levigarrett76

with stock fueling it seems like the restriction might help build up boost at low rpm faster thus reducing particulate??

I know with my AFE horn on my 07 and GDP horn on my 06...and the jr set on SW#1 they come on HARD at around 1500 rpm

PourinDiesel

Levi,
Your thinking is right in my opinion...
I would say the intake is restricted to help boost the turbo up faster (via increase turbine speed).

Think of a garden hose nozzle.

The more restriction offered by the plumbing and engine the faster boost comes up.

Emissions make spooling the turbo as fast as possible critically important. This is probably why the 5.9 CR motors come with the 9cm2 turbine section.

AH64ID

I think its a production line thing... easier to cast, shorter cheaper bolt, etc... Same reason we no longer have hubs...


How do you like the GDP, its on my list of things to get.

levigarrett76

i think of a leaf blower...put your hand over the end and it spools up much faster!

levigarrett76

Much better money spent rather than the AFE of the CFM.

Its right up there with the CFM according to dyno.

Gave the same 1500-2200 torque increase you can feel that i felt when i put the AFE on my 07..

Ive been thinking of selling the AFE and Buying another GDP for the 07

AH64ID

Sweet... Yeah I looked at an AFE the other day and looks to be a bit more than needed...

CTD NUT

For the pumping the most air to the combustion chambers, restrictions should be minimized up stream. Boost pressures before the necked down portion of the intake horn restriction is fairly irrelevant - what enters the chambers is what really matters. If you add a restriction, you will slow down the flow of air which will make the compressor work harder and slower spool up will be the result. By minimizing restrictions and creating laminar flow, it is possible to see lower boost pressure...but this can also mean higher air flow to the chambers as a result - by minimizing the resistance to flow. A free flowing intake system void of unnecessary restrictions will result in quicker spool up - not slower spool up. Pressure could very well be lower, but flow and spool up will be higher.

PourinDiesel

Not necessarily true.

You can add a larger intercooler. Larger compressor wheel. Larger compressor housing. Larger plumbing diameter and you will probably see slightly laggier spool-up with off/light throttle operation.

Sure free flowing is great for modded engines and heavy throttled operation but for stock engines only to a point where it starts to affect bottom end performance.
Same thing applies to camshafts that are designed for flow at certain RPM ranges.

Back about 4 year ago we dynoed my stock 600 with Cat/Muffler OEM exhaust and later dynoed with an air intake and free flowing exhaust....
Guess which dynoed more? (same dyno and operators by the way).

levigarrett76

it takes an air compressor longer to fill a large tank rather than a small tank...?
the restriction sort of acts like a smaller tank since in stock form the motor is being driven by less than optimum fueling

CTD NUT

My anaology did not include changing the compressor....only removing restrictions from the plumbing it had to pump through. Larger compressors will require more power to turn them and will typically be slower to spool than that of a smaller one. This is outside the scope of what we are talking about. We are talking about restrictions in the intake plumbing down stream of the compressor.

levigarrett76

I just cant see cummins reducing power and efficiency unless it it to meet epa regs.

Has anyone figured the area of the restriction and compared it to the area of the 3" intercooler pipe?

TexasCTD

I agree that air/exhaust mods don't make much difference or may even hinder power on a stock truck. In my case, under stock to stock power, the Air intake and exhaust mods made no difference on my truck. They were around 280hp/522 tq...same dynojet dyno......before air box and exhaust mods.


However, FWIW, I did recently notice about a 15hp increase on my truck adding the DTT intake horn on the same dynocom dyno with additional fueling etc. And I can tell a difference in the seat of the pants low end power.

http://s177.photobucket.com/albums/w...Intake%20Horn/


http://www.dieseltrans.com/dodge/Intake.htm

..

dminer

Hmm... great debate here but I'm going to lean on the side of CTD NUT. Placing a restriction so it can build boost faster is going to add resistence to the turbo and that just doesn't make sense.

On the flip side.... what engine manufacturers have to do to get emissions down never seems to make sense.

The analogy of the less restriction with larger piping, intercooler, etc looses merit with the addition of a larger turbo.

It may be emissions driven, it may be cost driven (assembly line), either way that's not what most of us are wanting from our trucks.