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New Hif 44 Stubstack Design


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#1 Retroman

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Posted 31 October 2018 - 09:55 AM

New design

 

TMF price £30

 

Turbo Phil tested the old ones at over 5% flow increase, these should improve on that.

 

http://www.retromini...roducts_id=1017

 

They will only fit the HIF44 carb and can use the standard screws to fit

 

Has slots on the back for the dashpot vents

 

JE2d9Pj.jpg

OcvtRyul.jpg

 

Engineered in England  so they actually fit

 

 



#2 ukcooper

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Posted 31 October 2018 - 11:05 AM

looks good and I would have but have  mpi now  :shy:  :shy:  :shy:  :shy:  :shy:  :shy:



#3 Icey

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Posted 31 October 2018 - 12:56 PM

How does it compare to the MED stack (£25)?



#4 luismx123

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Posted 31 October 2018 - 01:13 PM

Is there something like this for a hs4/hif38?



#5 Retroman

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Posted 31 October 2018 - 08:38 PM

Don't know how they compare to MED ones maybe Turbo Phil has tested them

 

They are based on Vizard type ones but we put the slots in the back which should help the airflow more

 

For 1 1/2 inch carbs H4 Hs4 and HIF 38

 

http://www.retromini...roducts_id=1241

 

EW6rjvP.jpg

 

wfC1SGbl.jpg



#6 nicklouse

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Posted 01 November 2018 - 01:53 AM

one thing i have often wondered with the HIF carbs is they already have a radiused opening so would these not be better having a extension going into the carb to smoothen that out? as that step and radius can not be good for flow.



#7 Retroman

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Posted 01 November 2018 - 09:46 AM

I think the slight radius at the mouth on HIF carbs gives them a slight advantage over the HS type when it comes to bare flow

 

Compared to a bare carb a stubstack will flow over 5% more.

 

Air will flow round a 15 degree un-radiused corner without any losses

 

The flow loss starts once the flow separates from the surface which it will at an angle tighter than 15 degree

 

The concept is to get minimal flow separation, by reducing turbulence and thus increasing laminar flow

 

Think TOLL booth

 

A bare carb suffers "vena contracta"   https://en.wikipedia.../Vena_contracta

 

A 6mm radius is difficult to improve on

 

David Vizards findings and comments follow the above

 

Turbo Phil tested the earlier version and measured a flow increase of over 5 % which is perfectly inline with David Vizards figures



#8 luismx123

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Posted 01 November 2018 - 09:52 AM

stupid question but does one add a filter ontop of the substack?



#9 Retroman

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Posted 01 November 2018 - 10:10 AM

Thats up to you but a nice K&N is best, by that I mean not a cone type

 

The stubstacks are designed to go inside the filter

 

j6ZHuxA.jpg



#10 luismx123

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Posted 02 November 2018 - 09:46 AM

Thats up to you but a nice K&N is best, by that I mean not a cone type

 

The stubstacks are designed to go inside the filter

 

j6ZHuxA.jpg

Why wouldnt you recommend the cone type for the sub stack? 
Im guessing one would have to match the metal fitting to the inlet first, then throw the substack inside. is it because of space or the way the air wants to flow in there? 
Which filter is in the picture above? classic pancake?



#11 Retroman

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Posted 02 November 2018 - 10:32 AM

The one above is a pancake K&N withan offset hole on an HS4

 

I am no fan of cone filters, the only real advantage is easy to fit, but not good for power, plenty of noise though.

 

https://www.calverst...air-filtration/






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