NA engine compression

[irishkev90]

Simple question really. Should an NA engine be high or low compression? I know everything needs to be lightweight, along with intake and exhaust upgrades. I just need to know about compression. Thanks for the help guys.

 

[xJAZx]

high compression

 

[irishkev90]

Okay thanks. So what are some ways to increase the compression? Longer rods? Different pistons? And what about valve clearance? Sorry for all the follow-up questions, I'm new to actual engine work. So far all I've done is an intake.

 

[irishkev90]

And does anyone know how much space is between the cylinders on the 1.5L Z5? I was thinking of having it bored, but not sure if there's enough room. Thanks.

 

[br289165]

Mill the head or block, higher compression pistons, weld quench zones onto combustion chambers, all these raise compression ratio. Valve clearance to piston you mean right?

Okay thanks. So what are some ways to increase the compression? Longer rods? Different pistons? And what about valve clearance? Sorry for all the follow-up questions, I'm new to actual engine work. So far all I've done is an intake.

 

[JamesCH]

Make sure you rebuild with a head gasket/crank/pistons/rods designed to take the higher compression ratio, obviously.

What are you aiming for? 12.5:1 or higher would be awesome... Also think about upping the engine's redline if you're doing a serious build. You can start getting over 100HP/Liter with compression ratios above 11:1 and higher(ish) redlines.

 

[irishkev90]

Yes clearance to pistons. Stock compression I believe is 9.4:1 so maybe 11:1 would be fine, I don't want to go crazy as this will just be a daily driver, but if I can easily get more it would be great. Does anyone have any suggestions for where to get some lightweight crank/rods/pistons for a 2.7mm bored Z5? Or I guess maybe easier would be those parts for a B5-ZE, since that is what I'm basing this build on.

 

[irishkev90]

Bump for help.

 

[Droopy]

Did you change you header? I just did and I really did notice a big difference

 

[irishkev90]

I havnt gotten any parts yet. dont hav any money but i'll be working this summer and just wanted to know where i could get parts. and i didnt know they had different headers for the 1.5L. where'd u get it?

 

[JC-MP5]

Did you change you header? I just did and I really did notice a big difference

Not exactly a big help, but ok.

 

[Droopy]

Not exactly a big help, but ok.

I just figured I'd mention it because I noticed an increase of high end power. Also, he mentioned exhaust and intake in the begining but no header.

 

[JC-MP5]

I know everything needs to be lightweight, along with intake and exhaust upgrades. I just need to know about compression.\

(ugh)

 

[niky]

I havnt gotten any parts yet. dont hav any money but i'll be working this summer and just wanted to know where i could get parts. and i didnt know they had different headers for the 1.5L. where'd u get it?

You might want to check for differences between your engine and the JDM 1.5... that will give you an idea of how much "easy" power is there for the taking... but if you're hoping to do a wild high-revving high-power build, you might be looking at a lot of custom-made parts.

 

[Droopy]

(ugh)

Look bro, I was trying to help someone out. There's no need to be an ass about it.

 

[irishkev90]

You might want to check for differences between your engine and the JDM 1.5... that will give you an idea of how much "easy" power is there for the taking... but if you're hoping to do a wild high-revving high-power build, you might be looking at a lot of custom-made parts.

I have compared them. The JDM "performance" 1.5L (B5-ZE) is 1498cc compared to the US (Z5-DE) 1489cc. The JDM ,obviously, has a larger bore, different camshafts, and different fuel injectors, but the same compression and stroke. The Z5-DE puts our around 92hp and the B5-ZE puts out closer to 120-125hp, I think. About the same power as the BP, but the Z5 is a lighter engine which would make for better power-to-weight ratio. So I know parts for this build are available, I was just hoping maybe I could them here in the states instead of importing them from Japan. Or I could go the custom route depending on cost. I don't plan on making a huge powerhouse of an engine, just a little more get up and go as I plan on staying N/A (obviously) and it's just a daily driver, not a race car.

 

[niky]

You could get the Japanese parts, but it would be problematic getting the ECU if your car is OBDII. Without the ECU for the high revs, you're probably looking at a tiny boost in power only. Something that could be matched with some simple IHE and management mods.

For the cost of everything, it might actually be simpler to swap in a bigger motor. That'd give you both more power and more torque. A high-revving 1.5 is fun and all that, but for a daily driver, a 1.8 liter engine with similar power and more torque will definitely be more enjoyable.

 

[Droopy]

^^^^ I agree with niky on this...

 

[irishkev90]

Good point on the ECU. Forgot about that. I think you've officially changed my mind, I'll go with a BP swap instead. Thanks guys.

 

[Ice88]

If your after power, changing compression e.t.c youll be wanting a stand alone ECU anyways so i dont see why OBDI or OBDII matters.