1300 pound go kart? How fast will it go?

Jimbo67

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Hi everyone,

Over the past few months I put together a street legal "go kart". The car is powered by a 212 cc Predator engine and has a 5 speed transmission with a comet 44 torque converter between the engine and gearbox. A lot of my ideas actually came from this forum. So thanks for that!

The goal of this project is to get the car to go 50 miles per hour, it's not going to be easy, but I think I can do it.

Anyway, I made several videos, including some dyno videos. I think you folks might enjoy these videos

This is the first video in the series.

 

itsid

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hmm
~2592 Watts for fighting the road
and
~3237 Watts fighting the airdrag @50mph *
makes
5829 Watts ( almost 8 horses)
that will need to hit the road

with a 44 magnum TC you will at least loose ~23% of the motor power to belt slippage
making the targeted motor power in the realms of 7600 Watts at the very least.
No IDK how good the transmission still is in terms of efficiency, but I'm guessing another ten percent is easily lost

So 8500 Watts is what Im guessing you'll need to tickle from that poor 212
11.5 horses or thereabouts

in short: you need to almost double the output power if you want to reach the 50mph mark.
possible, true true, but not exactly easy
mostly because you should not insanely increase the rpms as most performance mods do
you need a thumper instead... (else you loose more to belt slippage and gain very little if anything at all at the wheel..)
plus thanks to the 5 speed you don't actually need high rpms at all
I'd suggest to increase compression, decking the block, maybe thinner head gasket
and in case it fits an oldschool Honda GX160 head (the 14cc one)

billet conrod is highly recommended since that amount of compression does not play nice with cheap chinese casts ;)
up until now I'm guessing we're in the solid 8-9horse range
a low rpm increased lift and duration cam (unchanged timing i.e. custom ground)
with a somewhat bigger (say gx390) carb and some nicely cleaned
least restrictive intake and exhaust should crack the magic ten...

I'm unsure how you could actually get the last few watts from just torque tbh..
maybe bigger valves and a smidge (just a smidge mind you) higher rpms (4500-5000 max)
with certainly no more than 4° timing advance really (maybe 2° is even better if any)
just to move the torque curve over just ever so slightly to high rpms
without having to sacrifice lots in the low rpm range...
but yeah tough call to get reliable 11.5horses from mostly torque (rpms is easy but won't help you anything really I'm afraid)

this ain't going to be cheap :(
but yeah... that might actually work :D

'sid

* assuming here cw of 0.28 and 1.7m² of frontal area abouti'sh no?

PS funny I think an old stock ungoverned gx270 with just intake and exhaust might do the trick .. cheating? yeah, maybe but still :D

[EDIT]
Oh wait we can make some assumptions...
16.5m/s current top speed.. (37mph... assuming 35 up the small inclines and 39 down ... 37 reliable level road speed)
all else being equal that means
you needed
1293 Watts to fight airdrag and
1910fighting the road

3203 Watts are actually on the wheels in your test,
assuming a "close to spec" predator 212 with 4600 Watts of output power
your efficiency is only 69.6%
no matter how wrong my above estimation was about cw and frontal area and efficiency of the transmission and so on..
it should remain about the same (unless you can reduce that somehow)
sooo needing 5829 Watts on the road the engine needs to provide
8380 Watts 11.4hp (hah.. all the hassle from calculating for 0.1horse... what a waste of time LOOOL)

that's an "insight", right? I'll need to find the exact air-drag specs for it..
 
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chimmike

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So, why'd you eliminate the hybrid system? Why not get it to work in conjunction? Anyway, seeing it do 30mph is rather impressive, haha.
 

ol'joe

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I would be tempted to go with the preditor that has electric start, then add another engine. With a pair of them, you could always get home if one of them failed. VERY nifty project and nice execution of the plan...my complements......Joe
 

Jimbo67

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8380 Watts 11.4hp

that's an "insight", right? I'll need to find the exact air-drag specs for it..



Hi itsid,

I really appreciate the in depth calculations for power requirements. As I recall the CD is .24 and the total frontal area is around 10 SQ feet. This makes the car is very slippery when it comes to wind resistance. I agree with your calculations that 11.4 HP is right on the money for going 50 MPH.

My goal is to have this $99 engine go 50 MPH. The fun/challenging part is the modifications to reach this goal. While the 212cc engine is not the best starting point, it is the most popular engine used by enthusiast and that is why we chose it. I think it will be a fun journey to take this engine from bone stock to a high performance power plant. Here at DIY Go kart, I think this group would enjoy the engineering aspect of the project. Additionally, using the Insight as a 'go-cart' is really unique. Plus, many of the modifications can easily be utilized in go-carting.

So far there are four finished videos and several other videos being edited together as we speak. Your analysis is pretty close, without revealing too much about the content in the unpublished videos.

I look forward to more feedback from the forum.

So, why'd you eliminate the hybrid system? Why not get it to work in conjunction? Anyway, seeing it do 30mph is rather impressive, haha.

One of the reasons i got the car on the cheap is because the hybrid system was non functional. The added benefit of removing the hybrid system was a significant weight reduction.

Thats cool...
Lets see some pics on how you made the motor conversion....




