It would almost certainly be based on the “X1” shifter chassis. The cost for modifications will depend on the extent of the changes and the volume of chassis that you’re buying.
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I was thinking more about the fact that there is a slight additional weight and that it affects the dynamics of a standard kart, so it might be necessary to consider other aspects that differ from the internal combustion experience. Of course, the track factor and weather conditions are other factors to take into account.
I agree that you’ll want a KZ chassis for the stiffness and the torque. Keep the third bearing support so you have the option to tune with it.
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In the case of BSR, the good thing is that the chassis doesn’t need to be adjusted for the power unit’s requirements. They are designed to fit on any standard chassis without any additional modifications. Plug and Play - you can install it on any chassis in 15 minutes with 0 experience. X1 sounds good for 25kW and 25kW+ models
What recommendations would you have for achieving a high top speed, around 150-170 km/h (up to 105 mph)? Any tricks and tips from Chassis, tires another adjustment perspective?
If you want high top speed you’d narrow the track width, pump up the tires, and lay down the seat.
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Time to science the heck out of this. I am available for extensive testing. 
Honestly, I would be intrigued to try electric on a conventional race chassis. LMK if that becomes an option in the NE.
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I think it is less about top speed and overall weight than balance and torque. Ideally with the torque of a KZ and good side to side balance a KZ chassis would probably work best. However, I was told several years ago that even many KZ chassis that were once 32 mm were going to the 30 mm frames, because the had a wider tuning range.
That said, I would guess it depends on the karts balance with the BSR unit mounted to it. Most chassis these days are based on the use of ICE power plants that put more weight on the engine side and offset the driver to compensate. It is clearly evident in the seat placement measurements. My question would be how does the kart scale with the BSR unit? Secondly, nearly all modern chassis have two rails on the engine side and only one on the non-engine side. BSR plants place a large weight in the form of Battery Cells on the non-engine side. How does that effect the flex in the chassis and does it introduce a sag in the long term?
Perhaps there is no winner in this race and like with 4T, the chassis design has to be modified to accommodate the new power plant and its battery bank. I am thinking maybe the traditional 2 rails on the engine side and also 2 rails on the battery side. Maybe mixed tubing. Larger diameter up front to withstand the torsional loads and smaller diameter at the rear, because the loads are distributed over more tubes. Maybe Factory Kart would be a good partner in that they are small enough to accommodate design changes to find the best options in a short amount of time.
Just a thought.
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Chassis wise, I would imagine something bespoke (based on an existing design) might be best due to the overall weight of the kart.
For 100 MPH+, at long circuits (ie car sized road courses) using CIK bodywork it usually takes something like a TaG engine to just touch that, so you could use an FR125 as a reference point. KZ on the same track would be somewhere around 110 - 115 MPH.
As you might imagine, those speeds are mostly affected by aero vs power to weight. So essentially it’s power to drag ratio.
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Yes, this is one of the best ways to understand what works and what doesn’t. Yes, you must try it, I recommend it.
Technically, the electric motor is mounted 1:1 as the internal combustion engine, and together they weigh 30kg. The battery is on adjustable clamps where the radiator is mounted, weighing between 18-32kg depending on the model. Technically, the weight is balanced 1:1 on both sides. The battery mounts and the battery casing are designed so as not to block the chassis, allowing it to flex according to the pilot’s needs. That’s why many pilots so far say that with the BSR electric power unit, it’s even easier to drive, as the kart is technically more balanced.
Perfect can see in this picture:
The weight in the smaller classes is very similar to the weight of internal combustion karts. In the 25kW and 25kW+ classes, when compared to KZ2, the BSR kart is heavier by 10-15 kilograms in total weight. But from the pit stops, we usually hear comments that they don’t really feel that it’s much heavier.
But of course, one should test and feel it for oneself, then perhaps it would be easier to recommend precise adjustments.
Which class do you race in?
"Yes, of course, for achieving a top speed that goes above 150km/h (100mph), aerodynamics plays a significant role. We also observed this during the tests. Naturally, other factors also come into play affecting it, so I’d be keen to know what adjustments should be made to the KZ2 chassis, tires, etc., to maximize top speed. In this case, we didn’t modify anything outside the standard.
Here is a video from the last tests in Gorland Ring GP - Sweeden: Beyond Limits | Gotlandring | 150km/h | Blue Shock Race - YouTube
Yes.
For high speeds - you have enough power - you just need a long enough straightaway. Apex Kart Raceway in Perris CA gives 150 km/h on a KZ kart with 35 kW, so if you have 25 kW you need a straightaway that’s 600m long.
I think the X1 chassis with three bearings will work well for this application.
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25kW+ version we have 33KW of power. So it should be close to KZ2.
But can KZ2 reach 170km/h with standard racing chassis?
Yes, a KZ will go around 190 km/h on the freeway!
Most tracks have KZ maximum speeds around 140 km/h.
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2010 Trackmagic Prototype 30/32 Chassis with front brakes.
This is the chassis I took in 420cc to 30 wins out of 36 wins over 3 seasons with a worst finishing position of 3rd. The 420cc engine weight was around 60lbs. (12lbs flywheel!)
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I race in TaG Senior/Master. If you are not familiar, that is a 125cc water cooled 2 stroke on a tuned pipe, with an onboard starter and a single fixed gear using a dry clutch. TaG is a somewhat open category allowing multiple engine manufacturers, but following the same general formula. Power discrepancies between brands are moderated by minimum weights. I am a big guy. In Senior I am 50 lbs over minimum weight and 20 lbs over in Masters. Adding more weight will not help my situation. 
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For me the chassis must have the seat centered with the searing wheel and pedals. I see the offset seat as a legacy of hot wide engines and a unnecessary quirk for electric karts.
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I’m not sure if I’m divirging from the topic, but I’ll give the context of some of the stuff they do in the US on long tracks.
Very easily, with one caveat, it’s not typically possible on dedicated kart tracks. Otherwise, it’s just a gearing change and go.
The next trick to add extra top speed is a larger nosecone, this is a non CIK bodywork part that can be used in certain shifter kart classes in the US. Essentially the theory is to use a large cone to “punch” a hole in the air and have the rest of the kart go through it.
@Rapid1 probably has some photo examples of these. I’d say the are good for at least another 5-10 MPH in top speed. Here’s a similar nose style:
The ultimate in top speed of course is to get the driver out of the air and make the kart as narrow as possible. Ie, laydown karts.
Some amazing looking examples here: Coolest, Fastest Karts from WKA Kartweek 2018 at Daytona
You seem keen on crazy ideas, I think if you wanted to showcase your power package, a laydown kart on the banks of Daytona would be a very unique way to do it and would be great content. Of course you’ll have to discuss with the WKA, but you have a few months to prepare 
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These already sound like small figures; with 2 motors, it would be even more impressive. In the case of BSR, they would be around 250Nm per motor, or approximately 500Nm on the rear axle. That’s already as much as a 2-ton Tesla Crazy.
It would definitely be interesting to work with these superkarts. They are not that widespread in Europe; I know they exist, but we haven’t had direct contact with such top-level ones.
In the US, within 3-4 months, we certainly won’t manage, but it’s definitely one of the steps that should be taken. Sounds like a lot of fun 
Here is one of the projects that one of our clients has implemented in their student formula car; it’s something similar, in my opinion.
