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View Full Version : IC thoughts.. am i wrong???



James Kanteraki
09-13-2002, 08:53 PM
I've been looking at the magnum powers new FMIC (its awesome) and was thinking about what the IC actually does for us (being SC drivers, not turbo drivers).

Obviously, the IC lowers the temp of the air coming into the engine after going through the SC. This is where i come into a lack of knowledge. How much heat does the SC make when your cruising down the freeway???

Lets say: i'm cruising at 80 mph (yeah i know, slow, haha) but at this speed i'm reading approx 10 inches of vacuum. Sure the SC is turning fast, making heat (i got 5% too). I'm trying to get at this, is the new FMIC neccesary unless you are a racer, or will i actually benefit from it all the time?? Is the stocker good enough??? I mean when you are cruising the air goes through the IC and round about and through the dump and cools the SC, when not in boost. so is the FMIC gonna improve my (low blow) power. I saw that it has a much lower pressure drop, which is good for the HG's i take it, but other than that, am i only gaining when in boost???

Just toughts... like running the IC fan when not in boost, is it really doing anything?

I hope you get what i'm trying to say here.

jim

Ryan A Harris
09-13-2002, 09:21 PM
I'll try my best for you here:

The FMIC is to further cool the air, this will make the air going into the sc colder, making more power. You would see an inpprovment in power an perframnce. Also you have a large area to cool the air, thus more air. making for the drop in pressure. Check out som eother companies for FMIC, there are a ton of them. Also you could make up your own IC, in front of the rad, that would be better.

Thomas A
09-13-2002, 11:51 PM
Check out this article that Charles Warner wrote:

http://www.magnumpowers.com/intercool.html

Thomas

John Shelton
09-15-2002, 01:08 PM
When you're into boost, you're making hot compressed air. The intercooler removes heat from that air, making the charge air even denser, improving performance. The more efficient the intercooler, the more performance benefit.

When you're not in boost, but under vacuum, there's no hot compressed air that needs cooling down, the incoming air is routing through the bypass tube and into the cylinders at roughly ambient temp.

Under vacuum, since the temp of the air being drawn into the MAF, etc. is the same as the temp of the air cooling the intercooler, a better intercooler wouldn't improve performance.

MIKE 38sc
09-15-2002, 01:51 PM
Originally posted by John Shelton
When you're into boost, you're making hot compressed air. The intercooler removes heat from that air, making the charge air even denser, improving performance. The more efficient the intercooler, the more performance benefit.

When you're not in boost, but under vacuum, there's no hot compressed air that needs cooling down, the incoming air is routing through the bypass tube and into the cylinders at roughly ambient temp.

Under vacuum, since the temp of the air being drawn into the MAF, etc. is the same as the temp of the air cooling the intercooler, a better intercooler wouldn't improve performance. John you have made a mistake there. You have the air flowing backwards through the by pass valve under vac. conditions. This is not the case. Air never flows from the intake plenum through the by pass valve and into the engine thus by passing the SC altogether. When you let off the gas the by pass valve opens thus dumping the boost pressure back into the intake plenum at the back of the SC. Air is ALWAYS passing through the SC, so you WILL get cooling of the intake charge even if you are NOT making boost.

John Shelton
09-15-2002, 02:34 PM
Thanks for pointing that out, Mike, about the direction of flow in the bypass. So, under vacuum, we've got a loop of air flowing counterclockwise: sc -> top tube -> ic -> bottom tube -> bypasss -> sc, etc. Then the engine takes what it needs and it's replaced with the same amount coming in the TB, etc.

I do disagree about the cooling at the ic when the engine's under vacuum. If the air is in this short-circuit loop, pressures on both sides of the sc are practically the same, it's not being compressed, therefore not getting hotter than ambient, so no cooling at the intercooler. What do you think?

James Kanteraki
09-15-2002, 05:47 PM
guys, thanks for all the help, this clearing up everything for me and others too it seems.

John,
theoretically, you would be right: "pressure on both sides equal, means no increase in heat" or maybe actaul theory would say that after coming out of the SC would be less pressure because the engine is pulling SOME from that air flow, actually decreasing the temp.

but what your forgeting is this: the SC is turning. 1. it has close tolerances and friction exists, so there will be heat generated, and 2. if your running 80MPH that SC, boost or not, is turnig REALLY fast.

(i guess i understand it all now) so yeah the IC is always cooling the charge, and especially with a smaller pressure drop (why is it called that??) it will be more effecient.

Tom, thanks for the link, i hadn't been to the MagPowers site.

so, what, we have to look forward to a decrease in max boost, when we put this thing on??? but power will actually increase???
we just have to remember that boost is a relative term

thanks all
jim

XR7 Dave
09-15-2002, 09:52 PM
Regarding pressure drop, when you measure airflow, you tend to think in terms of an absolute value like 500cfm or 800cfm. However, it is not an absolute value. With naturally aspirated applications the pressure that the air is fed through the meter is always ambiant pressure, or an approximation of 14.7psi(or -0- on a boost gauge). However, once you start talking boosted applications, airflow no longer follows that constant. Now you have elevated pressures and variable flow rates. Our stock intercoolers WILL flow 700cfm. But at what kind of a pressure drop? Pressure drop refers to the difference in measured pressure on one end of the intercooler vrs the other while maintaining said flow. This is a testing method for IC efficiency, not to be confused with actual airflow through our motors. Since our blowers are positive displacement, the air WILL make it's way through the intercooler to the motor, therefore our IC(or any other for that matter) WILL flow 700 cfm if it needs to. What does happen however, is that the air is flowing so fast through the IC that very little cooling is accomplished. The pressure drop that they are talking about will not occur in our motors. The only pressure drop we will see will be due to the smaller space taken up by the cooler air charge as it enters the motor.

MIKE 38sc
09-15-2002, 09:59 PM
Originally posted by John Shelton
Thanks for pointing that out, Mike, about the direction of flow in the bypass. So, under vacuum, we've got a loop of air flowing counterclockwise: sc -> top tube -> ic -> bottom tube -> bypasss -> sc, etc. Then the engine takes what it needs and it's replaced with the same amount coming in the TB, etc.

I do disagree about the cooling at the ic when the engine's under vacuum. If the air is in this short-circuit loop, pressures on both sides of the sc are practically the same, it's not being compressed, therefore not getting hotter than ambient, so no cooling at the intercooler. What do you think? James is right on everything. I however do not agree with his opinion that the tolerance's of the blower are creating heat that is transfered to the intake charge air under vacuum. I feel at this point the most determining factor for the heated intake charge air is the heat transfered to the blower by engine heat itself. This engine does not see ambiant temp. ever, exccept when the engine is started after setting overnight. Lets not forget that glorias piece of engineering marvel, the LOWER IC tube! Now heres something that defies ALL logic. Lets cool the intake charge air with an intercooler[to make the engine run better and help reliability] now lets route that cooled air charge right over the TOP of the exhaust manifold, now thats smart as hell. At this point why cool the charge air at all? The system has merit, but must be reworked to do any real effective intercooling. But then again thats just my opinion.

John Shelton
09-15-2002, 10:21 PM
Good points, guys.

I was thinking about the heat generated by compressing the air. Since the intercooler can also help get rid of the other sources of parasitic heat that were mentioned, then it's accomplishing something even at cruise. I think that was James' original question. Any heat that can be blown off the intercooler is a good thing.