Interesting and agreed.
I’d be interested in a read about injectors and carbs. I love learning about this kind of shit.
[quote=“cky89,post:22,topic:40039"”]
I’d be interested in a read about injectors and carbs. I love learning about this kind of shit.
[/quote]
:word: i was amazed when i learned what kind of rail pressures the new Honda diesels are running
Awesome thread buddy! I got some real world data for a 525 crank hp STi so I can make this math come off the page a bit more. This car has an APS turbo and APS D/R 725 intercooler and these are actual numbers recorded by APS.
Here are the real numbers:
crank hp = 525
ambient temp = 70 F
compressor outlet temp = 415 F
intake manifold (post IC) temp = 105 F
Pressure Drop Across Core and all Ducting (psi) = 1.5 psi
Now the math:
Figuring out the efficiency of this intercooler:
Compressor outlet temp minus ambient temp:
415 - 70 = 345 F {this is the temperature gain from ambient to what comes out of the turbo}
Temp gain from turbo - temp dropped by intercooling + ambient temp = intake manifold temp.
345 - X + 70 = 105
X = 310 {this is the temperature dropped by intercooling}
Now that you have these numbers, you can calculate the efficiency of the intercooler under these conditions:
Temp gain from turbocharging * cooling efficiency = temp drop from intercooling
345X=310
X=.898 = 89.8 % efficient
At almost 90% efficient this is working nicely.
Now…how does this affect power? The density charge affects power and density is related to temperature.
Here we go:
Dc = Density change
Dt = Compressor outlet temp
It = Intercooler outlet temp
Dc = [ (Dt + 460) / (It + 460) ] - 1
Dc = [ (415 + 460) / (105 + 460) ] - 1
Dc = (875/565) - 1
Dc = .549 (rounded to 3 places)
This means the intercooler made a 54.9% increase in density over the non intercooled charge. Some of the power increase this denser air causes is negated by pressure drop and flow restrictions in the core and piping do play a role as well. That said, this IC only has a rated drop of 1.5 psi across the core and piping under these conditions (26 psi, above listed temps, etc.).
NOW THE BIG QUESTION!!! How much power am I going making because of this intercooler?
HPr = Rise in HP
Dc = density change from the intercooler
Ap = Ambient Pressure (I’m using 14.7 for sea level)
Bm = Boost pressure at the manifold (26.1 psi)
Bc = Boost pressure at the compressor (27.6 psi)
HPr = Dc + 1 – [ (Ap + Bc) / (Ap + Bm) ]
HPr = .549 + 1 - [ (14.7 + 27.6) / (14.7 + 26.1) ]
HPr = 1.549 - (42.3 / 40.8)
HPr = 1.549 - 1.037
HPr = .512
That’s a 51.2% increase in power which basically means you’d have around 350 crank hp if you removed the intercooler, but had similar flow restriction and pressure drop. Of course that’s not realistic, but you’d still be under 400 hp without the intercooler. Sound too good to be true? It’s not…as long as my Sunday morning math isn’t off.
Now lets say this intercooler was heatsoaked because it’s now a top mount sitting over the engine in the staging lanes before an autoX. Again I’m going to simplify here and say the post IC intake temp is all that changes from this. Instead of a post IC temp of 105, lets say the core is at hotter than before and it’s not quite as efficient, so it only cools the air to 200 F.
Compressor outlet temp minus ambient temp: (THIS STAYS THE SAME as the above example)
415 - 70 = 345 F {this is the temperature gain from ambient to what comes out of the turbo}
Temp gain from turbo - temp dropped by intercooling + ambient temp = intake manifold temp.
345 - X + 70 = 200
X = 215 {this is the temperature dropped by intercooling}
Now that you have these numbers you can calculate the efficiency of the intercooler under these conditions:
Temp gain from turbocharging * cooling efficiency = temp drop from intercooling
345X=200
X=.58 = 58 % efficient
Dc = Density change
Dt = Compressor outlet temp
It = Intercooler outlet temp
Dc = [ (Dt + 460) / (It + 460) ] - 1
Dc = [ (415 + 460) / (200 + 460) ] - 1
Dc = (875/660) - 1
Dc = .326 (rounded to 3 places)
So now the intercooler only bumped the density charge up 32.6 %
The power difference?
HPr = Rise in HP
Dc = density change from the intercooler
Ap = Ambient Pressure (I’m using 14.7 for sea level)
Bm = Boost pressure at the manifold (26.1 psi)
Bc = Boost pressure at the compressor (27.6 psi)
HPr = Dc + 1 – [ (Ap + Bc) / (Ap + Bm) ]
HPr = .326 + 1 - [ (14.7 + 27.6) / (14.7 + 26.1) ]
HPr = 1.326 - (42.3 / 40.8)
HPr = 1.326 - 1.037
HPr = .288
Now the intercooler is only making 28.8% more power than having no cooling at all (again assuming other things being equal).
The difference between the intercooler adding 51.2% power or 28.8% power is sizable in this case…about 75 hp.
I’ve kept these numbers realistic for a common situation many of you face. Now imagine it’s 80 degrees out with a track temp of 120 F and you’re at an autoX or drag event where you’re hot lapping. Just think how enormous your losses can be when that intercooler gets even hotter!!!
What determines how efficient an intercooler is or can be?
I couldn’t have done it without you champ!
Articzap if you can’t get those numbers from the manufacturer you’d have to test the temps at compressor outlet and intake mani inlet and do the calculations just as I did to figure it out. I didn’t have the efficiency until I figured it from those temps.
top mounts suck.
after 4 hot laps at moroso in 95 degrees my intercooler was too hot to touch.:picard: prolly real good for lowering those IATs isnt it?
i need a FM desperately.
This calculator fits nicely with this discussion:
http://www.stealth316.com/2-turbotemp.htm
It helps you calculate compressor outlet temps.
Intercooler efficency is why drag cars all use liquid units. An air unit can never get the intake charge below ambient, or even close usually. But combine the heat absorbtion capability of water along with the fact that it can be cooled with ice, shows just how much HP can be given back to the engine by removing all that heat. When you look a the numbers, its not too hard to see where the 1,000 hp 4 cylinder drag engines get that hp from.
Not to mention you can remote mount with a water to air which means less piping which equals quicker spool times!
great readWhat effect would different diameter (before /after IC) IC pipes have on this?
diameter will have a greater effect on velocity and the amount of air being moved.
i guess i need to hunt down the write up i did on that a while back too.
A friend of mine had a innercooler with a compartment in the front for a solid slab of dry ice! This worked pretty good at the track, but useless on the road.
Do you think I’d gain much by installing a larger innercooler on my GN? I run alchy, & installed an electric fan as a puller behind along with a "water sprayer, kinda like whats on a WRX, STI. ATS at the TB is showing 255 degrees F at the end of a 1/4 mile run. Car does seem to fall off at the big end. See lousy MPH. Thought it was my “small” turbo.(TE49)
/\Get the pte bolt on intercooler…255F is hawt.
A general rule of thumb for intercooler piping is to match out let size of turbo. Any smaller could be a restriction and any larger can cause turbulence which becomes a restriction.
Run the calcs and you’ll see that if you get that 255 down to 120 for instance you’ll gain a ton of power so yes, better intercooling would certainly help.
Spent hours trying to get this fan to fit, along with sprayer. Screw it, buying a 23 row, stock location IC. Thanks for helping me spend $750.00!