Physics Help!! 2.4inch Turbo . Benefit to get a 3" inlet pipe et intake??

[Obababoy]

Ive read tons of topics before on whether to choose a 3inch inlet or 2.4 on the turbo but what if 2.4 was the only choice and since I need to buy a new inlet, I buy a 3inch inlet (with 2.4 reducer) mated to a 3 inch "big maf" air intake?

I am trying to think of the physics but I am A not an engineer and B rusty on even the basics these days.

Would I be close in assuming that the larger the diameter of Turbo inlet pipe and Intake, the less of a vacuum(meaning less work for compressor)?

I understand that the turbo opening is 2.4"***8960; but if I were to "suck" (I know, science does not suck) air through a 2.4"***8960; washer and then a 2.4"***8960; hose that was 5 feet long, it would take more effort to suck air through the hose than the washer therefore reducing the volume and/or velocity? Which in turn would mean a 3" hose after that 2.4" washer would be more efficient...Right?


Hahaha I hope I dont get too bad.

~Chris

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[Mr Wrex]

If you're not going to use a turbo with a 3" opening, don't use the larger inlet. Think about it like this... vaccuum attachments cover different amounts of surface area. The larger the surface area where the air initially enters the "system", the slower the air will move. As the area for the air to move through becomes smaller, the air will start to move into the "system" faster. If, for example, we use a vaccuum attachment that has the same inner diameter as the rest of the piping leading to the "system", the air's speed will stay the same speed at all times. Overall, it doesn't matter which size attachment you use... the air will still flow through the "system" at the same rate since you aren't changing the diameter of the piping all the way to the engine.

Another example... go suck air through a straw. Then after, attack a cone with a larger opening to the end of the straw and try sucking air in again. Notice a difference? (you shouldn't)

In summary, you will only flow as fast as your smallest part will allow you to. I don't even have to discuss the possible downfalls of the adapter/reducer to prove that this is no bueno.

[Obababoy]

Fair enough thank you, Now what about stock vs aftermarket for the inlet? LOTS of claims from after market companies about improvements...

[tuzzio]

Aftermarket inlets all the way. A silicone 2.4" will be just fine.

[Mr Wrex]

Personally, I run 23psi on my stock inlet + vf52 and haven't had problems. You can't go wrong either way, but just as a piece-of-mind kinda deal I'd go aftermarket silicone. You will have quite a fun time stuffing it under the intake mani if you do it yourself regardless of what option you choose...

[Obababoy]

Well Im doing injectors and TGV's so the intake manifold will be coming off. But so far I still think silicone will be my route.

[tuzzio]

Stuffing a 2.4 under the intake manifold really isn't all that bad. Getting on the compressor inlet helps to have 2 people. Regardless, the worst part of doing it all was the evap purge solenoid. Don't break it.

[danger1138]

Aftermarket turbo inlet all the way, not for the advertised 'hp gains' but for the simple fact that the stock inlet tends to rip over time at the most important part, where it attaches to the turbo. With the heat and all the rubber becomes soft and jelly like eventually tearing if u over- tighten the worm clamp.

[Obababoy]

im sold

[CarverHouseRally]

Originally Posted by Mr Wrex

In summary, you will only flow as fast as your smallest part will allow you to.

This is not true.

The goal is to minimize the pressure drop between the inlet of the intake system and the turbo. To find the total pressure drop you sum the pressure drops across each component. A 3" hose will have a slightly smaller pressure drop for a given mass flow rate compared to a 2.4" hose, as the velocity will have to be higher to maintain the same mass flow rate. Velocity=frictional losses within the fluid. So even if you flow through a 2.4" orifice (the compressor housing inlet) in both cases, you will still have a higher total pressure drop using a 2.4" hose. In reality the difference will probably not be noticeable though.

[Psychoreo]

Originally Posted by tuzzio

Regardless, the worst part of doing it all was the evap purge solenoid. Don't break it.

[Mr Wrex]

Originally Posted by CarverHouseRally

This is not true.

