Barn Cat - Supercharged CL175

[Doc B.]

AMA reg is also 1.35 gal. minimum for fuel tank.

[JimL]

Re: the 6V battery trick (meaning 18V to coil), there are multiple reasons this works.  First, at high RPM there is not enough dwell time to have the coil actually saturate at 12 volts. 

Second, the additional plug gap (available) will ensure that even a leaner or "surging mix" condition will have a better chance of in-cylinder burn.  A late, or incomplete, burn will result in too much heat in the exhaust valves.  These 160/175 heads are famous for overheating the exhaust valve springs, which winds up tagging (and bending) the valves at sustained high RPM and full throttle.

These engines actually started as a 125 and were only made into 160 to get around a mid-60s California freeway law requiring 16.5 HP or more.  The intake tuning, port sizing, etc were all set up to provide the necessary speed to sell in California freeway legal.  They really kind of needed more head cooling, but there was no room to do it cost effectively.

If you need to find odd things, like the center roller for the cam chain, check out David Silver Spares.  They are about your last resort for genuine parts.

[John Lawrence]

Welcome to the small displacement supercharged group within the LSR community.......

Can't wait to see your bike run at El Mirage and or Bonneville..

Thoughts: the firing of the sparkplugs under-boost can be an issue, however at low boost levels (5 to 7.5 psi) just closing down the the sparkplug gaps to .018"-.020"  can work wonders.

Just measuring off the computer screen the picture of your pulley system looks to spin the blower at about 70% of the crankshaft speed.... That is too much as these blower do move 300cc per rotation.
So two c/s turns means the blower is going to move (300cc X 2) X .70 = 420 and the engine is moving 175cc on its own so 420/175 = 2.4 pressure ratio absolute (which is 21 psi of boost at sea level).

I'd start with about a 1.4-1.5 pressure ratio and your pistons will thank you for it...and pull you ignition timing back a few degrees as well.

Check out My racing partner's blog as there is a lot of info on our bike which runs the same blower that you have....

red-baron-racing.com

Good luck and ask questions if you get stuck.

Robert "Smitty" Smith
Red Baron LSR race team

Smitty,

You are very right? Thank you for catching that! I was dumb and calculated it assuming the engine would be taking in 175cc per crank rotation + the 300cc from the s/c? yikes. I will look into getting the correct ratio of pulleys. That being said, do you guys use a v-belt on your bike or something else? Is there a manufacturer of pulleys you use specifically? I found a company (Jones Performance) that makes an assortment of pulleys meant for racing alternators, and I thought I may give them a shot. I can stick with a v-belt, but now that the crank pulley is going to have to be so small (around 1.5? OD if I stick with the current blower pulley) I am worried that is a pretty tight radius for a v-belt to navigate without slippage. Let me know your thoughts.

I checked out your blog and it has already been extremely informative. I will probably be sending questions your way quite a bit during this initial development/design process?

Again, thank you for catching my egregious error!

-John

[salt27]

I use a micro-v serpentine type belt but it is spinning a centrifical blower so the load might be less than a positive displacement blower.

My pulleys are made by a local machine shop.

  Don

[generatorshovel]

I use 20mm x 5 Gates belts
https://www.gates.com/us/en/power-transmission/power-transmission-components/sprockets.html

[TheBaron]

Hi John,
    I'd try to use a v-belt as the power requirement is low for you ( about 2 to 3 hp max) to drive your blower, and the pulleys  available are cheap, easy to setup, and cover a lot of sizes...

Rule of thumb is about a 2" inch min pulley with an "A" (1/2" belt).... Notched V-belts do run cooler and will tolerate more stress from small pulleys, and 3/8" inch belts are also available.

The Red Baron run a "Gilmer" timing belt for one reason only....to minimize the belt tension required...The blower hangs from tabs on the upper bike frame and a lot of belt tension on top of the 5-6 hp drive load was not considered a good idea.

Plus, as our race event require such short run times, changing out a cooked V-belt now and then isn't such a big deal.

The Red Baron starting motor is  6 hp and it uses all of it to spin the rear wheel at 20 mph... a 1/2" belt handles it with ease......

[thefrenchowl]

Hi, nice project!!!

I use an AMR500 on my bike but it's a 900cc so have to spin it a lot faster than yours...

I do find your AMR300 to be a touch big for a 175cc... Meaning, yes, you can slow it down a lot but then, you'll end up with  a lot of intake pulses which will require quite a big plenum chamber to compensate... (the moment one of your intake valves open might not be at the right high pressure time in the pulses sequence...)

I have been playing with the idea to supercharge a small 125 Honda, haven't got the bike, but I did purchase a small air pump that displaces 130cc per rev, thinking to spin it at engine revs to double the charge.

It looks like this, 3 lobes "a la Bugatti"...







Patrick

[John Lawrence]

A quick update:

I received the aluminum tubing I was waiting on to fabricate the charge pipe, so I was able to knock that out over the weekend. (I'll post some additional pictures in a follow up post). Everything went together ok and I am happy with the final product. I ended up using a v-band to connect the charge pipe to the intake plenum, just due to lack of space. I would have actually rather used a slicone coupler to allow movement due to thermal expansion, but oh well. Note: The plenum isn't quite finished as you can see - I am still trying to figure out where I will be plumbing in a boost gauge, BOV, etc.

I also redesigned the upper supercharger mount and got its support tacked on to the frame.

