Supercharged 212cc Think Tank / Idea Board

[bob58o]

Maybe this will happen? Maybe it won't?
That is what this thread is for.
A place for me to gather some information and ideas.

https://www.aliexpress.com/item/Car...-Displacement-0-8-1-8L-model/32273549916.html
AISIN AMR300 mini Roots supercharger Compressor blower booster Turbocharger Kompressor Turbine Auto Car Snowmobile ATV 0.5-1.3L


Feel free to input anything you want, or feel free to ignore this altogether.

The plan (I should say idea, it's not a plan yet) is to supercharge a 212 Predator with an AISIN AMR300 Roots-Style Supercharger. It would be a Draw-Through Set-Up.

Air Filter > Carb > Pump > Cylinder Head Intake Port

I think I can use an unmodified carb on a Roots Style Draw Through Right?

Starting with what I know (or what I think I know)....
1.) The 300 in AMR300 means 300cc output per revolution.
2.) A 212cc 4 stroke engine uses 106cc of air per crank revolution if operating at 100% volumetric efficiency.
3.) A stock 212 Predator is ~8.5 Static Compression Ratio
4.) If ordering the pump with an A-type, V-Belt pulley, the pulley is ~3.27" (83mm)
5.) The AMR300 is reversible. (Spin it either direction)

I assume in order to make a 300cc / Revolution Pump output 106cc/Revolution I would need to UnderDrive the Pump 2.83:1 from the crank (3.27" Pulley on pump : 9.25" Pulley on "Crankshaft").
That would be operating at 14.7 psi (NO Boost).

If I want to double the amount of air the engine consumes, 212cc per crank revolution (424cc per complete 4 stroke cycle), then I UnderDrive the Pump 1.42:1 from the crank. (3.27" on Pump, 4.64" Pulley on "Crankshaft" (or with the pulley on a jackshaft spinning 1:1 with the crank).

At 212cc output/revolution, I MAY be operating at 29.4 PSI (14.7 PSI Boost). Pretty sure, but like I said - I only think I know the 5 things above.

Effective Compression Ratio for a Forced Induction Engine????

At first I thought if I double the PSI, I also double the Effective Compression Ratio (ECR). And I found this formula online.
http://www.theblowershop.com/wp-content/uploads/2015/08/Effective_Compression.pdf

ECR = ((BOOST + 14.7)/14.7) * CR
Meaning if running 14.7 PSI Boost, Then ECR = 2 * CR.
An 8.5 CR Engine would be 17:1 with 14.7 PSI Boost.
An 8.5 CR Engine with 29.4 PSI Boost (318cc per crank rev?) would have 25.5:1 ECR.

But then I came across this formula.
http://www.xcceleration.com/cr-boost 101.htm

" The problem is that most people use an incorrect formula that says that 14.7psi of boost on a 8.5:1 motor is a 17:1 ECR. So how in the world do people get away with this combination on pump gas? You can't even idle down the street on pump gas on a true 17:1 compression motor. Here's the real formula to use:

ECR = SQRT((BOOST PSI + 14.7)/14.7) * CR"

Meaning if running 14.7 PSI Boost, Then ECR = SQRT(2) * CR = 1.44 * CR
An 8.5:1 CR Engine with 14.7 PSI would be 12:1 ECR
And 8.5:1 CR Engine with 29.4 PSI boost would be 14.7:1 ECR

So which is it?
Does 14.7 PSI Boost make 12:1 ECR or 17:1 ECR on an 8.5:1 Compression Ratio Engine???
And 29.4 PSI Boost? 14.7:1 is very different than 25.5:1.

I'm ABOOT to try a little ideal gas law, but I've got P's, V's, n's, R's, and T's. But I don't have any squared terms?

Let's hear it.

Also, would a Draw Through set-up need a Bypass Valve or Blow off?
When the throttle is closed, a bypass that routes some of the output of the pump back to the input side (after the carb)? I don't think you need it with a draw-through, But I don't know? Maybe needed at idle? Or for starting?

Lots of ideas floating around right now. Don't want to lose focus yet.

 

[Kartorbust]

Lot cheaper than the mini turbo people buy. Wonder why they decided on a roots and not a twin screw? Hopefully this would work well on the 212, considering it's half the size of the 500cc they recommend.

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[Whitetrashrocker]

The 1471 we have on the dragster has no blow off valves of any sort.
You tune it to what the engine needs be pulley size. Smaller pulley more boost.
Other than that it goes with proportionally with RPM. More rpm more boost. This curve changes with the pulley size obviously.
We have charts for all the specs but seat of the pants is kinda how we tune.

