So im trying to make endurance race in my home country. But still unsure which engine should i choose. My local track length is 1.2km about 0.7 miles. Its a clockwise track. I got a sponsor for the engine. But idk which one. Dont want it too slow or too fast. The chassis will be rental chassis.
The choices is.
270cc 9hp
390cc 13hp
460cc 16hp
Depends, would it run stock or can you modify it ?
Obviously the more powerful the engine is the faster it will be but by no means dangerously fast. If you are doing endurance races i would consider fuel consumption, reliability and maintenance costs. Do some research and see what engines other circuits as yours use. If it’s possible can you not test the 460cc engine and see how it goes? The 390cc is probably your best bet if you looking for something in the middle.
Full stock engine. No any modification.
I was leaning towards the 460cc. Definitely will test it out first the 460cc. If its too fast then im stepping down to 390cc. Thank you 
Is that actually enforced ? Also the power figures seems a bit strange. G250/G460/G620 all show the same power output despite the torque being different.
Not sure I understood correctly but are you a competitor or the organizer ?
Im the organizer. By far there is no a proper rental kart race in my country.
Depends on the price, but I would go with a clone GX270 of Aliexpress or something. Those engine are 100 dollars a pop. Remove the RPM regulator, put on some moped performance intake and a unrestricted exhaust such as RLV.
Those changes are minimal to do and will allow the engine to breathe a lot more at higher RPM. And the 270 is lighter than the 390. Those two things combined will allow your kart to get up to 75kph (even a bit more, we were hitting 80kph at Atlanta with such engine).
270 or 390
270 would be the typical 9hp rental.
390 would be a bit faster and more tiring.
The 390 is physically large and an elbow killer (at least the Honda is).
How long a race? How many stops etc?
Who is the race gonna be targeted at? Will it be experienced folks or a mix?
Im not buying the engine. My friend is the distributor of that engine so he gonna lend me the engine. Okay. Rpm regulator? Whats that? The exhaust is what im trying to do.
Between 270 and 390. Is the speed different really noticeable?
The race is around 2 hrs per class. Class will be by the age and weight of drivers. Target is a non-pro racers.
I’d say so. The 390 is quicker. It’s not a huge difference though. It’s also a very reliable engine. Either would be fine.
On those engines, you have a Governor to make it run at steady rpms. So you would have to remove it. Then the exhaust is really easy to do. Doing both intake and exhaust should take 10 min per engine maximum
Yeah, can be several seconds over a 1200m track
If you can’t increase the max RPM you need to consider gearing and clutch. That would leave a very narrow range. You don’t want to be slipping the clutch a ton and end up overheating it.
All things being equal and stock, 460.
Yes, the 460 heavier, but if you think about total vehicle weight (guessing 180KG/400lbs) then an extra 10kg is worth having almost double the HP.
/edit. OK you are asking what engine for a fleet. I missed that. A track that long is going to want a 270 or larger.
Swapping the exhaust and removing the stock intake will add HP if needed.
As some mentioned, you’ll likely want to remove the governor. The problem is that your supplier might not be super keen on that. The governor limits RPM to 3600, it’s going to be difficult to pick a gearing ratio with will work well on a track that size if you’re limited to 3600.
Oh. Swapping the exhaust from the stock square-ish to longer pipe does make an increase? Thats new to me, i thought its just a looks n noise.
And another thing. Since engine is checked either 390 or 460 imma have to test run first. But. Regulation wise, hows the rental endurance race in te us ? Classes divided by age n weight. What about refuelling? Do i need some helper or like a refuelling station for that or just leave to each team how are they gonna do the refuelling?
No way you are gonna run those engines without an exhaust
Why are we making this complicated? Slap one of those engines on and race!
We run gx270 and it’s fine. I’d say if the field is experienced, grab the bigger engine, run it stock and let it rip.
Gx270 will drain its tank in approx 2hrs. So, you will need refuel. This is the tricky bit.
Generally you don’t want accelerants near the customers. The way Chris (endurance karting) does it involves a kart swap and a refuel area.
Basically you come in to pit… the next guy gets in and then, once pit timer is done, instead of leaving onto track, they follow the “other” lane to refuel.
They pull in and are given a timer. They get out of kart. The attendant removes the number plate and puts it on a refueled kart in the front. The driver then gets in the new kart and is waved out after X minutes.
I don’t think you want the racers at all involved with refueling. That should be done in a seperate area by employees.
Stops:
Endurance karting has strategy ideally. Because mandatory stops.
For a race, I think a good rule of thumb would be to take the total time and divide by 20-25min sessions. Depending upon length, you will need to also include fueling as part of those stops.
For a two hour race, 1 stop is fine. But that makes it simple and limits teams to 2 as there will only be one stop midway for refuel. Any additional stops = lose the race.
For 4 hours you could maybe get away with one refuel midway. However I’m not sure what range is. Probably cutting it too close.
The Chris races are usually 6 hours, and iirc they are two refuel required.
In addition for the 6 hr races it’s 14 stops total with 2 of them being the refuel.
Regular stops you come in and are held for like .5 mins. Enough time to swap comfortably.
Fuel is 3 minutes. You pull in and are handed egg timer. The attendant notes your entry and starts the 3 min clock on the egg timer, moves your number plate to the fully fueled kart in front of the line.
Pits close with 10 to go. They also close before the midway point as we do a reform halfway through.
