Porks bike carbs and boost project

[Enuo]

I think I might have to move my throttle body to before the supercharger

with the belt super tight, it squeals, at idle it's ok(bypass open),
But then blip the throttle and it slips the belt
think the build up of pressure is stalling/slowing the blower compared to the crank rpm, skipping the belt

If I rev it standing still and then off throttle, the force if the air that comes out off the bypass valve is crazy! Il have to put a pressure gauge before the throttle to see

Anyone got any thoughts on this?

Wanna get everything right(ish) before mappikg

Bear in mind it'll be venting the same amount of air as turbo at full chat with a BOV... and its usually fed back into the intake so you wouldn't notice. But you have an M24 and that recirc is for an M45, do it should be more than man enough. Have you checked the recirc is working properly yet?

 

[pork]

It's fine on idle (mani vacuum keeps valve open, recirculating air)

It's when you slightly open throttle(bypass closed)
It squeals,

 

[Enuo]

I believe a bypass valve should be proportionate? Not on/off like a bov?

 

[frank]

centrifugal clutch maybe neil ?

 

[pork]

My thinking is ( probably rubbish lol)

With the TB after the s/c, the s/c will always be running at wot.
It's a positive displacement pump, so will be pumping all it can all the time against a closed door.
At idle, the idle bypass is open, venting out the boost,
At partial throttle (where it squeals the most) the bypass is closed whilst the s/c is still blowing it's full amount at a partially open door, backing up the pressure, so causing the rotors to slow, slipping the belt.
I did pop off a boost pipe the other day just whilst the car was still and revved engine.

 

[Enuo]

What about a switch on the pedal that only engages the electro clutch above 3/4 travel say?

 

[pork]

Could probably do somthing with the ecu outputs too

But might make things bit twitchy, on and off rapidly, if needing light throttle

 

[pork]

centrifugal clutch maybe neil ?

View attachment 31152

Mines on a magnetic clutch allready maye

 

[frank]

thats the problem with petrol turbo,s eh neil, i re-routed my boost gauge pipe to the chargepipe today.
so now my boost gauge does,nt register any vacuum at low throttle (it just stops at zero when idling etc)
but what it does show now is that the turbo is creating boost most of the time, but that boost is being blocked by the slightly open throttleplate ie, at 70mph cruise when the mani and post throttleplate has about minus 5 psi , the chargepipe/pre throttleplate has plus 3 or 4 psi

 

[frank]

Mines on a magnetic clutch allready maye

an additional centrifugal one would be more progressive tho

 

[Enuo]

Could probably do somthing with the ecu outputs too

But might make things bit twitchy, on and off rapidly, if needing light throttle

Well once you've got going you'll spend nearly all your time in the turbo range (3-3.5k+ RPM) and any time you spend below that will be cruising, and probably not using more than half throttle, and when you're cruising above half throttle will be motorways where gearing will keep you above the supercharger range anyway
It'll effectively only pull the sc in when you are pulling away or fighting for a spot in traffic

 

[pork]

I must rig mine up like that too, try do it tomorw.

Like I said, the boost that comes out off the bypass valve is immense, blows the bypass tubes apart!

So am I right in thinking, that this suoercharger is a air 'mover/blower', not a compressor, I mean, it doesn't compress air in the actual charger, only after it in the inlet mani and pipes?
So the surge that us created against the partially opened throttle, would cause the rotors to slow?

 

[frank]

I must rig mine up like that too, try do it tomorw.

Like I said, the boost that comes out off the bypass valve is immense, blows the bypass tubes apart!

So am I right in thinking, that this suoercharger is a air 'mover/blower', not a compressor, I mean, it doesn't compress air in the actual charger, only after it in the inlet mani and pipes?
So the surge that us created against the partially opened throttle, would cause the rotors to slow?

yes mate, because its positive displacement, the pressure levels will alter with the different throttle openings

 

[Enuo]

Yeah thats the jist of it. It moves a discrete volume of air with every revolution. If it moves twice as much air as the engine is consuming, you end up with twice the mass of air in the inlet at all times, but taking up the same volume so the density doubles

 

[pork]

So would moving th TB help?

Or would I need a TB on the plenum stil?

