K24 increase compression ratio

**Fredoops** · 17-04-2011 05:38 PM

I've had this idea in my mind for a while. Sorry if I sounded noob

I've been reading k20.org for a bit and I've came by quite a few thread where it's basically:
"I've got mailed TSX pistons instead of my CRV pistons... I'll just swap them out and reflash...bam! compression ratio increased from 9.7:1 to 10.5:1.... goody"

hmm... is it THAT simple?

If so then can I swap out a set of K24z3 piston's (11:1) onto my CL9 (K24a3, 10.5:1) to get more out of the block?

**fatboyz39** · 17-04-2011 07:20 PM

You can swap out the pistons to the new k24z3 pistons. Did you get the right pistons for your block? There is a A and B set unless you got the over size pistons which won't matter.

Adding slightly more comp will only benefit with other mods done to the car. i.e headers/intake/exhaust and etc.

Is it a worthwhile mod to a stock engine? I would say no... the time and labour isnt worth it.

**Fredoops** · 17-04-2011 08:56 PM

Originally Posted by fatboyz39

You can swap out the pistons to the new k24z3 pistons. Did you get the right pistons for your block? There is a A and B set unless you got the over size pistons which won't matter.

Adding slightly more comp will only benefit with other mods done to the car. i.e headers/intake/exhaust and etc.

Is it a worthwhile mod to a stock engine? I would say no... the time and labour isnt worth it.

CL9 is K24A3 I believe.... Anyway... So it IS just the piston? I always thought you'll need a new set of cam gears as well or something.

**dougie_504** · 17-04-2011 10:11 PM

Originally Posted by Fredoops

CL9 is K24A3 I believe.... Anyway... So it IS just the piston? I always thought you'll need a new set of cam gears as well or something.

Full head build sure wouldn't hurt if you're doing pistons mate.

**Fredoops** · 17-04-2011 10:22 PM

Originally Posted by dougie_504

Full head build sure wouldn't hurt if you're doing pistons mate.

You know Im by no means a mechanic, but I do have greasy fingers. So the cam + piston thingy will cost about 1200.. in total.. God bless America
and it's still cheaper than the ECU tune/reflash... lols

**dougie_504** · 17-04-2011 10:33 PM

Pistons + cam gears?

What's the point in getting cam gears alone? I see minimal purpose unless you get shafts too, in order to reap the real benefits. Then a supporting valve train to handle it, a good intake and exhaust setup to help the car breathe. Head work wouldn't hurt while you're in there ---> 3-angle grind, port job, matched manifolds.

Then tune it up, otherwise it's a waste.

Add in labour, then suddenly your $10g worse off and wondering why you didn't just go F/I or buy a different car.

**Fredoops** · 17-04-2011 11:20 PM

Originally Posted by dougie_504

Pistons + cam gears?

What's the point in getting cam gears alone? I see minimal purpose unless you get shafts too, in order to reap the real benefits. Then a supporting valve train to handle it, a good intake and exhaust setup to help the car breathe. Head work wouldn't hurt while you're in there ---> 3-angle grind, port job, matched manifolds.

Then tune it up, otherwise it's a waste.

Add in labour, then suddenly your $10g worse off and wondering why you didn't just go F/I or buy a different car.

Good Point.

**dougie_504** · 17-04-2011 11:26 PM

I'm all for modding engines, but I just believe that you go like this (for power):
1. I/H/E
2. Head build (mild) - mildly aggressive cam shafts/gears + tune
3. Head build (aggressive) - more aggressive shafts, supporting valvetrain, head work, TB/IM + tune
4. Block (mild) - larger displacement + tune
5. Block (aggressive) - high comp pistons, lightweight crank maybe, forged internals a good idea + tune

Flywheel upgrade a fun idea. Clutch upgrades as appropriate.

To me personally it just makes more sense to do things this way due to accessibility to head/block for labour, power gains, laws regarding engines swaps (block numbers), being able to put a built head on a bigger block if you need more power later etc.

**stndrd** · 20-04-2011 02:26 PM

the order in which you say to build a motor ends up being a very costly way to build it. i understand where you are coming from but with the way people love to rev to 9000rpm, i would recommend upgrading valve springs/retainers etc when you do your first cam swap because its always better to be safe than sorry. also the majority of valves in modern cars already run 3 angle valve grinds. these days go for a 5 or even 7 angle valve grind and you will make some good power with a good port job and match porting the head with the manifolds.

in regards to your question about bumping up compression ratio, the 0.5 in ratio can be achieved simply by shaving the cylinder head (remember to always check piston to valve clearances) when you go to fit non standard camshafts. also look into the adjustable vct gears instead of 'fixed' adjustable cam gears. this allows you to further shift your power and torque curves when combined with a good aftermarket computer (i recommend using haltech ep3r plug'n'play computer)

**dougie_504** · 20-04-2011 04:43 PM

I agree with your point about the valvetrain, however there are several people that run very mild cam setups without upgrading the valve train. I don't like the idea personally...what I listed is a suggested progressive build.

TBH I would just skip all the 'mild' steps I mentioned. I think if you're opening the head or the block you should just mod it. No point buying OEM replacement internals to me lol. WOTAM.