Running without a BOV

[bradc]

http://www.lancerregister.com/showth...3&pagenumber=1

Seems as if a couple of people are running without them on EVO's and are reporting less lag, and no-one seems to have blown up a turbo yet. Is this really worth doing on our cars with less lag and less boost that on the EVO's?

[Wodjno]

http://www.lancerregister.com/showth...3&pagenumber=1

Seems as if a couple of people are running without them on EVO's and are reporting less lag, and no-one seems to have blown up a turbo yet. Is this really worth doing on our cars with less lag and less boost that on the EVO's?

Must admit, i heard plenty of cars running with no bovs at Coombe last weekend.
Nissan 200sx's and Evo's.. Didn't seem to be affecting there performance

And all the Group B rallys used to run with no dump valve..

What do the current WRC cars run with ?? None or recirc ?

But then there is the bit about it coming back onto boost quicker after gear changes ! Is this only cos the compressor wheel is stalling so you are feeling the surge yo get back on the boost !

[valmes]

Must admit, i heard plenty of cars running with no bovs at Coombe last weekend.
Nissan 200sx's and Evo's.. Didn't seem to be affecting there performance

And all the Group B rallys used to run with no dump valve..

What do the current WRC cars run with ?? None or recirc ?

But then there is the bit about it coming back onto boost quicker after gear changes ! Is this only cos the compressor wheel is stalling so you are feeling the surge yo get back on the boost !

Few points:

- Aftermarket BOVs are performance devices only compared to stock leaky ones...
- Of course you can run down the strip without a bov if you have some form of "flat shifting" (in this case you don't close the throttle on shifts cause you don't have to lift your right foot off the accelerator... just retarding timing with "clutch-in" and getting down the revs range with ignition cut).
- In rally people couldn't care less about such thing as "reliability"

In case of flatshifting you will not come off boost in the first place, but if you start lifting your foot to shift - your turbos will be stopping more rapidly, hence your spool up should also degrade as is their (turbos) lifespan in a long term.

In short - you can probably get away without one, but at a cost of "reliability" of your turbos or you can run great all day long with a good aftermarket BOV and don't sacrifice anything.

[mpau009]

Dumb amateur question time.

So if the problem they are trying to avoid is switching back to vacuum between gears, and having to build boost pressure again, as well as not trying to stall the turbo compressor wheel. Couldn't you get a happy medium with an adjustable BOV set to keep some pressure in the intake side? Or is this just as bad?

Also, i have to kind of agree with that post at the bottom of page 1, if you don't need it, why is it there... and that discussion about the quality of aftermarket turbos over factory.

So in short.. Brad, you first... let us know how it works out.

[bradc]

Thats basically it Michael. You could probably restrict the outlet of any VTA BOV to do what you're suggesting, but it would be difficult to test and accurately do it though.

I won't try it, I want to keep my turbos in good condition for when I sell them so I can make money off them

[valmes]

A lot of people do silly things to their turbo cars...

If someone told you that running with actuators/wastegates disconnected is better then stock, would you believe it? But it is true!!! Well, to some point and on some cars... Never mind the problems that will eventually destroy the engine... you can get more HPs out of "knocking" car, why not just ignore that "knocking" sound?

Sure you can run without a bov and you can get used to shifting without closing the throttle 100% and not releasing your foot from the "gas pedal" as rapidly, but why in hell would you want to?

I think there are minimal performance gains in doing so, if any (i really doubt that), over aftermarket BOV that is, and a it's bit more harmful to your ride... IMHO

Few more suggestion for "cheap" power:

- Take off your exhaust completely... you will see boost going up so fast and so hard... ehhhrr, never mind fuel cuts - they will soon disappear... along with your engine.
- Above mentioned free actuator mod is also good for few quick HPs...
- Getting rid of the BOV in this kinda config is... a good weight reduction!

In fact the list is too long... just get rid of everything!

[bradc]

lol ^^ so overall it is quite a bad idea unless you know the turbos are on their way out anyway

[bernmc]

I fitted a FORGE FMEVO15 BOV to my leggie - got it from a guy off MLR. It comes with different springs and spacers to adjust the vent point. I'm sure he told me he left the thing with the stock supplied spring, so I just bunged it in without checking. I noticed that my car was jerking quite harshly on high rev gear changes and when backing off on the throttle. I wasn't sure whether it was the new boost controller being silly, or the new BOV as I'd done both at the same time.

Anyway, had an hour of daylight after getting back from work, so I whipped the valve out and pulled it apart - turned out to have the 'medium' blue spring in it. Changed to the softer yellow spring, and the car is much better. I suspect that the valve wasn't opening quickly enough, and the turbo was stalling.

So the BOV is important for normal street driving, and so is the spring tension!

