Supercharged 212cc Think Tank / Idea Board

[Forge fixer]

supercharged 212cc

I have used a smog pump on a 212cc It boosted up to 14psi until the carbon vanes wore out. Was driven off flywheel side of engine with a pulley welded to the starter cup I spaced the recoil out enough to clear a narrow surpentine belt.

 

[bob58o]

I have used a smog pump on a 212cc It boosted up to 14psi until the carbon vanes wore out. Was driven off flywheel side of engine with a pulley welded to the starter cup I spaced the recoil out enough to clear a narrow surpentine belt.

That is awesome!!! How long did it last? What carb? Draw through right?
What fuel? What jetting? How did it run? I have so many questions.
I wish there was a thread detailing your trails.

 

[karl]

Ill leave this here.

I peaked 5psi of boost, but needs a revisit with a draw through carb.

The smog pump I used had no inlet, and blow through caused alot of issues.

https://www.youtube.com/watch?v=FRxE4gsHtp0

 

[bob58o]

Ill leave this here.

I peaked 5psi of boost, but needs a revisit with a draw through carb.

The smog pump I used had no inlet, and blow through caused alot of issues.

https://www.youtube.com/watch?v=FRxE4gsHtp0

What is special about a draw through carb?
I thought one of the benefits of draw-through was that you don't need a special carb, or a pressure chamber enclosing it.

 

[karl]

What is special about a draw through carb?
I thought one of the benefits of draw-through was that you don't need a special carb, or a pressure chamber enclosing it.

I am saying draw through is the way to go, blow through is messy and tricky , as I learned. So I need a pump with an inlet , that a carb can be put on.

 

[Denny]

Karl, Bobs a little slow so you kinda gotta explain things to him with long math formulas.


Denny

 

[bob58o]

Karl, Bobs a little slow so you kinda gotta explain things to him with long math formulas.


Denny

This is my minibike simulator device. I've been putting in hours.

 

[Forge fixer]

predator 212cc

In answer to your question Bob I don't think it lasted more than 15 hours of runtime I used a mikuni 26mm carb blowthrough with regular pump gas. I may have drilled the jet a little and adjusted the needle. It was a bit of a pain to run it liked to stall do to fuel coming back through the line pressuring the gas tank. I would not bother using a smog pump a AMR300 draw through would be a better option or a vz21 turbo blow through which produces an astoning amount of power.

 

[bob58o]

This is the way to do it, right?
Or vent to atmosphere?
What to use for bypass?

Does the bypass valve protect the blower from blowing up on back fires?

 

[bob58o]

What to use for bypass?

How about something like this?
https://www.amazon.com/dp/B01MUD0ZI...ZG&pd_rd_r=49JNXBEE7NENVM0JRSNC&pd_rd_w=KGqBn

Qkparts Recirculate Diverter Valve Turbo BOV Boost Black fits for VW and Audi 1.8T 2.7T

Just started looking at bypass and blow off valves.
Guessing I hook up a vacuum line to the top of the bypass valve (next to the bypass return line on the blower intake side).

Seems simple.

Throttle closes.
Creates Low Pressure between the carb and blower.
Bypass valve opens.
Some Air gets routed back to blower intake (instead of engine) to attempt to equalize pressue.

Not sure the type of bypass I would need, or how to tune it with springs for my application.
Trial and error I suppose.
I think I’ve seen some knob adjustable ones?

 

[Forge fixer]

predator 212cc

I havn't ever done a draw through but a blow off valve should work.There's a $10 one on ebay thats adjustable.

 

[bob58o]

I havn't ever done a draw through but a blow off valve should work.There's a $10 one on ebay thats adjustable.

Blow off and bypass are basically the same right? But Blow Off Valve vents to the atmosphere if I understand correctly, where a bypass for a roots blower reroutes it back to the the blower intake.

Think I read something about wanting a bypass back to the intake to prevent the vacuum on the intake side of the blower when the throttle closes. Better for the blower, IIRC. If venting to the atmosphere, the blower is still pulling against the closed throttle and that Vacuum remains. Think this is bad for the blower?
This might not be correct? I just starting to learn this stuff.

Pretty sure I also read a bunch of people saying a bypass isn't necessary with a draw through roots system. Since the intake valve is always opening and closing (not like the throttle, which can stay closed), then the pressure doesn't build up the same like it would if the blower was located before the throttle (as it would on a blow through set up).

I'm not really sure about any of this, so feel free to input anything.

 

[NewbCarter]

Wouldnt you simplify it alot if the blower was driven the whole time ? No real point in it standing still until needed , because with it not spinning its just an airflow restriction and it complicates your tubing ...

Unless i read wrong and driving it the whole time isnt possible ?

 

[bob58o]

Wouldnt you simplify it alot if the blower was driven the whole time ? No real point in it standing still until needed , because with it not spinning its just an airflow restriction and it complicates your tubing ...

Unless i read wrong and driving it the whole time isnt possible ?

