Loss of power - Supercharger Bypass Valve Issue

[freefall_junkie]

So, my first serious issue with the car after 18 months. Cruising at a moderate pace yesterday I came to overtake, put my foot down and the car felt completely lacking in power and stayed that way for the rest of the drive. In the performance meter in the central screen it is showing zero boost pressure at any throttle opening and I noticed in the rear view mirror that the supercharger bypass valve actuator was not moving at all. On closer inspection the actuator seems to be stuck in the fully open position which would account for the lack of boost. There are no warning lights on the dash. It looks like the actuator is a simple mechanical vacuum device and doesn't have an electronic controller. I've never heard of anyone having this issue before. Anyone got any ideas what the cause might be? The vacuum hose to the actuator looks to be connected correctly, so I'm wondering if the butterfly valve inside the supercharger has become stuck.

Lotus Glasgow can't take the car in for over 3 weeks and in the meantime I appear to have the only normally aspirated Emira in the country

 

[scc.131.fe]

Sorry to hear that, hope it's simple. On a side note, thanks for observing that "Boost" read zero. I was wondering if that value was sensed/actual or synthesized from a table. Now we know!

You know, with everyone obsessed with rarity, maybe "1 of 1 N/A Emira" would bring a premium on BAT!

 

[Kimmax]

I was wondering if that value was sensed/actual or synthesized from a table.

I wondered the same but there is a boost pressure sensor present in the service notes, so we can be pretty certain it’s real. Also readable via OBD

 

[freefall_junkie]

It has been diagnosed as a faulty bypass valve actuator, seemingly a rare problem. New part ordered, hopefully will arrive within a week, although I know from past experience that Lotus parts delivery timescales should be taken with a large pinch of salt. The car also had the latest software updates, the HVAC water shield fitted, and I was given a demo Emira for the day. Excellent service from the guys at Lotus Glasgow.

 

[scc.131.fe]

@freefall_junkie
car fixed? any interesting details?

 

[freefall_junkie]

As it happens I have just picked up my car from Lotus Glasgow this morning. As expected the bypass valve actuator has been replaced and on the 40 mile drive home the car was running fine again. It’s very nice to have all 400 horses back

This seems to quite a rare problem, certainly the first time Lotus Glasgow have seen it. Presumably the cause was just a faulty part from Eaton rather than anything Lotus have done during manufacturing.

 

[Lotus 110]

Same but different. Emira has 3800 miles and while driving not seeing bypass actuator rod moving. Car has power and shows boost upon acceleration, but rod does not move. I have tried to move the rod manually but does not budge. Hoses and connections seem OK. I have watched the supercharger assembly video, and I should not have power, but I do. I called dealer and they agree. It's under warranty but the hassle of 90-mile trip to dealer. Anyone else have similar problem?

 

[freefall_junkie]

Same but different. Emira has 3800 miles and while driving not seeing bypass actuator rod moving. Car has power and shows boost upon acceleration, but rod does not move. I have tried to move the rod manually but does not budge. Hoses and connections seem OK. I have watched the supercharger assembly video, and I should not have power, but I do. I called dealer and they agree. It's under warranty but the hassle of 90-mile trip to dealer. Anyone else have similar problem?

Sounds like the valve is stuck in the closed position, which means full boost all the time, potentially damaging for the engine. The valve is normally closed when the engine is off, then fully open at idle which means there is no boost from the supercharger (i.e. it is fully bypassed). As you put your foot down, the vacuum from the inlet manifold progressively closes the valve increasing the boost pressure. You would only have no power if, like mine, it was stuck in the fully open position. I would drive to the dealer on a light throttle and get it checked. As I understand it the valve actuator is not a serviceable part so replacement is the only option. At least it is a fairly quick job.