I am waiting on a smaller pulley for the crankshaft side of things, as well as a different sized belt.

I also put the original tank on the bike just to see how it looked, and I have to say, I really like the look. I may end up using it until I can get around to fabricating a custom tank (aluminum sheet isn't cheap...).

Hi John,
    I'd try to use a v-belt as the power requirement is low for you ( about 2 to 3 hp max) to drive your blower, and the pulleys  available are cheap, easy to setup, and cover a lot of sizes...

Rule of thumb is about a 2" inch min pulley with an "A" (1/2" belt).... Notched V-belts do run cooler and will tolerate more stress from small pulleys, and 3/8" inch belts are also available.

The Red Baron run a "Gilmer" timing belt for one reason only....to minimize the belt tension required...The blower hangs from tabs on the upper bike frame and a lot of belt tension on top of the 5-6 hp drive load was not considered a good idea.

Plus, as our race event require such short run times, changing out a cooked V-belt now and then isn't such a big deal.

The Red Baron starting motor is  6 hp and it uses all of it to spin the rear wheel at 20 mph... a 1/2" belt handles it with ease......

Great info, thank you. I am going to try to run a 3/8" notched v-belt.

Would you (or anyone else for that matter) have any sort of recommendation on a carburetor to use on this setup? Like I mentioned before, a couple vendors had recommended using a Mikuni TM33 with accel pump, but I was wondering what other people thought may work better. Thanks!

Hi, nice project!!!

I use an AMR500 on my bike but it's a 900cc so have to spin it a lot faster than yours...

I do find your AMR300 to be a touch big for a 175cc... Meaning, yes, you can slow it down a lot but then, you'll end up with  a lot of intake pulses which will require quite a big plenum chamber to compensate... (the moment one of your intake valves open might not be at the right high pressure time in the pulses sequence...)

I have been playing with the idea to supercharge a small 125 Honda, haven't got the bike, but I did purchase a small air pump that displaces 130cc per rev, thinking to spin it at engine revs to double the charge.

It looks like this, 3 lobes "a la Bugatti"...







Patrick

Patrick,

The blower is definitely large for this engine capacity, but it should be a fun challenge . That air pump is pretty awesome! I can't wait to see it mounted to that 125.

-John

[John Lawrence]

Close up of the charge pipe/intake

[donpearsall]

I am curious as to why the choice is made to use a supercharger instead of a turbocharger on small engines like these. The SC uses power to make power, but the TC does not. I can see where on small engines the SC uses more power than it contributes. Is the exhaust flow required for the TC too small on these small engines? Or what?

Thanks
Don

[interested bystander]

finding a turbocharger for ten+ cubic inches might be difficult.

That little Rootes blower looks like a jeweler made it.

Neat!

[thefrenchowl]

interested bystander: That little Rootes blower looks like a jeweler made it.

It's aircraft technology... I believe (not sure!!!) that it is used to supply fresh air in quantity to a small helicopter turbine on start up...

As far as carburettors are concerned, I would never use a throttle carb on anything that's sucks a lot of air, too much danger of it being stuck open by the air inertia in the venturi...

So I prefer and use all kinds of butterfly carburettors as used mostly on Harleys... Linkert DCs, Tillotsons, S&S, Keihins and the like

I also use like you what I would call a "torque plate" between drive and supercharger to help the multi V belt track true:





It also helps the belt tensioning via an eccentric bearing, so supercharger stays where it's intended!!!

Patrick

[John Lawrence]

Sorry its been quite a while since I?ve been able to update this thread. My wife and I recently welcomed our baby daughter into this world, so any spare time has been few and far between.

That being said, in the past few weeks I've been able to start working on the bike again!

First thing I needed to address was the front end. The forks were extremely bent and had quite a bit of rust on them. I also wanted something a bit more substantial, so I contacted a gentleman who races these bikes and he made a recommendation that I went with. The forks are off a 1979 CM185T and the triple tree is off a XL175. It?s a direct bolt up and they feel great. There is a small boss on the left fork leg that I need to remove, but that should be the only modification that is needed.

Next was to mount the battery and regulator/rectifier. I decided to go with a 4-cell Anti-gravity Lithium battery, accompanied by a Rick?s Electronics Lithium capable regulator/rectifier combo. I ran the same combo on my last build and I was super happy with it. I went ahead and started making a simple under seat tray to house the fuse block and relay, as well as mounting points to mount the regulator rectifier. Once that was complete, I fabricated a battery tray and mounts behind the seat. It will be eventually covered with some sort of rear cowl. The battery tray is rubber-lined, with a hinged steel hold down to secure the battery.

In a previous post I had mentioned that I had planned on fabricating my own fuel tank, however I decided that for now I would just order one until I can find the time to make my own. That being said, I ordered a generic universal tank off of eBay, and welded on some mounts and installed it on the bike. I did run into a small problem where the tank would not clear the ignition coil. So I cut out the old mount and welded in a simple plate with a couple of mounting points for the coil and condenser. It?s actually much easier to access both of those components now, so overall I am happy with the result.

I think that is everything for now, but I am hoping to update this thread a little more often? thanks for reading!

Pictures will be following this post.

[John Lawrence]

Pics

[thefrenchowl]

John: My wife and I recently welcomed our baby daughter into this world, so any spare time has been few and far between.

Welcome in this world to your daughter...

It's certainly another huge challenge on top of the Salt Bike, so good luck from me for these two endeavours!

Patrick