Hi all,
I am rebuilding the engine on my R56 MCS, with the dream being to of push the power to the 300ish range in the long term, but am teaching myself as I go along, and I only want to teardown and rebuild this engine once, so I had some questions:
1) Compression ratios. I'll be putting in new pistons, but based on what I have read so far, it seems like no one really has any idea what changing CR actually does or why to do it. it feels like there is no rhyme or reason to what I've read. should I lower my CR? why or why not? Any advice would be welcome.
2) On a related note, Turbos. can anyone point me in the right direction for selecting a turbo, or any personal experience in this area?
3) Conn Rods. Should I be switching to forged? how far can you push the stock internals?
4) Anybody know of a good tuner local to the Portland area or the greater PNW?
Thanks,
Dan

 

Hi Dan, let me start by referring you to my build threads. Latest one is here --- https://www.northamericanmotoring.co...ec-2018-a.html note the links in the 1st post to earlier threads for the same build. I too taught myself the N14 --- you might learn something by reading all these linked threads, without spending any money.

Compression ratios - I found that when increasing boost above 22PSI, the CR needs to be lowered from 10.5:1. I went all the way down to 9.0:1, based on input from people I trusted. Actual CR to be used depends on many factors, most of which I can't explain. I started with 10.5:1 forged pistons but with 30PSI they caused a cylinder wall to collapse within an hour or so of operation.
Another consideration ---
N12 uses 11.0:1 CR pistons --- no turbo
N14S uses 10.5:1 CR pistons --- 22PSI Max
N14JCW uses 10.0:1 CR pistons --- 24.?PSI Max (different turbo and MAP sensors)

Turbos - I found that the bigger the turbo, the more turbo lag you'll get. I highly recommend you get the smallest turbo available if you want more than 24PSI. Friend of mine used an Owens hybrid and produced around 320WHP with OEM internals. Don't know how long his engine lasted, but never heard about a failure.

Internals - Once you get familiar with 300ish power, you'll want more. Think seriously about a Cylinder Support System --- https://cylindersupportsystem.com and talk with CNCWerx's Jeff before you do any rebore. He likes to measure the new pistons and match the bore to them. If you're getting new pistons, go ahead and invest in rods too, unless you enjoy tearing down and rebuilding engines. Also, ensure the pistons and rods are compatible --- no interference with each other.

Tuning - My 1st custom tune was done by Jeff Perrin and one of Cobb Surgeline Tuning of Portland's main tuning guy (forgot his name and he's moved to another Cobb facility). My dyno chart was still on their dyno web site, but I can't remember the site name. Chart or link is in my early build thread. Jeff Perrin was the AccessPort programmer for Mini's. Pretty sure neither he nor Cobb will do Mini's again, but you might try if you really want to stay with a Portland tuner. A current and popular tuner, based in FL, is --- Lou@Prototype-R knowledgeable, friendly, and has "remote" tuning capabilities. Talk to him about CR, turbos, and internals. He also posts on NAM. When you're ready for really big power, talk with Lorenzo at RPM Power Engine Management in Vancouver, BC --- need really big $$$ tho. He was working on a 600+WHP N14 when I saw him June 2022.

 

Hi OBW,
Thanks so much for your reply, tons of useful info here and in your build logs. just finished skimming through them and I've got a bit of a headache with all the info.
Based on what I've seen from your experience, I'll probably aim for a 9.5:1 CR. Seems to me like your first failure was more down to the unsupported block than your pistons. where I plan to go now, I could probably get away with 10:1, but as you said, once I get there, I'll likely want to keep going, and having a bit of buffer is good for peace of mind.
I was on the fence about CSS, but you definitely pushed me over the edge. Seems like a must have, and as much as I love tearing down and rebuilding, My wallet doesn't.
For turbos, a smaller, faster spooling setup seems to be the way to go.
Reading through your build logs made me realized that I was so focused on compression ratios and turbos that I had neglected to consider my head and cams. Were you running stock cams on your first build? I had my head remained at a local shop, but I didn't tell them my power goals, so I'm not sure if the finished project is up to the task. I'll probably run with what I've got until I start turning it up.
Thanks for the info on tuning. this is perhaps the area that has confused me the most, the more I learn the less I understand. Shame that Cobb isn't an option. I'll definitely reach out to Lou.