 

[frank]

it,ll create vacuum instead of boost tho surely ? same stalling issues

 

[Enuo]

What pressure are you expecting from the sc?

 

[pork]

it,ll create vacuum instead of boost tho surely ? same stalling issues

I would of thought the air that comes through for the engine to idle would be enough,

 

[frank]

if you blip the throttle without the s/c running is the engine free to inhale neil ? (bypass or whatever)

 

[pork]

What pressure are you expecting from the sc?

Last time with my home made changeover valve (really leaky one) I was getting 2-3 psi on idle (had boost gauge in boost pipies)

And 5-6 whilst driving up to 3.5k

But that valve leaked loads, so was recirculating most of the time, so now I've got a air tight changeover, god knows lol

 

[Enuo]

Seems like a lot of work when you potentially have an electrical solution curtousy of your ecu and electro clutch... but you'd definately get more control by repositioning the throttle.

 

[pork]

if you blip the throttle without the s/c running is the engine free to inhale neil ? (bypass or whatever)

It does seem to be a little restrictive....as is you press the pedal, it's not instant......not sure if that's a timing issue tho

 

[pork]

Seems like a lot of work when you potentially have an electrical solution curtousy of your ecu and electro clutch... but you'd definately get more control by repositioning the throttle.

Only one way to find out, I've got the room to do it, would jus need to make a couple of adaptor plates

 

[frank]

It does seem to be a little restrictive....as is you press the pedal, it's not instant......not sure if that's a timing issue tho

the engine will struggle to inhale through a positive displacement s/c that is start delayed tho surely ?

 

[Enuo]

the engine will struggle to inhale through a positive displacement s/c that is start delayed tho surely ?

You'd need a small one way valve the pressure side of the sc to act as an idle control valve and that would sort it I reckon

 

[pork]

Thought the bypass valve open would be enough

 

[Enuo]

Thought the bypass valve open would be enough

If there is no air getting to the sc then there would be nothing for the bypass valve to vent. It would then act (poorly) as a one way valve.

 

[pork]

The bypass is next to the TB, and recirulates/vents to the inlet of the turbo (which goes into s/c)

 

[frank]

Thought the bypass valve open would be enough

as long as it operates correctly yeh, if its causing mad vacuum or pressure surges when you blip the throttle tho, you will get those belt slip scenario,s eh

 

[pork]

The piston that operates it is connected to the mani vacuum. I can see it moving too

 

[h701micra]

Move the throttle body and the sc is free to feed the engine as it likes giving you a similar effect to turbo run-on on a knackered diesel

My 10cents says try and get your bypass to close at the same rate the throttle opens. So it doesn't create a huge pressure at the throttle

 

[pork]

If I did move the TB, there's gunna be quite a bit off volume off pipes, intercooler plenum........would this make a difference?

Or would I need to have 2 tb's, one where it is now, and one pre supercharger?

Disregarding the complexity issue for now, jus wanna know what's needed......il think of rest later lol

 

[padraicR]

Hows about the electric actuator used in busses ( my area) and modern cars for throttle ? Variable resistor on throttle body just fallowing your TB's movement and feeding to a solinoid on your SC so they open and close evenly

 

[pork]

Maybe not for the inlet throttle......but I may come back to that if my air powered changeover valve fails

 

[frank]

does drive-by-wire throttle not appeal then neil

 

[pork]

Neil does not understandy comprehendy

You forget, up until over a year or 2, all I've done is change a wheel over !
Never knew they existed lpl

 

[AlexValiant]

If doing twin-charging the only reliable way to switch over between chargers is using re-purposed flyby-wire throttle body controlled by ECU.
Failing that you can use waste gate actuator to open the bypass throttle on the supercharged when pressure from the turbo reaches certain point.

This is how VW does it:

this is what i want to tell you but i'm Portuguese and i need more training in my english and i now the car mechanisme
and you need to put a blow-off valve because your is over loading air wen you let go off the throttle.

 

[AlexValiant]

ps. the images are in german

 

[h701micra]

VW = Fail
Neil = Win
Lancia = Win

 

[pork]

If doing twin-charging the only reliable way to switch over between chargers is using re-purposed flyby-wire throttle body controlled by ECU.
Failing that you can use waste gate actuator to open the bypass throttle on the supercharged when pressure from the turbo reaches certain point.

