Just trying to get Opinions on both kind of karts. About the speed and torque or take off speed and top end speed. I have asked about this before about what people think of kart. But would like a opinion of people who have run both for a comparison ?? Thanks K1 Racer
It is an irrelevant question if you intend to race. You need to stick to the package that is run at the venues you intend to race at. LO206 is nationally run and the more likely package at most venues. However, there are a handful of track with Tilly classes and if you are near one and don’t intend to run regional or national stuff the Tilly would be more fun to drive.
If you are just laying down laps for kicks, the Tilly has a bit more oompf to it.
The Tillotson for sure makes more power but rpms also has a huge advantage when it comes to speed and acceleration. I’ve ran both and I like the speed of the Tillotson much more and this was before they added a 1000rpms more to the rev limiter. I run the Lo206 because there is more competition and more opportunity to race.
Here’s a more technical explanation. Let’s say both engines have the same gear ratio, a 4:1 at 6100rpms with an 11in tire is about 49.9mph at 6500 it’s 53.2 and at 7500 it’s 61.4 which means it’s a little more than 10mph with the same gear ratio.
You can also flip this around to understand the difference in power. I can’t rememeber the power figures exactly of both engine but let’s say the Briggs makes 10ft-lbs torque and the Tillotson is 12.5ft-lbs. That power is multiplied by the gear ratio in this cause x4:1 which is 40ft-lbs vs 50ft-lbs. If you made the Tillotson run at the same mph as the Briggs at 49mph, which would be about 4.9:1 gear ratio, the Tillotson then has 61.25ft-lbs of torque at the tire. That’s more than 20ft-lbs more torque for the same top speed. If both karts weight 365lbs that about 9lbs per foot-pound for the Briggs and 6lbs per foot-pound for the Tillotson at the same top speed.
Just add 7 more horsepower to a LO206, keep the drivability the same and that’s a Tilly. More torque, more top end grunt.
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Talking to a quarter-midget racing dad the other day, he asked why the Briggs World Formula motor never took off in sprint karting in US given (in his words) it’s effectively an LO206 with meaningfully more grunt.
I don’t know the answer, but it got me thinking, if there wasn’t really a large sprint market for that engine that’s been around quite a while - even in a 4-cycle only series already racing Briggs engines (looking at you, CKNA) - what is different about the Tilly that will lead to wider adoption?
I’ve heard enough drivers in senior LO206 classes belly-aching over the years about how the Jr Sportsmans run similar lap times that I would have thought by now a super stock or more powerful box stock class would exist if there was a viable market.
The World Formula costs more and weighs more because its onboard electric start is probably the most straightforward answer.
There are many other reasons, but cost and weight are today’s most relevant.
I hadn’t considered weight, that a good point too.
From a conversation I had a long time ago with David Klaus (Formerly of Briggs racing)… The 206 was a “lessons learned” from their previous engines like the Flathead and World Formula. It was very intentional in how it was specced, right down to the specific RPM limit.
As you would imagine, the WF had some parity challenges because rules were more liberal. Also, there was a run of reliability issues. Many of those were self-inflicted to be fair, but it didn’t matter in the end due to the perception. Of course, more liberal rules and higher performance meant that service intervals were higher.
Fun fact that some might now know about the the World Formula: It was actually a CIK class (Of same name) but I think Briggs might have been the only manufacturer to submit an engine. The first part of that I’m certain of (I’ll see if I can find the rules from that CIK rulebook).
One thing that stands out about the 206 program is how much racers value racing vs speed. I think that’s why there’s very little traction for more powerful options. Racers would have to take a big risk, at least at first. Some will complain, but they’re still showing up…
My thought is that a four stroke shifter would be a good intermediary. Something faster, while also adding a little to the driving experience. Done right (ie parity, reliability, ease of use and total cost of ownership) I think something like that could catch. Executing that is no easy task though. I’ve spent some time working on this and let’s just say when you get into the higher power levels you start to appreciate just how well suited two strokes are for karts. There’s many challenges to delivering on the promise of offering parity, reliability, ease of use and low total cost of ownership.
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I think simply that it’s a low maintenance 4 stroke with more grunt. That said the T4 Kart / Series is a chassis and 225 all supplied by Tillotson. Mainly European based such as the World Cup in Spain.
With the US having such an entrenchment of LO206 racing / support services plus the lower cost of entry I can’t see mainstream competition abandoning the LO206 anytime soon. If the racing / driving skill of the LO206 was low then maybe someone dips a foot in the water with a Tilly 225. But LO206 racing IS skillful.