Ok, "In theory" if you add an intercooler you will gain horsepower due to the cooling effect of the air. Lets review the facts.

1.) HP is based on how much air you move through the engine minus the drag on the engine.

2.) By adding an intercooler you increase the drag on the supercharger(engine) because you now have to flow through an obsticle

3.) If you only add an intercooler your supercharger is still spinning at the same speed moving the same amount of air.

4.) PSI drop across an intercooler should not effect overall horsepower because of #3 and the psi drop is seen because the air is more dense, but the same amount of molecules are entering the combustion chamber.

5.) Timing can be advanced because of the lower intake air temperatures and less of a chance of detonation.

6.) Timing advance HP gains are negligable to the extra drag added onto the engine because of the restrictive flow of the intercooler(highly dependent on intercooler).

7.) To see real HP gains you must increase the flow of the supercharger(pulley chagne or larger blower). Just adding an intercooler will not add horsepower. However by adding an intercooler with sufficient airflow you are able to increase the LB/MIN of air that the engine can safely combust without detonation.

From what I understand about the FI world I believe this stuff to be true. I'd like to hear whet the rest of you think about my "Theory". If I'm off on something please let me know.

 

Ok now i KIND OF disagree with #7...because in THEORY...if you add a nice and high flowing intercooler (greddy example) you only loose a little psi true but running the cool dense air you make horse power? For example...my friend Steph as a little GS-T eclipse and we did not change the boost or nothing (running 12psi stock) and we went to a huge nice intercooler and her boost stayed the same but the power was amazing.... it made it run cooler and it seemed way fast on the same boost?

So running a nice high flowing intercooler never hurts... but i guess it is a matter of opinion?

:D

 

Ok, now with the Eclipse we are talking turbo's not superchargers. And with at turbo here's what happens. The wastegate will open at a certain psi of boost. So instead of running 10psi of 200* air you are now running 10psi of 100* air, and if you recall your chemistry (PV=nRT) Less temperature at the same pressure means more molecules/volume or an increase in LB/MIN of flow as stated in #7. The turbo actually is spinning faster at that point which causes the extra airflow, kind of equivilent to changing the pulley on the supercharger.

 

yes i understand what you are saying but i know running intercoolers on mine and running with out it ran way better on my car with the intercoolers? But all in all...running an intercooler (a nice one) you are not going to drop alot of boost...and not only that you can cool the air down and make some good hp...but that is my 2 cents...

Intercoolers...good

no intercoolers bad...in my opinion :flag

 

So what you are saying is that you disagree with #6. I'm not saying that intercoolers are bad, at some point the become a must. I guess I was wondering if you were running a sc setup and wanted to add an intercooler adn change nothing else what would be the HP gain.

I understand that if you do run a "good" intercooler that you won't drop much boost, but you don't get any extra magic airflow, the blower blows x amount of air dependant on the rpm. And x amount of air is only good for y amount of horsepower given z amount of efficiency in combustion to hp. And the only variable that you can change by adding an intercooler of proper size is z, the efficiency of combustion to HP.

Or perhaps am I thinking of this wrong....Do you still make the same boost with as you do without an intercooler? Could it just take longer to pressurize the plenum? Hmmmmm, let me contemplate........ :rolleyes:



[Modified by mn_vette, 9:43 PM 5/16/2003]

 

good stuff...yeah i am sure if i went to a bigger and nicer intercooler i would game more horse.. but this is good stuff here :p:

 

Its not a matter of volume it is air density.
A small intercooler like the one ATI sells will restrict volume but if the rated flow of the intercooler is more than what the blower can flow then you will not lose volume but you will gain in air density. All you need to do to is look at dyno numbers with and without intercooler. If they didn't work why does every truck and farm tractor that has a turbo on it have an intercooler
It like at night a naturally aspirated engine will make more power than on a 90 degree day it is not getting more volume of air but the air that it gets is more dense.


[Modified by black bart, 9:41 PM 5/17/2003]

 

It's all about the max air / fuel molecules you can stuff into the cylinder without detonating. You don't need an intercooler to increase charge density; a D-1R with a small pulley will do that... but you'd need 110 octance to avoid blowing holes through the pistons!

A properly sized intercooled system allows you to increase charge density while keeping temperature constant to prevent detonation.

Just adding an intercooler without changing blower pulleys doesn't buy you much. To take advantage of intercooling and make more power, you must spin the blower faster- stuffing more air/fuel into the cylinders without detonation.

Remember forced induction generates effective compression ratios upwards of 16:1. In the theoretical world of infinite octance, intercooling isn't needed; in the real world of 91 octane it wins hands down.

 

Gcrouse,

This is the point I was trying to make.

Black Bart,

I do understand the reason why NA engines run better at night. However, in a forced induction system you have a set volume of air you can move and if you decrease the temperature in a set volume of air you decrease the pressure as well.

