whats up with ka pistons??

[datsunfish]

I am trying to put together a L/Z 2.3 motor and it seems as though one of my z24 pistons is a little messed up. I wanted to use the z24 pistons to keep the compression down with the A87 peanut head with 280z intake valves. I know that the ka pistons will make too much compression with this head but from what I can tell the KA24DE pistons have a much deeper dish than the KA24E ones. Would those be useable with a peanut head or are they completely different altogether? I really would appreciate some insight here. It seems as though every time I post anymore I get ignored regardless if its a technical question or not. So thanks in advance for any help. Or does some one have a decent z24i piston they would sell me??

[datzenmike]

There actually were two different pistons used with the KA24E, both would raise the compression compared to the Z24 piston. As I understand it the DE pistons have more dish than the E pistons. I've been searching to find the DE dish volume but no luck so far. If you can tell me the DE dish volume and pin height, I can easily work out the compression ratio for you. From looking at the other numbers I would estimate the DE dish at about 25-27cc. The DE piston pin height may also be shorter than the E which would also aid in lowering the compression by causing a bigger negative deck height.

 

Found this picture of a DE piston dish:

 

Edited March 18, 2009 by datzenmike

[sssr20det510]

i heard you can have the top of the piston milled down to lower compression

[datzenmike]

It will, but with a dished piston you are only removing a small width ring around the top. This also narrows the distance from combustion chamber to the top ring so it will run much hotter.

[Icehouse]

Mike could you backwards engineer it? The nissan forums say that installing the E pistions in the DE raises the compression to aproximatly 10.5-11 to 1 Shit what am I thinking of coarse you can do it, your mike the RAT KING!!!

Edited March 18, 2009 by datzenmike

[72240z]

I know I sound like a broken record on this but grove the head. Can do it yourself and that comp range won't even matter then, better hp, better tq and better mpg with no knock. Like Mike says if you mill it down it's going to run hotter. Imho too hot and inefficient to warrant doing it.

[athoose]

You could look into a thicker head gasket.

[datzenmike]

Mike could you backwards engineer it? The nissan forums say that installing the E pistions in the DE raises the compression to aproximatly 10.5-11 to 1 Shit what am I thinking of coarse you can do it, your mike the RAT KING!!!

 

Need to know the stock DE compression. EXAMPLE: IF it was 8.6 (not saying it is, I don't know) but IF it was 8.6 then the dish should be 21cc

 

OK I worked out that if the DE has a dish of:

19cc = 8.8 compression

20cc = 8.7

21cc = 8.62

22cc = 8.53

23cc = 8.43

 

I think it's safe to say that DE pistons will lower the compression more than the Z24 pistons. How much.... well lets see.

Edited March 18, 2009 by datzenmike

[datzenmike]

Hmmmm I don't see a problem with what you have. A 2.3 using a Z24 pistons and p-nut head is only 8.8 compression anyway. Just how low do you need to go?

 

Anyway from my complied list of possible DE piston dish sizes I get compressions of:

 

19cc = 8.41

20cc = 8.32

21cc = 8.23

22cc = 8.14

23cc = 8.05

 

I don't see any problem with running Z24 pistons with their 15cc dish. 8.8 compression is fine.

 

RAT KING enough for you jeff? :D

Edited March 18, 2009 by datzenmike

[datsunfish]

I just dont want to be over 10 to 1. I ask because the ka pistons are dime a dozen but I did find some z24 ones on ebay might just pick up those. New is better anyways.

[datzenmike]

Yeah I worked it out using old school math. :D The Jason Gray compression is rounded up to 8.9. I got 8.8 so there is an extra margin. I think you're good to go with Z24 pistons.

 

mike

[slodat]

I know I sound like a broken record on this but grove the head. Can do it yourself and that comp range won't even matter then, better hp, better tq and better mpg with no knock. Like Mike says if you mill it down it's going to run hotter. Imho too hot and inefficient to warrant doing it.

 

What do you mean "grove the head"?

[72240z]

Was a typo, st pats and all lol....

 

Grooved head by mr Somender singh.

Explained....

http://somender-singh.com/component/option,com_frontpage/Itemid,1/

[datzenmike]

Though it looks like those commercials for HHO generators I don't see where he sells anything, just gives the idea away. None of the tests or testimonials are any good BUT interesting reading and in theory.. may have merit. You do need a head/piston combo with some kind of quench area for it to work. Very interesting though.

[72240z]

Lol we could argue the same points every time it's mentioned Mike. :lol:

 

I have acquaintance'S who have used it with AMAZING results. Stock pistons, milled heads, 11.2-12:1 comp no knock at stock to 2 degree advance timing (depending on ambient temp), L series heads, 87 octane. That comp give you amazing tq and the design gives you way better mpg and better emissions. I mean it's fine to doubt, esp when not understanding the science behind it. Results are results though, throw those variables into a L series without the groves and watch it destroy itself. The groves did what they do.

 

It's been documented sooooo many times on soooo many different forums too I really don't understand why its so black magic. It's even becoming common practice with a lot of domestic v8 folk. Its free and it works, basically what it comes down to imo.

Edited March 20, 2009 by 72240z

[datsunfish]

So many different groove placements. I guess to try it blind go with 1 through the middle?

[Icehouse]

If it works so great why doesn't the factory do it?

[72240z]

If it works so great why doesn't the factory do it?

 

That's a valid question, I don't work for any of them so Idk, but in my opinion? Its not needed in a factory application, stock comps are rarely if ever to the point where the stock computer can't deal with any condition on 87 octane. Maybe the other benefits aren't worth it to them. It's also not exactly new but it hasn't been around long either, esp comparatively speaking. The automotive world is very fickle with new technologies.

 

Why aren't any of them using Coates i.e. rotary heads? Which are superior to ANY current head design in MANY ways. Why does Americas premier super car use a 2 valve per cylinder push rod motor? Granted they have their benefits but at over $100k pardon me for saying its ridiculous. Camless engines have been out even longer and where are they? If basic casting port work and smoothing provides such gains across the board of hp/tq/mpg etc why don't they do that from the factory? It's only one more step in the line, just like groves would be. One cnc machine that they already have, zip zip zip done zip zip zip done...... direct injection, variable intake manifolds etc.. I could go on all day.

 

I'm not trying to be an ass or anything like that answering your question with questions. just trying to make the point that they are many technologies that they don't employ, for I'm sure a host of reasons. That doesn't mean they are less efficient or don't work but that they have a bottom line that many technologies don't fit.

Edited March 20, 2009 by 72240z