Advice on Parts for Turbo K-Swap CRX Build?

brianduke523 said:

New to K-Series, Swaps, and Turbocharging. Been learning and have come up with a rough build, advice?

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Thanks for starting a new thread on your questions which you wrote in another thread. Here it finds the right link between topic and content and people find your posted stuff more easy related to their questions. Thanks for that.

As promised I will help to answer some of your questions. I made a calculation for boost, fuel mass flow, air mass flow for the 450 whp goal and referred it to the Garret side. The GTX3576 shows a quite good match with the 2.05 pressure ratio and 43.xx lb/min air flow flux, the G35-900 or G40-900 even better in terms of racing. In terms of DD I would tend to more to an GT3076R.

FI Honda engines like to be up shifted and not stuck in one gear. A stock engine may not like being on the autocross course with this kind of power near 500whp. As a lower hp will be faster in my opinion and easier on the engine, faster due to traction. FI Honda's are crazy fast when they are getting maximum traction. If I ever boost an engine again, I will be using forged internals.

eventually limited slip is a nice one.... for a autocross a 300 wHp turbo CRX.
With an open diff you'll turn tire into smoke, but not much into traction.

Them Witches said:

FI Honda engines like to be up shifted and not stuck in one gear. A stock engine may not like being on the autocross course with this kind of power near 500whp. As a lower hp will be faster in my opinion and easier on the engine, faster due to traction. FI Honda's are crazy fast when they are getting maximum traction. If I ever boost an engine again, I will be using forged internals.

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Oh ok thank you, I mostly want to go boosted for fuel economy and highway cruising. What is a better power goal for autocross? And where can I learn about forged internals? Any budget friendly brands for forged internals?
Thank you again!

LotusElise said:

Thanks for starting a new thread on your questions which you wrote in another thread…
The GTX3576 shows a quite good match with the 2.05 pressure ratio and 43.xx lb/min air flow flux, the G35-900 or G40-900 even better in terms of racing. In terms of DD I would tend to more to an GT3076R.

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Yah of course, sorry I’m still new to forums but hope to get better at it!
I’ll look into those turbos, seem like good sizes. Is the GT3076R ball bearing? I heard journal bearing is better for cruising and economy, is there truth to that and what are ball bearing better for?
Thanks again LotusElise, huge fan of your posts!

FI on a k20 will Not get you any improved fuel economy, especially during highway cruising. To run 70 mph on a flat highway you need like 40-50 HP.
For a 300HP 7-8PSI k20a2 conversion, there is no need to run forged internals. Get a good sump baffle and an oil pressure gauge.

For autocross in a CRX, I'll predict you'll be faster with a NA build than with a 350+ wHP turbo monster. For autocross, I'd even consider a NA K24a2.
Just watch some videos of chaps running 400HP turbo builds in older civics. They are happy to stay on the road in a straight line on full boost. I mean this things really move.

Here is a video of a about 450 to 500HP build k20a2 turbo in a race prepped S2000. Fun starts at 3 minutes in.

here is a UK vid of a 400HP k20z3 turbo. Hint, the owner drives on a low boost setting with some 300 or so HP most of the time as 400 is rather a lot.
With traction control of it spins the wheels in the first three gears in a straight line. Now turns do not improve traction.

I'd suggest you start the conversion with turbo in mind and getting it running reliably NA as in finishes auto cross runs and DD duty.
Then go turbo if you still have the desire to.
This in itself is not easy when it comes to peripherals and heat management.
As your comments suggest you are not that much into engines yet, I recommend to read a lot of the build threads here.
Just getting the conversion to run so reliably you'd trust the car to your mom or partner is a technical challenge. The turbo adds a lot of complexity.
Mind you that post some 350Nm the gearbox also needs to be payed attention to.

Again for auto cross, I'd rather K24 and/or supercharge as the throttle response is too much better.

Lotus said:

FI on a k20 will Not get you any improved fuel economy, especially during highway cruising. To run 70 mph on a flat highway you need like 40-50 HP.
For a 300HP 7-8PSI k20a2 conversion, there is no need to run forged internals. Get a good sump baffle and an oil pressure gauge.

For autocross in a CRX, I'll predict you'll be faster with a NA build than with a 350+ wHP turbo monster. For autocross, I'd even consider a NA K24a2.
Just watch some videos of chaps running 400HP turbo builds in older civics. They are happy to stay on the road in a straight line on full boost. I mean this things really move.

Here is a video of a about 450 to 500HP build k20a2 turbo in a race prepped S2000. Fun starts at 3 minutes in.

here is a UK vid of a 400HP k20z3 turbo. Hint, the owner drives on a low boost setting with some 300 or so HP most of the time as 400 is rather a lot.
With traction control of it spins the wheels in the first three gears in a straight line. Now turns do not improve traction.

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Those look so fun to drive! Love the sound of a k-series in high revs. Don’t get me wrong I love driving fast in a straight line but I also just love the feeling of taking tight turns with great traction, like driving up a long windy road on a big hill. Any way to have both?
I was going for the CRX because of its great handling, especially in turns. And the K20a2 because of its high revs, small size, and cheap swap. In your opinion how do I get the most out of a K20a2 CRX?
Thanks for getting back to me so quick!

Lotus said:

I'd suggest you start the conversion with turbo in mind and getting it running reliably NA as in finishes auto cross runs and DD duty.
Then go turbo if you still have the desire to.
This in itself is not easy when it comes to peripherals and heat management.
As your comments suggest you are not that much into engines yet, I recommend to read a lot of the build threads here.
Just getting the conversion to run so reliably you'd trust the car to your mom or partner is a technical challenge. The turbo adds a lot of complexity.
Mind you that post some 350Nm the gearbox also needs to be payed attention to.

Again for auto cross, I'd rather K24 and/or supercharge as the throttle response is too much better.

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Haha you just answered my question before I even sent it, I love all the support in these forums, always get all my questions answered efficiently and respectfully. The Honda community has never let me down
Thanks again for all your help! I think I’ll go that route, start NA and learn the engine, turbo when I know and trust it. Let me know if there’s anything I can ever help you with!