Vespa Dry Lake Racer lives...

[internetscooter]

Is this better?



That's the before and here's the after.



Note: We've made an interesting discovery (more power garanteed for free). Although the carb and head are both from KDX 200's, the carb is an early model + way way too underspec'd The carb we have is a 28mm and the cylinder is designed for 35mm!

[ben james]

hmmm, much better, might have to check that workshop out, don't take any notice of me, i'm suprised dr goggles hasn't been on this thread to tell me to pull my head in on your behalf. i probably need to spend a bit more time in my worksop working as opposed to keeping it organised.
regards ben

[hawkwind racing]

impressive workshop ( im very green) good luck with your project
cheers

[internetscooter]

An update for those that are interested... we've been doing some more testing...

http://au.youtube.com/watch?v=jsLyTC7YP7s

Vespa KDX Broadford Track Day. The scooter is now almost complete and we spent the day testing it out at Broadford. Unfortunately the top straight is up hill and into a headwind. The bottom straight was not long enough to get into 4th, however we rev'd it out to 10,000+rpm in 3rd which is 140+ Km/hr. The Vespa was really stable and reliable. It handled so well I actually passed a GSX-R on a corner. Next stage is dynoing the bike and setting up an expansion chamber to suit (yes, we aren't even running a good pipe!). It looks like will hit our target of 108 miles per hour (175 Km/hr).

[gennyshovel]

Well done 'scooter, I would have loved to have a beer with the bloke you passed@ broadford, lol,
Tiny

[internetscooter]

Here are some results from the first run on the Salt.

The top speed out of 3 runs was 82.201 mph. The first run I got a higher speed because there was a 8 mph tail wind, however due to slippery salt I throttled off through the timing markers (only getting 78 mph).

The Vespa was not complete, the main issue was the pipe was not designed for a KDX head.

We made a KDX pipe designed for the correct rev range however it was not perfectly tuned and we did not get time to reshape it to fit. The runs we did were with a standard Vespa pipe we put on for testing. Below we see a comparsion between road speed dyno results in 3rd.

1) These 2 runs are with the test pipe and shows that power collapses at 82 mph (in 4th). If we are lucky it will rev out otherwise it is all downhill

2) These runs are with the KDX designed pipe. We needed to go bigger in jets because it was running lean. The small circles show runs with lean mixture and the big circle is what we would have got if the correct jet was used (we did not have it available during the dyno)

3) Following the predicted curve down we would have got in the range of 100 mph with the KDX designed pipe... though only the salt will tell.



Next on the agenda is fitting the KDX pipe and road testing it...

[gazza414]

Good to see this project up and running and using some good science and data to go forward

[internetscooter]

Some pics of my own attempt at weld porn... make sure you drink lots of beer before hand to make it look pretty...

This is the new pipe cut up and reshaped to fit the scooter. As well as learning to weld good, the idea is an articulated exhaust that runs forward along the scooter to reduce drag. This will allow the underbody to be fully streamlined in line with the wheels.

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There will be a ball joint at the manifold to allow the whole thing to move freely.

Once we get this fitted it's off to Heathcote Park to try a 1/4 mile

[DON NOBLE]

http://members.bellatlantic.net/~vze2p5 ... xpcham.htm
found this site , um try and work the formula out
or the next one I like cos its got pretty moving picture
http://en.wikipedia.org/wiki/Expansion_chamber

[internetscooter]

That's good info, I think the Blair book is $150+. The whole site is interesting and also leads to http://www.mh-aerotools.de/airfoils/javapipe_en.htm which is a pipe designer done by the same guy that did the tear-drop calculator (another thread)

We were in a rush for 2009 so we just paid someone that already knew the KDX port timings to design the pipe using TSR software. It saved us pulling everything apart to measure and the maths headaches

[internetscooter]

The World's Slowest Build...

After about 4 months of no time, I finally got a couple of hours in the shed over the Xmas break. I managed to finish fitting the custom forward facing articulated pipe, a proper side-stand and replace the rusted brake cables. I took it for a spin around the block and everything works a treat



Next on the list is to dyno the scoot again and see if the reshaped pipe still has the power up in 100mph range... lets hope I won't have to wait till next Xmas to find some time!

[Rob]

Good to see some progress made Paul,

See you at the salt,
Rob

[BONES]

Intrernet- A mate of mine has a programe which will print out all the pieces to make a chamber any shape or size.Would you like me to chase him up?
cheers Bones

[internetscooter]

I used Cone Layout http://www.pulserate.com/ and that worked pretty well. Just printed the bits out and used them as a template.

We've booked a dyno for Sat the 16th - so expect a post on the results

[grumm441]

I guess the big question is, should i be making room in the trailer