Outer Limits 4x4 Board

as per the q, I want to put a / pair of snorkels on the 70, but want to know whatr CFM the 6.2 NA chev oiler draes at full noise so I can make an educated decision on 2 * 3" or 1 * 4" pipe

Cant find the info I want on Google, also if anyone has a link with info on these animals they could post I would be most gratefull

Tks

Tiny

Tiny,

try giving these guys a ring or email, they are in WA and specialise in GM Diesels

http://www.brunswickdiesels.com.au/new/index.php

Hope it helps,

Tim

It should tell you somewhere on the Holley carby site....
It is a calculation of capacity x revs.

thanks guys, will try that

http://www.4secondsflat.com/Carb_CFM_Calculator.html

used "cfm carb size" in google

Eric

scout392 wrote:http://www.4secondsflat.com/Carb_CFM_Calculator.html

used "cfm carb size" in google

Eric

thanks,

I based safe RPM at 5000 and an efficiency at 65% as I understand oilers burn efficiency is around that???

the required CFM came out at 618

based on that figure I would be thinking the two would be good, there is plenty of room to plumb them up

any sugestions?

no I will not put stacks on it

Tiny wrote:

scout392 wrote:http://www.4secondsflat.com/Carb_CFM_Calculator.html

used "cfm carb size" in google

Eric

thanks,

I based safe RPM at 5000 and an efficiency at 65% as I understand oilers burn efficiency is around that???

the required CFM came out at 618

based on that figure I would be thinking the two would be good, there is plenty of room to plumb them up

any sugestions?

no I will not put stacks on it

Base your RPM's on something closer to 4ooo

Tiny
my 6.5 diesel was fitted with a single 3 inch air intake manifold "top hat"
running about 500mm of 3 inch hose to a Donaldson air cleaner.
i didnt notice anything wrong with it performance wise.

Brunswicks gave me a Twin 3 inch "top hat " to swap to when i added the second Donaldson aircleaner. (they recomend twin 3inch)

after fitting the twin 3 inch i noticed a massive change in intake noise and exhaust note. i am still only running 500mm of air hose on each side and am fitting twin snorkels very soon and for the piece of mind i am upgrading to TWIN 4 INCH. the way i figure it i am tripling the length of my snorkel system so the larger diameter will be needed.

i have always been told diesels draw a lot more air than petrols so be wary if using a petrol CFM calculator .

for the peice of mind and allowing for future turbo or supercharger upgrades, twin 4 inch is the only way to go

Diesels are 2 stroke right? Does that change the intake requirements??

CRUSHU wrote:Diesels are 2 stroke right? Does that change the intake requirements??

some diesels are two stroke, but the chev V8's are not.

working out CFM is pretty easy.

volume (6.2 litres = 0.22 cubic feet) divided by 2 (because 4 stroke motor) times rpm (say 4000 as absulute top dollar) = 440cfm.

don't worry too much about the "efficiency" they talk about, that is volumetric efficiency, which is basically a measure of the flow characteristics of the head and intake - as you can see, it will be affected by the diameter of your snorkelation.

anything that can comfortably flow 400cfm will see you pretty right. it's not like you ever ever need to rev that motor out.

dumbdunce wrote:

CRUSHU wrote:Diesels are 2 stroke right? Does that change the intake requirements??

some diesels are two stroke, but the chev V8's are not.

working out CFM is pretty easy.

volume (6.2 litres = 0.22 cubic feet) divided by 2 (because 4 stroke motor) times rpm (say 4000 as absulute top dollar) = 440cfm.

don't worry too much about the "efficiency" they talk about, that is volumetric efficiency, which is basically a measure of the flow characteristics of the head and intake - as you can see, it will be affected by the diameter of your snorkelation.

anything that can comfortably flow 400cfm will see you pretty right. it's not like you ever ever need to rev that motor out.

thanks brian, so what would you suggest as far as snorkels go?

Toytruck, I presume your 6.5 is turbo? if so I would resume that the required flow would be significantly more, I am sure I could work out based on what psi the turbo is running, but CBF getting the furmulas, either way I am thinking twin 3" will be more than sufficent

ToyTruck wrote:
i have always been told diesels draw a lot more air than petrols so be wary if using a petrol CFM calculator .

CFM is CFM, diesel, petrol or otherwise. Diese's draw more air at idle/low rpm because they generally don't have a throttle butterfly, but at the top end which is where you need to work out the CFM for air flow requirements, it's all same same.

Tiny wrote: thanks brian, so what would you suggest as far as snorkels go?

