Garrett Advancing Motion Honda Civic Si Intercooler Test!

During the temperature saturation test, you can see how the stock intercooler’s exit air temps climb over 15 dyno pulls getting hotter and hotter.  Note how the pulls are significantly hotter to begin with.  Also note how much the temperature rises during the pull. The Garrett intercooler’s charge air temps hardly rise pull after pull.  The inlet temperatures are much much lower and the overall temperature rise during the pulls is about one fifth as much as the stock intercooler.  It is amazing how much more effective the Garrett intercooler is from stock.  Although the turbo spools faster, you don’t see the gains in power down low.  We think the car’s ECU is limiting the power here and retuning is going to be needed to edit the torque tables to allow more power output.

So how much power does the Garrett intercooler make? The peak power gains are 17 hp and 14 lb feet of torque! What is more impressive is that the power gains come from 2700 rpm to the rev limiter at 6500 rpm. The power gains are pretty consistent across the rev range. This is a lot of power under the curve.  Note that this is just by simply bolting on the intercooler with no tuning.  With an intercooler this effective, tuning to exploit the significantly cooler charge air temperatures can probably extract at least another 20 hp without any other mods.

The Garrett intercooler’s seat of the pants feel is greater than the dyno suggests. The car feels a lot more lively and responsive due to the reduction of lag. We didn’t test this, but we think fuel economy is probably better as well as emissions with the intercooler.  We would really love to tune the car around the Garrett intercooler and re-test it. We would also love to test the car with the Garrett intercooler and a full compliment of bolt on performance parts.  We bet the results would be even more impressive!


Garrett Advancing Motion

World Motorsports


  1. Such great results with this intercooler installed. I have a 2L Accord and would love to replace the equally as lame stock OEM unit with one of these someday if they make one. PRL already makes one for the accord but I trust the Garrett one to be better engineered.

  2. On page 7 you talk about how the turbo spools easier and doesn’t have to work as hard so less lag. But on page 8 on the dyno charge, you can clearly see the stock intercooler come up to power (therefore boost) quicker at the low rpm. If all of the stuff on page 7 is true, should that low rpm performance also be better?

    1. The temperature plot shows the boost is coming on sooner for sure with the Garrett IC. More boost = higher temps which is basic thermodynamics, so no doubt about that. As for why that doesn’t translate into more torque down low on the dyno plot, it’s likely so far outside the expected range of operation that the engine tune isn’t calibrated well. Or, possibly, Honda intentionally tuned the car to have limited torque down low to preserve the engine or trans. Because cold weather would have the same effect. This is where a custom tune with Hondata Flashpro would extract a lot more torque and power.

    2. I think the ecu is limiting the torque and the torque tables have to be edited to see gain here.

  3. This looks great. I would love to see Garrett develop a drop-in intercooler for the Veloster N. Right now the options for intercoolers are limited to offerings from some very small companies who offer almost no data on how their product performs.

    1. I have a VN also and will likely talk to Garrett/Spearco, provide them with my specs and goals, have them size their recommended intercooler and do the custom work to adapt it to the car. I’m past the one size fits all stage in modifying cars and the absence of critical design data with a “well it fits” does not sit well with my wallet. But if Garrett were to make my life easier (drop in) let the good times roll!

      1. Garrett/Spearco will not make you a custom intercooler kit, they are parts companies, not custom fabricators. This sort of validation costs thousands of dollars and Garrett spends a lot of money with us to help them with testing. If you really wanted to pay for it, we could build you a custom intercooler setup and do all of the physical testing and validation and provide you with data but we are talking thousands of dollars. Unless your VN is highly modded, the off the shelf Garrett kit is excellent and will be hard to beat without compromising other aspects of performance. If you wanted to do a custom system we could do it and if you trust our experience, you can skip all of the validation testing.

        1. Mike,
          Sorry my post wasn’t clear. I’m not speaking of having either manufacturer construct a custom intercooler, but meant talking with their technical staff and getting their recommendation for their off the shelf units and then doing all the piping and mounting work necessary to fit my car. I agree with you, for my goals they already have existing units that would serve my purpose well. I’m commenting on issue the destrux brought up, the existing drop in kits provide little or no technical data, just it’s better than stock. Wouldn’t the intended use of the vehicle and planned modifications come into play for intercooler selection, e.g. autocross vs. extended track usage?

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