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lawless
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Discussion Starter #1
hey here are a few pictures of a modded air box with bell mouth also a few shots of a ported 4.8 head that is going on race 5.2 stroker all flow figures

stock lid no filter flows [email protected]'' test pressure on superflow flow bench
stock lid standard papper filter flows 216cfm
stock lid k&n filter with k&n filer oil added 251cfm

easy mod (ported and cleaned) radius entry and short turn
lid and standard filter 234cfm gain 18cfm
lid and k&n 277cfm gain 26cfm

major mod machine lid to accept bellmouth and 3''donaldson cobra neck (90deg bend)
now with cut and shut with bellmouth and standard filter 331cfm gain 115cfm
now with k&n fitler 355cfm gain 104cfm

pics
clean ported stock lid





now major mod lid





 

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lawless
nissan
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578 Posts
Discussion Starter #2
ported 4.8 head will be on 5.2 stroker
with flow figures
on chart
GREEN is Stock flow
RED is ported flow
BLACK is potential flow for valve size







exhaust port



intake port

 

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lawless
nissan
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578 Posts
Discussion Starter #3
also a 4.5









will try and find flow figures also for 4.5 head and also pictures and flow figures for 4.2
 

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What sort of kw gain would you expect from porting a 4.2?
Also in kw what would the air box mod do approx?
 

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nissan patrol GQ
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why did you polish the air box?

the benefit is in having disturbed air entering the chamber. eg you will have bugger all reynolds numbers being generated from a smooth inlet. using a golf ball as an analogy, it will penetrate airspace faster because its dimpled than if it was smooth like a snooker ball. Its the dimpling that generates turbulence (and boundary layers) and "better" reynolds numbers

its been many moons, but I used to mod 351's and falcon x-flow sixes ... all the data showed that by orange peeling the inlets the air was mixing far more efficiently...

admittedly I'm unsure as to whether you're after absolute HP or trying to improve torque, so I assume that someone has told you that its a good idea for what you're trying to achieve

(we used to orange peel the bell mouth for hillborn trumpets)

the same philosophy went through for port/polishing issues, ie disturbed turbulent air is of greater benefit. although some of the arguments for and against eventually boil down to philosophical conviction..
 

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lawless
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Discussion Starter #6
we didn't polish the airbox

we actually used 60 grit tape to get rid of the smooth plastic polish finish

and the bellmouth after it was machined was also finished with 60 grit
photos may make it look smooth but the surface is rough

as for the ports in photos are all in 60 grit other than chambers as this helps reflect heat/promote combustion and also keep heat in the charge
 

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nissan patrol GQ
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we didn't polish the airbox

we actually used 60 grit tape to get rid of the smooth plastic polish finish

and the bellmouth after it was machined was also finished with 60 grit
photos may make it look smooth but the surface is rough

as for the ports in photos are all in 60 grit other than chambers as this helps reflect heat/promote combustion and also keep heat in the charge
thanks for explaining, from the photos it looked mirror smooth, which 20-30 years ago was standard practice - but not so much now as we understand airflow and fluid mechanics a whole lot better ...

so as we've both said now, turbulence is better for mixing fuel before all those controlled explosions occur... :)

nice job btw
 

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lawless
nissan
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Discussion Starter #8
What sort of kw gain would you expect from porting a 4.2?
Also in kw what would the air box mod do approx?
as for kw figures we dont have any as after this most of the time have had either turbo up grade / intercooler and other items to be giving a back to back gain but we have noticed a
50deg temperature drop in exhaust gas and impoved economy and power/torque also less lag in turbo spool
 

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lawless
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Discussion Starter #9
thanks for explaining, from the photos it looked mirror smooth, which 20-30 years ago was standard practice - but not so much now as we understand airflow and fluid mechanics a whole lot better ...

so as we've both said now, turbulence is better for mixing fuel before all those controlled explosions occur... :)

nice job btw

but in saying that turbulence promotes flow yes but the way that it stops adherence to the surface of the port but not to the extent of causing pulsations in the flow bench
 

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but in saying that turbulence promotes flow yes but the way that it stops adherence to the surface of the port but not to the extent of causing pulsations in the flow bench
the turbulence ideally should be creating miniature boundary layers within the port - so it shouldn't pulsate - if it was pulsating and generating back pressure then you'd be out with a porting brush straight away... :)

are you port matching the exhaust system to the manifolds?

it would be interesting to see this engine with compound turbos set up....
 

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I guess its been asked before but where does one go about getting the larger intake right angle fitting for the airbox lid mod?
Anyone know a make and part number?
 

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lawless
nissan
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Discussion Starter #13
in brisbane i go to queensland diesel spares

but they are made by donaldson
there are about three different number on the ones i have here and 1 also has all of them on it so here you go
p547694
hrc-90cb30 made in usa
r63544
if you have trouble call Joel at queensland diesel spares (07)3888 7755 he is a member on here also
 

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nissan
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Thanks for that actually re read the first post where it was writen and did a search and found them. for those who have bought them whats the going price.
 

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air box mod

hi there,
just wondering where you got the aluminium fitting to go from the cobra piece to the original intake piping . 3" to 3.5 " . Did you have to get someone to make it ? Been looking myself but no luck . Any info would be good.
Thanks Peter:)
 

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nissan
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What year is the 4.8? did you put a different airbox in? Mine is not like that...

Mines and 02 and looks like this:
 

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Thanks for that actually re read the first post where it was writen and did a search and found them. for those who have bought them whats the going price.

G'Day,

When i bought mine, i payed $30 + $10 postage. From a tractor place in Dubbo, NSW
 

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lawless
nissan
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578 Posts
Discussion Starter #18
hi there,
just wondering where you got the aluminium fitting to go from the cobra piece to the original intake piping . 3" to 3.5 " . Did you have to get someone to make it ? Been looking myself but no luck . Any info would be good.
Thanks Peter:)

turn out of solid to get the shape and size
 

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lawless
nissan
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578 Posts
Discussion Starter #19
What year is the 4.8? did you put a different airbox in? Mine is not like that...

Mines and 02 and looks like this:
[/QUOTE

either i have marked a photo wrong but all are 4.2 air box

only 4.8 stuff was the ported head mate
 

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Hey KcWorks Wot did that modded airfilter box set u back?? and who did the 4.8 head??
 
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