And remember more air means a need for more fuel so a change in blower means a change in fuel curves too.

 

[bob58o]

Other than that it goes with proportionally with RPM. More rpm more boost.

I thought that with roots style blowers the BOOST is constant (more or less), compared to centrifugal superchargers - which make more BOOST at higher RPM???

I was under the impression that Positive Displacement Pumps were better at making boost at low RPM for that reason.

If you tune a Centrifugal SC to make 10 lbs boost at 3000 RRM, then it will make much more at 6000 RPM, or am I wrong?

Where if you tune a Roots SC to make 10 lbs boost, it should stay fairly constant throughout RPMs, maybe dropping at high RPMs?

 

[Kartorbust]

I thought a centrifugal supercharger was more or less like a belt driven turbo, so the higher the rpm the more boost?

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[Whitetrashrocker]

It's a curve.
Based on the ratio between pullies.
But simply the greater the ratio the more boost on the top end.
I'm not good at gab'ing sorry.

 

[Joe-405]

It would be interesting to see if that thing works well. I’m thinking about turbo charging the Yerf dog. Or adding nitrous. When it’s done. If it’s a 600cc it will need a power adder to be as fast as I want it anyways. 140hp isn’t enough.

 

[bob58o]

I thought a centrifugal supercharger was more or less like a belt driven turbo, so the higher the rpm the more boost?

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That is how I understand it too.

BUT the AMR is a Positive Displacement or Roots- style, not centrifugal, supercharger.
I've only started researching this stuff.

Roots vs Centrifugal…which one??
http://www.redline-motorsports.net/supercharging-roots-vs-centrifugal/

Now here is the critical difference between a centrifugal blower and a positive displacement blower.

The amount of airflow a centrifugal delivers (literally blows) increases roughly at a square of its driven speed. It is NOT linear. So say at 3k rpm it delivers ‘X’ airflow. At 6k it now delivers roughly X^2 airflow. What this means is the airflow of the blower will increase faster then what the engines airflow requires. IOW, as RPMs increase the boost level will rise. Because of this you need to set the blower so that its max boost occurs at redline. This means that at every point below redline you will NOT be at maximum boost. So say you had it set for 8psi at 6500 rpm. Then you can figure that at 3250 rpm (half SC driven speed) you now how the square root of the boost at 6500 rpm… or 2.8 psi.

If you tried to set the pulleys up so you hit 8psi at 3250 rpm then figure out how much boost you would have at redline. Again the driven speed doubled so you square the boost…. 64psi! Talk about severely overboosting!!

Now a positive displacement (also called a fixed displacement) blower produces airflow in a totally different way. As its name implies for each RPM the amount of airflow it pumps is ‘fixed.’ IOW, its airflow is linear. Say at 3k rpm it produces ‘Y’ airflow. Then at 6k rpm it will produce 2Y airflow.

Notice how the airflow delivered is very much like what an engines airflow requirements are.

What this means is you set the pulley ratio for whatever max boost your require. Because the positive displacement supercharger delivers airflow linearly (like an engine) it will maintain full boost throughout the rev band. At 3250 rpm you would have 8psi and you will also have 8 psi at 6500 rpm. In theory you should have full boost at idle but it doesn’t actually work that way because of air leakage around the rotors inside the blower when it is turning at very low RPM.

 

[Kartorbust]

Then the last question and this maybe stupid, but with a pulley already on the pto, what room and options would their be for the clutch or cvt? 1:1 jackshaft and run them remotely?

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[bob58o]

Then the last question and this maybe stupid, but with a pulley already on the pto, what room and options would their be for the clutch or cvt? 1:1 jackshaft and run them remotely?

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Not sure how I would do it. I guess it depends on the vehicle.
For example I could use a Jackshaft and use a clutch with two sprockets. One chain to drive the rear axle and one chain to drive the JS. The pulley driving the supercharger will be on the other side of the JS.

If the SC pulley is spinning the wrong direction in the picture, then imagine the pulley on the other side of the the blower or I flip which side the carb is on. ? Not sure which way it turns to pump which direction. Guessing if looking at the pulley, clockwise rotation moves air left to right???

