My friend keeps on telling me I should boost my car. Then he says you should change your compression ratio, but he's not sure how to do it, but he keeps telling me I should.

Anybody know how this can be done? My friend is saying taht I take it to a shop and ask them to do it, but I always thought changing the compression ratio means putting in a turbo?

Sometimes it gets annoying when people start telling you things you should do to your car, saying: "you should put a body kit on there" or you should "put a turbo in your car", like it doesn't cost anything to do it.

Sorry, taht was a little segue (sp?). Back to the topic, compression ratios....

 

The KA's compression ratio is pretty low compared to many other engines. It is somewhere in the 8:1 ratio which is great for a turbo.

Compression ratio=the ratio of the maximum to the minimum volume within the cylinder, between the piston and cylinder head

Thus compression ratio is not adding a turbo but seeing if you compression ratio is low enough to accept a turbo. A high compression ratio would usually mean that you would rather supercharge than turbocharge, but you can definitely get more HP by turbo, but remember lots and lots of $$$$

 

So how would you actually change the compression ratio?

 

it's basic really, (yeah right) actually you have a couple options. you could get a stackable metal head gasket to increse(?) the space between cyl. head and block so the piston can't squeeze the air as much. that's an easy way to go especially if you won't be runnin that much boost. just remember*fuel* ka's can hold like 6 or 7 psi though. the other way is to go in and replace your 8.6:1 CR pistons to sumthing with more dish volume. the problem with turbo ka's isnt the CR its the rods.
hope that helps alittle

 

in NA cars, you usually want the highest compression ratio that you can run without detonation. you can increase the compression ratio by replacing the stock pistons with higher compression pistons (these are more dome shaped than the stock ones). a high compression ratio gives you more power.

in FI cars, you don't want as high a compression ratio because the risk of detonation is much higher because the air entering the combustion chamber is already compressed.

the KA's stock ~8-1 compression ratio is low for a NA car as some run up to 12-1 or even 14-1. 8-1 is a good ratio for FI engines.

screw the SR, the KA is just to be asking to be turboed!

 

i don't know what that dude was talkin bout with FI cars?? the 240's comp ratio is 8.6:1
you can run respectable amounts of boost with the right fuel management. but don't try a plain ol' boost sensitive pressure regulator. its not the compression ratio its air fuel ratio. trust me. how do tou think guys with b18c's run boost? that motor has like a 11:1 to 11.5:1 CR. fuel man, fuel. don't play your self. i;d hate to see you blou your engine.

 

FI = FORCED INDUCTION (turbo or supercharged)

there are many factors that come into play when trying to avoid detonation. compression ratio is one of them as is air/fuel ratio.

 

correction noted

 

If I am correct you can change your compression by changing your piston heads.

But reading the posts here it sounds like our cars are already in the low compression range and there will be no need for the change.

You might want to look at the available turbo kits out there and see what they change at different levels of boost. That will give you an outline on what you will be looking to change.

 

Yeah, you can boost your car but make sure the air/fuel ratio is correct. You may want to get better pistons and rods as a reliability issue at low boost, but if you plan on going into the upper pressure ranges there going to be mandatory.

Statik of Speed Thrill

 

Hey Rudeboy, looks like you had a rodbolt to break on that one!
Ouch!

 

luckily that wasent mine but bolt a T88 on a stock ka and see what happens

 

......The REAL compression ratio of the KA is 9.5:1....

 

sorry man but just before the put the car out they lowered it due to north america driveability issues. want the link???

 

Really? So my 92's FSM which has been patched with all updates current as of 2000 still indicated a 9.5:1 CR is wrong? Doubtful.