Intercooling - there's an expensive way to go about it and a cheap way to go
about it. If (like us) you find paying $2000-odd for a glorified heat exchanger
a little exorbitant, chances are you'll find gold at your local Japanese
importer. Japanese importers are a great place to shop for second-hand 'coolers
from Japanese domestic market (JDM) vehicles - it's not uncommon to see racks full of bargain intercoolers.
The big question is which of these intercoolers are the best in terms of flow
and thermal efficiency? In the second part of this two-part series, we look at
the remaining ten (out of twenty-five) intercoolers we have on test and
summarise the results.
Test Results (Continued)
Nissan R31 Skyline GT RB20DET Guard-Mount Air-to-Air Intercooler
Flow - Direction A (air exiting right-angled pipe) 181.2 cfm (21st
Direction B (air entering right-angled pipe) 162.9 cfm
Mass - 2.3kg (13th overall)
Core Measurements - 18.5 x 22.2 x 5cm = 2054cm3 (23rd overall)
Fitted to the Japanese market R31 Skyline 2.0-litre six-cylinder turbo, this
front-mount intercooler is typical of most compact Nissan 'coolers. It uses
plastic end-tanks, a relatively small core and looks quite cheaply manufactured.
Thermal mass is reasonable (partly thanks to a steel mounting bracket we
couldn't remove) but its poor flow means this is an intercooler to stay away
You could use it in applications up to about 150kW if you had
Nissan Skyline R31 GT RB20DET Top-Mount Air-to-Air Intercooler
Flow - Direction A (air entering large diameter pipe) 195.6 cfm
Direction B (air exiting large diameter pipe) 176 cfm
Mass - 1.9kg (equal 20th overall)
Core Measurements - 22.0 x 20.5 x 5.0cm = 2255cm3 (18th
This is the top-mount intercooler that was offered on some versions of the
Japanese R31 Skyline turbo. Similar overall to the
guard-mount version, this 'cooler has slightly different end-tanks and larger
core dimensions contributing to a better cfm rating than its cousin. Thermal
mass isn't up to the guard-mount version, however.
Again, we'd put up with using this intercooler only in applications up to
Nissan S13 Silvia SR20DET Air-to-Air Intercooler
Flow - Direction A and B 185.5 cfm (19th overall)
Mass - 4.6kg including cast alloy pipes (4th
Core Measurements - 22.0 x 16.8 x 5.8cm = 2144cm3 (22nd
This is the very heavily constructed intercooler that's fitted inside the
guard of SR20DET Japanese market S13 Silvias. Note that this 'cooler uses
dedicated cast aluminium entry and exit pipes that match flanges on the end
tanks. As such, we were forced to flow test this intercooler with the pipes
attached and we recorded a slightly pessimistic 185.5 cfm figure. On the other
hand, the extra weight of those thick aluminium pipes gave the Silvia
intercooler an overly generous thermal mass rating. Keep these factors in mind
when looking at the graphs further into the article.
Like the R31 intercoolers, we'd try to keep this intercooler out of vehicles
making more than about 150kW.
Nissan Pulsar GTi-R SR20DET Air-to-Air Intercooler
Flow - Direction A (air entering large diameter pipe) 236 cfm (8th
Direction B (air exiting large diameter pipe) 233 cfm
Mass - 4.7kg (3rd overall)
Core Measurements - 29.5 x 35.0 x 5.8cm = 5989cm3 (4th
We had high expectations for the Japanese market Nissan Pulsar GTi-R
intercooler and it didn't let us down. Factory-fitted to the 162kW version of
the SR20DET, this 'cooler offers good airflow together with very large core
area and thermal mass. A great pick if you're chasing every last bit of cooling
This is an excellent all-round intercooler we'd be confident using in
applications in excess of 200kW.
Toyota GX81-series 1G-GZE/1G-GTE Air-to-Air Intercooler
Flow - Direction A (air entering longer pipe) 212 cfm (equal 11th
Direction B (air exiting longer pipe) 209 cfm
Mass - 2.2kg (14th overall)
Core Measurements - 37.5 x 18.0 x 6cm = 4050cm3 (8th overall)
We're told this particular intercooler is the same as fitted to the 1G
supercharged 2.0-litre six and the 1G twin-turbo 2.0-litre six (the 1G-GZE and
1G-GTE respectively). A common choice for conversions in medium power
applications, this 'cooler has a generous core volume, average thermal mass and
Not at the top of the medium size intercooler field but certainly worth
considering for applications up to about 180kW.
Toyota Supra (JZA70) 2.5-litre Air-to-Air Intercooler
Flow - Direction A (air entering shorter pipe) 265 cfm (5th
Direction B (air exiting shorter pipe) 252 cfm
Mass - 3.8kg (5th overall)
Core Measurements - 48.7 x 17.8 x 7.2cm = 6242cm3 (3rd
Australian-delivered Toyota Supra turbos from the late '80s never came with
the option of the 2.5-litre 1JZ twin-turbo, which was available in Japan. The
206kW 1JZ-GTE in the Japanese JZA70 Supra is fitted with the long, skinny all
aluminium intercooler seen here. This 'cooler offers a huge core volume and
impressive thermal mass along with airflow that's bettered by very few in this
test. This really is a great unit.
