Turbo guys, BOV or no BOV?
Discussion
Heres one for debate.
Whether a BOV is necessary or can be a little detrimental to overall performance.
I will be at the pod on 19th July and will do 2 or 3 runs with the car as is. Around 10-12 psi, about 460 bhp with the BOV fitted.
Then the BOV will be removed and another 2 or 3 runs for comparison.
What do we think the results will be?
Pleas dont say a damaged turbo as i am certain at these levels of boost any back pressure will be very safe.
Whether a BOV is necessary or can be a little detrimental to overall performance.
I will be at the pod on 19th July and will do 2 or 3 runs with the car as is. Around 10-12 psi, about 460 bhp with the BOV fitted.
Then the BOV will be removed and another 2 or 3 runs for comparison.
What do we think the results will be?
Pleas dont say a damaged turbo as i am certain at these levels of boost any back pressure will be very safe.
Not only do you not have very high absolute boost levels, but you also have a long length of pipework and intercooler volume between compressor and turbine .. so you won't damage your turbine with any wave shocks by not having a bov , also you're not dumping that precious boost either ..
I understand the reasons why a blow off valve is fitted (reduces shock wave at the compressor, prevents the compressor wheel slowing as much between gears ..) but I remain to be convinced that either of these effects is of any consequence to the low boost / large volume systems the tvrs run.
So i will stick my neck out and say you won't notice a blind bit of difference between the runs ..
but if by chance you do see a difference then that is valuable info !
I understand the reasons why a blow off valve is fitted (reduces shock wave at the compressor, prevents the compressor wheel slowing as much between gears ..) but I remain to be convinced that either of these effects is of any consequence to the low boost / large volume systems the tvrs run.
So i will stick my neck out and say you won't notice a blind bit of difference between the runs ..
but if by chance you do see a difference then that is valuable info !
I am also looking to fit a clutch switch to let the MS know and to allow full throttle boost build for launch and as a limiter on the gearshifts.
I do try to minimise throttle lift and barely stab at the clutch on gearchanges as fast as i can but data logging shows i am off the thottle for upto 0.4 seconds. That adds up to 1.2 seconds off full power through 3 gearchanges on a typical run. I want to try flat shifting or bang shifiting as the call it in the good old US and A.
If i am 'accelerating' fully for that additioanl 1.2 seconds theory says i will gain a few mph and maybe save a few tenths on the ET.
Watch this space
I do try to minimise throttle lift and barely stab at the clutch on gearchanges as fast as i can but data logging shows i am off the thottle for upto 0.4 seconds. That adds up to 1.2 seconds off full power through 3 gearchanges on a typical run. I want to try flat shifting or bang shifiting as the call it in the good old US and A.
If i am 'accelerating' fully for that additioanl 1.2 seconds theory says i will gain a few mph and maybe save a few tenths on the ET.
Watch this space
I can tell you what to watch out for Derek.
If you're compressor makes significant boost when you lift off you'll have pressure stalling the compressor. You may hear a sonic type boom without the BOV. This has happened to me but after a short while I fitted a BOV. There wasn't any damage to the turbo but I didn't want to risk it.
If you don't hear a boom then you're probably not making any significant pressure.
My engine had very short pipes from the turbo's the the plenum as the turbo's were mounted at the side of the block. It wasn't a TVR.
If you're compressor makes significant boost when you lift off you'll have pressure stalling the compressor. You may hear a sonic type boom without the BOV. This has happened to me but after a short while I fitted a BOV. There wasn't any damage to the turbo but I didn't want to risk it.
If you don't hear a boom then you're probably not making any significant pressure.
My engine had very short pipes from the turbo's the the plenum as the turbo's were mounted at the side of the block. It wasn't a TVR.
DangerousDerek said:
I am also looking to fit a clutch switch to let the MS know and to allow full throttle boost build for launch and as a limiter on the gearshifts.
If you fit a clutch shift as a limiter then you can keep your foot buried on the throttle, thereby completely eliminating the need for a bov anyway under those conditions as the compressor never sees a closed butterfly during gearchanges
but feel the benefits will be less so with your well groomed pedal work (no I'm not joking) I have it all set-up but have yet to commit to the clutch pedal switch style (I do want it working however) 
Jools made a good point regarding the BOV 
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