BBR Turbo Issue

So I had my car in with BBR to get the stage 1 turbo conversion done but I am not sure its running right. Can any of you fellow BBR Turbo owners let me know if you have noticed any differences with how the car runs under 3k RPM?


Since the conversion the car randomly bogs down when pulling away with normal revs, also when accelerating at normal driving speeds its no longer smooth - I would call it lumpy.


I have taken it back to BBR but they are advising this is due to the larger injectors?

To a degree yes mine is the same… like a little splutter at times, I wouldn’t say its bad though and nothing that’s not to be expected from a highly modified engine…


I used to get bogging aswell BUT have had the BOV removed and she is smooth as silk now

The thing is this isn’t a splutter at times - its every time I accelerate without gunning it. I thought the BBR system recirculated and didn’t use a BOV?


Could you tell me more about how you removed it? Just a hose removal? Is it safe for the turbo?

apologies but yes when I say BOV I mean the re-circ valve…


bogging on light acceleration is not normal, epically if its happening all the time…


BBR removed the valve by blanking the vac line to it when the engine is off, this basically stops it opening and resolved ALL the idle drop issues I was having, it runs great now


its not needed as the car runs such low boost pressure…

The BOV is an interesting safety add-on, some think essential.  Last year when looking for a replacement daily and trying to decide between turbo-ed smaller engine or bigger non-turbo, I’d already heard so many stories justifying the pros and cons of turbos that I needed to do some research, and the following was one of the more useful articles I read.  Make your own mind up about what it says.

Very interesting about the BOV removal. Have you noticed any negative effects? Do you think this could have a detrimental effect on the longevity of the turbo?

I fitted the stage 1 kit a few months ago, the engine is smooth all the way through the rev range (even with 105k miles on the clock).

I did have an issue when my fuel injection plug came loose which meant that I was only on 3 cylinders. This meant that at low RPM it was very lumpy… but was smooth at above 3000rpm, I imagine that you would notice if you were on three cylinders, the engine warning light is a giveaway but it could be many other things, did you put in new spark plugs and gapped correctly?.  Was it always lumpy straight after the install? Did Neil put it back on the dyno when you went back?


Dont think so but it’s not firing on 3 for sure. It’s not lumpy as such - when maintaining the same speed in a high gear (5th at 2k rpm) it’s like an uneven idle causing the car to surge slightly. When it bogs down/baulks it’s very noticeable - changing into 1st while rolling and applying throttle slightly is when it happens most frequently. It’s like stepping on the brakes (this is after the clutch is engaged)

 New spark plugs were installed by them (provided by me) and I presume they re-gapped them to 0.8.

Looking into it I am pretty sure it’s the recirculation valve causing the maf readings to be out and I think bypassing this would resolve the issue. Maybe some mk3s are are a bit more sensitive than others. As it’s only low pressure I don’t think there will be much issue but then again I’m not well versed in turbocharged builds.


Correct, I believe the Valve can blow a little air back past the MAF causing miss readings and the bogging you are experiencing, this does only seem to happen on a handful of cars… Its was BBR themselves that removed mine and assured me it wasn’t required and tbf I’ve done a fair few happy miles now… I would suggest clamping the vac line to the valve with the engine off, start her up and go for a drive and see how she is

I’m not going to do anything myself as its going into BBR tomorrow for a week so they can take a look. I have suggested about the BOV delete. Lets see what the outcome is Smile

I’ve only done about 20 miles so far since DIY fitting a stage 2.  Mine pulls smoothly with no lumpiness.  The one thing I have noticed though is that there is more tendency for the engine to bog down when pulling away  than there was before - need to give it a bit more throttle and then it seems fine.


Did they manage to resolve your problem?

Not really. Neil blocked off the recirculation pipe and it did drive a lot better but it still hesitates on acceleration and bogs down randomly.


I am going through replacing everything like coils, maf, sparkplugs and cam position sensor to rule out any of this before going back again.


So far I have done the MAF and coils. It does appear there was an issue with one of the coils as it’s not undrivable in traffic now but does still bog down. I’m tempted to think there is an issue with one of the spark plugs and changing the coils may have made it better…


It’s only cheap to change out these parts compared to the price I have paid for the turbo and I have them as spares for the future. Just hoping it’s a dodgy/ungapped plug as at the moment I have paid a hefty sum of money for a car that now isn’t enjoyable to drive.

Scrap that - its still the same. I am going to have to take it back to Neil at BBR so they can give it a proper test drive.

I’m sure he will sort it out…he knows his onions…

Just think when you do finally get it working right and take it on a trackday your will forget all the annoyance, stick with it.

When you say it randomly bogs down is there any trend that you can think of? If the problem is not reproducable when you take it back to Neil you could ask to see if he will lend you one of the ecutek loggers to that you can record what is going on when you are out and about, exporting the data into excel you can do a lot of analysis (I do love a bit of excel). I presume that the car drove well when you took it in? 

To be honest I think Neil has only really taken it out down fast roads where it’s not too noticeable, it’s normal town driving and traffic when it’s terrible to drive. The idle seems to be getting worse on it now too with it hunting a lot more.

Once he has a decent test drive he will be able to see the issue. It just drives like an absolute dog at anything under 2.5k revs, then when you go to accelerate sometimes it just randomly cuts the power.

It did a new one today where I was traveling along at 30 (variable speed cameras) and it was surging as if the idle was hunting but while driving but very noticeable, people probably thought I was trying to wind up the car in front.

The car was an absolute joy to drive before taking it in with zero hesitation issues. I hope it does get sorted or I’m not really sure what to do…

Definitely something not right there.  I’ve now done about 400 miles and can only say what a blast the car is to drive now.  Got me grinning like a school kid .  As said, once sorted you’ll soon forget the current issues - it’s just so quick and tractable.  I let one of my oetrolhead friends drive mine last week - he’s got a Maserati GranSport and is a fellow Caterham owner (albeit his last one was 270 bhp).  He was seriously impressed with how “factory” it felt to drive, and also complemented the BBR suspension on its combination of composure and ride comfort.

yes it was a large chunk of money - in my case more than the car is worth as mine’s a 59 reg convertible - but I don’t regret it for one second!


Hi all, 

Following this thread with interest, but could someone clarify the actual valve or vacuum line that you are referring too?

Is it the Purge Solenoid Valve and its associated vac lines?

Low rev light throttle drivability is an issue for me, changing my Exhaust Gas Recirculation valve improved things greatly, but I still suffer from a slight surging on a constant light throttle at low revs, and inconsistent idle drop.

I would really appreciate any clarification.