Donations towards server fund so far this month.

 
£0.00 / £100.00 per month
Page:
Home > How To > Thinking of fabricating a plenum? Important

TurboDave16V
Forum Mod

10970 Posts
Member #: 17
***16***

SouthPark, Colorado

I've at last got round to flow testing a plenum (with the brass restrictor in place) and comparing it to a simple diameter flat restrictor, so you keep the same kind of resrtiction at the carb mouth on your fabricated plenum.

I've always used 40mm on my plenum, but have realised in the last few months that this must be incorrect, as the needle profile was extreme to say the least - it was far too sensitive at low rpm and needed to be wafer thin at the tip.

So, after boring a few different pieces of alloy sheet out to different sizes, we did tests on the plenum, then on the samples. The answer was then extrapolated as the change in area of the various diameters. To cut to the chase, 37mm is what you need.
It might not sound like a significant difference, but using (pi*D^2)/4 to calculate the area, 40mm ends up around 16% larger area than 37mm. I will be modifying my plenum to suit, then changing my needle after the winter rebuild...

Hope this helps you guys - i just wish i had access to a flowbench years ago!!!!

oh - if you do make a plenum, don't forget to add the holes just like in the std plenum to presurise the float chamber and piston assy!!! *laughing* *laughing* *laughing* *laughing*

D

Edited by TurboDave16V on 10th Nov, 2004.

On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better


Ready to feel Ancient ??? This is 26 years old as of 2022 https://youtu.be/YQQokcoOzeY



evolotion

User Avatar

2909 Posts
Member #: 83
Post Whore

Glasgow, Scotland

Take it this restriction is jsut flat sheet, not flowed in any way?

cheers for the info guna be makeing my own plenum. anotehr question though, what happens if you leave ou tthe restriction all together? not enough fuel due to a lack of pressure difference between float chamber(plenum) and venturi?

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.


Jimster
Site Admin

User Avatar

9392 Posts
Member #: 58
455bhp per ton
12 sec 1/4 mile road legal mini

Sunny Bridgend, South Wales

Dave would to be able to find out how mine flows? Although my plenum used the std restrictor ring, I'm still confused to why my car is not running lean on the std BDD needle.

Edited by Jimster on 26th Dec, 2003.

Team www.sheepspeed.com Racing

On 15th May, 2009 TurboDave said:

I think the welsh one has it right!


1st to provide running proof
of turbo twinkie in a car and first to
run a 1/4 in one!!

Is your data backed up?? directbackup.net one extra month free for all Turbo minis members, PM me for detials


minimark

User Avatar

2641 Posts
Member #: 19
Post Whore

newcastle

I was thinking that myself STU, great idea!

Edited by minimark on 26th Dec, 2003.

Everyone knows that instructions only have to be read if the thing doesn't work....


TurboDave16V
Forum Mod

10970 Posts
Member #: 17
***16***

SouthPark, Colorado

This was a totally flat sheet, no corner radius or anything.

Jim, the standard plenum measures 120.25cfm @ 15". The restrictor ring is the restrictor, no other part of the plenum will affect this... I don't know why yours is like that - it just is!!!

On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better


Ready to feel Ancient ??? This is 26 years old as of 2022 https://youtu.be/YQQokcoOzeY



jukka

302 Posts
Member #: 60
Forgotten more than most ever know

I did try removing the brass ring from the plenum. The result was that once the engine saw boost it refused to rev any further due to lack of fuel. Felt the same as a leak in the system. In short, it needs the ring !

I did cut the openings on the brass ring a bit larger because it looked like a major restriction to the flow. Well, basically that?s what it is !

Dave, have you got the "Turbomania" book ? It deals with the restriction rings or "modulators" for Dellorto carbs. Judging the data given in the book the ID size of the ring is roughly the same as choke diameter.

Jukka


b12

User Avatar

826 Posts
Member #: 247
Post Whore

Kent/Surrey Borders

SOrry to be a pain

but what is this brass ring you all speak of ????


GRIN

Steve

TurboLessTosser


Dars

10 Posts
Member #: 274
Member

I realy want to loos the restrictor. Is it possible to plug the pipe going from the plenum to the fuel bowl, remove the restrictor and put in a t-piece on the hose to the sense signal for full pressure regulator an connect this directly to the turbo.
I assume i would get an higer pressure in the fuel bowl as there is some pressure drop over the intercooler an thru the pipes.


Hope this is undeerstandbal and make sense.

Dag Roar
Norway


TurboDave16V
Forum Mod

10970 Posts
Member #: 17
***16***

SouthPark, Colorado

Dars, You could try and modify the restrictor, and if you pressurised your float chamber using the pipe just forward of the fuel inlet, the best place to take the pressure from would be before the intercooler.
Remember though, in a static sense this is great. Dynamically, it might not be ideal... It's up to you. Personally, i'm sticking with the restrictor...

