Hello all. My '06 MCS checkmate has the usual bolt ons, cat back exhaust, intake, IC diverter, screamin demon ignition, kingsborne wires, 450cc injectors, 17% pulley kit from WMW, etc Had car tuned last spring by Jan/RMW at Helix and it ran great. I have had overboost issues (car seems to be spiking at 18psi) and have changed every MAF/MAP sensor, every hose, line, etc. everything is right. When I get near redline or under hard acceleration at (ahem) speeds around 80+mph my DSC light and CEL lights come on. I get codes like absolute pressure intake manifold - barometric pressure + input high (0108) and the following fault codes: 5e14 - can connection to DME/DDE (DSC lamp on until ignition reset) 5DC3 and 5DB3 - wheel speed sensor left and right 5E5C - initialize run flat indicator 5E19 - CAN data error from DME/DDE (DSC lamp on as long as error is present Sooooooo....My car seems to be slightly over-boosting to 18psi. I spoke to Jan/RMW and he suggested I buy a voltage reducer from split second and hook it up. I'm good with a lot of things but wiring isn't my thing...Bought it from where he suggested and he said the instructions were in it to hook up. However the instructions are generic and not MINI - specific. Brought it to my friends shop here in LI (big BMW tuning shop) and when looking at the instructions (per Jan) noticed that the Voltage reducer is adjustable on the low hand high end. Jan told me to order this, so I called him, put him on the phone with my friend who owns this shop. Jan said that the high side should be set to less than 5, so maybe a 4.5 after hooking up a volt meter. When asked about what to set the low side too he didn't know and told my friend to just go out and mess around with it. Not big on "playing" with boost levels. Called Helix and they didn't know either. Does anyone know what to set the low side on this voltage reducer to? Can't find an answer and everything is wired and ready to go but don't feel like blowing my motor trying to figure out where to set the low side of this reducer. Any help is appreciated! Thanks!

 

I've been running 18lbs of boost since mods done in 2008.....

Not a problem for the R53.

Is the BPV dumping boost properly ?

Have you changed the PCV valve in the valve cover in last 40K miles ?

 

The BPV isn't going to regulate boost, once there is positive pressure in the intake tract the BPV is fully closed. It is in place for fuel economy reasons, as you would be under near constant boost without it.

18 PSI doesn't sound out of the ball park with your mods, especially since you don't have a BVH, sounds like the tune needs some parameter adjustments in your boost measurement. Or this could only be an issue for you during the colder months as the air is more dense.

 

Check the cat....a melted or plugged cat can result in higher than normal boost readings...
And the boost you are running..18 psi is pretty normal on a r53....

 

The PCV is perfectly fine. Checked it and it was replaced about 15k ago. From what I can tell the BPV is working fine but what do you mean "dumping boost properly"? If you're referring to the sweep from boost to vaccum when letting off throttle then all appears fine. The tune was done by Jan/RMW - I called and spoke to him yesterday as we put in the Split Second Voltage Reducer. There are High and Low settings. Jan reccomended keeping the high at around 4.5 (5.0 is normal) and didn't know (at the time nor have I heard since though I did just leave him a message yesterday afternoon EST) where to set the low off the top of his head. We set it at 0.1 since it's really the high pressure #'s I'm concerned about. As for adjusting the tune, if that's what it is then I'll have to wait until Jan comes back around here in the spring and just deal with it I guess. I've done everything suggested - changing all the sensors, and every line, fitting, clip, etc. has been gone through and either checked or replaced. This is not a cold weather issue as this was going on in the heat of the summner too. Getting a bit frustrated replacing or buying parts only to have the problem repeat itself. BPV seems fine. Boost builds normally and holds good vac.

To check the cat I need to pull the header off...and when I had this car tuned that's what Jan thought it might be so we pulled my headers off (stock) and replaced them with another one that Helix had with a cat that was fine so I don't think that's the case. Either way, if I have higher than normal boost settings this Split Second Voltage Reducer Jan had me order should be able to "trick" the signal so it doesn't throw the codes it's been spitting...and it still is even after I installed the Voltage Reducer.... :(

Ugh.... Anyone know how to set the Split Second up properly so I don't get codes or any other ideas? Thanks all!

 

I'm also leaning toward a plugged CAT, 18psi is a little high for a 17% pulley.
Normally a 0108 would be either a bad intake MAP sensor, vacuum leak or plugged exhaust.
Also, temporarily swap back to your OEM coil to make sure your not actually having spark issues at high demand, sounds weird but at this point I'd try and look all over for issues, if it hadn't been going on for very long I'd also look into a slightly slipping belt because of when it's happening.