Compression Ratio??

[91StanzaPusha]

Hey you guys. I'm curious as to what the compression ratio will be when i'm done mating the de head to e block. I've heard different things and all the compression ratio calculators are showing 12.5 to 1!!! I'll be done on tuesday when i get back from dc and it took me a total of 2 days work! i cant wait.

[deviousKA]

Only thing you are effectively changing during the headswap as far as compression ratio is concerned, is the piston dish volume.

Depending on the bore and the amount of decking that has been done on the head/block your compression ratio will be 11.1-11.4:1. 12:1 is not possible unless the pistons are flycut, or else the valves will hit (or come way to close). I assume you have the regular sohc non-early pistons which work well and give 11.1:1 compression ratio, they are -2cc dish.

Heres a couple simplified charts that i just made up (and revised).





-deviousKA
Modified by deviousKA at 1:26 AM 12/27/2004

[91StanzaPusha]

Thanks for clearing that up. One more question:WILL 93 OCTANE SUFFICE??

[91StanzaPusha]

And oh yea! What gains should i suspect in general. Searching brings up to many irrelevant results.

[91StanzaPusha]

Just thinkin. i got one step colder ngk plugs, would i need to advance the timing any farther than stock?

[eddiec]

deviousKA: what is the oem piston volume for de pistons? this is given for the "e" in the notes but nothing for de. thanks

[deviousKA]

oem de piston volume is 15cc dish.

[SMoKeM240]

if i put in 9.1 pistons, got the head surfaced, like avg. surfaced and the block decked, what would my comp be around, i was told 9.8

[deviousKA]

if i put in 9.1 pistons, got the head surfaced, like avg. surfaced and the block decked, what would my comp be around, i was told 9.8

Possibly, If you also had it bored. Average decking is usually no more than .010"-.015" (total block and head). Enough to remove a cc or two from combustion chamber. Your in that ball park id imagine.

[SMoKeM240]

it was bored .040 over

[MarkEmark]

Hey you guys. I'm curious as to what the compression ratio will be when i'm done mating the de head to e block. I've heard different things and all the compression ratio calculators are showing 12.5 to 1!!! I'll be done on tuesday when i get back from dc and it took me a total of 2 days work! i cant wait.

Let us know how it runs...I'm really curious. I miss my N/A KA. That thing was fun...do you have any other head work done (port and polish, oversized valves, cams, etc etc)? What about exhaust/header/CAI, etc. Anyway...update?

[91StanzaPusha]

I was going to do a port and polish but money wise it wasn't in the cards. I do however have a full custom 2.25 exhaust with a magnaflow highflow cat and flowmaster 60 series muffler.

[91StanzaPusha]

right now i'm trying to see if my ecu will pick up the altima distributor so i can start the damn thing. By the way, was it in 95 that the altima changed to OBD-II if so then thats probably why it wont read that distributor i got.

[deviousKA]

right now i'm trying to see if my ecu will pick up the altima distributor so i can start the damn thing. By the way, was it in 95 that the altima changed to OBD-II if so then thats probably why it wont read that distributor i got.

I believe it is obd-2, my 95 altima was.

[91StanzaPusha]

sh** guess i'll have to find one from a 93-94 then. that the only way to get it to start without changing the ecu and all the wiring

[91StanzaPusha]

ITS ALIVE!!!! At 330pm EST the ka24 officially cranked up! Now all i have to do is officially seal that leak at the top timing cover. FYI the DE distributor is a direct swap in other words it works without changing the ecu!

[deviousKA]

Good deal, Its probably safe to say you have the first and only one so far in FWD.

[91StanzaPusha]

ya damn skippy! i love it! THE FIRST KA24DE Nissan Stanza