Time for a long overdue, post-roadtrip update to this thread. I've been putting this off until the work was complete and, frankly, because I'm lazy.
Back story:
In relative terms compared to the problems I had on the trip the Ringmeet and back last year, the Smart performed very well during the roadtrip. The lack of power became very apparent on the high-altitude mountain passes, where the air was too thin to allow the boost provide sufficient boost and the robotic clutch hated the steep hills we occasionally encountered, however these were minor issues and the car was great fun on the trip.
The major issue that only cropped up once during the main part of the roadtrip was good old limp mode.
Two days before I was due to leave for the roadtrip I needed to drive the Roadster to work, around 17 miles each way. I wouldn't expect this to be a problem but around 12 miles into the morning journey the thing dropped into limp mode for no apparent reason. The rest of the drive was on slow roads and in traffic so I didn't do anything, just parked up and left it for the day. On the way home I stopped and reset it before I got to open roads where I would need more power, I also checked over what I could and found no problems.
That Sunday was S2Smarts' open day and the first day of my roadtrip. I had no issues with the car getting down to Watford but got them to run a diagnostics check, the only thing that showed up was the MAP sensor. I would've replaced it there and then but they didn't have one in stock. I got my spacers fitted and enjoyed the BBQ, at the end of the day I set off on my merry way to Kent.
Fast forward through the roadtrip, limp mode happened once on a day that I can't remember and I began disconnecting the battery every night to reset the computer. This worked fine until day 7, when the thing just kept going limp on me. The next morning
@D-Fence spoke to Mercedes and we got a new sensor from the stealership in Freiburg, however this didn't fix the problem and it went into limp mode several times on the way up to the 'Ring.
At Ringmeet I tried to investigate the issue by removing the rear end, however I didn't find anything. It turns out that there was a problem to find but I wasn't digging deep enough. I attempted a lap of the 'Ring and it went limp on me again, meaning the lap was slower than my Discovery but still faster than Dave's Kangoo at .
At some point, I don't really remember when, I noticed that the hose from the intercooler to the intake manifold wasn't seated correctly and the hose was in very bad shape. Some previous owner or mechanic had replaced the hose at some point and it wasn't the right size, added to that it looked like that had cut the hose by biting through it with their teeth. Ultimately, I think this was a red herring and I actually caused the problem rather than resolving it when I tried to tighten the hose clamps, I then had more problems with the hose coming off and leaking boost. Even with assistance from
@nicjasno, the hose wouldn't stay put.
I managed to get home with the hose in this state, slightly lacking power due to it's sorry state but without limp mode. It made some really funny squeaking noises at times, I tried to record them with my phone but forgot that it was paired to the bluetooth module in the dash that has no microphone...
Fixing it:
Anyway, when I got home I ordered the parts to sort the issues. Two silicone intercooler hoses, I only needed the one that replaced the plastic hose and rubber coupler going from the intercooler to the manifold but they came as a pair, a silicone TIK intake pipe and associated fixings. I also had a replacement boost control (cycle) valve as it's cheap and it's buried deep in the engine so I may as well replace it while I'm in there.
Note the length of the little dingus end pipes coming from the long intake hose, they will become relevant.
The back end of the Smart was removed again, along with the crash support this time so I could dig a little deeper. I disconnected the old cycle valve and found that one of the small rubber pipes was split, the same one that had caused me problems last year!
When this pipe was leaking last year it was obvious that something was wrong due to overboosting, however there was no telltale at all this time around, other than limp mode. I considered the option of buying the genuine parts from Smart but it was suggested on a Smart forum that I would benefit from moving the cycle valve to a more accessible place so I could replace it should it ever go wrong again. I ordered some high-temp silicone pipe from an eBay seller.
The next weekend rolls around and the new pipe is here, so I get stuck in with removing the old cycle valve and pipes, making these highly detailed images to remind me which pipe goes to which side of the valve.
The two intercooler hoses were then fitted, a bit of a struggle due to how tight they are and a lack of space in the engine bay, but at least they won't be popping off any time soon.
The cycle valve can just be seen at the top in the second photo, it was recommended that I zip-tie it to the intake hose. New lengths of vacuum pipe were then threaded down and connected up.
I attempted to fit the intake hose, but found that the dingus end pipes were too long and the breather pipes from the engine wouldn't fit properly. I considered complaining about this and sending the hose back, but after digging through old Smart forum posts I found someone who had this issue back in 2011 and found that these dingus ends sometimes need to be cut down. So that's exactly what I did. I had to cut off the original crimp clamps so got some genuine Jubilee clamps to replace them.
The engine breather pipes fitted much better and I could finally reassemble the whole thing, about three weeks after I started. This is now the view of the engine bay:
I actually didn't want blue hoses at first but it's all the seller I used had in stock, if I wanted black I would need to buy them elsewhere at a considerably higher price. The smaller pipe was available in black but I felt that blue is easier to see in the dark engine bay and matches the bigger hoses.
I went for a test drive today, listen to how it sounds now.
I also have a new sticker on the Smart!