Garrett Advancing Motion Honda Civic Si Intercooler Test!

We bolted on the front bumper cover in the reverse order that we removed it.

To the uneducated eye, you cant really tell that anything is different here, but those in the know will immediately spot the new and bigger intercooler core.

We returned to the World Motorsports wind tunnel dyno to test the new Garrett intercooler.

We repeated the same test protocol, we ran the car repeatedly until the power levels stabilized to obtain our power figures.  Then once we got what we felt was a good power run, we let the car normalize by sitting in on the dyno with only the air exchange fans until the coolant and intake air temps were stable.  We then proceeded to the thermal test where we did our timed back to back dyno pulls. Again, we ran the car as fast as the dyno could cycle until the intercooler reached saturation.  This is the point where the charge air temps stopped climbing after each pull.


Here is the typical temperature rise and decay of a single dyno pull on both the inlet and outlet side of the Garrett and stock Honda intercoolers.  Notice the inlet temperature rises more quickly with the Garrett intercooler, this is because there is less pressure drop restriction across the core so the turbine has to work less to create the power to drive the compressor.  Which also has to fight less to blow the charge air through the core.  This synergistic effect enables the turbo to spool faster and reach maximum boost faster, thus the inlet side of the intercooler sees a more rapid rise in temp!  With the turbine digging less into the exhaust stream to power the compressor, back pressure drops as well. These attributes cause a cascading effect that gives you more power with no negative compromises.

Note the intercooler outlet temperature.  The stock intercooler’s outlet temperature rises quite a bit over the course of a dyno pull.  The Garrett intercooler’s outlet temperature is remarkably stable.  Amazingly the Garrett intercooler’s outlet temperature hardly climbs above the ambient temperature!  Cooler intake air means a denser intake charge and more power.  It also means less thermal stress on the engine and potentially lower oxides of nitrogen emissions.  Again you are getting something for nothing.


  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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