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Old 03-23-2007, 12:30 PM   #1
keaniegenie
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Default TMIC discussion

This is probably a more advanced discussion of top mount intercoolers.

For anyone who's read the Newbie FAQ's, we know there's two types of intercooler designs. Tube/fin and bar/plate.

The large bar/plate designs offer the bigger pressure drops while the tube fin designs have been argued to be more efficient.

I had a nice discussion with Dan at Prodrive and Phil at Element Tuning about this subject. Dan felt the tube/fin design was much more efficient in terms of cooling. He liked the factory STI intercooler much more than most aftermarkets for this reason. Phil didn't disagree, but he pointed to the pressure drop of the large bar/plate designs as a way to increase power over stock.

I came to the conclusion that if you want a large turbo, you either choose better cooling (stock sti ic or ARC) or more power but the chance to heatsoak more (any large bar/plate).

There are many ways to improve the efficiency of the cooling of your TMIC. I've done almost all of them. I'm still curious to why tube/fin designs are more efficient.

Also, do tube/fin design ic's provide pressure drop if their larger? The bar/plate designs shoot for the largest size where the tube/fin ones do not. If a large tube/fin design also provided pressure drops similar to the large bar/plate ones, wouldn't this design be the best?

I don't know enough about ic's to know, but from what I've heard, tube/fin's are the best for cooling and efficiency.

If someone designed a big tube/fin design similar to the ARC or a big STI TMIC, would it provide the efficiency of a tube/fin and the pressure drop of a large bar/plate?
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Old 03-23-2007, 12:44 PM   #2
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http://www.bellintercoolers.com/pages/techFAQ.html pretty much is the God source of information that you are seeking. We can honestly debate this day and night, but without back to back testing of a few types with a MAHA dyno (the only dyno that creates real airflow), tempIN and tempOUT gauges to rate effeciency, and some logging of pressure through a flow bench of units......we are going to state our theories to infinity.

Personally....I have heard that tube and fin is more effecient, especially so for the JDM tube and fin models like ARC. Downside is they are terribly expensive. Another key is core thickness. Dan at Prodrive told me that Prodrive's test (for WRC?) concluded that at speeds, the rear of the Impreza engine bay becomes a low pressure region shunning flow downwards. Their testing proved that a thinner TMIC is better for effeciency. The only manufacturer who has found this to be true as well and has created a TMIC that is specifically thinner is the brand new Process West unit, though it's a bar and plate as they stated that quality Japanese tube and fin units would have killed the pricing. Process West also took the additional and HIGHLY important step of creating a purpose built splitter/shroud which is critical in the effeciency of the intercooler. Notice that only APS and Process West have been smart enough to have matched splitter/shroud units? Why? Those Aussies tend to test vs. zip a bunch of crap onto the market.
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Old 03-23-2007, 12:57 PM   #3
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I think this is interesting


Quote:
What are the differences between short tubes and long tubes?
The longer the tube the greater the pressure loss accompanied by a slight increase in efficiency.




Does the length of the tube affect efficiency?
Very little. The most heat comes out of the tube where the temperature difference between the inside and the outside is the greatest. That exists in the first couple inches of the tube. The last inch of the tube, wherein the charge temperature is rapidly approaching the cooling media temperature, will transfer very little heat, thus being of minor use.
So, maybe a thin intercooler with long tubes in a tube/fin design will give a desireable pressure drop while maintaining high cooling efficiency. Is that what this means? Is this how the ARC is designed?
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Old 03-23-2007, 01:09 PM   #4
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Well, in my finding of running air temp probes before and after the ic, I didn't really see much of a difference in temps between the b/p and the t/f. And to further throw things, I never seen a difference in air temps between a tmic and a fmic (while driving). Where the tmic gets into trouble is when you start getting into stop and go traffic. Which brings me to my next point. through all of my testing, the biggest factors that I have found is a larger scoop (sti), a good scoop to ic seal, and some kind of splitter that will send some of the sir to the front of the ic. This will not make the air temps any cooler, but what it does is lower the speed the car needs to be moving to see the air temps lower and make the cool down process happen quicker. With a good seal and a splitter with a sti scoop, I found at about 30 mph you can watch the post ic air temps start to drop (if the ic was heat soaked) and it usually only takes 1/2 to 3/4 mile for them to get almost down to ambient temps. Now, there are many things that I have found to effect this. Short ram intake=junk. You are sucking in the hot underhood air and it makes the cool down time HUGE. I will have to dig for some of my pics of my setup.


