A quick question for anyone with an adjustable Borla.
My new catback will arrive soon but which plate will give the best results, if I go for straight through (no plate) will there still be enough back pressure so that I don't reduce power?

 

You might move the torque up a little higher in the powerband, but you aren't going to ever reduce power like that.

Mike

 

Thanks, straight through it is then.

 

Needing backpressure for torque is a myth.

 

I have a cutout, I can definentally tell you there is more jump in the car throughout the powerband when i open it which is why i run it open all the time.

We have done straight pipes on quite a few friends cars and they all seem to like it and report more power.

Only thing you have to worry about is some engines require a little bit of backpressure to prevent valve float which wont bea problem for you.

 

An open exhaust will reduce low end torque. It's not a myth, it's a fact.

 

You dont "need back pressure for tourque". What you do need is an exhaust system designed to give you tourque WHERE/WHEN you want it. If you want the tourque off of idle for towing and such then get a smaller diamater exhaust. If you want tourque up high for high horsepower then get a larger diamater exhaust. As far as restriction goes I'm pretty sure it's a moot point. You would want the lowest restriction (bends, turns, kinks, baffles etc.) possible in either system.

Also, the only thing back pressure could possibly do to influence valve float is to make it worse, the valve has to close against the pressure of the exhaust system which is fighting to keep it open so less would be better in this instance. Then the valve has to open but I kinda doubt that back pressure is going to compress a valve spring instead of opening the valve. If you have valve float, get stiffer springs and lighter valvetrain equipment, dont change your exhaust. That's my take on it anyway, where did you hear that some engines need it?

 

My old '99 put down 346.4ft/lbs of torque at the wheels with the Borla wide open and no cats on the stock manifolds (talk about little to no back pressure). It did move up, but only a little to about 4,000 RPMs (which is only 400RPM's above the stock rating I believe). He's still going to have his cats (I'm assuming), which is where the back pressure lies in most aftermarket exhaust systems these days. Run it open and have fun!

http://memimage.cardomain.net/member...31_68_full.jpg

 

just for kicks here's a little 'backpressure' test if you want to call it that. here's my borla w/small open plate vs bassani tru-duals test i did on my wife's 99 formula.
http://www.stealthram.com/familypics...avsbassani.jpg
didn't seem to lose anything going from a single 3" to a dual 2.5"

 

might see a difference at below idle to about 2000, but after that it would be fine. i don't think you'd lose torque anywhere thru the RPM band though, with the open plate.

 

Backpressure or not just tweeks the TQ curve. No BP and you will get High RPM TQ, some BP and you will get low RPM TQ. My low RPM TQ is incredible. I've heard the mid plate is the best. I think mine is WO. Sounds NICE at WOT w/ my catted LT's ..... It sounds COMPLETELY different from the outside. I had a friend get my drive by on video.....!!!OMG!!!

 

Your only shifting the curve