The goal is to minimize the pressure drop between the inlet of the intake system and the turbo. To find the total pressure drop you sum the pressure drops across each component. A 3" hose will have a slightly smaller pressure drop for a given mass flow rate compared to a 2.4" hose, as the velocity will have to be higher to maintain the same mass flow rate. Velocity=frictional losses within the fluid. So even if you flow through a 2.4" orifice (the compressor housing inlet) in both cases, you will still have a higher total pressure drop using a 2.4" hose. In reality the difference will probably not be noticeable though.

Pulling air through a 3" diameter pipe into a 2.4" diameter pipe will flow at the same exact rate as using a pipe that is 2.4" all the way through if you don't take pressure drop into account. I didn't even bother mentioning that since, in reality, that pressure drop is barely noticeable.

[kellygnsd]

Originally Posted by Mr Wrex

If you're not going to use a turbo with a 3" opening, don't use the larger inlet. Think about it like this... vaccuum attachments cover different amounts of surface area. The larger the surface area where the air initially enters the "system", the slower the air will move. As the area for the air to move through becomes smaller, the air will start to move into the "system" faster. If, for example, we use a vaccuum attachment that has the same inner diameter as the rest of the piping leading to the "system", the air's speed will stay the same speed at all times. Overall, it doesn't matter which size attachment you use... the air will still flow through the "system" at the same rate since you aren't changing the diameter of the piping all the way to the engine.

Another example... go suck air through a straw. Then after, attack a cone with a larger opening to the end of the straw and try sucking air in again. Notice a difference? (you shouldn't)

In summary, you will only flow as fast as your smallest part will allow you to. I don't even have to discuss the possible downfalls of the adapter/reducer to prove that this is no bueno.

That's not true. The flow losses from point A to point B are cumlative. Your example used the same length of straw of the same diameter then you added a cone at the end. Instead make a new straw the same length as the old one but instead of a constant diameter, taper it from its original small diameter to say 3". That second conical straw would have much less flow restriction than the original small diameter straw eventhough the final diameter before the inlet is the same.

[Leafy]

It shouldn't matter greatly either way. I'd rather just run the 3" hard inlet since the hard pipe makes more turbo noises come out the intake.

[Obababoy]

Originally Posted by Leafy

It shouldn't matter greatly either way. I'd rather just run the 3" hard inlet since the hard pipe makes more turbo noises come out the intake.

Is this true? I was thinking of going with gimmicks v2 inlet for cost and non-collapsibility

[HinshawWRX]

The benefit over a hard inlet is it won't collapse and it's hard. It doesn't mean crap otherwise.

[Obababoy]

Gimmick, Perrin and Samcro boast about non-collapsible. I will likely jet for the cheaper Gimmick..

[savagesoob]

Would I be able to use a coupler from my 2.5 aftermarket inlet pipe to a 20g turbo that has a 3in inlet? 2.5 to 3" coupler or something?

[Seangraz]

Originally Posted by savagesoob

Would I be able to use a coupler from my 2.5 aftermarket inlet pipe to a 20g turbo that has a 3in inlet? 2.5 to 3" coupler or something?

You could but ruins the benefits of having the 3” housing. I’d just get a 3” inlet

[savagesoob]

Originally Posted by Seangraz

You could but ruins the benefits of having the 3” housing. I’d just get a 3” inlet

Thanks! yeah thats what I was thinking. Just a pain in my ass to get the manifold off. Might try snaking it but that looks a bit sketch.

[KillerBMotorsport]

At a 20G power level you're likely splitting hairs. The 3" compressor flange does not have a 3" inlet to the compressor. On a 20G it's going to be ~2" IIRC.

[savagesoob]

Originally Posted by KillerBMotorsport

At a 20G power level you're likely splitting hairs. The 3" compressor flange does not have a 3" inlet to the compressor. On a 20G it's going to be ~2" IIRC.

So a simple 2.5 to 3" coupler will do? Much easier and cheaper.