By having a curved section instead of square angle section will always be better. But how much better? Is it enough to justify the cost increase of having curves sections everywhere? Maybe, maybe not. Mitsu and big R&D companys have fluid dynamic software that can come up with those approximate answers. Figuring out the solutions by hand would not be fun.

Most intake manifold manufacturers don't do these type of calculations. They just make them bigger and do there own personal touches to them. Some of them may test the intake manifolds on flow benches to see if the flow has increased.

 

My concern is that, just like with an undersized injector not pumping enough fuel and running to lean, that the opposite would occur. The engine is starved for air so the A/F ratio becomes extremely rich.

 

non fluid dynamics question

how do I compute CFM from the karman frequencies ??

And any explanation for a 15degree temp drop only during an acceleration run ???I get around 90+ IAT during normal driving, but once I mash on the throttle, the temp just keeps dropping until I let go of the accelerator .. anyway to tell if there's positive pressure on the intake side ??

 

Again, a simple concept in fluid dynamics clears up this misconception. Mass flow rate through the turbo is equal to the mass flow rate through the MAF and through the intake manifold (assuming the piping is a closed system and has no leaks). Thus whatever the MAF reads is whatever is going in to the intake, so the beauty of an EFI car is the A/F ratio will not become too rich from what you are concerned about.

 

Actually that is a fluid dynamics question since karman vortex unit is a fluid flow measuring device Not sure on the actual CFM numbers, would be an easy thing to chart with a flowbench and voltmeter though.

The temperature drop is due to cooler air intake once you get rolling. You will see the IATs climb when you stop at a light. You will actually be making less power with a unit like the HKS suction kit at lower speeds since the stock airbox flows just fine and sources colder outside air rather than warm underhood air. If anyone doubts me on that, try dynoing their Evo with the hood shut and post up how much power you lose There is no way you will have positive pressure on the intake side ever in a turbo car.

 

I second that!

 

I agree with Fenris Ulf concerning positive pressure in the intake. Or at least I cannot come up with a condition.


As far as after market intakes, Vishnu's One Lap of America Car performed spectacular with a stock intake. I have begun to believe that only modifying the intake with the stock MAF does little to improve power and in some cases wreaks havoc on the Karmon Conversion. The lack of gains may be mask by the benefits of aftermarket cams, exhausts, injectors, etc. and dyno tuning.

Speedlimit...

 

You can use a hand held Manometer to determine if there is positive pressure in the airbox. Like I said before, it is possible to get some positive pressure in the airbox, but I have not tested for it on the EVO air box (the Turbo may also effect this too). On a Kawasaki 636 it can produce .3-.5 psi at 150-160mph.

Are you measuring the IAT at the intake or after the intercooler? Where are you taking the measurment from? Stationary (relative to WOT) air in the air box is always going to be warmer then air rushing in on a high speed run through the ram air.

 

just for some (relatively) solid numbers, i busted out the old fluid mechanics book and got the effective head loss for the 90* bend in the intercooler pipe (calculated as a standard elbow...). the equivalent length L /D diameter is equal to 30. this if your diameter is .0635 m (2.5 inches), then that bend has the same head loss as a straight pipe of the same material equaling 1.905m or about 6.25ft in length. that is a long *** pipe. now ideally to minimize the head loss of the replacement pipe without the 90* bend, you are going to want a curved bend of 6.25 inch radius which will have an equivalent length of about half of the elbow, or 3ft. i think that curve is very managable if you are going to actually make one. oh and if you are going to make it, use the equation: 2.5 = r/D where r is the radius from the center of the pipe to the center of the circle (or pipe bend radius), and D is the diameter of the pipe. this should leave you in the neighbor hood of an equivalent length of 13 = L/D where L is the equivalent length of the pipe bend compared to a straight pipe, and D is the diameter. hope that helps some.

*note, i am not a fluids engineer, i am a systems/controls engineer. fluids was really interesting to me, but i only took one class and i could very easily have botched some of these numbers.

*note #2, WUUUU on the 5% discount for ASME members!!

 

I have an airscoop directed straight to the filter .. not one of those heater pipe deal, but the airbox snorkel scooping air from the outside

the IAT is measured from the intake side .. measurement is taken on the move ..strange thing is I was expecting a snorkel to get ambient temp air .. yet I was reading consistent 6-9 degrees higher on the move .. its only during WOT that the temps drop dramatically (sometimes below ambient even)

scary thought .. there could be a big pressure drop during WOT hence the drop in temp ..

 

https://www.evolutionm.net/forums/sh...2&postcount=18

Planning on making an "S" from the intercooler to the TB. I can also relocate the oil catch if I need to.

 

It's almost funny that you are delving so deep into the mechanics of laminar airflow, but do not understand the concept of a MAF system as it relates to VTA bypass valves. Not only are you running a VTA diverter valve, you are running a HKS valve which is a completely incorrect application.

One reason the OE airbox is the best approach is that being a box, and having a specified vloume, the turbo draws in air from this specified volume therefore having semi-laminar flow of air (pure laminar airflow is unattainable...especially in an engine bay). It seems to me that the only way to improve on the intake is to increase airfilter area, increase airbox volume, and provide a direct path to the top side of the airfilter from a high pressure area (like in the airstream in front of the vehicle).

I do belive that insulating the intercooler pipes from engine bay heat would net some marginal gains, however the large hole in the factory extractor hood does help to keep under hood temps down.

 

I'm not running an SSQV anymore. Why bring this thread back from the dead? I've probably posted 50 times about how the SSQV was a bad deal in excrutiating detail. I already received my laminar flow thrashing in a previous thread.

 

why is hks valve improper application? how is your bov more of an appropriate application?

the oe air box's specific volume should have nothing to do with the maf. this is why if you run the box with the lid off nothing really changes.

there is no semi laminar flow in turbochargers or in any sort of turbine or compressor system. to say so is to not have had a good enough flogging by fenris ulf already. laminar flow is air sitting still or close to still, or moving as one large block (picture an icecube going down a river) that's laminar. real world flow is nothing of the sort unless you're talkin' about flyin' slow air planes through the plains on a windless summer day.

 

The ONLY time you'll ever see positive pressure inside of an Evo's air box is when the vehicle is at speed and either of these two criteria are met:

1.)the throttle body is shut
2.)the engine has stopped running

As good as the stock airbox is, it isn't exactly a ram-air design in the usual sense. It does provide a constant, consistent source of outside air which DOES keep the MAF and ECU happy.