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Old 03-23-2007, 02:32 PM   #5
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Quote:
Originally Posted by WRX1 View Post
Well, in my finding of running air temp probes before and after the ic, I didn't really see much of a difference in temps between the b/p and the t/f. And to further throw things, I never seen a difference in air temps between a tmic and a fmic (while driving). Where the tmic gets into trouble is when you start getting into stop and go traffic. Which brings me to my next point. through all of my testing, the biggest factors that I have found is a larger scoop (sti), a good scoop to ic seal, and some kind of splitter that will send some of the sir to the front of the ic. This will not make the air temps any cooler, but what it does is lower the speed the car needs to be moving to see the air temps lower and make the cool down process happen quicker. With a good seal and a splitter with a sti scoop, I found at about 30 mph you can watch the post ic air temps start to drop (if the ic was heat soaked) and it usually only takes 1/2 to 3/4 mile for them to get almost down to ambient temps. Now, there are many things that I have found to effect this. Short ram intake=junk. You are sucking in the hot underhood air and it makes the cool down time HUGE. I will have to dig for some of my pics of my setup.


Russ
Hmmmm. Here's something interesting.

Ever since my TMIC situation wasn't ideal (small saabaru scoop, no splitter for a while), I monitored the temperature of my ic for a while via the hand test.

The stock splitter/shroud (not really a splitter, really only a shroud) was removed because the surface areait covered was less than half of my upgraded Turbo XS TMIC. Of course, my splitter was getting ridiculously hot under these conditions. No turbo blanket or heatshield at the time.

I also have a short ram intake, so I'm sure that made it worse. Before I made a custom shroud for my TMIC, I bought a Cusco heatshield and lined the entire underside of it with a heat repelling/absorbing material. Voila! My IC was always cool enough to touch.

The ic temps were even more improved when I added a modified STI shroud/splitter to my car. Because my scoop is way too small to fit the entire splitter, the splitter section was removed and only the shroud was used. I wish I could get some air splitting benefits, but unless I designed an entire custom one, this is impossible since my hood scoop is way too small.

Either way, my IC was VERY cool to the touch after very spirited driving. I'd drive hard, stop, drive hard, stop, and the IC was always very cool to the touch every part of the surface.

Then I installed my water injection kit. It currently stays off because it isn't tuned completely, so I keep my car on a low-octane map. When we installed the kit, I removed the factory intake piping for the silencer. I used to keep the cold-air piping that went to the intake box because I thought it forced cool air into the K&N filter on the intake. I figured it worked pretty well because the K&N filter always had a ton more debris where the factory piping faced. I've actually noticed my TMIC seems to get hotter lately than it did before, and the only changes I can relate to are is the factory cold-air piping being removed. Would this change the TMIC temps?
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Old 03-23-2007, 02:51 PM   #6
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Here are few thoughts I've had over the years.

Capacity is important, but consistency reigns supreme. ICs are about providing a consistent charge of air to the engine, no matter what the boost is. The air temp that exits from the end of the IC doesn't have to always be the same as ambient (the closer the better), but you do want it to be cooled to ambient, or above, following a consistent ramp of temp vs. boost.

Optimize the internal surface area for pressure drop and the external surface area for cooling capacity, but above all keep that IC temp consistent, and you'll have something works about as well as it can.

When I had my top mount and put the car on the dyno, the TMIC became so hot you couldn't touch it. Then I had an FMIC and an even larger turbo, even after several pulls it was at most slightly warm. The TMIC does not offer a consistent cooling effect and that limits your tuning options---you could have an "interheater" afterall. Better safe than sorry, and that means tuning for the most heat soak possible.

We could all probably get by with top mounts or at least V-mounts if we never sat in traffic, but for a little more pressure drop and a little more intake volume, I get a more consistent charge that allows me to tune the engine to a limit that I could not if I occasionally had an interheater instead of a intercooler.
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Old 03-23-2007, 04:47 PM   #7
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^^^But the heatsoak has to do with the fact it is sitting on a dyno. I can run my car up to 140mph (on a track ) and my post ic temps really only jump 8-10 degrees, while I am pumping in 310-320 pre (22psi with a fp18g). I have even tracked my car with my tdo4 at 20psi (325) and my post temps never went over 110 (ambient was about 80). Track sesions usually lasted about 12-15 min. But again, with a good seal between the scoop and ic to force the air through the ic. I think the key to a tmic is keeping the underhood temps as low as possible and keeping cool air flowing though the ic.

