Two pistons have carbon build up, two pistons don't
 

https://www.northamericanmotoring.co...ium/dyno13.jpgAfter getting my car dyno tuned from Jan I'm trying to find the reason why my numbers are low. I did get very good gains but my baseline was very low. Compared to other tunes that same time frame, I can see that my top gains are 14 hp lower than everyone else. After checking for leaks, etc I removed my plugs and saw that the top of the pistons in number 1 and 4 cylinder are shiny and 2 and 3 have carbon(black) build up. The plugs all look normal for all cylinders. I did replace the injectors with JCW about a month ago and the intake and valves are clean. I have 15% pulley, CAI, header with cat, Invidia C/B, JCW injectors. I'm running about 14-15 psi boost. Has anyone seen this before and why would 1 and 4 cylinders have no carbon build up? Have never had a CEL. Oh the injectors were on the car first and can contribute to the low A/F. But still I think my numbers should be higher.

What did a compression and leak down yeild? Whats your supercharger look like? Coating on the blades gone?

First thing that comes to mind is check the terminals on the coil pack for carbon buildup. They may need to be cleaned. Use something like STP carb spray cleaner or a brass brush to shine them up. Check the pack for good spark (may require shop diagnostics). If you replace it, keep the OEM. Aftermarket replacements are no good. Jan can confirm this.

Check plug wires for connectivity and/or cracking. Stock replacements are just fine. Don't buy the expensive aftermarket ones. Jan can confirm this, too.

compression readings
 

I took a compression reading "dry" today.
#1-166 psi
#2- 168psi
#3- 168psi
#4- 171psi

So my comp readings are good. I also looked in the cylinder and found after the seafoam treatment all the pistons look fairly clean now. Centers of each piston are dark with the outer looking shiny. Sooooooo, I think my original injectors were leaking or dirty and that caused my carbon build up on 2 and 3. The Seafoam did work and cleaned the carbon on # 2 and 3. I also swapped the Screamin Demon coil back to the stock with stock wires so we will see. Plugs will be thrown in a little later. I think I'm trying to find problems to justify the purchase of more performance products, i.e head, cam, meth injection, stroker kit, lightened flywheel, limited slip, etc. :thumbsup: By the way looking into the head and seeing all the casting, I can see why my hp drops off at top but a new cam should take care of that!

The old injectors being the problem is certainly a possibility. And I can understand chasing a problem that seems to never get fixed.

Having the stock coil and wires handy is good. I have read some posts that mention voltage issues with the aftermarket ones (more so with the Screamin' Demon than the MSD). Take your MINI back to the dyno when you get a chance to see if this helped.

As for plugs, get the NGK BKR7s. They work great with the pulley, CAI, exhaust, and tune. And they can go much farther than that when you get the head and cam. :thumbsup:

One thing a meth kit does help with is cleaning the combustion chambers and piston heads. It's a feasible option down the road as well. Or stick with the Seafoam.

I always thought the comp on the S is 150psi.

It's anywhere from 131-196 (min-max). The key is consistency.

it means 2 out of 4 pistons are dirty.. get it cleaned...then they all be shiny