Forced induction 100cc

[Drew]

Pull your head out of your arse Drew...I've been building pipes and silencers for race bikes and cars since before you were in nappies...

I won't recommend something if I don't think it will work.

Our blown 500 twin used two 2 in bore straight thru mufflers and was well under 100DB - at a time when the regs asked for 102max.
this muffler I'm recommending has plenty of muffler volume - which is the main thing you need - and i'm confident it wil be legal.
The one I'm using now is on a full house Z1 racebike - big cams and compression - and is runnng at about 89 DB.
In my experience,noise on a 4 stroke is directly proportional to cam overlap. Also in my experience, most people have no fucking idea how to silence a race bike effectively.

Meh, I will concede.

[speights_bud]

Try this, dunno if its any good but it was for noise testing and was super nice and quiet, old 2T straight thru can hooked off a mx straight thru can, i was told it could be promising with dyno and a bit more design time.... more quiet = more supercharger noise http://a8.sphotos.ak.fbcdn.net/hphot...10247627_o.jpg

[Grumph]

Try this, dunno if its any good but it was for noise testing and was super nice and quiet, old 2T straight thru can hooked off a mx straight thru can, i was told it could be promising with dyno and a bit more design time.... more quiet = more supercharger noise http://a8.sphotos.ak.fbcdn.net/hphot...10247627_o.jpg

I'm sure that is quiet..I'm equally sure it's too restrictive for a blown motor. Refer what I posted earlier about ex valve temps..

If Sketchy has machined his gears correctly, there shouldn't be any blower noise. That's the advantage of a polyvee belt over a toothed belt...after all, when was the last time you heard belt noise from your car's alternator or water pump drives ?

[Drew]

.after all, when was the last time you heard belt noise from your car's alternator or water pump drives ?

This makes a lot of sense, and is very disapointing!

Belt whine is the best part of supercharging! Except for the extra power.

[speights_bud]

I'm sure that is quiet..I'm equally sure it's too restrictive for a blown motor. Refer what I posted earlier about ex valve temps..

If Sketchy has machined his gears correctly, there shouldn't be any blower noise. That's the advantage of a polyvee belt over a toothed belt...after all, when was the last time you heard belt noise from your car's alternator or water pump drives ?

I told him he shoulda run a good 2" toothed belt but he just wouldn't listen....

I'd say your bang on about the pipe, as it was also too restricted for a std 145 with how it was setup.

[speights_bud]

This makes a lot of sense, and is very disapointing!

Belt whine is the best part of supercharging! Except for the extra power.

I'm guessing there will be some gear whine, almost always happens with straight cut gears to some extent, but with a nice finish and close fit they should be pretty quiet, it might just sound more like something with gear driven cams?

[Ocean1]

If Sketchy has machined his gears correctly, there shouldn't be any blower noise. That's the advantage of a polyvee belt over a toothed belt...after all, when was the last time you heard belt noise from your car's alternator or water pump drives ?

Mate, a straight lobed industrial roots blower direct driven by an electric motor absolutely screams. As in the cost of accoustic mitigation is a significant budget factor.

[Grumph]

Mate, a straight lobed industrial roots blower direct driven by an electric motor absolutely screams. As in the cost of accoustic mitigation is a significant budget factor.

Interesting...our 750cc straight lobed rootes blower was very quiet - even when revved to 13 grand. You could sit on it and rev it and literally not hear any noise from the blower. Straight cut gears too....

I remember the blowers pushing air through the yeast fermentation at DYC ChCh, ferkin big ones too, you knew when they were running but probably only around 90DB in the machinery room.

[Ocean1]

Interesting...our 750cc straight lobed rootes blower was very quiet - even when revved to 13 grand. You could sit on it and rev it and literally not hear any noise from the blower. Straight cut gears too....

I remember the blowers pushing air through the yeast fermentation at DYC ChCh, ferkin big ones too, you knew when they were running but probably only around 90DB in the machinery room.

Pressure differential makes a difference, they're often piggy-backed onto big vane vacuum pumps and they're quiet, (nothing to transmit the sound). On the other hand I've used them for fluidised transport, blowing, (sucking, actually) fibres around ducting, and when they're more or less unrestricted on the sucky side they howl.

[Sketchy_Racer]

I'm guessing there will be some gear whine, almost always happens with straight cut gears to some extent, but with a nice finish and close fit they should be pretty quiet, it might just sound more like something with gear driven cams?

Hey champ, Yeah there is plenty of whine, this is mostly due to the tooth count/pitch dia ratio is out of the recommended window. Interestingly is is only noisy at lower RPM and shuts up once the RPM come up.

