Performance Exhaust Testing On The Royal Enfield Hunter 350
The Royal Enfield Hunter 350 is an environmentally friendly little chap, but is the cat (catalytic converter) a hungry beast that's stealing away valuable performance?
Or is that standard silencer holding him back.
I spent some considerable time testing both of those things out and here are my results so far...
I admit it, I’m addicted to tinkering with my bikes and I was keen to know if it was possible to extract a little more go out of the Hunter 350. My first stop was to fit the DNA air filter and cover. You can read more about that
HERE.
Next, after getting more air and fuel in was to see if it was further possible to help the bike breath by changing silencers and down pipes.
For those of you who prefer watching to reading, this information is also alavilable in video form. Follow the links below:-
Downpipe Testing
Silencer Testing Std Down Pipe
Silencer Testing Delkevic Down Pipe
First stop was the purchase of the Delkevic stainless steel down pipe. This is much lighter than the standard down pipe, which is double skinned and fitted with a catalytic convertor. It also has a larger internal diameter. Fitting the pipe was delayed as I struggled to work out how to disconnect the lambda sensor from it’s mounting bracket. It would have been more obvious if the tank was off, then I would have seen the little tag that needs to be depressed. But, working from underneath, it took me a while to figure out what I needed to do. Once I’d got that sorted, I then found that instead of the exhaust nuts playing nicely and coming undone, one of the head studs insisted in winding itself out instead.
After sorting out those problems, it’s then fairly easy to swap the pipes over, so the first test was to test each down pipe using the standard silencer.
My test is a third gear, wide open throttle acceleration test, measuring the time to accelerate from 30mph to 50mph using the Dragy GPS performance meter. The test is repeated several times and then an average calculated.
The results showed that with the standard silencer and DNA air filter and cover fitted, the 30 to 50 mph acceleration time was 0.14 seconds quicker.
With that tested, it was time to try some different silencers. I don’t like the design of the Delkevic end cans, they look a bit too shiny and modern for the Hunter, so I went instead for a cheap, short universal can from Amazon and a universal SuperTrapp - which is billed as being tunable by adding or removing outlet discs.
Getting them to fit was another matter!
The SuperTrapp fitted over the standard exhaust gasket, but so tightly that I couldn’t get it off again! Eventually it was removed using a slide hammer affair bolted on in place of the outlet discs, but unfortunately also taking the gasket with it! For testing purposes, I decided to make up some split, steel sleeves to take up the gap and allow me to be able to switch quickly between silencers.
The Shorty can from Amazon required some modification to fit. Design to fit using loops and springs, I modified it so that it would clamp on and then made up a spacer so that it fitted snugly to the standard down pipe.
Both silencers required new mounting brackets to be fabricated.
With everything set up for ease of mounting and removing out in the field (actually the car park of a village sports field close to my designated test venue) it was time to go testing. Same test as before, 3rd gear 30 to 50 mph acceleration test.
The result of all that testing? A measly 4 hundredths of a second!
Although not perhaps the first choice of silencer to fit to the Hunter, I believe the Shorty and the SuperTrapp are representative of a typical aftermarket ones. Both are fibre packed around a perforated core with minimal resistance to flow, the SuperTrapp just goes a bit more upmarket with its outlet discs. And while the performance doesn’t change much, the noise does, with these producing a much deeper thump than the standard silencer. They also produced a greater volume of noise, with the tiny Shorty being the biggest (loudest) culprit here. That being said, you might be able to live with it…
After the slight disappointment with the silencer test results on the standard down pipe, it was then time to try them all again on the Delkevic pipe.
This required another bit of fabricating as the SuperTrapp didn’t want to fit the slightly flared end of the Delkevic link pipe. Eventually, this was solved by the purchase of an exhaust bend that did fit the SuperTrapp and, after cutting it to the required length, it was finally in place, but only after another bracket was made!
The standard silencer fitted straight on - as you would hope - and the Shorty fitted with the aid of the previously manufactured sleeves.
Time, then, for more testing.
Would it be more fruitful this time?
Yes, is the short answer.
This time the Shorty was 0.2 seconds quicker than the Standard silencer. The 6 disc SuperTrapp was similar to standard, with the 12 disc in between the two.
It’s worth noting that you can’t compare tests done on different days as weather conditions etc. will have a bearing on the results obtained. That’s why I change silencers out in the field, so that the tests can be run as close together as possible and so under (hopefully!) the same conditions.
I then did another round of tests after modifying the Shorty to take the SuperTrapp discs and making open end caps of different sizes for both the SuperTrapp and Shorty.
All of that work didn’t really make much difference as you can see from the results.
For the moment, I’ve decided to stick with the Delkevic down pipe and the SuperTrapp with 12 discs fitted. The Shorty, in any guise, is just too noisy for me.
