Which bov for a TTE?

[andywood]

OK, so very divided subject it seems on BOVs, but I am currently planning on going down the atmos BOV route. Probably more for the boyish fun factor than anything else  s:wink: :wink: s:wink:  

Anyone recommend a good atmos BOV or a good place to source one from??
Seems like loads of diff valves and kits out there, many for evo's and scooby's, assuming only needs to be simple.

Any strong opinions on what would be foresaken by getting an atmos BOV?? (this will be my first turbo/bov experience!!), or any real key factors to consider to stay BOV-less or go for recirc??

Cheers

Andy

[dj2k21]

I think my only point with a BOV would be that personally I do prefer not having one, I would say I am running pretty big power in comparison with some others, at over 350bhp currently, I dont have a BOV, I much prefer the waste gate chatter instead  s:) s:)  puts huge smiles on faces and all that jazz, the only time a turbo is hurt really is if you decide to use anti-lag, your pretty much looking at re-building the turbo 10 times per year lol.
I did have a skyline BOV at one point and found that the turbo took slightly longer to spool between gears as it was dumping most if not all the pressure out and made it slughtly less "streetable" . I dont think I have ever come accross any evidence to show that it benefits a turbo in anyway really, I dont think it can hurt them thats for sure, but personally wastegate chatter and straight cut gears in your gearbox are the best sounds ou can get  s:) s:)

just my 2p worth though

[andywood]

All good comments, I guess on the mr2 though the smaller turbo size means it would probably have negligible change in spool-up with or without the BOV.

I don't want to spend more than i need to here, so am stuck in the.........
....... extra cost vs not wanting to sound like a chav vs fun/grin factor of having a BOV on what will be an extremely fun car vs not wanting to loose the other fun turbo noises (chatter, wastegate etc..)

May just get that special coin out to make my mind up!!

Andy.

[muffdan]

I'm currently running a BOV (to atmosphere) on the MR2 and no BOV on the Elise, which has a 1zz with the same turbo as used by the TTE kit fitted. Although I do love the chitter on the Lotus, I love the pshhh from the MR2 much more! I can confirm that 35psi of pressure sounds epic when released through a BOV with a whistle on the end! I find with my particular BOV, you still get a little chitter under certain conditions.

Performance wise, I'm not certain which way it goes and I'm sure it differs depending on the engine/turbo/BOV setup, but I think for most cases you're better with a BOV. Here's my logic:

On gear change, with a BOV, the pressure is released without stalling the turbo which remains spinning at a hell of a rate. When you're back on it, its able to generate boost immediately. Without a BOV, the unneeded pressure is forced back through the compressor which is no longer being driven by exhaust gasses and so this stalls the turbo (which causes the chitter). When you're back on it, the turbo has to spin up from a much slower speed which takes longer. Both cases, you're loosing boost, either through the BOV or back through the turbo. What's different is how quickly boost is lost, and the speed of the turbo after the boost is lost. The BOV will bleed the boost faster, so depending how long it takes you to change gear, you will probably have less residual boost pressure when you're back on the throttle with a BOV, but more speed in your turbo and able to generate more boost faster. This will perhaps make a non-BOV system seem better on gear change but maybe not in reality. Its definitely swings and roundabouts and sensitive to the particular setup. I find if you're absolutely nailing it and you're snapping your gear changes as fast as you can, you barely hear the BOV releasing and it certainly doesn't bleed much though.

The big gain I've noticed with a BOV is on part throttle. If I'm going through a bend on part throttle to keep the rear under control, I can hear that the BOV is continuously open. This is good for two reasons. The turbo is spooling much faster than it would if I didn't have a BOV. Once I'm clear of the bend and open it up, the BOV instantly closes and I have instant boost with no lag. This makes a massive difference to throttle response. The second reason is in torque delivery. If there was no BOV that air that's escaping would be partly forced through the throttle body into the engine, which makes more power and spins the turbo faster and makes more boost which makes more power until the waste gate kicks in. People commonly state that turbo lag is the biggest problem with turbo cars and is definitely true with massive turbos that don't kick in until 5k, but IMHO it is the boost threshold that is a bigger problem for the setups we run on the MR2s. You have naturally aspirated torque up until the boost threshold and then this positive feedback cycle begins and within 300 rpms you've doubled your torque output. It is much more difficult to feed that torque in progressively. A BOV definitely helps with this by bleeding excess pressure to atmosphere, rather than feeding it into the engine. It gives the throttle pedal more control over how much air enters the engine and therefore more control over the torque delivery. Very useful for track and twisty road use.

[andywood]

Wow Jason, really good write-up thanks very much.

Would be interested to know which BOV you are running and also best places to source one?

I am guessing that you are probably running a lot more boost than i plan to, but does this really need to have an influence on opening pressure of the BOV? (Boost pressure is so much lower anyway than closed throttle increase) I assume that something relatively generic is all that is needed as the mechanical pressure release is fixed at a suitably generic level??

Cheers

Andy

[muffdan]

I believe I have a SARD R2D2, which I picked up second hand from Stu (kanujunkie). I say I believe, because I don't actually know! Mine looks the same as the R2D2 though!  s:) s:)  Google shows plenty of places selling them.

For simplicity, don't think of a BOV having a release pressure; they'll work in any setup regardless of boost pressures run. What they essentially do is monitor two air pressures. One pre-throttle body and one post-throttle body. If they see that the pressure pre-throttle body is higher, they open and release pressure until they're the same.

[andywood]

Cheapest I can find for the r2d2 is here:

 m http://www.nengun.com/sard/r2d2-twin-drive-type-2 m

...but they only seem to come in complete vehicle kits (£130ish) - guess that the valve is probably common so would just have to bin the other bits that are vehicle specific
Ebay not really showing anything significantly cheaper.