During the creation of this project, my primary focus was in creating videos. Unfortunately, I didn't take any photo's. But at some point I plan on putting a 420cc engine in the car, I'll make sure I take lots of photo's

I would be tempted to go with the preditor that has electric start, then add another engine. With a pair of them, you could always get home if one of them failed. VERY nifty project and nice execution of the plan...my complements......Joe

I like your thinking, but unfortunately there is simply no room for a second engine
 

itsid

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I really appreciate the in depth calculations for power requirements. As I recall the CD is .24 and the total frontal area is around 10 SQ feet. This makes the car is very slippery when it comes to wind resistance.

uhm 10ft² sounds wrong.. too small for the actual area, too big for cdA

Anyhow... I found several (sometimes conflicting) numbers for the first generation Honda insight..
and cw of 0.25 was quite often the the value given (for a 1996.. a 1999 0.28 for some unknown reasons..maybe a typo)
anyhow, cdA ranges from 0.475 to 0.582 m² depending on the source (means total frontal area of 1.9x m² [20.x ft²])
since I calculated with 0.476m² cdA (cw * frontal area [0.28*1.7]) and that was right on the lower end of the possibilities anyways,
I don't think I'd have to recalculate for another guess ;)

Indeed much better than the moving barns that are clogging up the streets these days either way :thumbsup:

it's indeed a very interesting project,
I don't normally subscribe to kart/car/bike related stuff (apart from some friends of mine that is)..
But I was about to cringe seeing the flipped driven and the red spring sticking out like a sore thumb..
and then you got me with that phone call ;)
So that's a first :D

'sid
 

Jimbo67

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What about the power steering, brakes? Is it just running down the battery while in use?

The car actually was equipped with electric power steering, however it was disconnected because it was unnecessary. The car is fully street legal, meaning all the mandatory safety equipment like lights, horn and wipers do work, but during the day when the car is driven, the only energy consumption is from the blinkers and brake lights. I put a charger on the battery every few weeks to keep the battery fully charged.
 

mckutzy

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Ok... Since this is DIYGK... ya a little outside the bounds... but howabout tell us how you mated the engine to the car transmission then if no pics??...
 

Jimbo67

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Well I do have some pics, however they were taken early in the build and may cause some confusion.

The first picture is of the almost finished powertrain. This is one of the photos that appear in the video. As noted in the video the driven pulley on on backwards.... but overall it give a good idea of what the powertrain looks like.

The second photo shows the adapter I made that mates the input shaft of the Honda transmission to the home made drive system. The adapter is made from the Honda insight clutch center that is welded to a go kart axle flange. The go kart flange is for a 3/4 axle. The outside diameter of the go kart axle flange is 1.5 inches

The third picture may be a little bit confusing because this is not how I attached the driven pulley. Anyway, the interesting aspect of the third picture is the transmission adapter plate. This was made from 1/4 thick 6061 aluminum plate. To make the adapter plate I traced the pattern of the bellhousing on to the aluminum plate and cut it out with a saber saw. as I recall it took a few hours to cut the plate and I went through several blades. You can also see the two support bearings in this picture. The big blue bearing mounted directly to the aluminum plate has a 1.5 inch inside diameter hole. This rather large hole is to allow the go kart axle flange to pass through. The second bearing that is semi hidden behind the driven pulley is for a 3/4 shaft. The two bearings help carry the radial load on the 3/4 inch shaft to avoid putting undue stress on the input shaft of the Honda transmission
 

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bob58o

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Cool project! Do you still really have a working rotary phone? I watched a video where a dad offered his kids money if they could figure out how to dial a number. LOL. Not that it is really needed, but I know for certain I would have an tachometer mounted inside the car. Did you ever see the 212 powered tow truck videos?
 
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Jimbo67

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Cool project! Do you still really have a working rotary phone? I watched a video where a dad offered his kids money if they could figure out how to dial a number. LOL. Not that it is really needed, but I know for certain I would have an tachometer mounted inside the car. Did you ever see the 212 powered tow truck videos?

Thanks!

The rotary telephone gag in the video was done with a prop phone. As a matter of fact that whole scene was videoed in silence and the audio track was recorded a few days later.

The car actually has two tachometers. One tach on the dashboard I can see while driving and another one along with an additional speedometer is set up for another camera to record vehicle performance.

The Predator powered tow truck is awesome, I kinda wish that guy had more videos of it.
 

itsid

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would a rotary phone even work in your area?
I mean landlines here stopped supporting pulse dialing in the early nineties afaik,
frankly we no longer have true landlines for a few years now (nearly all have been converted to VoIP by now)
Ah well.. it'd be fun to convert the pulses to DTMF and reactivate a phone like that.
Maybe because I still giggle about that gag from "In&Out"
sorry for straying off topic.

Now onto our regular progrram ;)

I know I know, most has already be done and it's just the videos now being finalized and such.
but after vid#3 I still think you have a better chance with decking the block;
or using at least a thinner head gasket than with further advanving the timing
a higher compression to create more torque works over all the rpm band,
and while the curve is impressively flat , lifting it up a bit would certainly
not only increase top speed a bit it'd also allow you to improve acceleration by almost the same percentage.

I mean I'd still look out for a 14cc GX160 head IIWY,
albeit I must admit I don't know if fits onto a predator at all (should.. but IDK for sure)

Anyways.. I like your videos, lots of effort,
nice story telling, good camera.
feels just like ThisOldTony :thumbsup:

'sid
 

Jimbo67

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Hi Sid,

Thanks for the kind words.
This YouTube series was shot between late May and early September. I'm finally finishing the edits and I started dropping the videos on YouTube last Monday. The fifth video should be released on Tuesday or Wednesday of this upcoming week. There is still a lot more to the story and more modifications to be shown. Obviously I cannot reveal anything yet, but I think you'll like the direction we take as far as the modifications go.
 

itsid

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no flattering; honest appreciation!

And thank you, I think I will.
and even if* I disagree with a step taken,
I more than likey still find them enjoyable to watch, I really like how it's told.
I hope you're gaining lots and lots of subscribers, since frankly..
that raises the chance for another series alike once that Honda hit Mach1 :D

'sid

*not saying I will, just in case I might ;)
 
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