[Wodjno]

One thing that hasn't been mentioned her though is ! Our cars don't suffer from a boost drop when changing gears In fact we get boost apikes
Reason being is most of us have Auto's and between the gear changes we are not letting off the Gas ! This in effect is the same as flat shifting
I still agree that the DumpValve is a piece of kit that is needed for the longevity of our cars, but surely if any car can do without a DumpValve it would be an Auto..
Still not sure if it would give any performance gains though ??

[The Vee]

Just as a note to this, when I first started mine after the conversion to a tt engine, I was reving it a little to see if I could hear the turbos working!! Forgot that the original dump valve was knackered and I suddendly heard turbo chatter. Didn't hesitate to fit replacement dump valve!!

[ako]

Think about it.

How could stalling the compressors possibly give a performance gain?

How can it cause the car to come on boost faster in the first place? Unless your BOV is leaking already?

The "countless cars" you thought were running no BOV were probably all running HKS BOV's, or failing that just had chattery VTA BOV's on them if thats what you were hearing.

[Wodjno]

Think about it.

How could stalling the compressors possibly give a performance gain?

How can it cause the car to come on boost faster in the first place? Unless your BOV is leaking already?

The "countless cars" you thought were running no BOV were probably all running HKS BOV's, or failing that just had chattery VTA BOV's on them if thats what you were hearing.

Sorry, but it was deffo turbo chatter..

[ako]

Did you look under the bonnet?

I know plenty of car's you'd swear were stalling the compressor until you actually popped the bonnet and WATCHED the BOV piston chatter away.

If they were indeed using no BOV... More proof brit folk are weird. If "Max Power" wasn't enough proof anyway

[nutrok]

i have no dump valve on my car and it is going finevand dandy, god i love chatter

[Axeboy]

Old thread, but ive removed mine.

I have spare turbeys and dont use the car thaaaat much, but s far so good...

But its early days.

[valmes]

I have nothing new to add here...

In my opinion - upgraded/aftermarket bov is still better and safer way of making sure it vents in right time only and doesn't leak under boost as stock does. Running without one is kinda "budget" way of doing it... sure it works in the short term, but will it be good for turbos in a long term?

Same with disconnected wastegates - if there were no boost/fuel cuts, you would see dramatic increase in engine power, but that is just a gamble! You have no idea of what is going on in your engine, it can eventually lead to engine/turbos failure... on the other hand you can probably drive it for couple of years like that... off gas pedal or applying it only briefly.

You can for example change engine oil once every 15000 miles, not 7000, it will save you some money and nobody knows how long your car will work... but you wouldn't have this "safety margin" when you push things beyond stock form.

Now think of it this way, until its stock boost it probably won't harm compressors of your turbos as fast and as badly compared to when they spin in excess of 180 000 rpm and you shut the throttle closed at high engine RPM. There are enough exhaust gases to keep it spinning for a while and nowhere for compressed air to go... couple stalls like that and... well its your car you can experiment all you like...

[Eurospec]

I agree with the point about not removing the Bov.

This is something i've observed on EVO's- where there is an obvious comparrison for the owners with the rally cars with their ch-ch-ch-ch sputtering turbos.

A lot of people want that sound because they associate it with the powerfull rally cars. Its the noise which a lot of people like because - right or wrong- it is cool. The issue is that this sound more often than not is the compressor stalling out the turbo and making that sound as it does so. Do you really want to do that? The turbo is spinning mega fast, as has already been pointed out its certainly in excess of 100,000 rpm, maybe 150,000 or more. I imagine with small turbos as on the galant, they are spinning up to the 180,000 mark.

When the air stream stops because the throttle plate is closed, the the air backs up untill it gets backs to the turbos and it stalls them out. It happens very very quickly. The compressor wheel then gets chocked and stops within say a second. The inertia of the turbine wheel spinning at such high speed must be considerable, and so the torque applied to the centre shaft must be way higher than the manufacturer intended. Sooner or later those forces must take their toll on the centre bearing.

My personal oppinion is dont do it unless you dont care about replacing turbos frequently. I cant honestly see a performance gain from it, unless like the rally guys do you have a tank in your boot you can fill with compressed air to supplement your air intake when you are on full chat. They can harness the compressed air trapped between the closed throttle plate and the turbo by 'tapping it off for later'. The reason why they do this at all i think is because they have a limited intake diameter of 38mm, so they cant suck enough air in to feed the car for full chat, so they just tap off the tank they have in the boot!

Now, i dont KNOW this, but its just my observation.

Cheers,

Ben.

[Pizza]

How do you know when your blow off is leaking? I hear a slight psssh when I shift (manual) but the car is stock on stock boost. I know the system should be recirculating. Would it make sense to upgrade to an aftermarket BOV for such low boost levels?

[bradc]

The stock one does leak slightly, but as you're at stock boost it probably isn't worth worrying about.

The noise you hear when you lift off the throttle is normal, you should always be able to hear a bit of noise even with a recirc.