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Big Turbo W/ Restrictor vs Stock Turbo

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Long time listener, first time caller.

I compete with my 2019 Civic Type R here in the US. The class I compete in is looking to adjust the rules for my class. I’m allowed to run a stock turbo, tuned, no limits OR I can upgrade my turbo but must run a 44mm flat-plate restrictor within 10” of the turbo inlet.

Does anyone have experience running a stock turbo vs a big turbo with an intake restrictor?

In my class I’m competing with Evo, STI, and other FWD and AWD cars.


It's all about your power curve - where you want the maximum power to be at. With larger turbo and restrictor combination you will get a bit more power at higher RPM but will loose a bit in the mid range and turbo spooling. The decisive facor usually is where in rpm range the engine spends most of the time... If it's mostly at red line than yes, bigger turbo with restrictor is a beneficial thing...

As Shota suggests - it's all about what you need from the engine. It seems to be some sort of timed event, such as SOLO, where the quicker response and increased mid'(depending on specifics of the set-up options) range potential of a well engineered set-up with a 'stock' turbo' may be a much better overall deal.

If you do go for the larger turbo', depending on the specific wording for the restriction plate, you may be able to use a 'bell' intake and smooth transition piece from it to the turbo' inlet, so minimising the penalty incurred.

Again, depending on what you're using the car for, you may even be better delaying the engine side and working on suspension tuning, tyres, brakes, etc to use what you have to the best advantage, and to be ready for when you build a more powerful engine.

Hi Aaron. That rule is definitely going to change because it was flawed in how it's written in the pre release of the rules in progress.

I'd hold off on buying a turbo til the rule is more final and we better know what the impact will be.

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