There's no reason why this intercooler can't be used on engines making
considerably in excess of 250kW.
Toyota Soarer (JZZ30) 2.5-litre Air-to-Air Intercooler
Flow - Direction A (air entering angled pipe) 268.5 cfm (4th
Direction B (air exiting angled pipe) 262 cfm
Mass - 3.15kg (8th overall)
Core Measurements - 23.5 x 20.5 x 10cm = 4818cm3 (7th overall)
The same 206kW 1JZ twin-turbo motor used in the JZA70 Supra was also dropped
into the late model Soarer body. In the Soarer, however, limited space meant a
'box style' intercooler had to be squeezed into the left-hand guard. Using
lightweight plastic end-tanks its thermal mass and core volume aren't as high as
the 1JZ Supra's, but it still rates well in absolute terms. The Soarer box
intercooler is also more restrictive than the 1JZ Supra's, but only by a slight
margin - this is still a very good intercooler.
Again, this 'cooler is at home on engines making over 250kW. Add a water
spray in extreme cases.
Toyota AE92 Levin 4A-GZE Air-to-Air Intercooler
Flow - Direction A (air entering plastic pipe) 207 cfm (14th
Direction B (air exiting plastic pipe) 187.6 cfm
Mass - 2.1kg including exit plastic pipe (equal 15th
Core Measurements - 18.7 x 22.5 x 6.0cm = 2525cm3 (16th
The 4A-GZE intercooler is the only example on test that's used on a factory
supercharged engine. The blown 4A 1.6-litre four-cylinder makes 123kW in
standard form and its 'cooler rates average in heat exchange and flow
performance. No need to search high and low in desperation to find this one.
Note that the plastic pipe remained in place for flow testing, meaning its cfm
figure is slightly handicapped.
A decent all-round intercooler for engines producing up to around
Volvo Front-Mount Air-to-Air Intercooler
Flow - Direction A and B 200 cfm (15th overall)
Mass - 2.5kg (11th overall)
Core Measurements - 45.0 x 41.0 x 3cm = 5535cm3 (5th overall)
This impressive looking intercooler has been pulled from a turbocharged Volvo - probably a 700-series.
Its 5th position core volume comes as no surprise, but its thermal mass is let down by thin plastic end-tanks and a very thin core. That thin core also let it down on the flow bench where it ranked in the lower half of the field.
Its huge frontal area means this might be a good intercooler for sustained
high-speed use (such as on a racetrack). Its poor flow, however, means it's
inappropriate on engines making more than about 150kW.
Subaru Version 2 (MY94-96) STi Air-to-Air Intercooler
Flow - Direction A only (air entering bolt-on pipe) 224.2 cfm with bolt-on
pipe attached (10th
Mass - 2.8kg (10th overall)
Core Measurements - 40 x 11.5 x 6.2cm = 2852cm3 (15th overall)
The Version 2 STi intercooler is very similar to the unit fitted to the
Australian Version 2 (1994 - 1996) WRX, the only important differences being a
slightly different end-tank and a high-flow entry pipe. Even with its separate
high-flow entry pipe attached, this intercooler flowed well - a top 10 finisher.
Its thermal mass and core volume fall in the middle of the field.
A decent 'cooler for use on engines up to about 200kW - especially if you add
a water spray etc.
New Aftermarket Front-Mount
Flow - Direction A and B 372 cfm (1st overall)
Mass - 7.3kg (1st overall)
Core Measurements - 29.4 x 58.5 x 7.5cm = 12899cm3 (1st
This is the only brand new Japanese aftermarket intercooler on test - it's a
yardstick to compare the OE cores. As you can see, this is a positively huge
intercooler that ranks Number One in core volume, mass and flow. Note that it
outflows the best OE intercooler (the Series 6 RX-7) by a relatively small 20
percent, but its heat exchange potential is in another league.
This intercooler could be used in pretty well any high-powered turbo or
supercharged streetcar - assuming it can be made to fit!
The Results At a Glance
As mentioned, the new aftermarket core beat the flow of its nearest rival
(the Series 6 RX-7) by 20 percent. The Series 6 core features large diameter
hose connections but - to prove that's not the only external indicator to flow -
the Volvo/Saab intercooler pipes are equally large and the unit flowed
miserably! The intercoolers fitted to vehicles near the Japanese regulated 206kW
output flowed very well. Just to put a slant on that, though, the little Familia
GTX and Charade GT-ti intercoolers were right up there with the best of
All this just goes to prove you can't assess the flow of an intercooler just
by looking. Flow bench testing really is mandatory.
This graph clearly shows the superior mass of the aftermarket intercooler -
the big bar-and-plate core construction is much heavier than the factory
Working back to OE intercoolers, the light truck intercooler rated second
best in thermal mass but probably largely due to its heavy cast end tanks
(rather than the mass of its heat exchange core). The Pulsar GTi-R intercooler
was the clear winner in thermal mass of passenger car cores and the Silvia
intercooler also looks impressive on the graph - note, though, the quoted mass
includes the cast alloy entry and exit pipes so this figure is quite optimistic.
The big power Toyota engines have good 'cooler mass with the Soarer and 1JZ
units rating in the top few, as does the large Japanese-spec VR4 'cooler. The
Isuzu Piazza intercooler also has a very good thermal mass, aided by its thick
The surprise disappointments in the thermal mass stakes include the Series 6
RX-7 intercooler. The Cappuccino intercooler's thermal mass is hardly a
And here is the second indicator to the intercoolers' heat exchange
performance - the volume of their core section.
Again, the aftermarket intercooler and the truck unit are the best, but the
Supra 1JZ and GTi-R cores aren't far behind. These would be great in a
front-mount race application. The Saab/Volvo core also put in a very impressive
core volume but - as seen above - its poor thermal mass largely offsets any
positive. The Japanese market VR4 intercooler is the next best, beating the
Soarer 1JZ unit and all of the Mazda rotary intercoolers. With the exception of
the baby Cappuccino intercooler, most of the remaining intercooler core volumes
range between 2000 and 3000 cm3.
Obviously, we have a clear winner across the board - the aftermarket
front-mount intercooler tops the field in flow, thermal mass and core
volume. If you're prepared to spend the extra money, you can certainly get a very
But what about the cheaper second-hand import intercoolers?
The top three finishers in the OE intercooler category are the skinny 1JZ
intercooler (5th for flow, 3rd for core volume and
5th for mass), Pulsar GTi-R intercooler (8th for flow,
4th for core volume and 3rd for mass) and the Soarer 1JZ
intercooler (4th for flow, 7th for core volume and
8th for mass).
The Mazda Cosmo intercooler (3rd for flow, 9th for core
volume and 8th for mass) also performed exceptionally well overall,
while the Series 6 RX-7 unit (2nd in flow, 19th in core
volume and equal 17th for mass) looks great if you augment it with a
fan and water spray. The Series 6 intercooler has truly awesome flow but needs
all the help it can get in the heat exchange department.
The top performer in the smaller category is the Isuzu Piazza intercooler
(9th in flow, 12th in core volume and 7th in
mass), followed by the GX81-series 1G (equal 11th for flow,
8th for core volume and 14th for mass) and the Mazda
Series 5 RX-7 unit (7th for flow, equal 13th for core
volume and equal 17th in mass).
We were surprised to see the humble Familia GTX intercooler perform as well
as it did on the flow bench - give it a fan and water spray (as we've covered in
previous articles) and you've got a very effective little unit. The same goes
for the 3-cylinder Daihatsu GT-ti intercooler, which flowed amazingly well for
There are also a few shocker performances worth mentioning here.
The Mitsubishi Lancer GSR intercooler flowed abysmally (only the tiny Suzuki
Cappuccino intercooler was more restrictive), the Japanese spec VR4 intercooler
was extremely restrictive and the impressive looking Saab/Volvo intercooler was
out-flowed by more than half of the field. Strangely enough, the much sought
after Familia GTR intercooler was also out-flowed by the everyday Familia GTX
unit - it appears Mazda decided to chase improved thermal properties for the
GT-R rather than prioritising flow.
As we've proven, things are often not as they seem when picking an
The second-hand intercoolers on test were all obtained from Adelaide Japanese
Dismantlers. The price of these intercoolers constantly varies depending on
supply and demand but, at the time of writing, these are the prices (quoted in
||Mazda Familia GTX
||Mazda Series 4 RX7
|Mazda Series 5 RX7
||Mazda Series 6 RX7
|Mazda Cosmo 20B
||Mazda 626/MX6 Turbo
||Mitsubishi JDM VR4
|Mitsubishi 1.8 GSR
|Nissan R31 (guard-mount)
||Nissan R31 (top-mount)
||Toyota JZA70 Supra
|Toyota JZZ30 Soarer
||Toyota AE92 Levin
||Subaru Version 2 STi
Be wary, though, these prices are subject to ongoing variation.
The new aftermarket intercooler on test retails for $850 (plus fitting)
through Adelaide's Exhaust Technology. However, for a limited time, AutoSpeed
readers can pick it up for the special price of $800.
Thank you to Frank Intini of Adelaide's F&M Cylinder Heads (+61 8 8294
2515 or email@example.com) for use of his
Superflow flow bench; Adelaide Japanese Dismantlers (+61 8 8369 1156 or
supplying the second-hand import intercoolers and Exhaust Technology for
supplying the new aftermarket intercooler and fabrication of the flow bench
adapter and tubes (+61 8 8272 7500).
All services and products were provided at no charge.