 

Hi Dan, glad you were able to get some use out of my build threads. How much you deviate from them is dependent on lots of things, so don't try to copy everything I did.

Main reason I changed cams was because the OEM intake journals got fried when the cylinder blew out the wall and gaskets allowing water into the oil passages. Ruined the head cam journals and the cam --- had to get a second head reworked by Thumper --- another complete rebuild, this time no trial-and-error. Speaking of head-work, I'm a firm believer in allowing the engine to breathe --- clean up the ports and get a larger diameter exhaust system. 3" is probably overkill unless you have a really big turbo, but eventually go for something bigger than OEM. R56 OEM valves aren't easily replaced with larger valves, they're already almost max, so not really worth the extra expense.

Be sure to talk with a tuner before buying cams. I was told to avoid the "biggest" Cat Cam set 'cause it was too difficult to get a good tune. But that was Manic, maybe a less aggressive tune would be OK.

Best of luck, and keep us posted ---

 

Hi OBW,
Thanks for the advice, again. I'll probably stick with what I've got --for the moment-- in that case. one last thing, you are running stock cylinder sleeves, right?
Dan

 

My last engine rebuild was with an OEM block. Sent it (upper half) with pistons to CNCWerx. They installed their CSS then bored cylinders to about 0.050 over, matching exactly the new pistons. They sent it back to me and I installed everything else, after balancing, etc. I consider "sleeves" to be replacement cylinder walls and very expensive to have installed, so I'm running stock cylinders, no "sleeves" --- just over-bored OEM cylinder walls. The CSS system I had installed fits snugly into the water jacket (but not the entire depth, maybe only an inch or so) forcing the cylinder top diameter to shrink slightly. That's why it's installed BEFORE the re-bore operation. The block deck is also shaved slightly afterwards to smooth it off. Talk with Jeff to get details and procedure.

 

Its been a second, and a lot has transpired on the project since my last post.
First, I sent my block with a set of CP 9.5:1 Pistons to Jeff at CNCWerx to get a CSS installed. He contacted me today to tell me he had accidentally gone over the target bore when honing and offered to have a custom set of pistons made at 78mm bore at his cost, which opens up the option to go to 9:1 CR, which I had decided against previously because I wanted to stick to off the shelf parts as much as possible. I am not sure if I want to go all the way to 9:1 as I am afraid it may be too far. Ideally I'd like to tune this car for pump gas at first, or at most, E85. (Anybody know if tuners have the ability to adjust both the sport mode and standard mode tunes to be different?) I am still struggling to understand the pros/cons of changing compression ratios.
Meanwhile, I have ordered a set of Carrillo Rods and am saving up for a Thumper Performance head, as that was not in my original budget. Unfortunately work has brought me back to the east coast at least until the fall, so unless I have a chance to make it back this summer, Ill be unable to get the machine work and engine assembly finished. in the meantime, I may work on designing a cold air intake using the hood scoop. and I will start digging into the All4 swap plans if I have a chance
Any opinions, especially on CR, are very welcome
-Dan

 

On top of this, I have been trying to figure out dynamic compression ratio calculations, but I cannot figure out the intake valve timing, which is complicated by the VANOS. Anybody know the baseline numbers?

 

Did you decide on compression ratio. You could always lower your CR by using a thicker head gasket - so have room to play. I personally would not be happy with a CR lower then 9.5 ( or even 10 ): 1. You lose a lot of power at low boost, but make up for it by being able to run higher boost ( which gives you more power at high boost - which requires a bigger turbo and as what was said earlier, increased turbo lag ). Great for the track - not fun on the street. So depends what your purpose is

 

I wound up with 10:1 CR.

 

I just finished up my contract on the east coast and moved back to Oregon so expect more updates as i spend the summer focused on the build. Currently I have an assembled short block with 10:1 CR pistons, cylinder bored out to 78mm, and a CSS deck reinforcement. CNC Werx did an excellent job. My head is ported with +1mm Exhaust Valves from Mike over at Thumper Performance. Fantastic work. Currently, I am trying to figure out what spec of rockers I need so that i can test assemble and check piston to valve clearance. still considering a slightly more aggressive cam (does anyone know the stock lift?).

Short Block in from the machine shop

Detail of the Pistons and CSS Work

CSS

CSS

Short Block On the Engine Stand

CSS

Old and New Head

Thumper Head As it arrived