Intercooler problems

[EldarO]

Just to get alittle technical ....

You dont always want the cooler with the most fins! If they are too close it can cause a wall like effect where it is easier for the air to flow around the cooler rather than through it.

But you are on the right track.

yeah, well i guess its a balance.

if you can "sort of" see through it, its good

Elmo.

[ReQuieM]

from what size piping did you change?

From stock piping and stock FMIC to 3" Aluminium and big FMIC...

[Big rob]

Limiting factor on power is air speed. That is once the airspeed in the piping starts reaching supersonic speeds, transonic the air does some crazy things and disrupts flow.
I did some mass flow calcs last night, from my maths I kinda concluded that 2.5" is verymuch towards the end of its rope at about450HP, approximatly 49.5lb air/s.
THat is inner diameter, and remember that there are shear forces inside the pipe that does reduce the overall inside diameter, bends also create friction thus reducing overall inner diameter of the pipe.

Rob

[30psi 4agte]

Big rob: When you do your calculations do you take into account pressure ?
Or is that 49.5 lb/s the amount of air that can be passed at that pressure.( 49.5 lb pressure inside the pipe)

Understand ?

IE: When a port is flowed they may give you a reading of say..... 100 hp . This is what the port is capable of under vaccum but if you add pressure / Boost through the port its abilty to flow more hp can doubble some times tripple.

[Big rob]

I just realised I fucked up my calcs by a decent amount. But I'll run through it the right way.
The limiting factor here is air velocity, once it reaches transonic speeds or so weird shit happens and flow is reduced I believed.

Anyway, simple mass flow problem where we are looking for a velocity(air speed).

mass flow in = mass flow out.

By looking at the compressor map of the turbo you are using you can figure out what is the maximum flow you can run. I am planning on using a garrett GT3076r which can efficiently flow a maximum of approx 50lb/s of air.
0.3788kg/s of air.

mass flow = density * area * velocity
say it the pipe has a 2.5" inner diameter = area approx 0.003167m^2
density is dependent on boost pressure(gauge presure) and temperature.
From a table like this:
http://www.engineeringtoolbox.com/ai...ity-d_771.html
We can see that at 140F(60C) and 30psi, density of air = 0.201lb/cubic foot. Metric = 3.219711kg/cubic meter.

With all our data we can solve for veloctiy in the pipe.

0.3788kg/s = 3.219711kg/cubic meter x 0.003167m^2 x velocity

Velocity is approximatly = 37m/s

Transonic is agreed to start around 0.8Mach1, mach1 = 340.3 m/s
therefor eair at transonic velocity is around the 272m/s which is much much larger than our small 37m/s.

Take note that if using a NA engine the density is much less, at the same temperature = 1.057219kg/cubic meter.
Air speed for the same pipe and mass flow would be 113m/s.

Cheers
Rob

[30psi 4agte]

LOL slight miss calculation

To be honest i havent really got in to all the clac's for flow etc etc (I am starting to learn more of the theory stuff to get more of an edge. I grew up in the test and try era )but i do know of a few cars from back in the day that were making 400 odd hp at the fly with 2 inch IC piping. ...... So i thought something didnt sound right.

[Big rob]

The calculations I did before a pretty basic stuff in the terms of pipe flow. I would suggest going and reading some some books, and in terms of racing and such or just general build up for modified cars any of the Carroll Shelby's 'tune to win" series.

In my calculations I didnt acount for surface roughness or viscous shearing forces, which basically reduce the effective flow area by creating a force opposite to the direction of flow. There are many other things to look at but for what I am aiming at 2.5" should be fine. Only prob is i wont get new tubing till friday and have to be at uni on monday with a host of home work due lol.