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Old 03-23-2007, 05:18 PM   #8
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Quote:
Originally Posted by bboy View Post
Here are few thoughts I've had over the years.

Capacity is important, but consistency reigns supreme. ICs are about providing a consistent charge of air to the engine, no matter what the boost is. The air temp that exits from the end of the IC doesn't have to always be the same as ambient (the closer the better), but you do want it to be cooled to ambient, or above, following a consistent ramp of temp vs. boost.

Optimize the internal surface area for pressure drop and the external surface area for cooling capacity, but above all keep that IC temp consistent, and you'll have something works about as well as it can.

When I had my top mount and put the car on the dyno, the TMIC became so hot you couldn't touch it. Then I had an FMIC and an even larger turbo, even after several pulls it was at most slightly warm. The TMIC does not offer a consistent cooling effect and that limits your tuning options---you could have an "interheater" afterall. Better safe than sorry, and that means tuning for the most heat soak possible.

We could all probably get by with top mounts or at least V-mounts if we never sat in traffic, but for a little more pressure drop and a little more intake volume, I get a more consistent charge that allows me to tune the engine to a limit that I could not if I occasionally had an interheater instead of a intercooler.
If that were true, would that mean the largest risk you would ever put your car in is a WOT pull right after driving in stop/go traffic?
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Old 03-23-2007, 05:20 PM   #9
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I'm also curious to how much wrapping your downpipe or headers helps with heat.

I know the majority of the heatsoak comes from the exhaust housing of the turbo being it's right underneath the IC and it get extremely hot. I would think the downpipe would be the 2nd thing, with headers being the next.
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Old 03-23-2007, 05:22 PM   #10
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Quote:
Originally Posted by WRX1 View Post
^^^But the heatsoak has to do with the fact it is sitting on a dyno. I can run my car up to 140mph (on a track ) and my post ic temps really only jump 8-10 degrees, while I am pumping in 310-320 pre (22psi with a fp18g). I have even tracked my car with my tdo4 at 20psi (325) and my post temps never went over 110 (ambient was about 80). Track sesions usually lasted about 12-15 min. But again, with a good seal between the scoop and ic to force the air through the ic. I think the key to a tmic is keeping the underhood temps as low as possible and keeping cool air flowing though the ic.

Russ
While there is a lot of truth in this post it does overlook one important factor I believe. That is actual air flow through the engine. Even with the 18G you can probably get away with the TMIC and those pre/post temps you are talking about. But I know with the Green sized turbos like I am running after a 1/4 mile worth of WOT the temps coming out of the stock and/or aftermarket TMIC are getting near +40-50F over ambient... even after cruising at hwy speeds to start with a cool TMIC.

I know I can dip in partial throttle and get around 10-15psi and pre temps shoot to 100-150F over ambient and post temps only go up maybe 5-10F over ambient, but that is a low air flow through the engine and intercooler situation. Once I go WOT and start flowing 280-300g/sec through the engine the TMIC QUICKLY heats up

Don't know if the author of this thread has found my old post yet about this subject but just in case:
http://forums.nasioc.com/forums/show...highlight=tmic
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Old 03-23-2007, 07:14 PM   #11
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Guys

These pics are worth a look. As Unabomber said ealier my new TMIC comes complete with a replacement splitter/shroud.

This pic shows a view of the splitter with rubber seal from underneath.



mock up of splitter sitting on the intercooler as it would be in the car.



with the hood scoop



this pic shows the difference between the factory splitter (rear) and the Process West unit.




Here are some pics of the core/y-pipe




Kevin

Last edited by Process West; 03-23-2007 at 07:27 PM.
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Old 03-23-2007, 07:40 PM   #12
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Very nice.
Do you make these to fit all model years? Say a my99/00?
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Old 03-23-2007, 08:03 PM   #13
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Oops...Kevin stumbled on our little post. Not to toot his horn any more than I already have, but his pictures state the case: Process West has their **** together with their TMIC. Aussie to US price conversion makes the price (from what I've seen, I ain't a Vendor so don't hate if I'm wrong) around $650. While this seems steep, you have to consider that it comes with a purpose built, splitter/shroud and those normally run $100-200 extra for other TMICs and they fit like ass so you have to get all ghetto fabulous with them or deal with their lack of function.
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Old 03-23-2007, 08:44 PM   #14
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.........

