what will be an optimum CR on a CA18DET

[skyshack]

Zombie thread bump.

Removal of squish is something that allows a big drop in comp ratio without using dished pistons (thinner crowns).

Using a thicker gasket renders the squish worthless.

Comes at the cost of needing rich mixture and ignition pulled to suppress det in the mid range. Engine is now committed to drag racing and isn't worth considering as a street car.

[alanjuggler]

Zombie thread bump.

Removal of squish is something that allows a big drop in comp ratio without using dished pistons (thinner crowns).

Using a thicker gasket renders the squish worthless.

Comes at the cost of needing rich mixture and ignition pulled to suppress det in the mid range. Engine is now committed to drag racing and isn't worth considering as a street car.

I'd agree with the cost of dropping the CR - 1.9mm headgasket on a CA, the car was as flat as a pancake until it came on boost.

[black smoke]

So whats the best to do I am in a quest for 500bhp and done the squish job on my cylinder head I dont mind to run rich but that mean I can only use it as drag set up ??

[Actual_Ben_Taylor]

So whats the best to do I am in a quest for 500bhp and done the squish job on my cylinder head I dont mind to run rich but that mean I can only use it as drag set up ??

Maybe try just removing the squish on the inlet side like Nismo did on the Z-Tune RB26?

[zeppelin101]

So whats the best to do I am in a quest for 500bhp and done the squish job on my cylinder head I dont mind to run rich but that mean I can only use it as drag set up ??

Rather than buggering about with silly low compression ratios, I'd probably look at octane additives to avoid knock and retain smooth driveability off-boost.

Methanol injection is hardly new ground to break and has worthy results. Tuning doesn't have to be overly complex if you've got exhaust temperature measurement and knock indication.

- pure methanol is bloody dangerous mind, best to run a 50/50 mix by weight in deionised water as the water renders most of the more dangerous properties of methanol inert.

[Rochester]

1.9mm headgasket on a CA, the car was as flat as a pancake until it came on boost.

I'm using a 1.6 after the head was skimmed to within - just- OEM minimum tolerance.

Feels a little bit flatter off boost than it did with the previous 1.3 pre-skim, but nowhere near pancaked.

Not much in it, perfectly driveable with the 1.6 offboost, plus worth every penny in peace of mind stakes.

May be slightly subjective but it also feels as if there is less of a thump as it comes on to boost, a smoother gradation from off boost to on boost than before. Drives more like I just had a larger engine than a turbo'd 1.8.

PS. All of the above using GT28R (the early S15 good 'un) and Jez Stage 2 chip at max 15psi (like what she is wrote for).