Thread: Exhaust system....I need your ideas?

OK, after travelling up to Crail Raceway on Sunday (a round trip of 150 miles), the one thing that bugged the s**t out of me was the drone from the exhaust.

Having the side exit exhaust as pictured below, is excellent for producing maximum power, but the noise on long distance driving is just too much. It also attracts the attention of the Police, and I just don't need the hassle to be honest.



My neighbours also don't think much of the noise, so I need something new and improved.

What I am thinking of doing before I make the long trip down to Shakesphere County Raceway (5 hours drive away) is going with the biggest possible downpipe (probably an initial bend of 3.5" like I had on the Micra before the crash, as the alternator is very close) then going up to a 4" system, or going with a dual 3" system.

I would be using multiple silencers as I do not want the noise anymore, but still want to retain the power. I recon with 4" piping or twin 3" systems that the back pressure will still be kept to a minimum and the power will not suffer.

But will it fit under the car and over the rear axle...that is the question!

My car (the N15) uses virtually the same chassis and floorplan layout as the B14 SE-R.

Please give me your opinions.

Thanks

Dave

That's way too excessive. Just stick with a single 3" and you'll be good to go. 4" is rediculous for our cars, and dual 3" is even more rediculous. You want flow while keeping velocity up. With too large an exhaust you lose all your velocity thus losing power. Stick to a 3".

For a 400whp FWD B14, 3" is just fine.

3" is fine to 500 or more.

Im liking that side exhaust...
any more pics?

and yeah you can stick to a 3" exhaust

Why not do a 3" all the way back with a 24" resonator with a nice muffler and just put a cutout where the DP meets the cat(where the cat would be). Quite for daily, open the cutout and have a open downpipe for when you want to have fun.

Incorrect. Please don't spread this bad information.

I agree. While I'm a big proponent of huge exhausts, I don't think you've outgrown a 3" full length exhaust at 400 WHP yet. I recommend a 3" system the entire way. If you plan on going for way more power then maybe I'd recommend larger. What are your plans? Keep things the same for a while, or going for more power ASAP?

That's pushing it. Yes you can make 500 or even 600 WHP on a 3" exhaust but you're really choking that engine at that point. By 500 WHP I like to see something larger than 3" for sure.

I was always under the impression that 3" became a restriction (i.e. excess back pressure) at about 350 WHP. Since I had a very short side exit system, with a single short muffler, I always assumed that it would give me a bit more to play with.

The only down side with this setup is the noise!

My car makes 403 WHP in 5th gear, so probably more like 420ish WHP (as would be measured usually in 4th gear).

I thought that in order to keep the same power, while reducing the noise, that I would have to go for at least a 3.5" system, or maybe even more!

So you're telling me that the exhaust professionals are full of sh!t?

You want to maximize flow while reducing back preassure. However, maximizing flow over velocity can end up impeding exhaust gas scavenging and overall flow. I wasn't aware that you just wanted to have the largest exhaust possible and not worry about efficiency.

I take back my original post. Just go with a 5" and call it a day.

You're correct when relating to exhaust gas in header primaries or secondaries or exhaust gas previous to any merges. However, once the exhaust from all cylinder banks is completely merged you will want the largest exhaust you can fit and afford. Ideally, you'd want an open exhaust (maybe with a horn on the end) immediately after the last merge.