Piston Slap: A hotter cam for the dirty diesel?

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white VW Jetta dynamic action front three-quarter
VW

Jon writes:

Do you know which would be the best replacement camshaft for the BRM engine in my 2006 VW Jetta TDI?  I’ve been told that in 2005–06 VW camshaft suppliers had bad steel in some. I have done oil samples since the car was brand new. I will see on the next sample at 7500 miles. The car has about 162,000 on it. It’s mostly stock; I have a G-force chip added 10 years ago, which I love: It picked up 5 mpg with it; I get 39 mpg (A/C off) in the city!

Sajeev answers:

Now hold on a second!  You don’t need to change a BRM camshaft because it might fail.

Will it actually fail, as your frequent oil sampling suggests you’re religious on regular maintenance? And even if your maintenance regiment cannot save the camshaft, you can wait until it wears enough to trigger drivability issues: a check engine light, reduced performance, or a bad idle. Which you’ll likely experience before yours sounds like the example below (skip to 0:24).

If you really want to know your camshaft’s health, get a smartphone-enabled endoscope or pop off the cam cover: look for signs of wear (scoring, some lobes are flatter than others, etc.) before considering replacement. I see no mention of an improved camshaft available from VW, but as you mentioned, the aftermarket has you covered. Even better, most alternatives likely improve power with no engine re-tuning needed to remain legal. Such is the perk of driving an older, emissions-exempt TDI vehicle!

The only problem?  Finding data on each vendor’s actual improvement on an engine dyno, using the same components elsewhere to get a level playing field. It’s not like you can open up a copy of Hot Rod magazine and get the data, as this is far from a small-block American V-8. (If I didn’t Google and forum search this correctly, I’d love to be proven wrong!)

That said, for a street-driven TDI, remember that bigger isn’t always better. Febi, Colt, and Frank06 make aftermarket cams, and they all have fanbois online. I’m leaning toward the Frank06 kit as it modifies the cam bearings to address the TDI’s inherent oil flow issue. If a camshaft doesn’t come with improved bearings, I’d pass on it.

No matter what you choose, odds are you won’t see a big improvement until you upgrade the turbo. Modifications are fully exploited when multiple, complementary parts are added; the camshaft will definitely make a big impact at some point.

But if failure of the stock cam is your only concern, do nothing until you experience drivability issues or a check engine light.

Have a question you’d like answered on Piston Slap? Send your queries to pistonslap@hagerty.com, give us as much detail as possible so we can help! If you need an expedited resolution, make a post on the Hagerty Community!

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