Do intercoolers add power directly?
Thread Starter
TECH Enthusiast
Joined: Aug 2003
Posts: 596
Likes: 0
From: Downers Grove,IL
Do intercoolers add power directly? The popular calculation of every 10 degree temp drop = 1% power doesn't seem to apply to an air charge that has already been compressed and confined.
Seems to me they can't add power by temp drop alone because the mass of air is already set by the blowers output and then confined. The actual air MASS has not changed even though the density of the charge is increased by lowering the heated charge. Regardless of the heat of the charge the same amount of mass( and oxygen) will be admitted into the cylinders.
Rather they make power by allowing more timing or more boost from the lower charge temps to be used before detonation becomes a limiting factor, adding power in an indirect fashion.
Correct?
Now of course dropping temp into the blower will increase it's mass output as the air is more dense and that temp drop will equate to a direct power increase.
Anybody with more smarts than me have any input?
Steve
Seems to me they can't add power by temp drop alone because the mass of air is already set by the blowers output and then confined. The actual air MASS has not changed even though the density of the charge is increased by lowering the heated charge. Regardless of the heat of the charge the same amount of mass( and oxygen) will be admitted into the cylinders.
Rather they make power by allowing more timing or more boost from the lower charge temps to be used before detonation becomes a limiting factor, adding power in an indirect fashion.
Correct?
Now of course dropping temp into the blower will increase it's mass output as the air is more dense and that temp drop will equate to a direct power increase.
Anybody with more smarts than me have any input?
Steve
Thread Starter
TECH Enthusiast
Joined: Aug 2003
Posts: 596
Likes: 0
From: Downers Grove,IL
Take a sealed box of air and heat it up. Pressure rises but mass and volume in the box stay the same.
Cool it back down and pressure drops, air density rises but mass still the same.
Or,
Let's say I move 65lbs/min of air mass through the blower and into the engine. The blower compresses this mass of air into the intake as the engine is running.
The blower heats the mass of air decreasing it's density and pressure rises a little solely from the temp increase.
We now cool down this same 65lbs/min of air mass with an intercooler and increased the density and pressure drops a bit now.
But the same amount of air mass and oxygen content has passed in and out of the motor regardless of the air temperature or density change we make with an intercooler (I'm using a blower output of exact same impeller speeds in my examples.)
Now run the blower on a colder day and maybe 70lbs/min of air mass passes through the blower as the air is denser.
Then you get a gain in power from a direct temp lowering effect.
I can drop my charge temps 50 degrees with intercooling and not notice much effect IF I keep the timing and fueling the same and the engine was not detonating before intercooling.
Now run the motor on a 50 degree cooler day and a big power effect is felt as the blower moves more air mass through it.
Probably no need to analyze this as we all know intercooling is very beneficial. I'm just trying to understand things a little better is all.
Steve
Cool it back down and pressure drops, air density rises but mass still the same.
Or,
Let's say I move 65lbs/min of air mass through the blower and into the engine. The blower compresses this mass of air into the intake as the engine is running.
The blower heats the mass of air decreasing it's density and pressure rises a little solely from the temp increase.
We now cool down this same 65lbs/min of air mass with an intercooler and increased the density and pressure drops a bit now.
But the same amount of air mass and oxygen content has passed in and out of the motor regardless of the air temperature or density change we make with an intercooler (I'm using a blower output of exact same impeller speeds in my examples.)
Now run the blower on a colder day and maybe 70lbs/min of air mass passes through the blower as the air is denser.
Then you get a gain in power from a direct temp lowering effect.
I can drop my charge temps 50 degrees with intercooling and not notice much effect IF I keep the timing and fueling the same and the engine was not detonating before intercooling.
Now run the motor on a 50 degree cooler day and a big power effect is felt as the blower moves more air mass through it.
Probably no need to analyze this as we all know intercooling is very beneficial. I'm just trying to understand things a little better is all.
Steve
Originally Posted by S_J_H
Regardless of the heat of the charge the same amount of mass( and oxygen) will be admitted into the cylinders.
That might not be a perfect explanation, but you get the idea. Thermo was a long time ago...
-Geoff
Adkoonerstrator
iTrader: (4)
Joined: Nov 2001
Posts: 21,420
Likes: 0
From: Deep in the seedy underworld of Koonerville
On a supercharger spinning at a fixed rpm it might not help but, on a turbo that forces air in until the set boost pressure it might since the cooled air takes up less room and therefore should show less boost. Probably not enough of a difference to matter but, something to ponder while you're 
Teching In
Joined: Feb 2004
Posts: 19
Likes: 0
Originally Posted by White_Hawk
Nope. Colder air is more dense - more oxygen means you can add more fuel. Temperature and density are inversly proportional - temp goes down and density goes up or temp goes up and density goes down. From ideal gas law: pressure = density x temperature. So at constant pressure, if temp goes up, density goes down and visa versa.
