Turbo's and air density.

RonA

RonA

Active member
I'm looking at putting a water to air cooler between stages. Looking at an air density chart and assuming 40psi out of a primary charger(ballpark), I see that 1 cubic ft of air at 40psi and 100 degreeF weighs .264 lbs. At 200 deg it weighs .244lbs and at 300 deg it weighs .195 lbs. That makes an 8% difference going from 100deg to 200 deg and a 35% difference going from 100 deg to 300deg. I have never checked temperatures after either turbo but was told to expect 300 deg + after the primary, and 450 after the secondary. How does the density of the air change the flow through the compressor? Will the secondary move more lbs per minute with the higher density air and if so is it directly related to the density going in. Basicly I'm asking if dropping the air temperature between stages from 300 deg F to 100deg F will increase the amount of air exiting the seconday charger by 35%?
 
i would expect think the added stress on the charger from pumping dense cool air may effect the flow,the math sounds correct, but the charger will probably need to work much harder to flow the expected 35% more.
 
I don't think it will increase flow from primary as much as make the secondary more efficient. Seems to close the gap between primary and secondary. I'm looking into doing this myself.
 
I would think you go could use a smaller compressor on the high pressure turbo but not change the flow out primary assuming no restriction on the flow from the air to water cooler. I want to try this idea also, would be nice to get away with a smaller secondary turbo for DD use
 
I agree that I think the efficiency would be increased. I noticed a huge difference from sea level to 4200ft elevation, I "lost" 10 psi. Same concept.
 
your secondary meets the demands placed on it by the engine VE, rpm, aftercooler and pressure ratio. feeding it cooler air will mean it has to move fewer CFM to move the same lbs/min. since you are moving the same mass in a smaller volume you would see/need less boost. so you can use a smaller secondary to accomplish the same job. at least thats how I see it.
 
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Primary temp is at 418 degrees around 35lbs boost. Not hard to imagine how much harder it is to compress 418 degree air at the second stage.

Throw an ice box in the back and cooling the primary air below ambient would be the ticket.
 
On the street I would think the benefiet would be negated by the extra piping needed. The cooler air sounds good but you would be adding a flow restriction and more pipe volume before the turbo would be making boost. More lag over all. I am not an expert but it sounds catch 22. Now for something that stays under boost conditions this sounds like a sweet idea.
 
Depending on placement, the additions piping over a normal interstage pipe would be minimal. VERY worth the spool and weight penalty. Remember, when the air the secondary sees is cooler, it will think there is more there.....and spool like it;)

Chris
 
Signature600 said:
Depending on placement, the additions piping over a normal interstage pipe would be minimal. VERY worth the spool and weight penalty. Remember, when the air the secondary sees is cooler, it will think there is more there.....and spool like it;)

Chris
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I agree, I recently switched from using engine coolant as my coolinng medium to a stand alone loop with heat exchangers to cool my interstage. intake temps to the secondary dropped significantly and spoolup/ response improved, my water temp to the interstage cooler is usually around 15-30* hotter than ambeint temps which is a lot better than the 190* engine coolant i was using. I also think that my interstage piping was easier to make than the normal way.
 
burnin oil said:
On the street I would think the benefiet would be negated by the extra piping needed. The cooler air sounds good but you would be adding a flow restriction and more pipe volume before the turbo would be making boost. More lag over all. I am not an expert but it sounds catch 22. Now for something that stays under boost conditions this sounds like a sweet idea.
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To add to what Chris just said, the increase in lag would be minimal. Consider that Ron has a turbo that flows 2500 CFM, how long do you think it would take to fill the pipe/IC that might have 2 cu. ft. of volume? Granted, it won't be flowing 2500 CFM at the time, but even at 400 CFM, it would take less than half a second to fill the charge pipes. Has to be better than the way WOP does their triples with pipes crossing over the engine twice.
 
gs1000 said:
I agree, I recently switched from using engine coolant as my coolinng medium to a stand alone loop with heat exchangers to cool my interstage. intake temps to the secondary dropped significantly and spoolup/ response improved, my water temp to the interstage cooler is usually around 15-30* hotter than ambeint temps which is a lot better than the 190* engine coolant i was using. I also think that my interstage piping was easier to make than the normal way.
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That's what i was thinking. A separate tank and electric pump with radiator and fan going to the intercooler.
What gauges are available to measure intake temp at the secondary? I see an autometer unit and Fluke has a hand held temp gauge with various probes.
 
Seems to me fluke has a really nice dual probe meter that would be handy checking efficiency. Quick response exposed element thermocouplers are nice, react instantly. 1/8th probes and then you can use 1/8 pipe to 1/8 crimp to the thermocouple. More or less the same as my superflow. Logging would be nice though lets you see the whole picture.

I wouldn't cheap out on the probes, those quick response are the meat of the whole deal....I could live with something cheap to read them.
 
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gs1000 said:
I agree, I recently switched from using engine coolant as my coolinng medium to a stand alone loop with heat exchangers to cool my interstage. intake temps to the secondary dropped significantly and spoolup/ response improved, my water temp to the interstage cooler is usually around 15-30* hotter than ambeint temps which is a lot better than the 190* engine coolant i was using. I also think that my interstage piping was easier to make than the normal way.
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Ron, I would call this guy. I really liked his setup, very well put together.
 
Ron that would work ok, I think ultimately you will find it a restriction. Not sure how hard you plan on pushing that gtx, but we have seen as high as 5psi drop across that same cooler with the same charger as a single.
 
So it needs to be rated for a bit more flow like this one?

Water to Air Intercoolers

RonA

By the way, my hat is off to you for being able to run it as a single. I had to take a half day off after holding it in place and getting the bolts started.
 
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