Cylinder Bore
 

I couldn't find any other posts on this subject, so i started one. I want to get my engine bored out. to bore it 40 over, it is like $160, and i was wondering what is the best size to bore a 1.8 litre, and with that size what size pistons would I need. Also, what is a good place to buy the pistons, and are street legal. I know, how will a cop know if it isn't. But Hey, either way, legal or not.

There is nothing illegal about overboring an engine, and there are no "street illegal" or "street legal" pistions, they are simply pistions.

The 1.8L has the same bore as the 2.0L, it just has a shorter stroke. So you can bore out the 1.8L the same as the 2.0L, which I think is 2mm overbore is the limit. I'll have to check the manual at home and check with Red to make sure the books are right.

1mm is actually the limit, which equates to something right around 0.0394 inches or some crap like that. It might as well be 0.040 wink.gif

In any case, Hyundai sells OEM pistons that are 1mm overbore, you simply need to order them from your local dealership (that must be where you got $160, because they're around $40 each)

However, you ALSO must bore the block to match. Your brand new 83mm piston isn't going to fit in the 82.03mm hole in the block... Which means, the entire motor comes out of the car, it's taken apart into it's individual parts (oil pan comes off, crank comes out, rods and pistons come out, head comes off, oil pump and water pump come off, et al) and then it's overbored.

Also when you overbore your block and drop in bigger pistons, your rings have to be replaced as well. Don't forget to add that to your parts list...

When it's all said and done, the 1mm overbore you just did takes your 1.8L to around 1.9L or a bit above -- and the horsepower increase will be almost the same weenie amount. Your stock 133HP will probably bump to 137 or so; barely worth the $800 you'll spend having it done. If you can do most of the work yourself, you can chop that figure down to basically the cost of parts and the machine-shop bill (bore and hone work).

Still, another 4-5 horsepower is NOT worth $800. Your torque will not increase that much either; low end or otherwise. You're simply dealing with a motor that's too small to enjoy the benefits of a big-bore. A longer stroke would help that, such as the longer stroke found in the 2.0L motor.

For another 4-5HP, go pick up a good cold air intake, or have your throttlebody and intake manifold ported. It'll be cheaper, you can probably do all the work yourself, and you'll probably also end up with more power in the end.

-Red-

wow, that's a lot of money. If i would only get like 1.9ish litres, how is it possible to get like 2.2 L. I remember hearing somebody saying that the 2.0 and the 1.8 are the same blocks, cylinder size, etc. If i was to shave a little off the exaust and intake ports, and add the whole piston from a 2.0 would i see much gains. I think it was random that said that the compression was higher, maybe i'm wrong. but if it got the rods, etc, how much gains would I see. If they fit, that is.

For the 2.0L motor, since you have more stroke overall you end up with more displacement when you slap in bigger pistons. The 1.8L has a relatively short stroke but has the same size bore.

It stands to reason that the 1.8L *block* is the same as the 2.0L block, but the internals are obviously different. The 1.8L comes with a different crankshaft (shorter stroke is dependant on crank) and also comes with longer rods (shorter crank in same size block = needs longer rods) I believe the compression is slightly less in the 1.8L as well -- 10.1:1 compression versus the 2.0L 10.3:1 compression.

The thing to consider here would be engine longevity as well. Theoreticall speaking, the 1.8L motor with it's longer rods and shorter stroke has a MUCH better chance at living a long life than the 2.0L -- based on a mathematical formula simply known as Rod/Stroke ratio. The higher your rod/stroke ratio, the less sidewall loading your engine suffers. And less sidewall loading means less sidewall wear means less wear and tear on the cylinder walls, piston skirts, rings, etc.

You also have to think of the limitations of the block... If you punch out your block to the full 1mm overbore, you're basically at the very edge of what Hyundai recommends. Anything over 1mm, and you're in uncharted territory. Why would this matter, when you're *only* doing 1mm? What happens if you drop a valve later in life and need to re-bore the cylinder walls to clean up the damage? You're outta luck, because the block is already bored to it's max.

It's really not worth it IMO. Keep the stock displacement, and spend the HUGE money on something else. If you've done every other modification you possibly can (and I'm talking ALL modifications, $20,000 worth or more) then you can go back to raising the displacement.

-Red-

if the 1.8l and the 2.0l are the same block, couldn't ya just change the crank and the rods to give it more stroke?

just a thought, if so wouldn't that be a nice mod for an accent?

that's what i was hinting at, sorry.