That might not be a perfect explanation, but you get the idea. Thermo was a long time ago...
-Geoff
That might not be a perfect explanation, but you get the idea. Thermo was a long time ago...
-Geoff
...but you're not in a contained box.....At a low mass flow that would equal 1 psi an intercooler would almost be worthless as the inlet/outlet temps would be close....that's a "contained flow"......but you keep increasing the mass air flow through higher impeller speeds/higher inlet temps and the intercooler reduces the outlet temp and increases the outlet density...and you keep increasing the hotter mass air flow until you run out of intercooler/octane,etc.
Trending Topics
indirectly.. intercoolers allow the same mass of air to enter an engine at a lower psi. this in turn allows you to run MORE boost which makes more power.
if you put an intercooler on and don't change impeller speed then youre gains will be minimal and only related to heat engine efficiency
if you put an intercooler on and don't change impeller speed then youre gains will be minimal and only related to heat engine efficiency
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Not sure if it helps this thread, which has an interesting direction, but I am running 7-8 more degrees of timing than Scott's setup, and it's because his old twin 'coolers were maxed out.
TECH Enthusiast
Joined: Dec 2001
Posts: 553
Likes: 0
From: Columbia, MD
Originally Posted by MIGHTYMOUSE
indirectly.. intercoolers allow the same mass of air to enter an engine at a lower psi. this in turn allows you to run MORE boost which makes more power.
if you put an intercooler on and don't change impeller speed then youre gains will be minimal and only related to heat engine efficiency
if you put an intercooler on and don't change impeller speed then youre gains will be minimal and only related to heat engine efficiency
You can test this during different times of the year. When its colder, your engine runs marginally better, because the air is denser. But nobody picks up 100 horses just because its cold. The real benefits of cooling come from the fact that cooling fights off detonation -- therefore you can CRANK up the boost much higher before the pinging starts.
Registered User
Joined: Jun 2002
Posts: 453
Likes: 0
From: Forced Induction Heaven
Cooling the charge helps to resist detonation..thats it! Its like using higher octane fuel. Everytime I have seen somebody switch to a larger single IC (vs. twins) they have been able to add more timing and also had lower IATs..it all works together..bottom line is efficiency and the ability to resist detonation.
9 Second Club
Joined: Nov 2001
Posts: 1,445
Likes: 0
From: Bay Area, CA
Originally Posted by Pro Stock John
Not sure if it helps this thread, which has an interesting direction, but I am running 7-8 more degrees of timing than Scott's setup, and it's because his old twin 'coolers were maxed out.
its exactly that, cooler intake charge less detonation issues, equals more power potential.
if you add a good intercooler, a blown car should see a slight boost drop, you need to pulley up AND/OR add timing, watch your IATs a good intercooler will keep it within 10 degrees of ambient, with proper airflow going over the intercooler.
even a turbo car which can sustain the boost drop, and can benefit from timing if it was down. I have a roots blown car with no intercooler its murder on my performance when it gets warm, I can see a change in boost also from weather.
Thread Starter
TECH Enthusiast
Joined: Aug 2003
Posts: 596
Likes: 0
From: Downers Grove,IL
good answers everybody.
I used to run around 170' at peak boost using 20 degrees timing and alcohol injection at 13 psi. Eventually lifted the heads from some detonation.
Without the intercooler my tune was always on the edge.
I added the intercooler I just built and charge temps are much lower now.
I seem to have lost a good 1lb of boost through the intercooler. But I now run 22 degrees timing and no hint of detonation at 12psi.
Even though I have a maxed G-trim and really can't get any more flow out of it , I feel the intercooler has given me a much more reliable combo.
And that alone is pretty darn important to me.
I used to run around 170' at peak boost using 20 degrees timing and alcohol injection at 13 psi. Eventually lifted the heads from some detonation.
Without the intercooler my tune was always on the edge.
I added the intercooler I just built and charge temps are much lower now.
I seem to have lost a good 1lb of boost through the intercooler. But I now run 22 degrees timing and no hint of detonation at 12psi.
Even though I have a maxed G-trim and really can't get any more flow out of it , I feel the intercooler has given me a much more reliable combo.
And that alone is pretty darn important to me.
