I have been looking at increasing my beta II's displacment but stroking is not a good option because I am going to bump up the redline to 8K and the stroke is an already huge 93.5mm....the stock bore is 82mm....how far do you think I can go before i compromise cylinder wall strength...I am going to be running 20-27psi...should i just get it over bored and sleeved so I can increase the bore without weakening the cylinder walls?...i am not the smartest when it comes to increasing displacement ...help me please or tell me who can help.

 

There's only 8mm between the cylinders. You can go up to 0.40 overbore...and you don't need to resleeve. The Cylinder liners currently touch/contact at the deck and have a strengthened/braced 1mm water gap below the deck. Due to the design of the deck/block and the braced nature of the "sleeves" it really can't be resleeved by your average machine shop.

Rather than shooting for such high boost levels, consider making the power with a more efficent turbo, better intercooler and more head/port work and a decent cam. There are plenty of 300+ WHP engines that are under 20psi of boost. Sure you can always turn up the boost and make more power, but lets face it. 350 WHP @ 15psi is a hell of a lot more impressive that 350 WHP at 28psi...

 

According to my workshop manual, the Beta can be bored to 1mm over stock for reboring purposes. This would net you a displacement of 2025cc.

 

what is the safest you can go. i was going to go 1mm over, they ppl here have gone as far a 2mm over but i have heard lots of bad thing about going 2mm over. what do you 2 think??

 

do the math. There's 8mm between the cylinders. with a 1mm water gap below the deck. That means each cylinder liner is 3.5mm thick.

Overboring them 1mm (0.040 ) drops the liners down to 2.5mm thick liners. That's getting thin. Especially for the high cylinder pressres a boosted motor will see.

Shaving them down 2mm would leave you 1.5mm of material. Barely thicker than the water jacket space...

considering the cost of the work, and the cost of forged parts, don't screw around. 0.040 over get's you and extra 52cc.. 2mm (0.080 over) would get you 104cc.
Is it worth risking your investment for that extra 52cc? Do think that extra 52cc is going to make that big of a difference that it's a "gotta have"?

I didn't think so.

 

How about an N/A aplication? Would 1.5mm be "safe"?

 

For an N/A application, I would spend the money on getting the crank balanced and lightened, and good light and balanced rods.. once you got those down, you can see about removing the rev limitor and spin the engine a little faster than 6500rpms for more power.

There IS a reason engines in the Toyota Celica, Any honda, and most Ferrari's rev out to at least 8 grand.. Horsepower is a combination of torque and RPM.

I would also see about getting some of the restrictions in the head taken care of before I would even contemplate going more than 1mm overbore.

 

The ONLY way I would contemlate a 0.050 overbore is if you run the Hybrid engine (1.8L crank in the 2.0L block and run longer custom rods).

The 2.0L rod/stroke ratio is too high, it puts too much stress on the sides of the cylinders /piston skirts(and the reason for our long piston skirts). If you did the "hybrid" engine, you could shorten the piston skirts by about 10-15mm( about half an inch, maybe more). or keep the long piston skirts and deal with the added weight/mass.

 

ok so 1mm is the limit? as for the hybrid idea...wouldnt the shorter stroke decrease my displacement when i just spent the money to get the the overbore so i could increase it...lol am i wrong here? as for the 20psi i am also going to get a full port/polish, and all lightweight internals, and killer cams...i am planning on making this a race care that is rarely driven on the road...only when i feel like burning up some little highschooler in high riced out civic lol.gif no body has respect for a hyundai except for hyundai owners/tuners..well at least in America

 

thank you, Random & machine.. very informative. btw Random you know quit a bit do you run a shop? Pm me with the ## i have some more questions for you
thanks a lot smile.gif