Temp drop through FMIC?
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Supreme Member
Joined: Feb 2002
Posts: 2,663
Likes: 9
From: Buckhannon, WV
Car: 84' Monte
Engine: 350
Transmission: 700-r4
Axle/Gears: ferd 9" posi 3.50 gears
Temp drop through FMIC?
What is the average temp drop for a decent sized front mount? I know there are alot of factors that dictate the amount of drop, but I'm just looking for a ball park estimate. I'm also interested in the mass flow rate through the IC. I know the average 350 hp motor flows something like 255 grams per second, i'm sure you MAF guys know all about that, but CFM would work fine too, that way I can try to corelate temp drop to amount of air flowing through the IC.
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Joined: Sep 1999
Posts: 888
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From: West Hartford, CT
Car: '89 Z28tt
Engine: Dart Little M Twin Turbo
Transmission: T56
The Spearco catalog had a chart with intercooler efficiencies, based on different airflow going through it (5 mph, 10 mph, 15mph, etc...) Even though you may be driving at 80 mph, the air going through the core most definitely is not.
To be on the safe side, you can crunch out CFM by converting 5 mph to ft per minute (5*5280/60=440 ft/min), then multiply by the area in ft (figure 18"x12"=3.6 ft^2), so you get 1584 cfm ambient air through the IC core, cooling it down.
The mass flow rate of charge air through the core will be the same through the MAF, so it'll still be the 255 g/s your MAF measured, but now cooler. The IC does not change the total mass of the air, it just changes the density (colder air is more dense).
IC efficiency will typically be 60-85% or so, from absolute zero. If you're charge air is 170 deg above ambient (figure 80 deg), and the IC is 80% efficient at 5 mph, you'll now only have 170*(100%-80%)=34 deg hotter than ambient, and a 136 degF drop in temp.
Don't forget about IC pressure drop. Using a too-small core will have a high (over 2 psi) pressure drop, and start the vicious cycle where you want more power, so you turn up the boost, which creates more heat, so you intercool it inefficiently, so you need even more boost (hotter) because the IC core just took away 2+ psi, and on...
In short, avg temp drop for a front mount should be 70%+, more if you've got good airflow out of it (ducting after the core, not just dumping into a high-pressure engine bay which stifles the flow...). The temp chart from Spearco (I have it somewhere, and could scan, or you can probably find it on google images. For reference, I'm running a 2-182 core for the Z28tt.
From my z28tt logbook page a few years back:
This guy has a thorough analysis:
http://www.teknett.com/pwp/drmayf/chgair.htm
http://www.turbosaturns.net/articles...er_sizing.html
To be on the safe side, you can crunch out CFM by converting 5 mph to ft per minute (5*5280/60=440 ft/min), then multiply by the area in ft (figure 18"x12"=3.6 ft^2), so you get 1584 cfm ambient air through the IC core, cooling it down.
The mass flow rate of charge air through the core will be the same through the MAF, so it'll still be the 255 g/s your MAF measured, but now cooler. The IC does not change the total mass of the air, it just changes the density (colder air is more dense).
IC efficiency will typically be 60-85% or so, from absolute zero. If you're charge air is 170 deg above ambient (figure 80 deg), and the IC is 80% efficient at 5 mph, you'll now only have 170*(100%-80%)=34 deg hotter than ambient, and a 136 degF drop in temp.
Don't forget about IC pressure drop. Using a too-small core will have a high (over 2 psi) pressure drop, and start the vicious cycle where you want more power, so you turn up the boost, which creates more heat, so you intercool it inefficiently, so you need even more boost (hotter) because the IC core just took away 2+ psi, and on...
In short, avg temp drop for a front mount should be 70%+, more if you've got good airflow out of it (ducting after the core, not just dumping into a high-pressure engine bay which stifles the flow...). The temp chart from Spearco (I have it somewhere, and could scan, or you can probably find it on google images. For reference, I'm running a 2-182 core for the Z28tt.
From my z28tt logbook page a few years back:
2-19
The Spearco Intercooler catalog arrived today, and I've chosen a good core. It will go lengthwise across the area in front of the radiator (narrow and long), with one inlet and one exit. The inlet will have a Y so both turbos can join together. The wide and short intercoolers had pressure drops that were much larger. The usable frontal area couldn't have been as large either, since you have the tanks going the length of the IC, instead of just at the ends. My choice for today is the Spearco 2-182 core, which at 735 CFM and 10 mph of ambient airflow has a pressure drop of 0.6 psi and an efficiency of 82%. I'll scan in the performance chart when I get a chance. I will most likely have to fabricate my own end-tanks to place the inlet/outlet at the top of the intercooler facing rearward. This will get rid of 4 90 degree elbows, which are around a 1% loss per 90 degrees (just add up the degrees of turning, and you've got a rough loss number...) I'm still working on the details...
The Spearco Intercooler catalog arrived today, and I've chosen a good core. It will go lengthwise across the area in front of the radiator (narrow and long), with one inlet and one exit. The inlet will have a Y so both turbos can join together. The wide and short intercoolers had pressure drops that were much larger. The usable frontal area couldn't have been as large either, since you have the tanks going the length of the IC, instead of just at the ends. My choice for today is the Spearco 2-182 core, which at 735 CFM and 10 mph of ambient airflow has a pressure drop of 0.6 psi and an efficiency of 82%. I'll scan in the performance chart when I get a chance. I will most likely have to fabricate my own end-tanks to place the inlet/outlet at the top of the intercooler facing rearward. This will get rid of 4 90 degree elbows, which are around a 1% loss per 90 degrees (just add up the degrees of turning, and you've got a rough loss number...) I'm still working on the details...
http://www.teknett.com/pwp/drmayf/chgair.htm
http://www.turbosaturns.net/articles...er_sizing.html
Thread Starter
Supreme Member
Joined: Feb 2002
Posts: 2,663
Likes: 9
From: Buckhannon, WV
Car: 84' Monte
Engine: 350
Transmission: 700-r4
Axle/Gears: ferd 9" posi 3.50 gears
Thanks Andris, thats exactly the kind of info I was looking for.
This is a bit off subject but, I met one of your friends while visiting a friend down in North Carolina. His name was Mike, he drove a wicked SS imp and he was going to Nascar tech with my friend Scott. We were talking cars and he mentioned a buddy named Andris who had a twin turbo camaro, ended up I had been following your build up on the net. Small world.
This is a bit off subject but, I met one of your friends while visiting a friend down in North Carolina. His name was Mike, he drove a wicked SS imp and he was going to Nascar tech with my friend Scott. We were talking cars and he mentioned a buddy named Andris who had a twin turbo camaro, ended up I had been following your build up on the net. Small world.
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