Hey Guys,

In looking for pistons for my D16Y8 and I would have loved to have kept the stock CR of 9.6:1 but I'm not finding any aftermarket pistons that do that. My choices are Vitaras at a very low 8.4:1 or aftermarket 9.0:1 or 10.5:1.

From playing around with Mustangs for many years I know I don't want lower CR. It kills throttle response and gas mileage and mpg is one thing I really love about this civic and don't want to ruin. So it's looking like my choice is 10.5:1. Do I need to be concerned with that high a compression on 91 pump gas (premium in KC)? I assume I can just pull some timing to compensate for the added CR.

I'm only at 10 lbs of boost right now too. Also if it ever does become an issue one day when I want to add a little boost I can always run water/meth injection to kick the octane way up if needed. I run it on the Cobra and it works fantastic.

 

10.5 to 1 is still not very high. If your gonna boost it just make sure they are forged pistons. The weak point in the single cams are the rods. im running 20PSI on pump gas right now, so with your 10 you should be fine ( depending how much power your making off that 10 PSI ). I dont get how you think lowering your compression will kill your MPG? Im running 9.0 to 1 and still get almost 32 MPG outta a 370WHP B16, MPG is all in how lean you run at half throttle. basically its all in the tune

 

Thanks for the info. If these motors will take 10.5:1 with no problem on pump gas then all the better.

Oh that is absolute fact. Not only is it in every piece of automotive literature but I've found that out first hand many times playing in the Mustang world. Simple physics, less compression makes less power on the same amount of fuel and requires more fuel to power the car along. The affects I'm sure are a lot less pronounced on a small 1.6 motor vs the larger v8s but it's still going to happen.

Not entirely true. CR plays a big factor in the motors efficiency and of course mpg. There will be a point in leaning out the A/F ratio to much to where you're getting counter productive because it's requiring more throttle (and more gas) from the driver to keep the car cruising at X mph.

Not to mention cruising at very lean AFs can be bad too. Heat is one major concern.

Greg Banish explains these concepts very well in his books. If you're not familiar he's an OEM calibrator for GM and does a lot of aftermarket performance tuning and training classes. I highly recommend his books and DVDs if you're into tuning.

 

In my opinion 10:1 is the new 9:1 compression. Do it. Stop driving a low compression slug.

 

I got my threads crossed but while calling Real Street to inquire about their pistons they highly advised I do not go with the 10.5:1. They said unless I'm running C16 or E85 I'll be loosing HP because of the amount of timing I have to pull. He said honestly loose a little mpg and go with the 9.0:1 and I'll make a lot more HP on the high side.

 

sigh, everyone has different opinions. I think 10:1 compression is very mild. You see plenty of stock block Hondas with similar or higher compression using pump gas. Cylinder pressure makes power and that is relative to boost and static compression.

 

I'm with you on that. I'm a fan of higher compression motors for sure. I'm just new to these motors and looking for real world experience and feed back before building it. BTW the pistons I'm finding are 10.5:1 not 10.0, not sure if that's pushing it to far or not.

If the 9.0 pistons are more boost friendly and the motor will make more power I'm open to that too. Like I said looking for feedback from guys that have actually done this.

 

10.5.1 isnt high compression at all. That **** is super mild, especially with it being 2012 and all the tuning advancements and available knowledge etc. 10.5.1 on pump gas should be a breeze with a good tuner. I dont know why people still insist on doing these 8.8.1 -9.1 compression setups................ why not get that compression up where it needs to be ladies.

 

I am running Arias pistons with a 10.2 to 1 compression myself. My engine is running now but just naturally aspirated until I can save up the rest of the money to finish her up. Feel free to check out my build thread if you wish sir.

 

One such theory I see is because boost is a multiplier as I've seen it put but some. Meaning you'll make more power with a 9:1 motor because of how much boost you can run. Stepping up to 10.5:1 you have to run less boost and overall you make less power. At least that's the theory. Is that old school of thought or still current with today's times?

As for tuner... well it's just me playing with my project car so that maybe something to consider. If 10.5:1 is territory with little room for error and tuning excellence I might be better off with a little less compression.

 

Old myths...

 

Go 9.5 to 1. You can still manage 30+ MPG and make great power. You mentioned water meth, that will help you out a lot as well. My tuner ( TrackForged ) actually said I should went with a 10.0 to 1 piston... Ohwell

 

Again im not here to dispute just adding my little .02. I would sure rather have a 10.1 compression setup than 8.8.1. Makes for a dog out of boost and casual driving around town. Its bad enough our cars make no torque in the first place......

 

I agree with you, but in his original post 10.1 isnt in his options of choices he has found

 

your're right especially on 91 octane......... Welp go with the 9.0.1 man that should be solid.

 

this is why u dont want 9.0to 1 most of the b16s i tune make 400 plus whp at 20 psi and all run 10 to 1 plus comp we have a bone stock b16 with only arp headstuds makeing 407whp at 19psi so if i where u i would go 10.to1 or higher and run a few pounds less boost. not to mention ur spool sooner with more comp.

 

The 370 whp was made with a failing headgasket on the dyno so im sure its a bit higher now that I replaced the HG. But ur 407 WHP on 19PSI, you probably used a bigger turbo. Im using a pretty small turbo, precision 5431 with a .63 A/R. Im sure if I got a bigger turbo id see 400 easy with less PSI. My set up isnt to bad as far as spool up, Port and poished B16 head, full supertech valve train, 1mm oversized valves with GSR cams, I see the full 19-20 PSI right around 5400 RPMS with an 8200 RPM redline so its pretty quick. Not fast by any means, but its decent for driving on the street.

 

If I'm reading all your responses correctly I think almost everyone on this thread is in agreement that 10.5:1 is the better way to go.

 

Do you not have 93 octane available?????? only 91?

 

I wish I did. We have 87, 89, and 91. That's why I run water/meth on the mustang because it's at 20 PSI. I could eventually run water/meth on the civic too but straight 91 would be so nice and easy for a daily cruiser.

 

With water meth you can run a lot more then 20PSI on ur Y8. What size of turbo are you going to be running?

 

Again only my opinion if u had 93 available I'd say go forged 10.5.1 compression all day and cruise. Since your limited to 91 I'd roll with 9.0.1 compression and have fun

 

Doesn't the midwest have lots of Ethanol?

 

Yes it does, but E85 is nothing like it used to be.

 

Its still better than 91 **** water!