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Home > Help Needed / General Tech Chat > Blow through SC problems

Chalkie

1909 Posts
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Northamptonshire.

What is a the main issue with SC blow through setups again

cant remember if it the was the part throttle/ cruise issue or something else

I'm still trying to work out a way of doing my 998ish engine blow through.

thanks
stephen


slater

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Suffolk / Birmingham

With a carb you have the butterfly after the blower so you need to dump the excess pressure when the throttle is closed. I would imagine it might be hard to control the fueling on part throttle. I dont know of anyone whos done it with a carb.


Chalkie

1909 Posts
Member #: 9764
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Northamptonshire.

I'm sure the throttle has got to be before the charger on a blow through to work off memory

Trying to find out how bmw did it on the cooper s I


Turbo This..

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1767 Posts
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Previously josh4444

Australia, brisbane

how do the v8 guys do it then dont they have blower carb intake engine ?


slater

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Suffolk / Birmingham

It doesnt need to go before the blower, but if you have it after you need a bypass much like a dump valve on a turbo. I was designing a system for my Fiesta that had the throttle after the blower and was going to use a normal recirc type dump valve for the bypass but the project has ended up on the back burner so couldn't say if it will work. It will be injected too of course!

V8s tend to suck through. Blower goes straight on the manifold.


Sprocket

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Preston On The Brook

The big V8s work either way but when the carb is after the blower there is another throttle infront if the blower to keep the pressure ratio across the blower low.

On 26th Oct, 2004 TurboDave16v said:
Is it A-Series only? I think it should be...
So when some joey comes on here about how his 16v turbo vauxhall is great compared to ours, he can be given the 'bird'...


On 26th Oct, 2004 Tom Fenton said:
Yep I agree with TD........


stevieturbo

3569 Posts
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Northern Ireland




On 26th Jan, 2015 Chalkie said:
I'm sure the throttle has got to be before the charger on a blow through to work off memory

Trying to find out how bmw did it on the cooper s I


With fuel injection lol.


I'm sure you could do it ok as long as the air bypass was sufficient so there would never be excessive air in front of the carb at low loads.

But it could be tricky. Most common route with a carb is such through.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will


Chalkie

1909 Posts
Member #: 9764
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Northamptonshire.

Yeah I now bmw used fuel injection but they put a bypass valve in aswell after the throttle

and I don't like suck through fuel across the blades.

Podifold made one but i seen he didn't make what he expected


stevieturbo

3569 Posts
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Northern Ireland




On 26th Jan, 2015 Chalkie said:
Yeah I now bmw used fuel injection but they put a bypass valve in aswell after the throttle

and I don't like suck through fuel across the blades.

Podifold made one but i seen he didn't make what he expected


All blower setups will have a bypass valve.

And I'd imagine the Bini has the throttle blade in front of the blower ?

And sucking fuel across the rotors is a good thing, as it helps keep them cool, which also means cooler charge temps.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will


Rammie2000

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belgium

but doesn't it make fuel go back into drops instead of vapour?

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018


Sprocket

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Preston On The Brook

Blow through is just wrong with an open supercharger intake

On 26th Oct, 2004 TurboDave16v said:
Is it A-Series only? I think it should be...
So when some joey comes on here about how his 16v turbo vauxhall is great compared to ours, he can be given the 'bird'...


On 26th Oct, 2004 Tom Fenton said:
Yep I agree with TD........


slater

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1030 Posts
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Suffolk / Birmingham

If you set it up right the blower just free wheels when the throttle is shut either way round, assuming you have a working bypass that is. My only uncertainty is if it will be too hard to set up correctly with a carb.


slater

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Suffolk / Birmingham

Then again it works with a turbo so why not!


stevieturbo

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Northern Ireland




On 26th Jan, 2015 Rammie2000 said:
but doesn't it make fuel go back into drops instead of vapour?


No idea what it does...but the yanks have been doing it for decades and it works.

When there are other design issues with a blow through install, and little real benefit...sometimes isnt worth trying to fix something that isnt broke when it really isnt going to gain you anything.

