Hi Guys,

TLDR: With a 17% pulley and 380cc injectors, would going back up to hotter "6" plugs keep the car from going too rich? Or do just need to go back to stock injectors? Tuning is an option, but not smog legal anymore in California? Anything I should be aware of with 17% and stock injectors?

I'm hoping you guys can help me get pointed in the right direction on this one. I just installed a 17% pulley along with the 380cc Injectors and the colder BKR7EIX plugs in my 2006 MCS Automatic. For the most part, it feels really great driving. It revs very smoothly with the bigger injectors and the transmission handles it all very well. It used to take a while to crank, but has speed it up back to normal on it's own.

The issue is that it seems to have a less than smooth, somewhat rough idle at a stop. Also I noticed that O2sensor1 in Torque is reading pretty high on the upper RPM ranges, about 0.95. As far as I understand, it should read about 0.7 - 0.8 if the air to fuel ratio is good. I am also getting the P0172 Too Rich code in stored faults.
The fuel trim sensor seems to go to -29, I think that is bad? I'm not sure since I'm still new to learning all this. In sport mode, the car seems like it doesn't want to go to redline on WOT. It will shift at 5900-6000ish instead, but before it went t redline on it's own. I assuming the computer is not going redline due to AFR, but just a hunch.

It seems like it just needs a tune, like I have read about with these upgrades, but I live in Cali and with the new smog laws against ecu tuning, I'm not sure what my options would be to get the car just a tiny bit more leaned out. Do you think going back to hotter plugs will do it? Or should I just go back to the stock 330cc? I'm down to learn the ECU flashing and coding to the JCW 210 but again, I'm not sure if it's worth the hassle for smogging.

I will point out that I did accidently snapped the vertical vacuum tube that connects to the big plastic thing that connects to the throttle intake boot. It happened when I was putting the car back-together. I was on my 13th hour and got careless plugging it into the intake boot. I tried to silicone tape it back together as a quick fix, but maybe this causing some of the issues if it's not sealed 100%?

 

Quick update,

I repaired that vacuum joint / connector that goes into the intake boot with an o-ring plus JB Steelstik and cleaned the MAP sensor. Also ziptied the o2 sensor so it doesn't rest on the heatshield, like I found it.

I also cut a bigger hole into my modified stock airbox to see if allowing more airflow helps, like on the JCW. I cut out almost the entire width of the back, and is about 3" tall rectangle shape. I would say it's about 4 or 5 times larger that the original and is connected by a bellow to the cold air near the driver side vent which also is cut to the same size.

Cleared the fault codes and went for a spin. So far so good and then car seems to feel more responsive and isn't bogging down at the lights or in park. Supercharger is super loud now and bangs on upshift sound like they got alot of punch. Trim vales and o2 sensor readings look alot better now. 15.7 psi of boost pulling onto the freeway, wow! I'm happy!

edit: I'm also using the K&N high flow panel filter inside the airbox. Might do a coupler and put in a foam filter similar to Alta.

 

I too have a modded SC pulley (15%), 380cc's, NGK blue wires & colder plugs. In addition; I preformed a similar CAI to my stock air box.. The colder 7s' seem to be ok for now. Until I can get it dialed in with a tune.
Definitely upgrade to a K&N cone filter. You can adapt one with a short piece of 2-1/2"(?) pvc from the intake inlet to the inside of the stock box and hose clamp it to the base of the cone filter. There is a max size cone filter that can fit inside the stock air filter box. I adapted the K&N High Flow air filter #RU-5090. I don't recall the exact spec/size...(2-3/4" diam x 5-1/2" L...???). I'm sure someone else can provide more insight/recommendations.
However, upgrading to a cone AF is the way to go and made a world of difference....(to me) .

 

Thanks you for the info, I was wondering what the exact sizing was! I'm definitely gonna play around with it now. I might switch over to aftermarket CAI with an EO# in the end though. It seems like all the same concept though, so I can't think of why a modded stock airbox couldn't compete in earnest. I wonder if I could 3D print some honeycomb type baffles to try to add character to the s/c note.

What differences did switching to a cone AF did you experience? I'm definitely curious.

 

Well you already (re)-discovered the whine has come back or is most audibly apparent.
More airflow = HP...? I'm certainly no seasoned mechanic. I'm guessing a small percentage. Maybe 2-4% (?).
My DIY CAI was simply a modest, well crafted, from polypropylene = 2-3/8" diam round piping into the air box, w/a flat 4"W x 2"H rectangular snorkel end extended directly under the outside air vent.
I didn't want to go nuts cutting apart my plastic heat shield. So I grafted (plastic welded) that shape/design from shop-vac attachments to exact tolerances (tight) to deter engine heat...Which is why I also went with the enclosed OEM air box.
The results of my design efforts gave my Mini a distinct high pitch "wind up toy" note. That intoxicating whine makes me want to twist the rpms at every chance...Probably why I think I gained more hp (?) .

I believe the inside portion of the stock air box inlet is about 2-3/8" ID. I dug up a scrap piece of 2-1/4" OD PVC that I used to adapt/glue into the inside diam of that inlet. So, IIRC; the short PVC "reducer" pipe I bought from Home Depot, had a 15° turn and measured 2-1/4" OD - 2-3/4" OD . This is the K&N filter I use. *Currently unavailable*, but those are the specs that worked for me.

According to K&N: Their cone filter achieve " 881 cfm vs 319 cfm with the stock flat/panel filer."... *(results may vary depending on part# & vehicle)*.

 

plugs do not alter the AFR, if the afr changes it's because your hitting knock tables and the spark curve is being retarded. Not good

run colder plugs when you increase boost, or you run the increased risk of knock

 

Thanks man. Yeah I realized that the question was misguided and confused with plug reading. Definitely keeping the cooler plugs in a working on getting it re-mapped for better AFRs.

 

I would think that you could run a JCW tune and get some performance benefit, but it's still an OEM tune so I feel like it would be california legal.

 

That was going to be my starting point. Got a cable coming in and gonna give a go at backing up the current stock rom and flashing the JCW tune. After researching some tutorials it seems like some thing doable for me. Just gotta get the actual JCW210 tune file from somewhere. I think the smog test looks for the checksum of the official rom, so I think I can backup the stock rom for smog testing.

As is right now, it works fine when ECU is using the lambda readings to adjust AFR while driving. The instant fuel trims seems to be negative, which I think means the ECU is cutting back fuel to adjust for the bigger injectors, right? It seems to just be too rich on idle in park, when it is running off a map I am assuming. Revs bounce between 740-780ish but kinda yo-yo a bit. On WOT I'm not sure if it's map or if it's dynamic like from the lambda readings, but it seems to throw the "too rich" bank 1 code when doing WOT to redline. At the WOT the fuel trims is 0. Does that mean it's right amount of fuel in WOT?

Any insight would be appreciated, as I'm still a noob and learning.

EDIT: The spark plugs looks pretty good when I pulled after a month of driving I think. The porcelain and strap looked the same when I put them in, but a noticeable sooty deposit around the end of the socket.