seems to be some great comparisons and tech info there!Test Results...
Version 2 (MY94-96) WRX Intercooler
Flow 282.7 cfm
143.9 cfm with standard WRX feed pipe attached
Mass 2.8kg
Core Measurements 40 x 11.5 x 6.2cm (2852cm2)
The Version 2 intercooler is immediately recognisable as the poor cousin in the WRX range. It's the smallest and lightest of the bunch, its end tanks and core section are oddly arranged and its core volume isn't particularly large. The plastic intercooler feed pipe (which is notorious for splitting at high boost) also flowed appallingly - installing it reduced flow bench figures by 50 percent!
Version 2 (MY94-96) STi Intercooler
Flow 285 cfm
224.2 cfm with standard STi feed pipe attached
Mass 2.8kg
Core Measurements 40 x 11.5 x 6.2cm (2852cm2)
This imported Version 2 STi intercooler is a rare find. Visually, only the silver finish and a different rear end-tank shape distinguish it from the contemporary WRX part. So how much better does the STi intercooler perform? Well, not much. A slightly larger charge-air entry into the rear end-tank allows a tad more flow than the standard WRX 'cooler - 285 cfm versus 282.7. Thermal mass and core volume, meanwhile, is identical to the stock WRX - pretty minimal.
While the STi intercooler holds a slim flow advantage over the base product, its cast alloy/silicone hose feed pipe flows considerably better than the standard plastic part; the absence of a convoluted section (which causes massive in-pipe turbulence) is the major reason for this improvement. Once bolted together, the STi intercooler and feed pipe assembly outflows the standard WRX combo by more than 50 percent - a good net gain. Note that the Version 2 STi feed pipe won't bolt onto the conventional WRX intercooler (damn!).
Version 3-4 (MY97-98) WRX Intercooler
Flow 309.8 cfm
159 cfm with standard Y-shape feed pipe attached
Mass 3.150kg
Core Measurements 37.5 x 14.5 x 6.2cm (3371cm2)
Subaru took a major step up in the size of the Version 3 core - and the benefits show. Compared to the earlier Version 2 WRX intercooler, airflow is up 10 percent, thermal mass is around 12 percent greater and the heat exchange volume is 18 percent larger. While this is certainly an impressive upgrade (for an OE part), bear in mind the aftermarket Version 2 core still performs better in every aspect.
Interestingly, bolting on the standard Version 3-4 WRX Y-shaped feed pipe (which is a combination of cast alloy and plastic) caused nearly a 50 percent flow loss - similar to that seen on the Version 2. Again, we can blame a portion of this restriction on the convoluted section of the plastic feed pipe.
Version 3-4 (MY97-98) STi Intercooler
Flow 315.7 cfm
Standard STi Y-shape feed pipe unavailable
Mass 3.150kg
Core Measurements 37.5 x 14.5 x 6.2cm (3371cm2)
Ah-ha - here's an intercooler that many WRX owners are prepared to spend big money on. But is it worth it? On the scales, the imported STi 'cooler is virtually the same weight as the WRX equivalent and the core dimensions are identical. In short, there's no heat exchange advantage to be seen.
And what about airflow?
Well, the STi intercooler flows 315.7 cfm at 28-inches of water - about 2 percent better than the basic WRX core. Again, we're talking about a minimal gain. The reason for this slightly superior flow appears to be linked to the fact the STi intercooler doesn't have the recess found on the left side of the conventional Version 3-4 WRX rear end-tank.
While the Version 3-4 STi 'cooler is barely any better than the WRX part, once again we'd expect its associated silicone feed pipe to out-flow the normal plastic one. Unfortunately, though, the STi Y-shape feed pipe was unavailable for our tests.
Done a few basic mods to your Subaru WRX? Not interested in the hassle and expense of going for a front-mount 'cooler? Well - following the five top-mount 'coolers tested in Part One of this article - we'll now continue with the five remaining intercooler and give you the overall wrap-up...
Version 5-6 (MY99-00) WRX Intercooler
Flow 286.3 cfm
134.8 cfm with standard Y-shape feed pipe attached
Mass 3.8kg
Core Measurements 37.5 x 14.5 x 6.2cm (3371cm2)
As mentioned in Part One, the Version 5-6 intercooler has the same core dimensions as the previous model but has much denser external cooling fins and revised internal fins. This contributes to a big 21 percent increase in mass over the Version 4-5; we can only guess Subaru suddenly decided to get very serious with charge-air cooling.
