Review: Greasehouse Growler - Royal Enfield Interceptor Exhaust

Royal Enfield and modifications go hand in hand. In fact, the company offers multiple customization options across its bikes. The one modification that many owners seem to want is louder exhausts. But good exhausts are not easy to get, and most aftermarket exhausts you get aren’t really all that well made.

To address this, our friends at Indimotard’s Greasehouse Customs have made slip-on exhausts for the RE 650 twins - the Growlers. So we spent a lovely weekend afternoon installing them on our long-term Royal Enfield Interceptor 650 and a few days riding them around Pune to find out just how loud they are, whether they make a difference in performance, and if they have any impact on fuel efficiency as well.

Installation

Installing these exhausts is an absolute breeze. A couple of spanners is all you need to take off the stock exhausts and fit these Growlers. And immediately, you’ll realise how heavy the stock mufflers are -- 5.1kg each. These Indimotard exhausts, on the other hand, are just 2.3kg each. As Lotus’ founder Colin Chapman famously said, “Simplify… and add lightness”. After installation, all you need to do is let the engine idle for about 20 mins, and the ECU will automatically calibrate itself for the new exhaust flow.

Sound levels

Now, coming to just how loud these new exhausts are…the stock exhausts of the Interceptor are surprisingly quiet. But the same can’t be said for these Indimotard mufflers. The following tables will give you the sound levels we recorded in our semi-scientific test (basically using a dB app on our phone inside our studio).

Sound levels	Stock Exhausts	Growlers (with dB killers)	Growlers (without dB killers)
Idle	79dB	89dB	91dB
3,000-3,500rpm	90dB	103dB	106dB
Near Redline	96dB	119dB	121dB

Honestly, these sound levels make these exhausts highly illegal for road use, and we’d recommend them only for track use.

Performance

So do these make a difference in performance? Greasehouse claims about 7-8 hp extra, but we can’t really vouch for that because we couldn’t do a dyno test.

Acceleration	with stock exhausts	with Growlers
0-60kmph	3.21 seconds	3.03 seconds
0-100kmph	7.45 seconds	6.96 seconds

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But we did test on a VBOX, and the run from zero to 100kmph is about half a second quicker. Now that might not seem like much, especially at lower revs, but the engine seems to rev more freely and feels more unrestricted. In fact, you’ll find yourself hitting the limiter more quickly and easily. So when you’re riding faster, you can really feel the difference in the way the bike responds.

Roll-on acceleration	with stock exhausts	with Growlers
30-70kmph (3rd gear)	5.10 seconds	4.66 seconds
40-80kmph (4th gear)	5.83 seconds	5.19 seconds

In our roll-on acceleration tests, the difference in performance becomes even more apparent. You’ll find the Interceptor responds between half to one second quicker when it comes to in-gear acceleration.

Fuel Efficiency

It doesn’t make a massive difference at highway speeds - you might get a couple of kmpl more. But at city speeds, the difference is even more -- we got about 6-7kmpl more with the Growlers than we did with the stock exhausts.

Fuel Efficiency	with stock exhausts	with Growlers
City	25.35kmpl	31.95kmpl
Highway	33.17kmpl	34.64kmpl

Handling

With 5.6kg off the back of the bike, these exhausts do affect handling. Overall, the Interceptor felt much lighter with these Growlers installed. So, while attacking corners or filtering through traffic, the Interceptor did seem a lot easier to handle.

Legality

So now the big question - are these Greasehouse Growlers road-legal? Well, unfortunately, these haven’t been homologated for road use. While we don’t condone it, you might get away with using these with the dB killers installed. But they can still be cop magnets, especially in cities like Mumbai, so we recommend you keep these exhausts purely for track use. But because they’re so easy to install, you can just slip these on every time you’re going for a track day.

Price & verdict

These Greasehouse Growlers cost about Rs 11,000 and can be ordered from the Indimotard online store. We think they’re well worth the price because they’re very well made - solid stainless steel finish everywhere, and, of course, they look and sound good. But as we mentioned, they’re not road-legal, so use them on public roads at your own risk.

But if you’re getting your Interceptor, or even better, your Continental GT ready for track use, we recommend these wholeheartedly.