Compression Ratio.

**Inabj2** · 08-30-2002, 04:23 PM

Yo i was thinking of upping the compression ratio. From i dont know.. 8.8-1 to 10 maybe 11-1. how much would this cost? How much power would I gain? And I know its shitloads of work.

**shepherd79** · 08-30-2002, 04:29 PM

well, i am not sure how much power you will gain but i am sure it will good power.
i don't think that anyone makes high compression pistons for our cars.
yeah you will have to rip engine apart, while you have it apart may be you should do intake manifold port and polish.

***carotman*** · 08-30-2002, 04:46 PM

You can get JE pistons or Wiseco

**YK86** · 08-30-2002, 05:14 PM

I remember someone telling me as a REALLY general rule of thumb, 0.5 increase in compression (ex: 8.8:1 up to 9.3:1) amounts to 10% more power. How accurate that is, I have no clue. But is sounds about right since the 86/87 and 88/89's had the 0.5 increase and the power difference is 10-12HP (assuming most of it was due to the pistons).

***AZmike*** · 08-30-2002, 05:53 PM

The 88-89 LXi had an improved intake manifold that likely added some horsepower. Did the 86-87 have the 4-2-1 exhaust header? If not, that added some of the 10 hp difference also.

Tearing apart an old A20A and rebuilding it will likely cost enough that you might want to do some swap research before jumping in. The A20A is a really tough engine, but with only one cam you still get somewhat limited performance compared to the DOHC alternatives.

How much for 4 forged pistons? What about connecting rods? New journal bearings? Crankshaft crack check? Honing? New seals?

Once you add it all up, is working with the A20A still a beter deal?

To compare, how much is a decent B20A usually?

**89BlackH-Back** · 08-30-2002, 06:04 PM

im sure if you called open loop motorsports they would make something for you go to www.openloopmotorsports.com

**Inabj2** · 08-30-2002, 08:21 PM

See if i were in mexico i coulda done this for free. I thought all i needed was adjustment.

**1989 DX R** · 08-30-2002, 08:54 PM

Actually, SOHC doesn't nescessarily mean slow. Look at the Corvette ZO6. Albeit, that the Vette has mucho better heads than our shitty one.

**smufguy** · 09-01-2002, 12:01 PM

ur compression, if u have carb, its 9.1:1 and efi had 9.3:1. Going to a 11:1 ratio would blow your head off (not the one above ur neck, but the one above the cast iron engine block). 10:1 sounds like an awsome set up, but i dont know if our heads would hold it. I am sure u need some clearance on em. turbo mike had his dropped and other than him, i dont think anyone tried changing the pistons other than getting a piston with stock configs on em. I really wanna do just a piston upgrade if its gonna give me more torque, cause more hp is just given. I am sure its not just changing ur pistons right? its a lot more right/ its gonna cost more right? shit too many questions.

**night** · 09-01-2002, 01:20 PM

haha, blow the head off ?

you can run up 12.5:1 on street gas, but it has to be tuned to perfection with very well designed pistons.
if u really wanna raise compression, dont bother milling the head. have some pistons made and it will run great. i would go for 11-11.5:1. but it has to be done right. and you better change the rods to.

and the only way to really get power from compression is to get a good cam too

**Inabj2** · 09-01-2002, 04:08 PM

Shit in mexico we did this to a V8 all we did was getting new valve springs and other detaile djob it was 3 day job.. but it costed 0 bucks.

**pric** · 09-03-2002, 04:06 PM

DRAG sport MAG. did an artical on compression this month that got a huge chart showing the increase and decrease (%) differences. Here's the formula they use.

R=original compression ratio
r=new compression ratio

power increase or decrease (%)=[(1-1/r(0.4 th power)divide 1-1/R(0.4 th power))-1]x100

The chart shows going from a 9.0:1 to a 10.0:1 is a 2.9% increase. going to a 11.0:1 is a 5.5% increase. and 12.0:1 is a 7.7% increase.

**Glitch** · 10-09-2002, 04:42 PM

how much compression are yall pushing? Last i checked in my 89 lx-i i was pushing 10 in each. I thought i was getting kinda shitty compression. For me anyway. But I was curious on what yall was pushing?

**Inabj2** · 10-20-2002, 12:52 AM

1-1??? i cant type that on my calculator.. lol. But 7.7 power increase from an increase of the ratio of 3.0? GEEZZZ that cant be right, If it is it really is quite pointless!

**Kevin** · 11-20-2002, 08:26 PM

I have a buddy with a 94 accord with an H22 and had 11.5/1 comp and the block is decked and he has a hard time tuning Bc it takes perfect tuning to get perfect performance and no knock!!! He has to the local airport to get 100 octane to keep running good!!!!

**Inabj2** · 11-20-2002, 08:51 PM

That sucks

***carotman*** · 11-21-2002, 03:46 AM

the A20A can handle the compression... the head too

**markmdz89hatch** · 11-21-2002, 08:03 AM

ummm... ...dumb question, but where can I go to get the compression tested? i got a feeling that's why my car's acting so sluggish. I mean the engine runs great, but compared to my 88 DX Coupe, my 89 DX Hatch is a damn sled... WTF... I've also driven another 88 DX Hatch, and it had comparable power to the coupe, so would the major power loss in the 89 hatch be due, in part, to reduced compression?

**88bluelx** · 11-21-2002, 12:27 PM

Ross racing pistons can also make custom pistons for any honda engine for 424 dollars plus the cost of the pins. Check out their website. Also I think that you can have Pauter custom make forged connecting rods for in the neighborhood of 700. Just a thought.