was on ttr and saw them with the diffrent compression ratio and diffrent bore whats the diffrence between the two compression rations, which one would be better for a n/a build running nitrous and with the overbore of 20, do you have to do anyhting to your stock sleeves? thanx

 

Higher the compression is the better for building a N/A car

 

Our stock compression is 10:1. If you are going for an NA nitrous build then you may want to stick with stock compression(or higher) but you want to call wiseco and make sure they can handle the amount of power you want to make under nitrous.

Overbore requires you to modify your sleeves and it just gives you a bit more displacement.

 

You will want the 10:1 CR. You can run a good shot of nitrous with these (over 100 as long as it is tuned correctly)

 

one would get overbored pistons so a machine shop can bore your sleeves to tighter tolerances and to tolerances that forged pistons require opposed to cast (since forged expand more than cast once warmed up)

 

Just open up your ring gaps a bit more if you are going to spray on those pistons.

 

If you get the .20 overbore, you will have to get your sleeves bored out .20

Even with stock bore, it's still a good idea to get a slight honing done on them because like they said above, the forged aluminum expands more than cast.

 

Whenever you replace rings for the most part, you will want to hone the walls slightly. Even on stock bore... Allows the new rings to seat.

 

call weisco and tell them what you want made. i'd go with a higher compression than stock if you plan on building the motor. more power

 

Here the skinny...

Wiseco makes 2 compression ratios. A stock compression, and a reduced. The 10:1 stock ratio is designed to be used in cars that will remain NA, but make more power. So, as you can probably figure, that would be nitrous. The lower compression ratio (8.9-1) is for forced induction applications, like a turbo. Those are the pistons I have.

The .020 overbore (not 0.20, that would be huge) is for REPAIRING a damaged engine. It is really not designed to be used as a means for increasing displacement. When you go overbore, you have to recut the particular sleeve that was damaged .020 oversize to match the piston. This process is used to cut away any kind of deep scratches in your cylinder that might have happened as a result of a rod breaking. It is designed so you can replace one piston, and still leave the rest alone at stock size. It is not meant to replace all 4 at once.

Do the math. The L61 Ecotec has a bore and stroke of 86mm * 94.6mm.

86 diameter, 43 radius.

3.14 x 43 x 43 = 5808.8 x 94.6 = 549512.94 cubic mm of displacement per cylinder.

Times 4 cylinders is 2198051.74, or 2198 CC's for the whole engine (the actual published spec is 2189).

Now change the bore from 86 to 86.5 (the .020 overbore), and the new number is 2223684.78, for a difference of 25633.04. That's 25 CC's if you overbore all 4 cylinders.

You would gain one percent of displacement. And the cost to get it would be rediculous.

 

^^ ive never heard of only running one overbored piston. Everything else you say i completely agree with but i dont think anyone will buy one overbored piston and 3 stock sized ones

 

On a 4 cylinder engine, sure they will.

 

it's not uncommon. OEM spec rebuild shops do it all the time.

now, in the case of my M10 that i'm building, i AM overboreing for more displacement, but, i'm all stroking it out, so i'm going from 1.8l to 2.2l.

that's a big difference.

i don't know if it's possible to do, but it may be worth looking at fitting a 2.4 litre crank to your car, give you a little more stroke.

 

the crank swap might work, but will cost alot, i mean the 2 engine have the same bore, ,just diffrent cranks

 

well, i don't know what the difference between the two bare blocks really is.

again, in the M10 (which i realize is a 30 year old engine from another country) the different blocks were just machined differently and any block can be bored to the max size.

 

this isnt true. the LE5 has an 88mm bore, whereas the LSJ, L61, and LNF all have a 86mm bore. the 2.4 is slightly bored, and decently stroked to make the added displacement

 

hmmm, u dont say oh well...i guess crank swap wont work than

 

someone else brought it up too...i think it was a big hassle due to something about the crank reluctor wheel, so in addition to boring out the block (or getting a 2.4 block), you would need to swap electronics as well. in the end, it was decided that the HP gain is definitely not worth the cost

anyway, thanks for the info on the overboring. i learned something new today