95Racer Development

Many thanks to all the people who have shown an interest in our little project and who have asked questions. We’re more than happy to answer them, although certain engine specifications will not be revealed.

Here are some answers to commonly asked questions so far.

1. What type of fuel do need to run with this engine?

This question came mainly from our readers across the pond in the US, probably because fuel from the pumps there tend to be lower in octane to what is available in the UK. Of course, the required octane is dependant on the engine’s compression ratio and the spark timing. Our compression ratio is not a million miles higher than what you’d find in some of the high power Japanese bikes and our timing has not yet been altered from stock. We haven’t done extensive tests of how low of an octane we can safely run, but we know that the 99-102 RON octane fuels that are readily available from the pumps in the UK are sufficient. Octane is usually displayed in a PON (pump octane number) in the US and 100 RON roughly equates to 96 PON.

Some people asked about “race fuels". No, we don’t use race fuels because, strictly speaking, they are banned from club racing in the UK. Of course, the two-strokes commonly use aviation fuels or “av-gas".

2. What are you engine life expectations?

First of all, let’s hope that our expectation will be met. These are that we can get a full season’s racing from it without having to touch the bottom end. The top end may need a mid season refresh but we’ll see how it goes in 2008.

If there is a weak spot in the engine it is likely to be the stock conrods. We may well upgrade these early next season if we can source better ones at a reasonable cost. There are plenty of sources for custom rods such as Carillo and Arrows, but the cost is not insignificant. Still, we may just have to bite that bullet to prevent an even costlier engine rebuild.

One thing we don’t expect is that this will now be a very fragile engine. The tuning that was done was fairly standard things which is well understood.

3. Where will you race it?

With 95Racer not being based on a standard road bike was always going to be a limiting factor in terms of its race eligibility. It won’t be eligible for the Mini-twins category as these require road based bikes and are limited to 72 HP. This class is dominated by Suzuki SV-650s and the odd Kawasaki ER-6.

Our options appear to be the Thunderbikes classes and Sound of Thunder. Derby-Phoenix runs a Thunderbikes class which use essentially the old WSBK rules permitting 1000cc twins and 750cc four cylinders. This is where we raced it in last year when it was still only making 68 HP compared to the Ducatis and Suzuki GSX-R750s producing easily twice the horsepower. While we won’t win any races in that class, we’ve proved that we can finish at least mid field and surprise quite a few of the bigger bikes. There is a lot to be said for light weight!

The other main option is to add ballast to the bike and enter it into the Thunderbikes with BMCRC (Beemsee). That class has a 4 lbs per HP rule as the main restriction for eligibility and now allows one-off chassis such as the 95Racer. Given that we are at roughly 240 lbs, we would likely have to add 32 lbs of ballast to even run the standard engine. This class also attracts quite a wide variety of bikes which makes it interesting.

We’ll just keep our options open and will decide early in 2008.

4. Will there be “upgrade” kits available? Will you produce “frame kits"?

The short answer is we don’t know yet. Engine wise there are a few possibilities but we really need to get some mileage on the tuned engine before we can decide what makes sense.

Of course, we do have a slipper clutch available that is now an off-the-shelf part. We used it all last year and has proven to be a very worthwhile upgrade for riding even the stock motor on the track. We can now supply version with a spider spring for racing and a spring loaded post version that is better suited to road use due to its lower maintenance requirement. Both versions retain the stock clutch basket and clutch plates and are easy to install.

You can find more details here: http://www.3upracing.co.uk/index_files/Page2232.htm

Others have asked about a “frame kit". I must admit this is very intriguing and we plan to get the 95Racer type approved for road use under the UK’s Single Vehicle Approval scheme. A frame kit would probably include the frame, the swinging arm, the tank, the subframe, and a few smaller pieces. All the other parts would be from standard road bikes. One thing I do know is that this bike is a lot of fun to ride on the roads even with the standard engine, mainly due to its light weight and fantastic handling. Clearly, the road version would weigh slightly more but would still be significantly lighter than any other roadbike including the much missed Aprilia RS250 and many of the smaller capacity bikes, except for some of the enduro bikes.

If you have any interest in this, let us know. We might just do it!

Well, it’s taken far longer than we’d hoped but we finally got our first dyno results today. Weather was a seasonably normal of about 15 deg. C, so pretty much ideal. As you can see from the graph below the results have exceeded even our expectations. Keep in mind that this is the first (internally)tuned ER-6 engine our engine guy had done. Clearly, his experience in tuning ZX-6 and ZX-10 engines for British Superbikes has been put to excellent use.

We won’t disclose the exact engine specification as you may understand, but the list of modifications includes:

- massively lightened and balanced crankshaft with altered balance factor
- replacement of balance shaft with straight shaft to retain water pump drive
- reworked and balanced pistons and conrods
- reshaped combustion chamber
- increased compression ratio
- flow optimized intake and exhaust tracts
- custom ground cams with increased lift and duration
- shortened crank with minimal flywheel
- lightweight race generator
- custom airbox and straight-through, ram-air intake
- custom exhaust with seperate pipes and common silencer
- modified injection system, bellmouths and larger throttle body diameter
- and a few other things like aftermarket ECU with raised RPM limit and launch control

In addition to the obvious increase in power and torque the engine is also 8.8 kg lighter and now weighs 43.2 kg. The engine revs up incredibily quickly (and down!). The throttle response is amazing. Idle is 2300 RPM and while the vibrations has naturally increased due to the elimination of the balance shaft, they are not excessive and the chassis doesn’t seem to get too upset. The tubular steel chassis helps, I suppose.

The dyno runs were done with air blowing into the ram-air at around 120 MPH, and the airbox pressure sensor showed the slight rise. Without the fan assist, it seems to loose about 2 HP. It will be interesting to see what airbox pressure the sensor records during on-track testing.

Based on our engine simulations, we built 4 different exhaust systems. All were tried on the dyno. Being naturally sceptical, I must admit the simulation results are amazingly accurate. I have no previous experience using computer-based engine simulations but they clearly work. The final exhaust is still quite loud and we need to add more silencing methods before we can clear the 105 dB noise restrictions now in effect at most tracks in the UK. Hopefully, this won’t cost us too much horsepower.

The engine simulation also accurately predicted the best cam timing and that’s one area where the software beat the engine tuner. Even he was amazed as it gained massively in the upper mid range, although peak power only gained about 2 HP. We will definitely continue with simulation experiments. It’s far cheaper than building and dyno’ing various hardware such as throttle bodies, cams, exhaust, valves, etc.

So, in summary, things have worked out extremely well, albeit a lot work, time, and money were required. We can’t wait to take it onto the track!

Stay tuned!

Not being experts in website maintenance and upkeep, we decided to provide our latest news in the form of blogs. We hope that using this method will eliminate some of the excuses heard around here why more frequent updates are impossible. Maybe we’re kidding ourselves, but we’ll try to make a good start.

Feel free to shout at us if we are falling back into the old trap!

As you can see in this picture our first track testing was fairly cautious. This was taken at our very first testing session at Croft circuit in North Yorkshire in early August 2006.