The only reason to go to the effort of blow through would be to allow the addition of an intercooler...and that in itself creates even more issues and work.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will


slater

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Suffolk / Birmingham

Its a lot better for your charge temp to be running an intercooler!!

This is the problem with blowers, they get a bad rep because 99% of installations are a crock of shit. People just seem to ignore the basic principles because 'the yanks did it that way and it works' or 'thats the way its been done for years'

Lets face it suck through blower is almost as bad as suck through turbo. Look at the average installation on a mini

Suckthrough = Crap
No Intercooler = Crap
Carb = Crap
No Bypass = Crap
C/R = Crap

I know with a mini theres space limitations but with a little outside to box thinking it could be done.


stevieturbo

3569 Posts
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Northern Ireland




On 27th Jan, 2015 slater said:
Its a lot better for your charge temp to be running an intercooler!!



This assumes you're running enough boost to warrant an intercooler. A lot of Rootes style simply dont.

Some opt for a small heat exchanger underneath etc.

But when you try to design a blow through using one and a carb, that in itself raises issues.

Doesnt matter what approach you take, you could say there are compromises with them all. Just pick what is easiest for the individual user that gives them the results they want

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will


Chalkie

1909 Posts
Member #: 9764
Post Whore

Northamptonshire.

I want to supercharge cause i love the sound of them, also low down torque

i may just have to roll with suck through then


Rammie2000

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belgium

it just makes me wonder... anyone ever heard of seen or dreamed of a twin charger. like charger for low down torque and then turbo for the high revs... or even twin turbo's?

you can do anything if you set your mind to it...
i rather blow it up winning than keep it together losing.

finish date set for project 1... march 2018


slater

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Member #: 1291
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Suffolk / Birmingham

Yeh you can do that. Lancia Delta S4 is probably the most famous example. Wonder where they put the throttle!


jakejakejake1

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Northants

VW do an engine that has both a supercharger and turbocharger.
http://www.volkswagen.com.sg/en/technology...ger-motors.html

The problem with doing it wil a mini would be the packaging, plus the cost. Whereas either a supercharger or a turbocharger alone will give a reasonable compromise for a lot less effort.


stevieturbo

3569 Posts
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Northern Ireland




On 27th Jan, 2015 Rammie2000 said:
it just makes me wonder... anyone ever heard of seen or dreamed of a twin charger. like charger for low down torque and then turbo for the high revs... or even twin turbo's?



Quite a few have done it, but it can be complicated to get nice.

As for throttle placement....just one throttle ?

There are a multitude of ways of doing it...the biggest problem here is trying to retain a carburettor.

Almost all twin setups will be fuel injected.

If you want fast spool and turbo...a small diesel VNT turbo is probably the simplest option, along with a good ecu to control the turbo vanes

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will


Chalkie

1909 Posts
Member #: 9764
Post Whore

Northamptonshire.

I don't want to keep the carb I don't mind running injection, could you run a blow through supercharger like a turbo set up with a plenum camber and a dump Valve?


Turbo This..

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1767 Posts
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Previously josh4444

Australia, brisbane

at the end of the day its just a belt driven turbo and its just boost so why should anything be diffrent? make some plates with pipes comeing in and out like a turbo and plumb it like a turbo the harder bit when compared to turbo is mounting and the belt drive

my point is its just boost so why should it be different??? make a blower go threw a IC and have the carb see boost just like a turbo

i think if its done well it will be grate to have a blown mini


Tom Fenton
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Fearless Tom Fenton, Avon Park 2007 & 2008 class D winner

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TM legend.

Rotherham South Yorkshire

Wrong, its totally different, close the throttle on a turbo and the boost soon falls away as the exhaust gasses subside, close the throttle on a supercharger and its still pushing just the same amount of boost out as its mechanically different.


On 29th Nov, 2016 madmk1 said:


On 28th Nov, 2016 Rob Gavin said:
I refuse to pay for anything else


Like fuel 😂😂


Turbo This..

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1767 Posts
Member #: 9165
Previously josh4444

Australia, brisbane

youll still have a bov just like a turbo whont that take care of pressure behind the butterfly? butterfly closes pulls vacuum opens bov dumping the pressure so long as its able to pass the full flow from the blower

not haveing a go want to get my head round it

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