This focus on improved cooling has come with a trade-off, however. On the flow bench, the Version 5-6 WRX intercooler dropped to nearly to the performance of the Version 2 WRX intercooler. With just 286.3 cfm flowing at 28-inches of water, this is certainly one of the most restrictive Subaru top-mount cores.
Airflow continues to decline when the standard Y-shape feed pipe is bolted on; this part is identical to that used on the Version 3-4 and caused a similarly massive flow loss. The result - at 134.8 cfm - is the worst flow figure of all the 'cooler/feed pipe assemblies.
BG (MY97-98) Legacy Twin-Turbo Intercooler
Flow 314.3 cfm
255.7 cfm with twin cast alloy feed pipes attached (not including plastic pipes to turbochargers)
Mass 3.6kg
Core Measurements 37.5 x 14.5 x 6.2cm (3371cm2)
Hmmm, these figures look familiar. It seems the imported BG Legacy twin-turbo intercooler core is the same as used in the Version 3-4 STi - that's not surprising considering they're from the same timeframe and are used on engines making similar power. On the flow bench, the TT intercooler flowed around only half a percent less than the Version 3-4 STi job - this margin is so miniscule, however, it's likely to be variation of the flow bench.
In terms of heat exchange performance, the Twin-Turbo intercooler is around half a kilogram heavier than the Version 3-4 STi - though we suspect this is only because of some extra brackets and a metal core garnish. The core volume is identical to the Version 3-4 STi and WRX; that means, amongst the OE intercoolers, its core volume is beaten only by the Version 7 part.
BF (MY92-93) Liberty RS Water-to-Air Intercooler
Flow 221.1 cfm
211 cfm with standard RS feed pipe attached
Mass 3.9kg
Core Measurements Unable to measure, but smaller than Version 2 WRX (at 2852cm2)
First, we must point out that the 3.9-kilogram thermal mass quoted for the RS water-to-air heat exchanger is a little misleading in the context of air-to-air intercoolers. Some of this mass can be attributed to the external water jacket with two water necks and the alloy feed pipe that's cast as part of the intercooler body. Oh, and - since it's contained within the water jacket - we were unable to measure the volume of the water-to-air heat exchanger core.
And how did the RS intercooler flow? Well, we recorded 221.1 cfm but - again - this figure is misleading. As mentioned, the RS intercooler body integrates a large section of the feed pipe; this inevitably causes extra flow restriction compared to the rest of the 'coolers, whose feed pipe connect at the base of the rear end-tank. In other words, the flow figure for the bare RS intercooler is at a disadvantage.
On the other hand, only a short length of plastic pipe (which incorporates a blow-off valve fitting) is required to link the beginning of the alloy feed pipe to the turbocharger. Adding this to the intercooler saw just a 5 percent flow loss; the relatively small loss from fitting this part helped bolster the flow of the complete RS intercooler assembly beyond that of the Version 2, 3-4 and 7 WRX!
Summary
The top-mount intercooler location will always be less than ideal, but we've demonstrated that good flow and heat exchange gains can still be realised.
For those on a budget, the imported Legacy Twin-Turbo intercooler is one to look out for. Within the collection of OE air-to-air intercoolers tested, it provides the equal highest airflow (shared with the Version 3-4 STi), the equal highest thermal mass (shared with the Version 5-6 WRX) and its core volume is bettered only by the current Version 7. What's more, these much-underrated 'coolers can be commonly bought from import wreckers for just AUD$350. And what will it fit? Well, we believe the TT intercooler can be made to fit Version 3-onward WRXs using your existing feed pipe (the twin-turbo pipe arrangement is entirely unsuitable for a single turbo application). Oh, and your blow-off valve arrangement will also need revision.
An interesting player was the Liberty RS water-to-air intercooler. Offering better airflow than some of the standard WRX stuff and the potential to allow better charge-air cooling - particularly in stop-start conditions - it's an attractive proposition. Despite being able to fit anywhere a standard WRX top-mount lives, the only drawback is the hassle and expense involved sourcing and installing a water pump, radiator and electric system.
do check the actual links as there are some good graphs on there too!
http://autospeed.com...intArticle.html
http://autospeed.com...19/article.html
enjoy!
Ive just got a just Jap 100mm TMIC will be interesting to see how it compares to the V3 one i have currently.
and yes its got a CAI and Exhaust. The only reason i was worried is because after reading this article i was thinking the TMIC might night be enough for this beast.