How do you mean simpler?

I haven't really decided how to drive the blower yet.
I could figure out a way to do it either way.
Can I put a chain on a flywheel starter ring gear? I'm guessing that is not advised.

If using a bypass valve, and the blower turns when idling, then the bypass stays open until I crack the throttle. Then the valve closes and I get boost. The engine revs and the clutch engages under boost.
I close the throttle. The valve opens. The engine slows to idle. The blower continues to re-circulate air with the bypass open feeding the engine only what it needs to idle.

If it engages with the clutch, at idle the blower doesn't turn. I open the throttle, the valve closes, the engine revs, the clutch engages under no boost, then blower starts to turn. Seems like it would come on more gently?
I close the throttle, the valve opens, the engine slows to idle, the blower stops. Not sure if the valve remains open without out the blower turning (I could probably tune the valve for how I wanted it). Seems like it would be hard to idle without the blower turning. Like you said... It is a big restriction.

I see pros and cons of each.
For more instantaneous violent Torque, I would want it spinning all the time, but it might be harder on the clutch???
For ease on parts and a more controlled feeling, I might want it to engage with the clutch, but the blower is a big restriction if not spinning - so maybe it won't idle without it spinning?

Tell me what you were thinking.

 

[NewbCarter]

By simpler i meant that with a draw through setup and with the blower driven all the time , you eliminate the need for all the extra tubing , except maybe a blow off valve to control boost , tho i suppose you wont be running that much to warrant one . Maybe a diverter valve would be better suited so you dont waste the fuel/air mix .

I get that you wanted to bypass the blower till the clutch engages so you save it from excess wear , but the strength of a blower is the low end power ... so the way i get it by doing the bypass you are cancelling out the blowers best attribute .

And as far as i know , diverter valves are not meant to be open for long periods , so dont know how would it behave .

Looks interesting , tho id go with an uprated clutch and drive the blower all the time ..

 

[bob58o]

By simpler i meant that with a draw through setup and with the blower driven all the time , you eliminate the need for all the extra tubing , except maybe a blow off valve to control boost , tho i suppose you wont be running that much to warrant one . Maybe a diverter valve would be better suited so you dont waste the fuel/air mix .

Still not sure I follow.

I don't see how the plumbing changes depending on how the the pulley is driven. If you are saying I don't need a bypass, I can dig it - but I don't follow the logic.

If I removed the bypass, wouldn't it make more sense to have the blower STOP at idle, as opposed to removing the bypass BECAUSE the blower is spinning at idle?

 

[NewbCarter]

Still not sure I follow.

I don't see how the plumbing changes depending on how the the pulley is driven. If you are saying I don't need a bypass, I can dig it - but I don't follow the logic.

If I removed the bypass, wouldn't it make more sense to have the blower STOP at idle, as opposed to removing the bypass BECAUSE the blower is spinning at idle?

I suppose the engine wont even run when the blower is in the way and not spinning , due to it being such a restriction => thus you need a diverter valve as a way to bypass the blower in order to run.

If you run the blower continuosly then there is no need to bypass it thus no extra hoses .

 

[bob58o]

I think I'm starting to pick up what you're laying down.
The bypass might work how I want, but otherwise i should Keep it Simple Stupid.

Even if the blower is always turning, I see benefits of the bypass.

1.) When I the close the throttle, the bypass will alleviate the pressure built up in the intake runner. - Acts like a blow off valve (not really sure it is needed because the valve opens and closes and the engine is consuming the air).

2.) When the throttle is closed, the blower won't be pulling against the closed slide in the carb. Seems like a lot of air would leak through. Maybe cause issues with gaskets?

3.) At idle, I'm not shoving more air in than the engine needs. It might be easier to tune the idle circuit and keep idle RPMs lower if bypass is open. Help with supercharger surging when idling or when throttle is closed.

All of those might help, but probably aren't necessary. And if the bypass doesn't work how I want it to, it becomes a big hassle. Maybe the bypass is only for fuel efficiency and to help the surging?

Good thread.
http://www.eng-tips.com/viewthread.cfm?qid=233418


Going back to the case where the blower engages with the clutch, it seems much easier to pull start an engine when you don't have to turn a blower and stuff a whole bunch of air through it and into the engine. Maybe not, just guessing on that.

 

[mckutzy]

An idea...
I have been looking up other ways to connect a starter with having a clutch... I found there is a bit of space between the motor side plate and the clutch..
Now if the clutch has a few washers to space it off from the drum edge, a sprocket will fit between if bolted to the drive plate of the cent clutch....
Now obviously it would need to be disassembled, drilled and countersunk head bolts used.......
But there might be something in this... If not to see how it goes...

 

[bob58o]

In this video I think they replaced the spacer (the one that keep the TC driver unit off the backplate) with a pulley to drive an alternator. Or maybe they just wrapped the belt around the spacer (with washers around it). Not very clear what they did.

5:51
https://www.youtube.com/watch?v=I1kU5YpcdIM