BMW M3/M4 Downpipe from Zima Motorsports

My friends at Zima Motorsports just released a new downpipe for the M3/M4 BMW. Now that BMWs are turbocharged, one of the best mods you can do is to put on a better flowing downpipe. But before we get into Zima’s new product, lets ask the basic question. What’s a downpipe and why do you want one?

ZIMA M3/M4 downpipe 2

Technically, the “downpipe” of an exhaust system connects the headers or exhaust manifold to the catalytic converter or muffler section. For most vehicles, the downpipe section is essentially incorporated with the catalytic converter section, and since there’s very little performance or fuel economy benefit to replacing a modern catalytic converter on a non turbo engine, no one really knows about them.

Zima M3/M4 downpipe installed

But on a vehicle equipped with a turbocharger, an after-market downpipe can make serious power increases. An engine is basically a pump. The more air you put into the pump, the more power you put out(huge generalization but good for explanation). And a turbocharger and you increase the amount of air going into the pump significantly. Mostly because the turbo is essentially a smaller pump which compresses the air to fit in the larger pump(the engine). So its important that the turbo is free to cram as much air into the pump as possible and the best way to ensure that is to open up any restriction into and out of the turbo.

By reducing exhaust gas restrictions, the turbocharger can spool up more quickly. Faster spool-up times mean more power and/or better fuel economy. On many turbocharged vehicles, the exhaust pipes coming in and out of the turbo contain numerous bends. The factory needs to make compromises between effluence mass production and performance. So a downpipe  with numerous bends and kinks can restrict exhaust gas flow in and/or out of the turbo. As a result, many after-market exhaust manufacturers offer over-sized exhaust downpipes with mandrel bends like the ZIMA pipes shown below.

About Zima’s M3/M4 Downpipe:

Rather than sell you guys on it, here is what Zima lists on their site. But I can tell you its a good thing their downpipe as

“The Zima Motorsports F8x M3 | M4 Downpipes are the ultimate solution for the ultimate driving machine. With an increase in exhaust note over stock and better throttle response these are the perfect solution to waken up your S55 engine. Design, fitment, and quality were all taken into consideration and these fit in position just like the OEM downpipes.”

Zima M3/M4 downpipe comparison

“The factory downpipes utilize a flex pipe which is crucial in aiding flex to the down pipes while under acceleration. Some competitors have not added the flex pipe but we have taken initiative and added one to ours. Being Twin Turbo’d the S55 engine produces a lot of heat in the engine compartment. With that in mind we had our down pipes ceramic coated so they emit less heat while driving by your feet and transmission while keeping the heat inside the downpipes as well.

Specifications :

  • 100% 304 stainless steel construction
  • For off-road use only; not legal in all 50 states
  • Lifetime warranty
  • Please note:The installation of our downpipes might cause a fault code in the car electronics. More information upon request.

$1,085 and you can buy it direct from Zima Motorsports.

Bill Caswell is a self-taught racing driver, mechanic, and fabricator, and rose to internet fame taking a $500 Craigslist BMW to a World Rally Championship event in Mexico in March of 2010. His exploits have featured in places like ESPN Magazine, Grassroots Motorsports, NPR Radio, Wired.com and Jalopnik.com. A lifelong fan of rally and motorsport, Caswell famously believes nothing to be impossible.