On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better


Ready to feel Ancient ??? This is 26 years old as of 2022 https://youtu.be/YQQokcoOzeY



clubman_dan

User Avatar

1128 Posts
Member #: 142
Post Whore

Winchester

where in the plenum is the restrictor?
i have a brass ring i mine where the plenum mounts to the back of the carb, it seems to be exactly the same size as the hole, it does not have a lipif you put your finger in to it and it seems as though it would not restrict anything.
is this the ring or is it somewhere else?
DAN :)


clubman_dan

User Avatar

1128 Posts
Member #: 142
Post Whore

Winchester

i'll get a photo i can't explain it very well *tongue*


TurboDave16V
Forum Mod

10970 Posts
Member #: 17
***16***

SouthPark, Colorado

That's it Dan - the brass ring...

It's a restrictor - look at the base of it - a restricted opening...

On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better


Ready to feel Ancient ??? This is 26 years old as of 2022 https://youtu.be/YQQokcoOzeY



clubman_dan

User Avatar

1128 Posts
Member #: 142
Post Whore

Winchester

i see it now, cheers dave
:)


clubman_dan

User Avatar

1128 Posts
Member #: 142
Post Whore

Winchester

here's a pic if anyone else is confused about the brass ring like i was
http://atlantic.photoisland.com/sessions/1.../25269051lg.jpg

Edited by clubman_dan on 22nd Jun, 2004.


Arno

User Avatar

583 Posts
Member #: 233
Post Whore

Beugen, Netherlands

does it mean that i can make my own plenum in any wich way as long as I use the standard restrictor and copy the holes?



TurboDave16V
Forum Mod

10970 Posts
Member #: 17
***16***

SouthPark, Colorado

What it means is you can make your own plenum in any wich way as long as you use a 37mm hole instead of a restrictor, and copy the location of the holes. *wink*

Edited by TurboDave16V on 10th Nov, 2004.

On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better


Ready to feel Ancient ??? This is 26 years old as of 2022 https://youtu.be/YQQokcoOzeY



akirch

337 Posts
Member #: 399
Senior Member

Austria

Hey!

I think this is the problem with my own plenum! On high boost the mixture is getting lean. The T-piece-trick is not helpful. The hole is too big:



Dave, does it have to be a ring with a certain thickness, or is a hole with 37mm sufficient?



Andreas


http://www.minifreunde.at


akirch

337 Posts
Member #: 399
Senior Member

Austria

At this time the diameter is 46mm!!!


http://www.minifreunde.at


akirch

337 Posts
Member #: 399
Senior Member

Austria

Now i made my own restrictor-plate with a 37mm-hole. So the cross sectional area is about 11cm?. I want to fit it between plenum and carb:



The restrictor of the original plenum makes a cross sectional area of about 18cm? (with a 48mm-hole). And when i add two-times the area of the rectangles which make the brass inside the plenum, its also about 18cm?. This makes no cross-section constriction:



So for me it's not logical, that i need a hole with 37mm. But i will try...
Is it compatible to the BCA-needle?

Regards, Andreas

http://www.minifreunde.at


akirch

337 Posts
Member #: 399
Senior Member

Austria

I looked at the plenum yesterday again, and saw that the brass ring makes a cross section constriction inside the cast part, because of the special casting mould, which I did not realised the first time. So you are right, Dave! *happy*

Hopefully my self-made restrictor-plate makes no turbulence of air inside the carb, which maybe has influence for the fuel-mixture generation?!? *oh well*

http://www.minifreunde.at


akirch

337 Posts
Member #: 399
Senior Member

Austria

Now it looks like that:

http://www.minifreunde.at


TurboDave16V
Forum Mod

10970 Posts
Member #: 17
***16***

SouthPark, Colorado

The results i got was from a flow bench test between a stock plenum, and a sheet of ally with lots of different sized holes...
I found the exact match out, and then tried it on the car! Easy Peasy!

On 17th Nov, 2014 Tom Fenton said:
Sorry to say My Herpes are no better


Ready to feel Ancient ??? This is 26 years old as of 2022 https://youtu.be/YQQokcoOzeY



akirch

337 Posts
Member #: 399
Senior Member

Austria

Forget the crappy self-made plenum...
I have problems with it. Now i make a new construction:





I will post pic's when its ready...

http://www.minifreunde.at


akirch

337 Posts
Member #: 399
Senior Member

Austria



http://www.minifreunde.at


wil_h

User Avatar

9257 Posts
Member #: 123
Post Whore

Betwix Harrogate and York

So akrich, did your homemade plenum never work?

What was the problem?

Wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

On 2nd Jan, 2013 fastcarl said:

the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.

Home > How To > Thinking of fabricating a plenum? Important
Users viewing this thread: none. (+ 1 Guests)   Next ->
To post messages you must be logged in!
Username: Password:
Page: