VDJ200 Landcruiser Intercooler Tech.

 

 

While there is nothing new about putting some fans on a VDJ cooler to assist engine performance, SQP's take on it and the technical investigation that triggered the motivation to build a better "mouse trap' as such is. SQP has always prided itself on selling the best product required for the task backed by the reasons why. Over 30 years of Research and Development and the knowledge gained by that ruthless persuit of the answers to the question- WHY? SQP back our sales with technical merit on a level many can't rise to and we pass this knowledge to our customers to better inform them so they can make buying decisions based on understanding- not beliefs. No gimmicks. No smoke and mirrors. Fans on VDJ are no different. Doesn't always make us the cool guys when it rains on some parades but popularity fades where good technical product stands the test of time. It is always hard to write these sorts of technical articles knowing that it is not only our customers we are educating but also in many instances- our competitors.

 

Early in the development of our tuning packages, it became very clear that the VDJ200 suffered from intercooler efficiency with power down rating on the dyno from one pull to the next. This lead in some strenuous investigation. Very rarely OEMs get things just a little wrong. We saw in 2000 how Holden got the Intake Air Temp Sensor (IATS) in the wrong spot with the VT Commodore. This lead to erronous reading on that platform and power suffered. Had Toyota done the same? How can a sensor reading reduce power in the VDJ? Lets start there... from intake air temps the engineers decide what density of air they are getting. From this density they will vary fuelling to match the oxygen that is availabe for combustion. But it doesn't end there. Once the intake air temps climb, they also limit boost again removing air and therefore oxygen. Why would they do that? Anyone that has been around boosting engines (and SQP has been for near 30 years!) has that answer straight up- when you compress you heat. Diesel engine couldn't work if that principle didn't exist. As the IAT climbs, the more it is compressed the hotter it gets. One thing that is not well understood with rooky performance "experts" is that boost is quite often the enemy of air density. We often see shoved around that more boost = more power but that is just a ignorant over simplification of moving air into engines. We need pressurised DENSE air- not high pressure HOT air! How do the engineers interpret this- "let's lower boost and give the cooler a chance to cope." Below is how those two principles are defined in the Toyota ECU code.

 

 

Here we see how how the engineers as removing fuel as intake temps climb- lower fuel = LOWER POWER!

 

 

 

Where did the air go? Table above shows boost being ripped out as intake temps climb.

 

Why are the engineers so agressive in removing air and fuel? As air temperatures climb, the density of air declines. Yes there is less oxygen and it leads to the engine not being able to burn the fuel being injected. We often hear people complaining about how their diesel engine is intermittently "dirty". 9/10 times it is because of how the injector pulse tables have been manipulated outside the engineers calculations- hacked in other words! It doesn't take into account variations in available air and sooting is the result. Starting to get the picture why so many state their VDJ200 derated towing a van up a hill? Some claim it is because of converter/trans temps and sell the punter a lock up box! But the facts are in the tables above- IAT in the 80C region (temp not hard to see with raised boost and high load) cause a massive removal of boost and fuel from the engine calibration.

 

So armed with the above understanding SQP went looking into how the intercooling was coping on the VDJ200. One thing that was observed over was 13 years of dyno running the platform was that the VDJ79 coped a lot better even without a fan on them on the dyno. How could that be? Boost was lower but it couldn't be the whole reason. SQP investigated the turbo location first- the VDJ70 series have a single turbo located to one side and well clear of the firewall where as VDJ200 being twin low mounts basically sitting on the fire wall with the cooler hard up on it also above... First place looked at was the intake air temp sensor (IATS) location. Now this is a sensor reading temps the above table is looking at AFTER air is boosted. Really could be termed "boost air temp". Toyota are great engineers and they build an awesome product but sometimes you simply run out of space. The packaging of the VDJ200 engine sees the sensor located at the rear of the cooler getting a shot at air temp after it has been through the cooler. The negative of this is it is exposed to the heat of the turbos coming up the fire wall. This would normally be of little consequence if Toyota hadn't engineered their sensor so well. Below is an image of that sensor design.

 

 

As can be seen the sensor is a very robust design. The thermistor (temperature variable resistor) is housed in a brass cage that limits airflow past it. As robust as the design is, it is an epic fail in this instance. The brass housing with integrated cage is essentially pulling the temp from the outside environment onto the periphery of the thermistor. The heat from the turbos in a low engine airflow situation is heating the sensor housing in turn introducing heat to the outer cage of the thermistor that then translates into eronous readings seen by the ECU! It isn't seeing the temp of the air flowing into the engine as a pure reading but a corrupted reading due to temperature sensor location! SQP was able to do nothing more than put a small leaf blower over the back of the intercooler deflecting airflow from the turbos and see a change in intake air temperature with NO AIR going through the cooler. The sensor is corrupted. Therefore the math the ECU is using is corrupted!

Initially SQP looked to relocate the sensor but this proved to be a project that the home handyman would not be able to perform without special tooling etc. How next to attack this issue? Move some air through the cooler and push it down the fire wall keeping the sensor reading pure. We had a look around at the fan systems on the market and they were simply "dumb" systems of fans that turned on at the ignition activation regardless of temperatures seen in the engine bay. They were little more than laser cut panels bolted to the cooler. We wanted a more OEM appearance with some control so that fans weren't running when not needed. In GM LS platform we were able to bring in custom ECU coding to turn on functions like we were after here. Not to be on Landcruiser.

 

Several prototypes later and we ended up with the system pictured below.

 

SQP got the look we wanted. The system utilises Aussie made fans and electronics and bolts on in minutes. Once the OEM cooler cover is trimmed of the internal grate it fits straight back on over the fans. SQP was able to employ a user programmable controller that digitally operates the fans at whatever temp is specified (we used 50C on temp in testing). Heat sensing for fan turn on is via a sensor located on to the intercooler itself. The controller (top LH of above pic) also has a manual over ride that can be wired into a dash switch for the guy that wants to take control outside of what is programmed. The wiring is simple and is really a home mechanic Saturday arvo intallation.

 

But how did it go in testing? Was any improvement in power seen? The simple answer to that is road testing saw temps at highways speeds at 10C lower than without fans. The recovery of intake air temps to ambient and above after a period of high load was far quicker with the fans installed thus bringing the ECU parameters back to regions where better power is made. The real bonus is the ECU is now seeing the REAL IAT readings- not corrupted reading from engine bay heat soak. That is the point of real gain on any of these intercooler upgrades. There is a measurable increase in cooler efficiency and intake air density as a result but fact that the sensor is relaying ACTUAL IAT (boosted air temp) rather than the engine bay temp is a massive gain in itself in light of the importance this data has on the the ECU internal calculations on fuelling and boost.

 

How much?? 

Fan support frame in powder coated finish complete with Aussie made Davis Craig fans and controller and mounting stainless steel bracket and hardware retails at $1100inc GST with a 10% discount coming off that for the first 20 sold. Installation and wiring is on an hourly rate depending on accessories etc already fitted to the vehicle. This kit also operates and fits onto VDJ70 series.

 

Call SQP for more details and availability.