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Old 03-23-2007, 08:49 PM   #15
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Quote:
Originally Posted by Bbee 4 View Post
Very nice.
Do you make these to fit all model years? Say a my99/00?
GC8 TMIC is in development now.

Kevin
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Old 03-23-2007, 08:52 PM   #16
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Kevin,

I'm very interested in this IC. I've recently set out to get as much off my stock VF39 as I can get out of it. The APS unit is the one I was going to go with but after seeing this I have doubts that the APS is the one. I know that this is in final testing but I'd love to get some information. Dimensions also some graphs of pressure drop etc. anything that could compare it to the APS unit. I know the APS unit is much thicker than my stocker right now, and as pointed above a different fin design. My question is that with the "thinner" but more efficient design, compared to the APS model, will I see better cooling with the idea of better power as well? I also love the splitter that comes with the IC to keep sufficient air flow, great idea. Also when will this part be available to us here in the US as I can't find it anywhere.
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Old 03-23-2007, 10:12 PM   #17
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sweet,interested
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Old 03-23-2007, 10:38 PM   #18
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I would pay $800 for the same tmic with the splitter custom made for a 92x.

I'd pay $1200 for the same setup with a tube/fin ic.
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Old 03-23-2007, 10:43 PM   #19
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Quote:
Originally Posted by Tbagger View Post
Kevin,

I'm very interested in this IC. I've recently set out to get as much off my stock VF39 as I can get out of it. The APS unit is the one I was going to go with but after seeing this I have doubts that the APS is the one. I know that this is in final testing but I'd love to get some information. Dimensions also some graphs of pressure drop etc. anything that could compare it to the APS unit. I know the APS unit is much thicker than my stocker right now, and as pointed above a different fin design. My question is that with the "thinner" but more efficient design, compared to the APS model, will I see better cooling with the idea of better power as well? I also love the splitter that comes with the IC to keep sufficient air flow, great idea. Also when will this part be available to us here in the US as I can't find it anywhere.
There is a fair amount of test data here which will answer most of your questions.

http://www.rexnet.com.au/forum/index...howtopic=67143

Kevin
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Old 03-24-2007, 01:19 AM   #20
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Efficiency is one thing. Final cooling charge is another thing. While a smaller unit is probably more efficient by nature, it probably will not have a cooler output temperature.

There are results to back this up as well. If you look at the APS units, they sell the 525 and 725 units. The 525 is for smaller turbos and the 725 is for larger. While being more efficient at cooling, the 525 showed about a 5 degree warmer charge than the 725 at the same horsepower level.^1

This is also why they say, there is no replacement for displacement. You can be efficient all you want but bigger is usually better.

^1: http://www.airpowersystems.com.au/wr...dr525_fmic.htm
and http://www.airpowersystems.com.au/wr...dr725_fmic.htm
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Old 03-24-2007, 01:32 AM   #21
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to respond to my post, its also important to know that efficiency will be used when you are sitting in traffic, and then gun it. That is when you want it to cool quickly.
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Old 03-24-2007, 01:37 AM   #22
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Quote:
Efficiency is one thing. Final cooling charge is another thing. While a smaller unit is probably more efficient by nature, it probably will not have a cooler output temperature
Remember that ambient airflow to an intercooler in the top mounted position is poor compared to a front mount. For efficient heat exchange to happen (and hence lower intercooler outlet temps) you need to have good ambient air flow through the intercooler.

This is the reason I have gone for the 3.5in thick intercooler. 4.5 inches (like most aftermarket TMICs) is a long way for the ambient air to efficiently find its way through the core especially after making a 90 degree turn through the hood scoop.

Kevin
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Old 03-24-2007, 01:41 AM   #23
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You also need it to flow enough CFM...
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Old 03-24-2007, 02:11 AM   #24
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Quote:
Originally Posted by Andrew View Post
You also need it to flow enough CFM...
Correct, the configuration of a Subaru top mounted intercooler (many charge rows which are quite short) give the best flow and least pressure drop characteristics.

Kevin
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Old 03-24-2007, 01:48 PM   #25
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i'll take 1 of those, please


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