 

[itsid]

Ogura TX02 is what I say...
https://www.oguraclutch.co.jp/e/product/supercharger/type.html

Anyways, As far as I understand the inlet and outlet ports of those blowers are more often than not of different size (to not create too much of a vacuum on the inlet port it's usually a tad bigger) soo reversible?? I'm not sure if that's true for the AMR.. *shrugs*

I think it'd be really cool to pick a 5k or 6k pulley on the blower
then drive the belt off a ribbed clutch bell
(bypass needed for idle of course)
the Maxtorque SS having an OD of 4.25" you might need to sleeve it,
IIRC the Noram clutches are bigger.

'sid

 

[bob58o]

Ogura TX02 is what I say...
https://www.oguraclutch.co.jp/e/product/supercharger/type.html
'sid

That's pretty cool. I sent a message asking about price.

Anyways, As far as I understand the inlet and outlet ports of those blowers are more often than not of different size (to not create too much of a vacuum on the inlet port it's usually a tad bigger) soo reversible?? I'm not sure if that's true for the AMR.. *shrugs*

'sid

I have no clue, but the auction description says
"1.Direction of rotation as you want,but the air intake and outlet will swap"
Those flanges in the picture make it seem like they are both the same size, possibly aftermarket flanges? Made the same size-so it is reversible??? And they mean swap which side the carb is on?

Or maybe I would just have to unbolt the two flanges and swap sides if they are different sizes?

I sent another message, but not sure it will be clearly understood in a different language (or in English)???

I think it'd be really cool to pick a 5k or 6k pulley on the blower
then drive the belt off a ribbed clutch bell
(bypass needed for idle of course)
the Maxtorque SS having an OD of 4.25" you might need to sleeve it,
IIRC the Noram clutches are bigger.
'sid

I'll look into that, but if you have ideas of how to do that I'd be willing to listen. Are there replacement ribbed clutch bells? Or something I'd have to fabricate? or Adapt?
Like cut apart a pulley, and just keep the ribbed part?

https://www.sip-scootershop.com/en/products/clutch+bell+malossi+maxi_m7715898

 

[itsid]

well you could always fabricate (turn on lathe) a sleeve
(ribbed outside with a bore that snuggly fit's the clutch bell)
IDK how well it needs to be turned (tolerances and such) to hold on tight and not let go even if the clutch gets hot... *shrugs*
but technically it seems to be a straightforward piece
(some small length of large diameter tube turned and ribbed to specs)
tack welded like the malossi (5.some inches.. a bit big, no?) in your pic?
or press fit is up to what'll work and is easier to make.

just an idea I tossed out.. not something I thought about for more than a few seconds really I'm afraid.
So yeah..
the more important part is that you will need a bypass .. as I mentioned,
since the blower is powered by the clutch bell, it's not powered when the engine is in idle (clutch disengaged)
and without a bypass the engine will just suffocate...;
I think that's the less trivial thing to think about tbh.
since it'd need at least one valve to open/close once the blower revs up.
will a mechanical valve do (like the one you have on your air compressor)?
Or does it need to be electronically actuated *shrugs*

I wouldn't care much about reversibility tbh..
that's a matter of changing the pipe-works to compensate if it's NOT reversible..
or just rerouting the drive belt (two idlers and a double sided belt.. and it runs in reverse at it's current position)
an unlayed egg.. that's worth waiting for before it's discussed IMHO.

I had another idea that's even weirder tbh.

it involves a modified series 20 driven clutch
with an old school centrifugal elevator brake system (centrifugal 'fly ball' governor)
so that the faster the series 20 clutch spins, the wider it opens up (w/o any belt forcing it open)

then, a series of idlers (to compensate belt length) to run the blower at variable ratios
(the faster you go the more charge it provides...)
Nasty, not?

Sketchy, I know.. I don't even know if it makes much sense to even try...
as I said I haven't thought about anything for more than a few seconds really.. it's just what popped to my mind.

IIRC those elevator brake 'flyballs' can be adjusted
(limited in stroke and positioned to adjust the applied force)
so you could in fact adjust the ratio limits and settings rather easily, which would be cool IMHO.

Also you had a set of balls whirling round on your engine which would give it some sort of mad scientist steam punk character (whirling balls of OUCH OUCH OUCH... LOL)

'sid

PS Sorry you said think tank and I toss out half baked ideas as if you said brain storm

 

[ezcome-ezgo]

Think, think, think...

 

[bob58o]

(the faster you go the more charge it provides...)
Nasty, not?

I thought about driving the SC off a TC Jackshaft.
Something like 0 PSI BOOST when the TC engages and full BOOST when the TC Reaches overdrive.

For example using 30 series ratios with a 6" Driven Pulley...

