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Circuit race Civic EP3 K20A turbo Need help choosing a turbocharger

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I am building a Honda Civic EP3 for circuit racing. K20A engine (2.0l).

In our championship there is a class 2.0Turbo. According to the rules, the engine must have a standard block, a crankshaft,

pistons, cylinder head and intake manifold. Forged connecting rods can be used. Turbocharger, intercooler,

exhaust system, free inlets.

According to the rules, the boost pressure should not exceed 0.7bar, and a restrictor with a 36mm hole should be installed.

The electronic boost controller is prohibited. The maximum turnover according to the rules is no more than 8500RPM.

Compression ratio according to the rules from 11 to 11.7.

The resource of the engine and turbocharger before repair or replacement in 5000 km will completely suit me.

There are 2 main questions:

1. Which turbocharger should I choose for my conditions?

2. What compression ratio should I use for my conditions, given the selected turbocharger?

P.S. Thanks to your advice, I might win our championship 2021!

Attached Files

Your choice is Garrett GT2560R or GT2860R or any similar size turbo that can be thermo efficient with Pressure Ratio about 1.7-1.8 and air mass delivery from 10 to 25 lbs per minute. That will give you 0.7 bar boost all the way from 4000 to 8500 RPM. I personally would go with GT2860R even if it is a bit luggy comparing to GT25 frame - that will give you the best thermo efficiency at high revs where you need engine to be most efficient.

Compression ratio should mostly depend on the fuel octane rating ( it should be high enough to withstand boost and overboost at high CR) and piston to valve clearance but since there is almost no difference in power gain between 11 and 11.7 I would go with lower CR 11 to 1 just to reduce thermal load on the engine a little bit.

According to the rules, we use monofuel with an octane rating of 100.

11:1 would be your choice then.

PS if you are going to rev the engine as high as 8500 RPM i would go with largest turbine AR available.

i would be thinking far bigger , like a gt32-35 , when the boost is so low , compression will involve testing with fuel but start high are cams on the table

I think you are missing the restrictor, Michael. It is very small opening for mid frame turbo - the engine just will not pump enough air to spool it up early enough...

curiosity - is the engine a jdm k20a with the 11.5:1 compression or is it a k20a1 or something like that? Im interested in applying boost to the jdm k20a i have in my ep3 but i am unsure if the engine will survive in its standard form with around 400whp pushed through it (people dont seem to work on these ones and turbo them and rumor is that they dont like any boost) - or if i will need to do rods and pistons - in which case i'll just get a lower compression k24 shortblock and use that - they seem very happy with a lot of power pushed through the standard bottom end.

Good luck with your race series - and please keep us updated on your engine results :)

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