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gunnix Offline OP
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Hello everybody
I am not sure if this is the right forum to ask a question like this but I will just try.
I built myself a racing combination using a former 500cc not 630 cc single cylider engine equipped with a supercharger.
Since this is my first experience with superchargers I do need some help with the tuning of the engine.
Ignition and carburettor settings are the main problem I guess.
Is there anybody here who has got some experienc with engines like that?

greetings from
Gunnar


in progress: BSA/Jawa 620cc supercharged sidecar racer
BSA/Jawa 600cc sidecar racer
BSA super Rocket
BSA B33 sidecar
Ariel VH
Triumph 6T custom
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Not a project that would even cross my imagination.
Good luck.
Goggle gives a modern version.
Aside from a plumber's nightmare, these guys might have some working basis numbers for you.

https://bikebrewers.com/triumph-thruxton-supercharger/

The old school way was flipping Triumph heads faceing forward.

I had a limited discussion some years ago with Mule on another forum.
Mule is a Master class fabricator, and New Trumph are plentiful, and my interest at the time.

I knew that I could chip my F-350 to about double the Hp,
and with the computer control, mapping, and injection coming common on the New Triumphs,
couldn't we remap and do something similar ?

I got a pooh, pooh from Mule and with my respect for the man, that is a definitive answer.

Long winded bloviation, but computer control, mapping , injection solves a pathway problem for your huff project.

Me? I like being a early century luddite.
I was not built for this 21st century.

Last edited by Chip H; 05/03/21 11:05 am. Reason: elucidation and bloviation.
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I've certainly thought about it. Draw thru is definitely the easier to get it to work, but you end up with a plenum full of fuel/air mixture apt to explode if you get a backfire back thru the carb. The "French Owl" on land speed racing did it on an old Harley, but got burnt when he tried to put out a fire which blew out thru his blow-off valve.

I would like to try blow thru, but regulating a carburetor to do that is tricky because the supercharger wants to blow the fuel out of the carb so requires some type of balancing the pressure to get the fuel/air mixture correct. Converting to electronic fuel injection would seem to be the best way, but you first have to convert to electronic fuel injection which requires a whole lot of electronic and computer know-how - - long learning curve which I don't know if I can master.

Looks like you're talking about a Jawa motor. I'll be interested to know if you are successful, so keep me posted.

Tom

P.S. I run BSA singles at the Salt Flats and have just about maxed out the 250, 500, and 600cc versions, so supercharging is attractive!

Last edited by koncretekid; 05/03/21 11:44 am.

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Cool project. Based on my experience with a turbocharged 650 I have a,couple of comments and questions. Are you using gasoline or methanol? Do your rules permit fuel injection or must you use a carb? If FI is ruled out and you are using gasoline (assuming it would be high octane racing fuel) then you need a fuel system/carb that will deliver the required amount. I use a fuel pump with 3 psi and a Mikuni HSR 42. Works perfectly. Start with total timing retarded about 5 degrees and go from there. Since you are blazing new trails you have to spend time on a chassis dyno in order to get it sorted out. PRT

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I used to run a supercharged Weslake 500cc single. Boost pressure was 28PSI I reduced the compression down to 8-1 and kept the original ignition timing. 100% methanol fuel
I started off using a big SU carb without float chamber, home made needle and jet and later tried mechanical fuel injection using a Hilbourn pump
It was brutal on blower drives, a 30mm wide HTD belt lasted 1/4 mile. I tried a pair of V belts and got a days racing out of them.
A longer pipe between blower and head improved things by damping out the pulses


BSA B31 500 "Stargazer"
Greeves 200 "Blue Meanie"
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GM500 sprint bike "Deofol"
Rickman Jawa 500 "Llareggub"
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These techniques are also relevant to supercharging NA engines, as well as turbo builds on carburetted engines,
though substituting rising rate regulators for boost-referenced carburettors and timing interceptors for boost-ready ignition systems.


https://hackaday.com/2021/05/07/how-to-build-a-turbo-car-the-cheap-90s-way/

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Thanks a lot everybody
I will answer to you one after the other.

To chip H:
Thank you for your hint, I will get in touch with them.
Fuel injection and electronics are not an alternatoive for the bike.

To koncretekid
I know about the explosive risk of draw throug. I use a plenum of 1,2 litres, which is about twice of displacement.
I have a very big overpressure valve installed.
Fuel injection is not an option, to much electronics for a classic bike.
You are right, the engine is based on a Jawa DT500 dohc.
I will keep you informed.
The bike is running now, but still some tuning of mixture and ignition required.

To pushrod tom
Injection is not an option.
I am running Gasoline 102 octane.
copmp. ratio is 9.3:1 at 0,5 bar pressure (7.2 psi).
I am running a PHM 41mm Dellorto carburettor with an accelerator pump(is it the right word?).

You say: " Start with total timing retarded about 5 degrees and go from there"
What do you mean with that?
My idea is to start with 28 to 30 degrees, then starting over 5000 rpm retard for about three degrees.
could that be a start?

To Andy Highham
I am using a HTD belt as well, still OK but I have not really done much on test riding yet.
The long pipe is what I called a plenum, I am using about twice the volume of my displacement.


Greentings to all from
Gunnar


in progress: BSA/Jawa 620cc supercharged sidecar racer
BSA/Jawa 600cc sidecar racer
BSA super Rocket
BSA B33 sidecar
Ariel VH
Triumph 6T custom

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