This is how VW does it:

this is what i want to tell you but i'm Portuguese and i need more training in my english and i now the car mechanisme
and you need to put a blow-off valve because your is over loading air wen you let go off the throttle.

Hi, thanks for the info, your English is a lot better than my Portuguese !

With my engine, I have the turbo going into the supercharger, the supercharger is from the vw golf engine you've mentioned, I also use the electromagnetic clutch from the golf too.

The changeover from supercharger to turbo is controlled by a throttle body attached to an air actuator..,,,.,.

....and instead of a blow off valve, I'm using a vacuum operated bypass valve from a BMW mini, (40mm hole)......

 

[h701micra]

Neil
Going back to what PadraicR said. You could use signal from the tps to to operate some kind air valve (word escapes my mush brain).. using the ecu or something so the closing of the bypass isn't as sudden? And the air is controlled

Just a thought I'll go back to making less impressive things now

 

[AlexValiant]

Hi. Probably the hole of 40mm is not bigger then what you need. But explain me a thing?! You have the turbo pushing air into the supercharger?
If is that, i will explain you one thing,(if you don't know, if you know forget this). The supercharger is for low rev, and the turbo for high rev, conclusion: the supercharger need to be first and the turbo second to put air on the inter-cooler if you don't have on this way your engine will go kaput before you know it.
Is in this way because the turbo loose is speed slower because the size of the waste gate from the turbo is small for the exhaust gases to be release before the supercharger release the air.

 

[Enuo]

Hi. Probably the hole of 40mm is not bigger then what you need. But explain me a thing?! You have the turbo pushing air into the supercharger?
If is that, i will explain you one thing,(if you don't know, if you know forget this). The supercharger is for low rev, and the turbo for high rev, conclusion: the supercharger need to be first and the turbo second to put air on the inter-cooler if you don't have on this way your engine will go kaput before you know it.
Is in this way because the turbo loose is speed slower because the size of the waste gate from the turbo is small for the exhaust gases to be release before the supercharger release the air.

Its a LOT more complicated than 'supercharger for low rev, turbo for high rev'
Superchargers are fixed displacement pumps (or at least this one is), so putting a supercharger feeding the turbo will result in the turbo doing absolutley nothing

 

[AlexValiant]

experiment pipe from the out of the SC into the turbo and from the turbo t the intake

 

[Enuo]

experiment pipe from the out of the SC into the turbo and from the turbo t the intake

It will result in the turbo trying to scavenge air the supercharger will not supply. A turbo can supply more or less air depending on demand/flow/revs etc. A fixed displacement supercharger gives a set amount of air and will not change. Increasing pressure means drawing air and squashing it. If the turbo can't draw the air, it can't squash it.

 

[AlexValiant]

Its a LOT more complicated than 'supercharger for low rev, turbo for high rev'
Superchargers are fixed displacement pumps (or at least this one is), so putting a supercharger feeding the turbo will result in the turbo doing absolutley nothing

and probably because of the size off the exhaust pipes

 

[Enuo]

and probably because of the size off the exhaust pipes

Exhaust pipes have very little to do with it, other than spool time of the turbo

 

[AlexValiant]

It will result in the turbo trying to scavenge air the supercharger will not supply. A turbo can supply more or less air depending on demand/flow/revs etc. A fixed displacement supercharger gives a set amount of air and will not change. Increasing pressure means drawing air and squashing it. If the turbo can't draw the air, it can't squash it.

That's why need the extra pipe with the regulating valve to the time that the turbo need air to work properly

 

[Enuo]

That's why need the extra pipe with the regulating valve to the time that the turbo need air to work properly

Or just feed the turbo into the sc, and let the sc multiply the turbo boost. There are lots of ways you can do it and there is nothing really wrong with neils setup. Be careful not to confuse a setup that won't work with a setup you don't prefer

 

[AlexValiant]

Exhaust pipes have very little to do with it, other than spool time of the turbo

That pipe connects before the intake from the SC and after the takeout from the SC and regulating the exhaust gate from the turbo to open later.( on the point that SC doesn't make more pressure.