Any ideas if this is a good price or is there anything as good out there for less, or is this really worth the money?

Andy.

[andywood]

Probably going to give up on the quest for a SARD R2D2 as not readily available and only long leadtime routes to get hold of one.

As Forge are only 20miles up the road from me, they are now the main contenders:
 m http://www.forgemotorsport.co.uk/conten ... t=FMDV004A m
 m http://www.forgemotorsport.co.uk/conten ... ct=FMDV004 m

Anyone have any knowledge/experience/rumour of Forge BOVs??

Cheers

Andy

[andywood]

....also, has anyone ever encountered any running problems when using an atmos bov? i.e. it will be losing metered air (post-MAF) to atmos and thus cause rich-running. I am not sure if this has a potential to flag a MIL lamp or not?

Can't see any reason why momentary running rich will be any problem for the actual engine but am thinking that the diagnostics might notice something is not quite right (although they are probably more focused on monitoring leaks in than leaks out?

Andy.

[Ilogik]

My biggest piece of advice for the TTE kit, don't fuck with it, it does not like aftermarket induction/works best with stock airbox. The original mappers couldn't get it right after 6 tries so maybe I had just lost hope   s:lol: :lol: s:lol:  

The guy who bought my kit also tried running with an aftermarket box on stock piggy back ecu on the tte with issues, but worked great without it. Give james355 a pm.

[Anonymous]

You cannot run a VTA BOV if it's post-MAF, as you correctly point out it'll mess with your fuelling and that's jot a good idea.

[andywood]

OK, so been thinking about this more and need to brain-dump a few thoughts........

Lots of people seem to be running turbo set-ups with BOVs – some are recirc, but some are definitely VTA and I have not yet heard of any problems or concerns with engine running or flagging MILs etc.... Would be interesting to know how many of these situations have the atmos BOV post-MAF, definitely some will!

Fuelling in theory would be upset a little if metered air is vented to atmos, but this will only be occurring at closing/closed throttle conditions when I assume the fuelling will already be out of closed loop control and being cut based on throttle demand (or lack of).

During steady/normal driving when the throttle is partially open then the BOV should be shut and the engine will be (generally speaking) trimming and adjusting the fuelling in closed loop control.

During increasing demand or WOT then BOV will also be closed and fuelling will be subject to open-loop control based on demand rather than closed-loop trimming.

The issue here is that during any given drive-cycle some metered air will never be consumed by the engine, but I am not sure if this really matters considering the ever changing state of the fuelling and the need/priority for the engine management to only be considering the instantaneous demands/risks. If this does not lead therefore to any engine damage or MIL flagging, maybe there is a risk that the optimum fuel trimming and adjustments over time are never quite optimized due to the frequent loss of metered air twisting the calculations – but in reality what percentage of engine consumed air would be vented? Negligible I reckon.

Don't know if all the above is spot-on or even slightly correct, but I do struggle to see the risks the more I think about it!

Andy.

[SteveJ]

VTA post MAF = Guaranteed stall everytime the car drops to idle.

Seemples!

[andywood]

How's that?? BOV will be shut at idle.....

..........or do you mean when coming down to idle from higher demand?

[andywood]

VTA post MAF = Guaranteed stall everytime the car drops to idle.

Seemples!

...and i guess that also means there is no-one out there running a turbo set-up with an atmos BOV post-MAF then?? Unless they just accept the idle-stalling as a slight side-effect   s:wink: :wink: s:wink:

EDIT - I am assuming that a MAP sensor as part of the piggy-back ECU functionality would also resolve any risk of these problems (planned for the system to go on my car).

[SteveJ]

Have you done your homework as to how a BOV works?

They open in response to the vacuum in the manifold rather than the excess pressure in the feed pipework (they have a reference feed from the manifold post-TB)

[andywood]

Have you done your homework as to how a BOV works?

They open in response to the vacuum in the manifold rather than the excess pressure in the feed pipework (they have a reference feed from the manifold post-TB)

Yeah, i know how the BOV works, i think i am just struggling to get my point/question out in the right way   s:wink: :wink: s:wink:

[loadswine]

I would really advise against doing this with the TTE setup. The attraction of the kit is the way it works fuss free most of the time. I doubt it will if you modify it, just as previous owners have reported when they did.
At the end of the day its your choice though.  s:wink: :wink: s:wink:

[andywood]

Not going to be running the TTET kit, but something very similar (T25 with boost control for up to 235-ish).

If i decide to bin the atmos-BOV idea, as I can accept there are some risks (although proof may be in the pudding after mapping), then I will still struggle to decide between no-BOV or recirc-BOV as I can see some advantages in both.

Running slightly higher boost than the standard TTET set-up I am guessing that the recirc-BOV route might be the way to go, although i will lose some of the turbo-chatter and will probably still not be in the boost pressure territory that really requires a recirc BOV to protect the turbo.
I will leave the turbo-veterans to debate whether no-BOV or recirc-BOV is better for spool-up and gear change, but I am just feeling it is a safer route to go with BOV (whether atmos or recirc)............

Maybe I am just losing the plot and should stop flogging this horse   s:wink: :wink: s:wink:  

Andy

[stargazer30]

Guys The SP turbo Kit I have is based on the TTE turbo kit.  I'm pretty sure it has a BOV which is post MAF (as the MAF is right next to the cone filter with a short pipe in between and thats it).  I'm also pretty sure its a VTA style one, as it makes the tell tale Whooosh when you lift off.   My car runs it fine, it doesn't overfuel or stall on idle.

Would be interesting to get Matts take on this thread as either you guys are wrong or my car has some clever mapping   s:D s:D

[s12vea]

Enjoy the turbo chatter im sure it will be more than enough for you  s;) s;)