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Im currently building a manual 97 prelude sh with a stock H23A1 engine and am looking to turbo it. how much boost can it handle without having to get forged pistons and a stronger block (without sleeving)
 

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JDM 4th Gen Prelude 2.2 Vtec Turbo
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It depends on the turbo, a bigger snail will place more stress on the engine at the same psi as a smaller one.

Regardless of the turbo, it'll be on limited time it it's not built properly.
 

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1999 Prelude. F20B/K20A hybrid rebuild
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First of all, there’s never been a Prelude SH that came with a H23a1, they only came with H22a4’s.
And 200ish HP would probably be the “safest”on that motor boosted. However i would never recommend boosting a stock motor, not worth it at all, any stock motor boosted is a ticking time bomb, and on top of that you’re missing out on the whole point of being boosted if you can’t run it at full potential. Sure plenty of people boost stock motors, but they either run low boost to be safe( Low and less responsive HP) or run higher boost and blow engines (Higher HP but more chance to blow up)
Not to mention how safe your motor can handle boost is how well it’s been treated it’s whole life, it’s a 20+ year old engine.
 

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speaking from experience, I would not take it over 10 PSI on ANY size turbo. A small turbo will increase torque downlow and that is what snaps rods. Big turbos won’t make low end torque will put more stress up-top. Stock motors deal with this better. I’m not sure why everyone has the idea of stock motor and turbo=bad when literally everyone does this with K24’s and such. I have an h23a1 swapped 3rd gen running 9psi. Conservative I’d say I’m putting down 290. Have not had the chance to get it on the dyno. But it’s considerably faster than my boosted b20a5 that was slipping under load on my stage 3 clutch rated for 300ho/ft-lbs (probably making 250 wheel) the true difficulty is tuning. An H23 baseman on hondata is non existent I had to make mine from scratch. Although a tuner can make a map it will be $$$$$.
 

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I reliably drive an internally stock H22a4 at 9psi and just this past fall took it on a 10 hour round trip drive without issue. Compression is good and cylinder walls are fine. Just make sure you're starting with a healthy motor and don't beat the snot out of it. Do the proper supporting modifications and get a good tune - the H22's are fine with low boost. But honestly, you will want more if going turbo and that will require a built motor to be reliable.

I'm a little concerned you have an H23 with an SH. As mentioned, that's not normal.
 

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I've been running my lude with t3t4 turbo and a jdm STOCK h22a for a year now. It's not my daily but I still drive it 3 times a week to meets or to work. Motor came at 40,000 miles thats the only thing I agree with the stated before is the older engine will eventually blow even with low boost. My healthy engined on low boost 8-10lbs is pushing 343 to the wheel and 278lns torque. It's an amazing machine.
 
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