Cast piston strength? possibly rebuilding for forced induction

[ryanh250ex]

Ok so i am turbocharging a 250EX. NO I DONT CARE what you think, i'm doing it because i can and because i dont need a YFZ, etc. i am trying to do it to put my engineering/fabrication/tuning skills to the test.

now that we've gotten past that issue, i am debating freshening up the top end. of course, a forged piston is stronger than cast, but the only 250ex forged piston available is either the powroll which is 10.25:1 and a .080 bore (no thanks), and the JE piston which is a .020 oversize piston BUT it's 11.5:1- yikes! I'm not sure if anyone makes a thicker head gasket, or using 2 factory gaskets sounds pretty ghetto, so i think i'm stuck using a Honda OEM oversize cast piston so i can keep the compression numbers low.

my question is, just how strong are the Honda EX cast pistons? can i expect to put out 25-30 whp on mine and keep it together given a slightly rich tune?

Thanks,
Ryan

[ZSK]

Call one of the companies you listed and see if they will custom machine a 9:1 piston for you in an overbore, I would even consider an 8.5:1. You're right that forged pistons are much stronger than cast. I personally would never risk putting a cast piston in with a forced induction system. Have you considered swithing to a fuel injection system using O2 sensors? More free flowing exhaust, added cooling for your engine, will you transmission and clutch handle twice as much power? I think 20 HP would be a more realistical number to shoot for, the 250 only throws down about 12 to start with.

[underpowered]

if you contact JE, Ross, Wiseco, ect, they can custom make any piston that you want, but it will cost you and you must buy four. If youuse two gaskets, remember it will screw up your valve timing and if they are too thick, you may need a longer cam chain. also, you will need an HD rod, the stock one will not hold up to that much of a power increase. i would also worry about the entire bottom end of the motor, it simply was not built for that type of power. there is alot more work than just sticking a new piston and a turbo on it. your motor would need a complete, bottom up, rebuild with heavy duty parts to withstand the abuse.

[MIKE400EX]

Machine the J&E piston crown down some and get Cometic to stamp you out a thicker base gasket. Unshroud the combustion chamber some and you could probably get near 9:1 without much effort.
Good Luck! Projects like that are fun and rewarding.

[ryanh250ex]

Originally posted by ZSK
Call one of the companies you listed and see if they will custom machine a 9:1 piston for you in an overbore, I would even consider an 8.5:1. You're right that forged pistons are much stronger than cast. I personally would never risk putting a cast piston in with a forced induction system. Have you considered swithing to a fuel injection system using O2 sensors? More free flowing exhaust, added cooling for your engine, will you transmission and clutch handle twice as much power? I think 20 HP would be a more realistical number to shoot for, the 250 only throws down about 12 to start with.

I already have a Pro Circuit full exhaust. If need be, i will run a unmuffled pipe with a spark arrestor tip, provided it is not godawful loud.

I am planning on intercooling the boost, to keep the intake air charge as cool as can be.

i have looked into fuel injection, that's just an additional expense however. It doesn't take much to convert a carb for blow-through use. all you need to do is jet accordingly and add a pitot tube downstream to pressurize the carb. i can tune a NA carb like it's my job, so i'm not concerned about that aspect of this project.

i was hoping to get away with the OEM clutch- i've beaten on it for 100 hours now and it shows no obvious signs of slipping- but i do realize that eventually it will go south on me. when that time comes, i will upgrade to EBC clutch discs and springs. i dont powershift- i always let off the throttle when i shift- so i'm not really concerned about the trans.

when i get all this stuff together- there is alot of piping, bracing, and tuning involved- i will start off small to see how it performs, and gradually turn up the boost. i will make sure i have a wide-band O2 to ensure even at full boost i am slightly rich and i will run higher octane than necessary.

[Chicksdigme423]

is this all on the 250ex in your sig??

[ryanh250ex]

Originally posted by Chicksdigme423
is this all on the 250ex in your sig??

way to read the FIRST sentence of the thread.