N/A Raising compression?? - TriStateTuners.com :: Home of Tristate Auto Enthusiast

Keyan · 03-19-2006, 06:35 PM

Hyundai elantra 2.0L motor runs a 10.1:1 compression ratio, and for $139 I can have 1.8L pistons imported from korea. I install them myself. If I install just the piston, the compression will be raised to 11.0:1. If I install the pistons and rods, the compression drops to (i think) 8.8:1. Now my question is, is going up .9 compression going to compromise much? What are the risks I'm taking when it comes to pre-ignition / detonation? Will I need a fuel tuner? I know some of these questions maybe hyundai specific, but I need the knowledge of N/A AND turbo peeps for help with this. I am considering but I don't want to blow up my motor!

Thanks.

StreetEG · 03-19-2006, 07:15 PM

not sure about what you would use for tuning.... but if you bump compression you need to compensate with tuning. You could have issues with valve tap, as well as detonation....but im not sure on your clearance for a hyundai motor...

Driven · 03-19-2006, 09:32 PM

Are you sure the 1.8L motor has the same bore and wrist pin height? Also, is the cylinder head the same?

You might be better off getting custom made pistons, (most major companies will make one-off's for not all that much more money) than shipping some in from Korea that aren't really for your engine.

What are your goals for the car? What else do you have done to it? Theres a lot of things to do to a car before worrying about the compression ratio. Theres a lot more that goes into swapping pistons than just swapping pistons too.

96s14 · 03-19-2006, 09:48 PM

I cant see why 1.8 ltr pistons would fit in a 2 ltr block.

Driven · 03-20-2006, 08:23 PM

Quote:

Originally Posted by 96s14

I cant see why 1.8 ltr pistons would fit in a 2 ltr block.

If it was the same bore with less stroke they could fit... as long as they didn't move the wrist pin and took up the stroke difference with rod length. I doubt thats the case, but it is possible.

Keyan · 03-21-2006, 09:12 PM

The 2.0L block and the 1.8L block are identical w/ bore. And the pin height is the same too, in korea, for turbo applications, it is a very popular swap to put the piston and rod, which drops the compression down to around 8.8 (not sure about that number but it is low). So it would be a direct swap w/ no valve interference if I did put them in my motor. But I would have to worry about detonation, of course.

sponsored1 · 03-27-2006, 01:07 AM

If using the same pistons will yeild different compression ratios depending on what rod you use, what is happening is the 1.8 rods are shorter. Which means the piston will not come up to the top of the bore. The closer the piston comes to the cylinder head the less chance of detonation and the better the performance. Leaving enough room between the head and the piston to drop the compression ratio that much is a horrible idea. It will creat "dead air" inside the cylinder and make for horrible performance and most likely detonation.

03-19-2006, 06:35 PM	#1
Keyan Tri-State Aficionado Join Date: Mar 2006 Location: Sparta, NJ Member #1577 My Ride: 1993 3000GT VR-4 iTrader: (0)	N/A Raising compression?? Hyundai elantra 2.0L motor runs a 10.1:1 compression ratio, and for $139 I can have 1.8L pistons imported from korea. I install them myself. If I install just the piston, the compression will be raised to 11.0:1. If I install the pistons and rods, the compression drops to (i think) 8.8:1. Now my question is, is going up .9 compression going to compromise much? What are the risks I'm taking when it comes to pre-ignition / detonation? Will I need a fuel tuner? I know some of these questions maybe hyundai specific, but I need the knowledge of N/A AND turbo peeps for help with this. I am considering but I don't want to blow up my motor! Thanks. Last edited by Keyan; 03-19-2006 at 06:41 PM.

03-19-2006, 07:15 PM	#2
StreetEG Tri-State Post Whore Join Date: Nov 2005 Member #1109 iTrader: (1)	not sure about what you would use for tuning.... but if you bump compression you need to compensate with tuning. You could have issues with valve tap, as well as detonation....but im not sure on your clearance for a hyundai motor... __________________ EscapetheApple.com 20,000 Miles, No Hotels, Every Amazing Road in America

03-19-2006, 09:32 PM	#3
Driven Tri-State Addict Join Date: Apr 2005 Location: PA Member #336 iTrader: (0)	Are you sure the 1.8L motor has the same bore and wrist pin height? Also, is the cylinder head the same? You might be better off getting custom made pistons, (most major companies will make one-off's for not all that much more money) than shipping some in from Korea that aren't really for your engine. What are your goals for the car? What else do you have done to it? Theres a lot of things to do to a car before worrying about the compression ratio. Theres a lot more that goes into swapping pistons than just swapping pistons too. __________________ 08 Evo X - Daily 95 Eclipse - 9.99 at 143 To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.

03-19-2006, 09:48 PM	#4
96s14 Tri-State Addict Join Date: Nov 2005 Location: Yardley, PA Member #1066 My Ride: KA24DET 240sx and BAMF Pathfinder iTrader: (0)	I cant see why 1.8 ltr pistons would fit in a 2 ltr block. __________________ 2005 Acura TL 6sp 1996 KA-T: Sold 1997 Pathfinder: Sold

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03-21-2006, 09:12 PM	#6
Keyan Tri-State Aficionado Join Date: Mar 2006 Location: Sparta, NJ Member #1577 My Ride: 1993 3000GT VR-4 iTrader: (0)	The 2.0L block and the 1.8L block are identical w/ bore. And the pin height is the same too, in korea, for turbo applications, it is a very popular swap to put the piston and rod, which drops the compression down to around 8.8 (not sure about that number but it is low). So it would be a direct swap w/ no valve interference if I did put them in my motor. But I would have to worry about detonation, of course.

03-27-2006, 01:07 AM	#7
sponsored1 Tri-State Aficionado Join Date: Nov 2005 Location: Buckingham, Pa Member #1049 My Ride: POS with a diff and giant brakes iTrader: (2)	If using the same pistons will yeild different compression ratios depending on what rod you use, what is happening is the 1.8 rods are shorter. Which means the piston will not come up to the top of the bore. The closer the piston comes to the cylinder head the less chance of detonation and the better the performance. Leaving enough room between the head and the piston to drop the compression ratio that much is a horrible idea. It will creat "dead air" inside the cylinder and make for horrible performance and most likely detonation.