Dyno testing and long-term road testing are where all of this theory meets reality when it comes to the Subaru WRX Top Mount Intercooler. Knowing that the same application of these design techniques resulted in intercoolers that work extremely well for the 04-17 STI and 02-14 WRX, we were confident in our chosen configuration. Our goal was to once again, produce an intercooler that offered excellent cooling capacity without a massive pressure drop. We tested the OEM TMIC, GrimmSpeed TMIC and a leading competitor TMIC in a back to back to back comparison that consisted of driving while everything reached a steady state operating temperature and then three consecutive pulls to redline. The car used in this testing is a GrimmSpeed Stage 2 car on 93oct and was equipped with the same charge pipe for all pulls. Ambient temperatures were around 65F all day. The GrimmSpeed TMIC tested was not thermal dispersant coated.
The chart below shows TMIC efficiency test results. Efficiency is calculated based on the measured inlet and outlet temperatures of the intercooler compared to ambient. If the outlet were to exactly equal to ambient temperature, then efficiency would equal 100%. This isn’t possible, so we strive to get as close as possible. As you can see, the GrimmSpeed and competitor intercoolers outperform the OEM intercooler handily.
The chart below is much less important, but shows the raw temperature data, to give you an idea of how much better performing the GrimmSpeed is compared the OEM TMIC.
The chart below shows the pressure differential between the inlet and outlet of each intercooler. The higher the pressure drop, the more restriction the TMIC causes. This restriction forces the turbo to work harder to build the same amount of boost (which increases heat and is counter-productive), so we want to get keep it as low as possible without sacrificing cooling. You see the the OEM intercooler has the lowest pressure drop, followed by the GrimmSpeed and then the competitor.
One interesting thing that we found is that during the second and third pull, when the car is transitioning from heavy vacuum to full boost, the GrimmSpeed and OEM intercoolers both spooled measurably faster than the competitor TMIC. The GrimmSpeed subaru wrx top mount intercooler has a larger overall volume, so that isn’t the cause. We’re going to continue experimenting to determine the exact reason for this, but it’s likely to be a result of the higher pressure drop and the way that air flows through the intercooler.
The bottom line is that both the GrimmSpeed and competitor unit offer a very nice upgrade from the OEM TMIC as far as efficiency goes. However the GrimmSpeed unit provides a lower pressure drop, and a substantially easier installation. If you have any questions regarding performance or our testing, please don’t hesitate to be in touch with us via phone or email.
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The moment many of you have been waiting for – top mount intercooler test results! In testing and developing a heat exchanger, there are countless bits of data to collect and analyze in order to facilitate the decision making process, but when it comes to evaluating the final product, performance can be quantified with relative simplicity. Everything boils down to temperature and restriction. The intercoolers primary duty is to lower and control the temperature of the hot charge air leaving the turbo and running through the intercooler. This is the first test that we performed on both the stock unit and the GrimmSpeed unit.We setup this test to simulate a real world scenario that’s typically demanding of an intercooler. The test vehicle is a 2012 WRX with a GrimmSpeed downpipe, boost control solenoid, prototype intake and tuning. On a closed course, we accelerated in 3rd gear from 3000rpm to redline repeatedly, with 5-8sec between runs. Temperature was logged via k-type thermocouples between the turbo and the intercooler and between the intercooler and the throttle body on both units. Ambient temperature here in Minnesota for both tests was between 20 and 22 degrees F.The results above speak for themselves, but here’s a breakdown. The phase differences between the runs are a result of how quickly we could safely get the car back down to speed for another run, but the important thing to notice is the magnitude of the temperature fluctuations. Predictably, both intercoolers were seeing similar Pre-IC temperatures on each run (180-190F peak), but while the GrimmSpeed TMIC kept Post-IC temperatures between 30-40F the entire time, the OEM TMIC fluctuated between 35-75F. This is the kind of consistent cooling that you should expect from a high quality TMIC and is a function of the geometry and design of the bar and plate core. Our high density core has a massive heat transfer surface area but maintains a large enough cross-sectional flow area that there’s no added restriction.
What’s Next – Pressure Drop, Aftermarket TMICs and Warm Weather Testing
The second part of our final testing will be to measure the pressure drop across each intercooler to demonstrate that the increased cooling performance comes with no sacrifice in flow rates. We’ll also run the same tests with a couple of other aftermarket TMICs. You can expect to see these results in the coming week. Lastly, in the spring, we’ll complete all of this testing again in warmer weather to show that the same effectiveness can be expected, regardless of ambient temperature. We’ll also try to find it’s limits with our 600whp STI.
The photo above shows the machining of the TMIC outlet end tank master. The Bottom received a finishing pass and then the part was flipped so that the top could be roughed out. When all is done, this will be a flawless part. Now that the master parts for both end tanks have been completed, we’ll make a cast iron match plate from each of them. You probably noticed that it looks a lot like they’re being machined from wood and that’s because they are! These master parts will only be used a single time – to cast the real molds from, so a heavier duty material only costs more and takes longer, with no added value.
Interesting Note: The master that you see here is not dimensionally identical to our final part – it’s actually larger. Based on the foundry’s preferences, standard shrink allowances and the geometry of the model, the pattern makers job is to determine how much the cast aluminum part will shrink/contract during solidification. An easy way to cut cost, especially if you’re casting overseas, is to skip this step. Ever had an application-specific intercooler that didn’t fit quite right? There’s a decent chance that uncontrolled shrinkage was at least partially to blame.
For those unfamiliar with high end casting processes, creating the tooling and molds is the giant hurdle standing between your design in CAD and real parts. With properly designed and manufactured tooling, casting and machining the parts is relatively straight forward. One of the many benefits of casting right here in Minnesota is that we’re able to sit down with everybody involved and work through potential issues to mitigate the risk of trouble during production almost entirely. That means lower production cost for us and lower pricing for you!