Interesting...our 750cc straight lobed rootes blower was very quiet - even when revved to 13 grand. You could sit on it and rev it and literally not hear any noise from the blower. Straight cut gears too....

I remember the blowers pushing air through the yeast fermentation at DYC ChCh, ferkin big ones too, you knew when they were running but probably only around 90DB in the machinery room.

Yeah if the gears were perfectly designed and manufactured they should almost be quiet however housing design and oil also has a large influence on the gear noise, I could always try some banana skins to hide my poor gears. Ideally I would have gone with at least a 30+ tooth count but I didn't have the cutters for it so will see how the coarse 24T lasts. I have a fixture and program to make some more if I need to.

Out of interest did you guys ever create an efficiency map of your blower? As a bit of a side project (mainly for curiosity but also for performance) I am going to map the super charger and see where's sweet spot is in relation to RPM vs Pressure ratio.

To do it I am simply going to do some steady state testing at suitable RPM steps using a variable speed lathe, a flow restriction valve and a temperature probe and plot a graph as there will be a optimal point where I can get the best pressure ratio vs heat to get the optimum volumetric efficiency - sounds like fun!

[Sketchy_Racer]

Progress is being made on the bike, last night thanks to Kyle and Rich Ban for his pipe I got into the workshop and got an exhuast together. I have gone with one of the chinese mufflers as it is very light and looks like it will do the job. I have set the muffler up sort of like some of the Moto3 bikes with it mounted just under the right foot peg. Hopefully ground clearanc shoudln't be an issue. Unfortunatley I don't have any pictures at the moment so I'll get some later.

I have however started to put the bike thought it's weight loss program. So far I have managed to drop 650g off the rear wheel assembly which is a good start. to do that I have machined a new sprocket carrier and lightened the disc carrier. I have also through drilled a lot of the cap screws and turned the cap heads into tapers. Might seem crazy but that was worth 50g on the rear wheel alone. I am currently looking at changing to a 415 sprocket like the RS125s but need to sort out some sprockets. Might look at getting some water cut or just mill them out of some 4mm plate (which means I'll be able to make a cool looking design)

Next will be replacement rear sets that will be lighter and stronger than the current ones. I'm going to look at making a smaller subframe as the current one is designed to hold two people so I'm sure it can lose at least half a Kg there.

The aim with the bike is to get to 90KG which is going to be a mission! But a fun one.

Also here's a pic of the latest perk done in the CNC - a custom brake caliper mount for a mates Starlet with a turbo 4AGE

[Skunk]

Next Project:
http://www.kiwibiker.co.nz/forums/sh...kes-up-buckets

Two conrod V8.

[Grumph]

Hey champ, Yeah there is plenty of whine, this is mostly due to the tooth count/pitch dia ratio is out of the recommended window. Interestingly is is only noisy at lower RPM and shuts up once the RPM come up.



Yeah if the gears were perfectly designed and manufactured they should almost be quiet however housing design and oil also has a large influence on the gear noise, I could always try some banana skins to hide my poor gears. Ideally I would have gone with at least a 30+ tooth count but I didn't have the cutters for it so will see how the coarse 24T lasts. I have a fixture and program to make some more if I need to.

Out of interest did you guys ever create an efficiency map of your blower? As a bit of a side project (mainly for curiosity but also for performance) I am going to map the super charger and see where's sweet spot is in relation to RPM vs Pressure ratio.

To do it I am simply going to do some steady state testing at suitable RPM steps using a variable speed lathe, a flow restriction valve and a temperature probe and plot a graph as there will be a optimal point where I can get the best pressure ratio vs heat to get the optimum volumetric efficiency - sounds like fun!

Ours was a prototype small Martin blower, 750cc displacement. The company had changed hands and the new owner had got an engineer I knew to look at the design and do some more efficiency testing. He used a setup pretty much exactly as you describe except it was a datsun gearbox as a stepup on top of his lathe driving the blower...i was shown the results once and told it would have a flat efficiency curve up to about 10 grand. As it turned out I reckon we didn't lose efficiency over 12 grand either. The engineer did a redesign of the case and put a separator bar across inlet and exit which he claimed reduced backflow and churning losses. Worked for me...
He reckoned 80% efficiency at 10 grand.

[koba]

Also in my experience, most people have no fucking idea how to silence a race bike effectively.

Got any tips for that?

Perhaps a new thread?

[Brian d marge]

Most people have no Idea how to silence a race bike , because they lack the knowledge of what "sound" is.

this also extrapolates to machining/engineering , many have no idea of load paths or or the loading on a material , or the dynamics of loading

When are we going to see this thing in action btw ?



Stephen