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Tech & How-to



Ask anyone who knows what makes motors run, and he’ll tell you the name of the game is getting as much fuel over the piston as possible and burning it as completely as you can at just the right moment. How much fuel you can burn depends on how much air you can get flowing in and out of the engine. And since you can’t flow more air through the motor than what the air cleaner will allow in, it’s easy to see that the wrong selection up front is going to hurt you big time. That’s why we’ve been doing a number of air cleaner installs in American Iron; this easy-to-do garage upgrade can reap you a nice increase in power. And if your bike is a 2007 or later model, like our test 2007 Softail Deluxe test bike, you don’t need to install a fuel adjuster. Unlike on earlier models, the 2007 and later machines have an O2 sensor in each exhaust header pipe. This enables the stock ECM to sense how the engine is running — too lean or too rich — so it can make the needed fuel setting changes. Of course, the ECM will keep the air/fuel ratio at the EPA-mandated 14.7:1 (14.7 parts air to one part fuel), so the engine will run just as it did before the air cleaner installation, but with more power. How much more power is what we wanted to find out, so we also put the bike on a dyno, but we’ll get to all that in a minute.

The latest in our quest for higher power brings us to Wimmer Performance Triflow air cleaner assembly. The Triflow design is as simple and unrestricted as you can get and still actually have a filter element in the equation. Made of CNC-machined billet aluminum, the Triflow comes in two versions, Stage I and Stage II, and fits all EFI-equipped H-Ds, including 2008 models. We opted for bolting on the Stage II unit, which comes with a slightly wider air filter element and an internal velocity stack. Wimmer claims these upgrades increase air flow over the stock air cleaner element by 70 cfm. That much of an increase should show up as a power increase on the dyno. We also went with the chrome outer trim option, but passed on the rain sock.

As for who would do the installation — though this air cleaner job is simple enough for a home garage — we went to see out buddy Mark Fabrizi at Marquee Customs. Mark has done many an installation story with us, as longtime readers know. We also asked our buddy Rob of Rob’s Dyno to do before and after runs, so we could know exactly what power increases we realized with this installation. By the way, it was about 95 degrees Fahrenheit that day: not the best for performance output. Thankfully, the humidity was low. The accompanying dyno chart tells the tale!
–Chris Maida, as published in American Iron Magazine, the world’s best selling Harley magazine.

3/16″ Allen Wrench
5/16″ Allen Wrench
5/32″ Allen Wrench
Red Loctite
Blue Loctite

Marquee Customs & Classics
72 Siemon St., Dept. AIM
Bridgeport, CT 06605

Rob’s Dyno Service
Dept. AIM
Gardener, MA 01440

Wimmer Performance
11690 Highway 17 Bypass, Dept. AIM
Murrells Inlet, SC 29576843/492-0412

1 Our opening shot shows our test 2007 Softail Deluxe up on the lift at Marquee Customs. Rob has already done the baseline runs, and Mark has removed the stock air cleaner assembly.

2 After placing a new stock gasket on the face of the throttle body, Mark uses a 3/16” Allen to loosely attach the Wimmer backing plate to the stock throttle body using a little blue Loctite and three Wimmer-supplied bolts.

3 The Wimmer-supplied spacers, complete with O-rings, go between the backing plate and heads. Mark uses a 5/16” Allen and a dab of red Loctite to secure the two Wimmer-supplied bolts.

4 Once all the bolts are in place and the backing plate is properly spaced from the heads, Mark tightens all the bolts (both the 3/16" and 5/16" Allens) to H-D spec.

5 The Wimmer internal velocity stack can now get popped into position in the throttle body venturi and over the three backing plate screws.

6 Mark then presses the Wimmer filter element into the inside face of the outer cover, which has a recess for the element. Make sure the element is fully seated in the outer cover’s groove.

7 The outer cover, complete with chrome cover, can now get bolted to the backing plate using the two Wimmer-supplied bolts, a little blue Loctite, and a 5/32" Allen.

8 Here’s how the finished installation looks. Pretty slick! But this setup is not just for show, as the accompanying dyno chart reveals! AIM


1 Comment

  1. Rebel June 27, 2010

    Great article but where’s the dyno chart?

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