300cc per revolution / 2.68 = 112 cc / revolution.
112/106= 0.82 PSI Boost

300cc per revolution / 0.90 = 330cc / revolution
330/106 = 31 PSI BOOST

Brings me back to ECR.

((Boost) + 14.7 / 14.7) * CR = 26.5 :1 Effective CR, If starting at 8.5:1 with 31 psi boost
or
SQRT((Boost + 14.7)/14.7) * CR = 15:1 Effective CR, if starting at 8.5:1 with 31 PSI boost.

And Even if the ECR DOES include the SQRT term, then think I need a camshaft, fuel octane, and ignition timing, that works with 8.5:1 ECR AND 15:1 ECR.

I decided it might be easier to keep the boost constant across the RPM range, in order to keep ECR constant over the RPM range.

 

[bob58o]

Reply about the direction of the SC flow...

 

[ezcome-ezgo]

Inverting the photo does not mean the flow goes either way.

 

[taotao110d]

That a vw smog pump?

 

[bob58o]

That a vw smog pump?

If you looked at the first post, you would know it is a AISIN AMR 300 Roots-Style Supercharger. It is used on Subarus.

People use smog pumps, but this is not a smog pump.

---------- Post added at 10:51 PM ---------- Previous post was at 10:38 PM ----------

http://www.elsberg-tuning.dk/supercharging.html
Supercharging Small Engines


"Well, the smog pump is an airpump, a supercharger is nothing but an airpump, so of course a smogpump can be adapted as one! My experiences with this cheap and plentiful smogpump is all good! But like everything else, the equation must sum up. Pumps have different sizes, and maybe not the size needed!

The most trouble I have had with a smog pump supercharger was a wrong sized pump! Intended use is important too! I have used the smog pump as a supercharger on a racebike for short distance races. I have not used the pump as a part of a daily transport vehicle. Unlike the situation of a racebike, which is "supposed to be" taken apart and inspected, before next racemeeting, a daily driver would present other problems. Will the five roller- bearings inside the rotating drum be washed out, by the fuel- mix present?

The most common, and cheapest, smog pump is the one mounted on GM and Ford V8 engined vehicles from 1969- onwards. Also known as an A.I.R. pump, this device can be found attached to the front of the engine, driven by a v- belt. These pumps gave a steady 5psi reading, when tested for functionality, and their mission was to ingest air, via small tubes to each exhaust manifold, just outside each exhaust port. This air- injection helped igniting the catalytic- converter, reducing emissions emitting the exhaust pipe.

Converting your smogpump into a supercharger goes like this:

Unbolt the rear cover, and pry it apart, but very gently! These are delicate thin- wall castings and you dont want a leaking supercharger. A little trick here is to drift out the two dovels, which lines up everything. After loosening the cover, you have to wiggle it from side to side to extract the cover-mounted axle from the vanes rollerbearings. Once out, you can see the internals. Most significant is the large metal drum, with two vanes protruding 180degrees apart. You can also note the rollerbearing which supports the barrel. If You want to change the direction of rotation, you must pull the bearing support from the drum. A simple special tool must be made for this operation. The support is a casting, and a bit fragile! Once the bearing support is removed, you can see the two cages containing the seals. These cages are asymmetrical because one of the seals has a spring behind it. If you try to run the pump counter- clockwise as is, this spring will be compressed. Result will be a major leak, and at high rpm, the seals can move around and break! So it is vital that the cages are loosened, turned around, and welded back in! If the six? spotwelds are carefully removed, the cages can be loosened without getting out of shape. When re- installing the bearing support, take care not to squish the curved end- seals.

As an alernative you can run a jackshaft, allowing you to run the smogpump as is - see drawing!
Most smogpumps has its air- intake in front, behind the plastic-fan, which also acts as an airfilter. This is no good since its quite impossible to fit a carb or much needed airfilter here. This intake can be closed by applying Devcon, or similar, into the hole."

 

[itsid]

oh, come on bob..
scroll a bit on the elsberg pages and you can see the VW smog pump taotao is talking about
laying right next to an a blower the size of an AMR300 (or AMR500?? can't remember.. 2kg vs 2.6kg [a pound and a spit smaller])
And you know why he asked that..
roughly the same size (impossible to tell from a pic let's say) exactly the same shape and style..
the only distinguishable difference really is the VW logo on the bearing caps at first glance..
so yeah.. it's NOT the VW smog pump, but it's surely it's close sibling
they even run the exact same lobe profiles internally...

'sid