Tech Torque:

We have now reached the final part of our Clubman Dyno test series. With just a Ron Moss prototype and a standard factory pipe left to test… it should all be straightforward, right?

Darrell Taylor unleashes the fourth part of his in-depth Clubman Dyno series.

BEST LAID PLANS AND ALL THAT…

We had hoped to have a Gori sport and the latest BGM V4 to test, but they didn’t transpire in time for press deadline. Despite this shortfall, we knew that initial tests by others in the industry suggested the BGM V4 might be a little quieter than previous incarnations, and as a result has lost just a small amount of power. The Gori line-up has the tiered product range of sport to racing to new GP50, which suggests it may be the case (performance wise) that the sport sits below the other two that have followed that trend. But as and when these pipes show up, we may follow up this report and include them. So that just leaves us with the standard Italian GP exhaust kindly supplied to us from Craig Standeven (LCGB committee member) and a development prototype pipe delivered directly by Ron Moss.

TESTING

As before, each dyno run meets a strict testing regime, to attain accuracy of results worthy of comparison. Unless noted otherwise, the dyno graphs displayed for each pipe tested are in red, compared to a standard SX200 in blue and a JL3 expansion pipe in green (as our upper and lower BHP benchmark) providing us with some useful indicators that most riders can relate to. The JL3 and all test pipes are being tested on a GT 186 kit, with 60mm crank (193cc) and 28mm carb.

STANDARD INNOCENT I GP EXHAUST

The positive benefits of a standard factory exhaust system and how nice a ride it provides are often commented on, and Craig (the pipe’s owner) is also a firm believer and living proof of its roadgoing characteristics. He has used this pipe on his SIL200 motor for thousands of miles and is very fond of its power delivery although he has yet to try an alternative pipe to find out if, indeed, he is living in the dark ages, or if this pipe really has ‘something extra’ hidden up its sleeve. Craig runs the engine/pipe on a TV200

gearbox, meaning it is a ‘tall geared’ box that most high-powered/revving motors struggle to pull effectively, but states it’s a very willing performer on his set-up. So what’s it all about? Well it’s got a small bore header pipe for a start, that previous tests have shown good for bottom-end power, but loses out ‘up top’. So expect it to be strong from the off. The pipe fitted up nicely to our test motor, as you would expect an original to do. First observations on the dyno test showed it to be more willing from the first touch of the throttle, with great bottom-end, and although this tailed off, it continued to rev out to quite a high rpm range. The result was an initially disappointing peak of 12.5hp and was considerably down on power against all other pipes tested. But… take a closer look at the graph, it reveals something quite amazing. Up to around 5000rpm it has outperformed EVERY other pipe on test so far in this four-part series. So, coupled with the correct gearbox and final drive set-up, one that can get the most from that 5000rpm (and over-rev), then it can make for good speed and progress. Cheeky.

RON MOSS EXHAUST :2017 PROTOTYPE

This British made ‘cottage industry’ pipe from successful 70s’ scooter racer Ron Moss has received a revamp in an attempt to catch up with recent advances from BGM, Gori and others. These are not up for sale yet, but expect to see a retail price of about £275 when released. The previous pipes were made in small batches since around 2011, but Ron recalls developing prototypes more than 46 years ago, from as early as 1971, for racing on the Isle of Man, so Ron has a few years’ Clubman development under his belt. He states the new version will also have a ‘loose chaincase bracket’ and will offer some adjustment upon fitting.

So what of this one? Well, his old pipes ran high-rpm with good peak power, and thus worked well on gearing set-ups of 5.1 and above, with the extra top speed being gained from that over-rev. That’s an alternative approach to the more ‘standard Innocenti’ example above, and with most customers not getting any younger, the effort to work the gearbox and rev high is not as desirable now. So this new pipe moves to a longer tuned length, to regain some torque and low-down power but not crop off too much over-rev, to still allow ‘standard gearing scooters’ to go faster through rpm extension. The fit was good, noise was a bit higher than most but not as loud as the VW that sets an upper noise figure, but Ron has a few mods to test in that area to improve it further but wishes to stay away from the slip-on silencer style which Gori use, as he wishes to appeal to the ‘must have original look’ customers.

CHART TOPPERS

I’ve added the old Ron Moss pipe from last month’s test, and dropped his new one in with the Super Clubman results, to see how it stacks up against them. This chart displays the results for the power output of each pipe at every 1000rpm step, from 4000-9000rpm. The 3000rpm results are left off the chart, as the roll-on nature of the test means that the motor has not settled till around 3500rpm.

POINTS MEAN PRIZES

Of the four exhausts compared here, I’ve awarded four points for the best performer at each RPM range, down to three, two and one for the lowest. So highest points wins. The first column shows results over the entire rpm range 4000-9000rpm. I then added another column to show the best results at 4000, 5000 and 6000 as an indicator of low-rpm performance, and another at 7000, 8000 and 9000 as an indicator of high-rpm performance.