Why do you need the under hood ducting for your Subaru

So you bought that super cool carbon fiber hood for your STI or WRX but you didn't swap over the under hood ducting from your stock hood for your intercooler. Is that hurting the way your engine performs? We did a test on two different 15+ WRX's on the same day to get you the info. Both of these car are running the same mods with stock TMIC. Only difference is one is running the stock hood with the ducting and the other is running a carbon fiber hood with no ducting. 

Here is what we found out and wanted to share with you. The graph above is the manifold temperature taken after the intercooler. The bottom line shows the temps from the car with the stock hood with the factory air scoop ducting. The top line shows the temps of the car with the aftermarket hood with no ducting. We already know that the stock TMIC on the 15+ WRX's are not that great and upgrading to a Grimmspeed or ProcessWest TMIC is the best thing you can do for the WRX. The whole pull on the dyno the difference was around 20 degrees this resulted in a power loss mainly at the top end of the power band start at around 4700 rpms.

​The chart below shows the intake air temp the temp sensor was seeing in the intake. The intake temps are pretty close to each other so you know the air coming in wasn't that different between the two cars. 

Here you can see the power and torque loss due to the increase in manifold temps. Some cars can be different, but this is what we found with these two cars. This was a loss of 21 whp and 11 wtq for the car with no ducting. Would have been more if it was in the summer months with the warmer ambient air. 

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In closing the hood does add some style to your car and that's what modifying cars is all about, but if you want the hood please install the scoop ducting or go FMIC.

If you have any questions feel free to give us a call be happy help you out. 

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Just a little add on since people where asking about it. This is comparing the stock TMIC to a Grimmspeed TMIC w/ chargepipe kit. You can see that the GS TMIC is keeping the charge air temp lower than the stock TMIC. Also a big improvement at the top end with almost a 40 degrees difference over a stock TMIC. Cooler air equals more power!!