The big thing I think I was thinking about was that by adding an intercooler alone won't be as drastic as some people think, but it will allow you to spin the supercharger faster to add more airflow to make more horsepower.


[Modified by mn_vette, 4:52 PM 5/19/2003]

 

:lurk:

 

I will not argue with you about it but I would suggest that you go to the Spearco web site and order their book titled ( ALL ABOUT INTERCOOLING ) :cheers:

 

I might have an example that will help you. On my truck, my liquid intercooler pump was broken (I didn't realize it at the time) I went to the track, my Mat started at 120 and went to 200. The next time at the track I fix that problem and added a torque converter lock up switch. My Mats started at 95 and went to a high 120 (stock IC isn't that great). I gained a solid .3 (with a best of .4) and 2.5mph, of course this is at the same boost level. However, I have notice that my truck usuallyt gain approx .1 and 1mph with every lb of boost. If I lose 1.5 psi through my IC, I would still be ahead with lower boost and an IC.

 

Black Bart,

I guess I'm not here for a debate, I'm sorry if I seem arguementative. I'm just trying to figure out if I understand this stuff right. That's why I tried to number my assumptions/steps of logic, to have someone point out where I went wrong.

If there is only so much flow through the supercharger, I'm trying to figure out how having an intercooler creates more horsepower(on the same exact setup with and without). Perhaps my assumption of "flow out of the sc equals flow into the engine" is incorrect.

Thaks for the feedback :cheers:

 

You are overlooking density.
If you were making 15 lbs of boost non intercooled and you added a
intercooler with say 1.5 pressure drop the engine will receive less boost but it will receive more air and make more power. It is not necessary to speed the blower up.
The added power will come from a combination of things more aggressive timing / More dense air contains more molecules. Also another way to improve efficiency is with a bigger blower. Most make comments like I don't need a D1 or D1-R because I don't need that much power but what they don't understand is that the small blower has to spin so hard that it makes heat a bigger blower can be turned slower and make the same boost without the heat. Less heat is less detonation. When you really start looking at how blowers and intercoolers work then you can see why I have a D1-R and a very large custom built intercooler. I can deliver a huge amount of flow and keep it cool. When my blower has to work hard enought to start making more heat than the intercooler can remove I use Water\Alcohol injection to remove more heat. As clear as mud isn't it. :leaving:

 

black bart put the smack down see that is what i was trying to say but we all know now how has the mad skills!

i know for example (just wondering) i took off the hose coming out of my blower and the car was hot and the heat was not even warm and that was after i was running the "you know" out of it? i was thinking it would be like fire spitting out from the way the blower was being spun on the last race? but no it was nice and warmish not hot not or nothng like a turbo.....so i know even with my 2-1core intercoolers and if i spray them down with NOS that should keep the temp nice and kewl! i know guys that have wrapped there tubing with heat stuff and they gained .20 on there 1/4 mile times?

also .20 when spraying NOS on intercoolers and keeping the same boost...
denser air more hp :D

 

Ok, so the consensus here is that the theory is bogus. :cry Definatly not the first time that has happened. But I have yet to here a good explanation why. Yes it cools the air. But ambient air does not change temp and the supercharger only sucks in so much ambient air per rpm per time.

How exactly does an intercooler effect the boost vs. rpm curve? Plotting boost on the vertical axis and rpm on the horizontal axis what does the normal curve look like, then how would it change in comparison to being intercooled? I'm kind of guessing that it takes a little longer to build up boost.


Ok, fact review, cfm vs rpm for an engine is linear. cfm vs rpm for a supercharger is an exponential curve??? The difference of which creates boost(unused air still trapped between the engine and supercharger)??

 

http://www.gnttype.org/techarea/turbo/intercooler.html http://www.turboneticsinc.com/compre...action=display



[Modified by black bart, 7:52 PM 5/20/2003]

 

:lurk:

 

Look at this typical compressor map ( Vortech S-Trim )



As you see the red lines are almost horizontal. Take the 35000 rpm line for example. It will give you the same boost (1.6 is 8.8 psi boost) at 350 CFM and 800 CFM. By reducing the air volume and having the same boost you will get more air into the engine. You will loose some boost with an intercooler, but not much if it is a free flowing one.

 

So if I spin my supercharger at 35000RPM what determines how much air it flows? Is it then the boost? Or in this case Pressure Ratio?(what is that anyways?) So This compressor will create a given pressure ratio at a given RPM, and is independent of the CFM???(within a few tolerances of course) So RPM does not determine CFM is what the graph is showing. So If I put the blower on a 350ci and then stroke the motor to a 400ci they will hit the same boost levels at the same rpm levels??? Are these assumptions correct according to the last post and the compressor map?