, is the best way to get power out of an R56. He explained that a 3" system will actually lose power in the low end, where one actually would like to see the greatest gains. This tuner also explained that either of the 2 piggyback ECUs on the market basically offer minimal short-term performance gains at the expense of long term reliability and stability. He explained these piggybacks are not true ECU remaps, but basically simple profiles that "trick" the car sensors into thinking it needs to run leaner, etc...He also shared that he has numerous customers who have had to send in their piggybacks up to 5 times for repair/replacement. He seemed equally critical of both brands, and did not distinguish between them. His performance mod suggestions basically focus on the turboback exhaust and suspension upgrades. He further suggested waiting another 6-12 months for a full turbo replacement and a proper ECU module, both of which are in development by multiple sources. He also said any CAI unit is more for aesthetics and sound purposes than performance purposes.


Tuner #2 admits the piggyback basically tricks the computer into running leaner, but claims there is absolutely no problem with this. He suggested that running a combo of ECU piggyback, cat-back exhaust, FMIC, and CAI pushes the R56 into 240+HP. He pushes a 3" cat-back exhaust system and says the turboback is not necessary for the car, and in fact is negative in many ways. To be fair, I did not ask as many technical questions of this tuner since I was in a hurry to get somewhere.

Who am I to believe?

 

What color is the sky, is it blue? You can show data that it is blue and that it is not. You can debate anything anyway. I know a 3" or a 2.5" on this car you will not notice a significant difference in power etc. One is insurance for future upgrades, the other is for current levels.

 

Oh yeah, you will not be outflowing a full 2.5" setup anytime soon with your stock turbo.

 

Actually, I seem to recall seeing several logical and convincing posts that explain exactly why a 2.5" system is preferable for the R56.

IIRC, isn't your system 2.5" at the turbo and 3" towards the back?

BTW, I am very interested in your system because it sounds great. However, I am not keen on chinese or other inexpensive parts. Where are your components sourced? Assuming it's China or other similar low-end country, would you be willing to assemble a "high end" version?

 

No, its 3" up front and 2.5" in the back. It comes out hotter so you want bigger up front. A 2.5" is fine though , i made it 3" for insurance.My price is low because we bend in house http://photos.revenanteagle.org/cache/car/Aarons%20FMIC/DSC_2561.jpg_768.jpg and cut in house http://youtube.com/watch?v=BuIwW7OsIzg not because its china stuff. I use Magnaflow mufflers. made in teh good Ol USA. I use walker tubing which is also from america and i make my own flanges. :

 

It's pretty obvious (i think....) who you probably spoke to.

I follow the tuner #1's train of thought...

 

x 2 Its not me by the way!

 

Following this thread (apols for the minor hi-jack)
If we are running stock turbo but with uprated boost (piggy back ecu /remap etc), do you think that a stock cat back would be sufficient in flowing the turbo gasses out? Or would you reccommend going upto 2.5" to cope with the extra flow?
What I am asking is do you think there would be much performance difference of having a stock downpipe linked up to a stock cat-back vs having a stock downpipe linked up to a 2.5" cat-back?

Will a remapped R56 turbo produce enough flow to require more than the standard system can offer, and does this become a restriction?

 

it sounds like #1 makes sense. That is until the CAI claim. It has been proven on dyno's that a CAI does provide more power with a free flow filter.

 

I have to agree with the 2.5 exhaust. When we made our WMW exhaust we tested several versions and decided the 2.5 was the best. You'll see the greatest gains with the Full turbo back system, there isn't much in just the exhaust alone. We argued over the 2.5 or 3 inch exhaust awhile ago and I've always said 2.5. Hope thise helps you decide on exhaust.

 

2.5" isn't a restriction on a 2.5l Subaru turbo motor so it's hardly so on a 1.6l MINI a/ tiny turbo. Perhaps someone has measure the exhaust on the Jcw stg II? That will certainly be an indication of what point the catback is a restriction

 

So what does the JCW remap do? Just make the engine run leaner?

Maybe these engines are fragile, but I have always run a little lean on my cars to increase power. You have to balance risk with power. The more power you want to make, the more strain you are going to put on a motor. IMO, I still think it is too early in the game to understand what mods will work best. For me, there is no need to drop a ton of money on mods that won't bring my car up to the level of a bolt on LS1. In fact, I am only adding mods that are helping with efficiency. I'll just wait until they come out with some bigger turbo options.

 

Put that bolt on LS1 on a road course with a stock r56 and see what happens. Really bad comparison, but with that said I believe the 2.5 theory is right. I did go with 3" for insurance and was the same price!!!

 

I don't roadcourse, so I don't make that comparison.

 

Hmmm .... Interesting discussion.
: )

 

2.5" good for stock turbo all day long, 3" insurance.

 

Even remapped stock turbo pushing more air out?

 

2.5 exhaust is used on 350 H.P. cars with no problem.

 

What about the theory that 3" reduces the backpressure TOO MUCH, to the point where you lose low-end power?

 

it's a turbo motor....the downpipe is where that matters, not the catback section so much. If someone is saying 3" on the catback but leave the stock DP, well, it's clear they're after one thing and it's not power (hint: it's green and in your wallet).

 

Backpressure is still a myth, however turbulence, flow velocity, and scavenging are highly relevant factors in exhaust tuning.

 

Ill raise you 50. Eclipse back in teh day did 400hp on 2.5"

 

Like i said, my personal preference is a 3" dp for insurance reason. I can make both and dooing a 2.5 is easier on me (less tooling change) but if its my car I would do 3" DP for insurance.

Some peeps say they loose low end tq but i dont care, you pick it up in teh middle on the top which is where I prefer it. If you want more tq down low, raise your boost and call it a day.


The turbo provides enough back pressure for the head and the back pressure changes as rpm goes up.

 

Great minds think alike.

 

Less back pressure after the turbo, the quicker it will spool. Flow velocity is the key here.