Lower Compression with Headgasket

[mid_life_crisis]

Originally Posted by diss7

Just because it's old school, doesn't make it false. Most JDM 2000cc motors can quite happily be boosted to 400whp unopened, on pump gas. This motor, because of knock, because of its high compression, it limited to 300whp or thereabouts.

Wow! Read into something much? I simply observed that using head gaskets to manipulate compession ratios is a trick that has been around a long time. How you could interpret that as saying the technique is BS is beyond me.

[Jason@DSG]

Rods ETA before spring

[Jason@DSG]

As to OP, lowering the head can cause potential for big issues with any piston blow by for guys running FI. Getting the head closer under high temps will just increase the chance of the pistons hitting the valves. Clearances on OEM may not allow the old school thinner head gasket drop. Ideally, aftermarket pistons with lower compression is the way to go to keep it more safe then cutting head gasket thickness.

[Team STILLEN]

Originally Posted by Jason@DSG

As to OP, lowering the head can cause potential for big issues with any piston blow by for guys running FI. Getting the head closer under high temps will just increase the chance of the pistons hitting the valves. Clearances on OEM may not allow the old school thinner head gasket drop. Ideally, aftermarket pistons with lower compression is the way to go to keep it more safe then cutting head gasket thickness.

I was saying to increase the thickness to lower the compression ratio a little. I know it wouldn't make a huge difference. But could mean a little less stress on the engine (or allow for a little more boost) for guys running mild FI to decrease CR by 0.1-0.4 maybe?

[diss7]

Originally Posted by mid_life_crisis

Wow! Read into something much? I simply observed that using head gaskets to manipulate compession ratios is a trick that has been around a long time. How you could interpret that as saying the technique is BS is beyond me.

My bad, I read your post as if it were sarcastic.

[SmsAlSuwaidi]

some guy is running the hks one i think

[zooki]

I would think too that increasing head gasket thickness would change the "quench" attributes of the piston/head relationship. Too much clearance may actually cause more detonation if the swirl characteristics are altered.

[cruizin01]

Did this on my vw 2l fsi engine. Lowered it about a point from 10.5 to 9.5. Helped keep knock at a minimum on 26-28psi. Car made about 500whp with no issues. Did this versus replacing pistons because the stock ones are pretty rebust.

With all that said you didn't have any of the potential issues you have here with intake/exhaust manifolds.

[Team STILLEN]

So the HKS gaskets

http://www.dynosty.com/2012/06/hks-s...s-for-frs-brz/

Say they increase the thickness by 0.1 mm (0.7 mm thick) to lower compression by 0.1 (12.4:1).

Do you think a head gasket could be made strong enough to hold us to ~300 whp while being maybe just 0.3 mm thicker (total of 0.9 mm thickness) without cause figment issues with the manifolds? That would put the CR closer to 12.2:1 (rough math). Would that be worth it for a little added safety from detonation on FI, or do you think doing head gaskets on a boxer motor is just too much for such a small cushion? Not think for big HP chasers, more for people who want to push a little more out of the stock bottom end.


Sent from my iPhone using Tapatalk

[Calum]

Give Cometic a call, they already list the FA20 on their site, and if you have any trouble getting the manifolds bolted up, I'm sure you could gain the extra room with a few minutes and a file to the bolt holes.

[Jason@DSG]

Originally Posted by Team STILLEN

I was saying to increase the thickness to lower the compression ratio a little. I know it wouldn't make a huge difference. But could mean a little less stress on the engine (or allow for a little more boost) for guys running mild FI to decrease CR by 0.1-0.4 maybe?

Oh! My bad, sorry I read it wrong, I thought you were going for a thinner one (which doesn't decrease compression lol).

Yeah, going a bit thicker will be fine for sure. I just don't think it's going to make an enormous difference however.

[D K]

Hello.
I'm new on this forum but...

You guys realize that changing valve cover thickness alters cam timing, right?
On the EJ it's a big no no.
One head gets advanced, the other one retarded.

The only correct way to lower static cr, is to change pistons.

David

[zooki]

Originally Posted by Calum

Give Cometic a call, they already list the FA20 on their site, and if you have any trouble getting the manifolds bolted up, I'm sure you could gain the extra room with a few minutes and a file to the bolt holes.

This is where those headers with flex joints come in handy... LOL

[Calum]

Originally Posted by Calum

I'd be curious about the length of the timing belts (chains I think, but either way) and how far off the cam timing would be when adding that much to the gasket thickness.

Anyone know the combustion chamber volume so we can do some calculations to find out how much deck height we'd need to add, otherwise this is just pure speculation.

Originally Posted by D K

Hello.
I'm new on this forum but...

You guys realize that changing valve cover thickness alters cam timing, right?
On the EJ it's a big no no.
One head gets advanced, the other one retarded.

The only correct way to lower static cr, is to change pistons.

David

Yup, it's been mentioned.

We do have variable cam phasing but I don't know if the stock ECU can correct the banks individually.

Not that some old school indexing of the cams couldn't fix the issue. Not everything can be fixed with a laptop.