Toytruck, I presume your 6.5 is turbo? if so I would resume that the required flow would be significantly more, I am sure I could work out based on what psi the turbo is running, but CBF getting the furmulas, either way I am thinking twin 3" will be more than sufficent

6.5 turbo is about 700cfm at 8psi.

by comparison my 4.2 yota flows about 630cfm at 4250rpm at 15psi boost. it has 3" (actually I think it is 70mm) inlet ducting, but no snorkel, and happily flows the required air, so even a single 3" will probably be plenty for the 6.2 since it is only 2/3 the airflow of my 4.2.

dumbdunce wrote:

Tiny wrote: thanks brian, so what would you suggest as far as snorkels go?

Toytruck, I presume your 6.5 is turbo? if so I would resume that the required flow would be significantly more, I am sure I could work out based on what psi the turbo is running, but CBF getting the furmulas, either way I am thinking twin 3" will be more than sufficent

6.5 turbo is about 700cfm at 8psi.

by comparison my 4.2 yota flows about 630cfm at 4250rpm at 15psi boost. it has 3" (actually I think it is 70mm) inlet ducting, but no snorkel, and happily flows the required air, so even a single 3" will probably be plenty for the 6.2 since it is only 2/3 the airflow of my 4.2.

sounds good, thanks mate.

you gunna be at J7?

Tiny wrote:

dumbdunce wrote:

Tiny wrote: thanks brian, so what would you suggest as far as snorkels go?

Toytruck, I presume your 6.5 is turbo? if so I would resume that the required flow would be significantly more, I am sure I could work out based on what psi the turbo is running, but CBF getting the furmulas, either way I am thinking twin 3" will be more than sufficent

6.5 turbo is about 700cfm at 8psi.

by comparison my 4.2 yota flows about 630cfm at 4250rpm at 15psi boost. it has 3" (actually I think it is 70mm) inlet ducting, but no snorkel, and happily flows the required air, so even a single 3" will probably be plenty for the 6.2 since it is only 2/3 the airflow of my 4.2.

sounds good, thanks mate.

you gunna be at J7?

yes, am fixing for Dave Koranyi (DX80) - whjole family coming so might be an interesting camping experience.

when chosing snorkel size. note that in this case 2*3" will only be marginally bigger then a 4".

area of intake...

3" > pie x R (squared)
> 3.14 x 3.75 (squared)
> 11.775 x 11.775
> 138.65 square cm of area
x2 snorkels > 277.3 square cm


4" > (as above)
> 246.49 square cm


therefore 2*3" is only getting you approx 30cm more air then the single 4".

im not telling you which one to do, but take that into account. i run twin 3" on my TB42 but it was more for looks. because the stock motor would have been fine for a single.

goodluck with it

PAUL

dumbdunce wrote:
yes, am fixing for Dave Koranyi (DX80) - whjole family coming so might be an interesting camping experience.

So Daves expecting to destroy his truck ?

Just tell him to make sure he takes the tow hitch out before he trys to show up. He'll know what I mean.

Nick

vanbox wrote:when chosing snorkel size. note that in this case 2*3" will only be marginally bigger then a 4".

area of intake...

3" > pie x R (squared)
> 3.14 x 3.75 (squared)
> 11.775 x 11.775
> 138.65 square cm of area
x2 snorkels > 277.3 square cm


4" > (as above)
> 246.49 square cm


therefore 2*3" is only getting you approx 30cm more air then the single 4".

im not telling you which one to do, but take that into account. i run twin 3" on my TB42 but it was more for looks. because the stock motor would have been fine for a single.

goodluck with it

PAUL

but thge friction losses on 2x3" will be less than 1 x 4. 2 would look better, but realistically I am after function not bling and bending on up and fitting the single into the airbox is going to be much less hassle than the twin set up

see ya there brian, will prolly see me snapping CVs........havent had time to get any spares, so will see how we go

Even a 1.5" tube can flow enough air to supply your engine. But the smaller (or longer) the tube, the more pressure drop there'll be along it's length.
The limit is the speed of sound (well over 1000km/h).

The bigger and shorter you make the tube, the less pressure drop at any given flow.

My turbo 3.9L diesel has similar air requirements to your larger NA engine. I have about 1m of 2 1/4" tubing on the intake, the vacuum gauge on the air filter doesn't show any measurable pressure drop.

The 60 is running a Safari snorkel into the standard air box (finer filter) and then through a 3" flex hose to the Brunswick standard 'top hat' on top of the 6.2. A vac gauge barely flickered from idle through to 2500 rpm.