NA KA24DE

[240Stilo]

I've been going round and round convincing myself why i should turbo my KA or do an SR swap and i finally decided i'm gonna try the NA route. The thing is that being a daily driver I don't wanna be spending too much on gas because this $1.65 a gallon for SoCal gas is no joke. With a turbo set up I've heard the boost can be lowered as much as possible to save more gas. Now if i take the NA route will the KA become a gas guzzler given the situation that the compression ratio will be increased?

One more thing....is the increase of the compression ratio a results of buying after market pistons or is it a piston and rod combo?

[Fresh 240SX]

Yes the pistons can lower or raise compression pending on what setup you want... Lower for turbo and higher for N/A tune

[95Blue240sx]

when you increase the compression, you usually go with a hi-compression piston. &nbsp;if you increase the the rod length, you are increasing the stroke. &nbsp;dont quote me on any of this, its late and im sleepy. &nbsp;when you increase the stroke you get more toruqe correct? &nbsp;someone correct me please lol &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/hehe.gif" border="0" valign="absmiddle" alt=':hehe:'>

[**rOb**]

ummm SOrry this might be off topic but did anyone hear of people going the NA route with an SR? any info on this?? thanks

-rOb

[240 2NR]

Well, so long as you don't go too high in compression then the overall efficiency of the engine will go up for the entire power curve. &nbsp;I say "too high" because once you pass about 11:1 you'll need to upgrade fuel management. &nbsp;The one guy I know running 11.5:1 is also runnning 100 octane and bigger injectors, though I'm not sure how much of that is being over conservative. &nbsp;

General rule of thumb is 4-6% increase in power for every full point of compression. &nbsp;So going from 9.5:1 to 11:1 is only 1.5 points of compression which will net a 6-9% power increase or around 164.3-167 hp at the crank, up from the stock number of 155.

At the same time, swapping pistons is a lot of work and money just to be saving a few bucks on gas (and I hope that price was for premium cause that's what you'll be running). &nbsp;It would be much cheaper and easier to swap cams for almost the same gains, but 1/3 the work and cost, and just eat the expense of marginally lower fuel economy.


An NA SR did come in the silvia J's and Q's. &nbsp;If you want, I'm sure you could import one of those real cheap. &nbsp;Or you could just go buy a sentra, G20, or any other US car that came with one. &nbsp;But why?

[ponyboy]

As far as naturally aspirated SR engines go, there is alwyas the ultra-rare, Japan-only SR16VE engine. It was basically a de-stroked SR20 with a 2.1:1 rod ratio, hand polished ports and variable valve timing. It made 200hp natrally aspirated. Not bad compared to an S13 silvia, making 205 hp turbocharged!

Also, the SR20DE was used in the Nissan Primera in the British Touring Car Championship, (using the 54C GTi-R block) to make 300 naturally aspirated horses!!!

So there is obviously alot of potential to an NA sr20, but the cost of NA is always astronomical compared to FI on four-bangers, so it dosen't really seem worth it.