Should we consider a BOV

[zukgod1]

The engine slows down more slowly that the turbo.  

So I read this earlier today and decided to check to see if this is correct. I do not beleive it is. I ran my car at WOT in second gear a few times today and observed that the engine would return to idle and the boost pressure would remain at 6-7psi for about 3 seconds before returning to 0 on the gauge.

So, that in mind, the engine is obviously slowing down faster than the turbo. This test was done only at about 15psi as I didnt have a lot of road and I didnt want to take my eyes off of traffic on the freeway.

What say the group?

If you still have boost reading on your gauge at idle you have a kink in the boost hose or a restriction somewhere.
There will be no boost at idle not even for a second, it takes fuel to spool folks.. Nothing else will create boost.

That's what this dude says

[Vincent Waldon]

My suggestion for those after the pssssst:  take all the time and energy and money you might spend on rigging up a vestigial BOV for our little turbos and donate it to charity... you'll get the same warm fuzzy "aren't I great" feeling, you'll arguably be just as attractive to the chicks (perhaps even more so, since you've demonstrated your sensitive side) and you'll actually be doing something useful. :roll:

But that's just *my* suggestion....  :wink:

[zukgod1]

I agree Vince.

I would love to see someone make one that works and ot have it cost hundreds..

Till then I'll keep my closed system.

I would like to add however it's threads like this that get us thinking about ways to improve and progress..
Good stuff here

[vanagonturbo]

You guys are missing the point. Yes, I drive my car like I stole it. Hence the reason why I dont want it to be broken. Hence the reason why I am even posting in this thread.

Yeah, I WOT frequently. Then there could be a stop light, or someone in front of me that is stopping or slowing down. Clutch in. Slow down. When coming to a stop, why would I leave it in gear? We drive these cars to get good mileage right? Leaving the car in gear reduces that mileage.

It seems to me like everyone reading my posts are either A. thinking I have been blowing up turbos, or B. should be driving like grandma.

I have not blown up any turbos (yet) and I most certainly dont drive like grandma. I beat the crap out of my car. Why? because I dont have millions of dollars for test equipment. I have my car. What do I do with this information? I apply it to working on other peoples cars.

Dont give me any crap about how I should be banned for running my car @ WOT and checking my numbers and sharing them here. Its obviously to get information. The same reason the rest of you are here.

zukgod: please reread my post. I assure you that I have ZERO kinks. The system is clean, no harsh bends or anything backyard going on. Remember, this is returning from full boost to clutch in for idle.

[Dr. Diesel]

it's all about the wicked sound. Just like putting a "BOV" on a G60 engine. Utterly useless.

Sorry for my ignorance.  A G60 is a supercharged Corrado correct?  

I'm trying to understand why a supercharged car wouldn't need a BOV.  Is it because the boost is made "POST-THROTTLE-PLATE"  So there's not Boost backing up against the throttle plate??

G60's (as do most supercharged cars) have a bypass valve which closes (give or take) inversely proportional to the opening of the throttle valve.
At part throttle settings, when boost isn't needed, the bypass valve is also partly open, allowing excess air to be diverted back to the supercharger's inlet. Effectively unloading the supercharger. Fuel economy and charger life is improved.
Some numbnuts thought it'd be cool to basically remove the bypass pipe  running between the bypass valve and the s/c inlet. That way, after a mid-high rpm run, closing the throttle valve opened the bypass valve, and all the excess air hisses out making a sound similar to a gas turbo car's BOV.
Woopee.
The downside is that the abovementioned benefits are lost, plus when the car sits, there's a wide open hole for crap/bugs etc to enter the engine. A small filter would eliminate that issue, but not help any of the others.
Seems like a lot of BS for a 'cool sound'.

[andy2]

To operate a BOV on a diesel you use can use boost pressure to open the valve.Use a micro switch to activate a solinoid valve which delivers boost pressure to the BOV.

[vanagonturbo]

sorry, I guess I kinda went off there.

the only reason why I would think it would consume more fuel is that the engine would be making the pump run at a higher rpm than idle. Kinda like why the Lupo 3l only comes in automatic version to be able to keep the pump rpms down during deceleration.

One thing to note, my vanagon does not make the noise that my rocco makes after pushing in the clutch. I assume that is because the Vanagon has a K03 so it can spool down much faster than the T3.

[zukgod1]

zukgod: please reread my post. I assure you that I have ZERO kinks. The system is clean, no harsh bends or anything backyard going on. Remember, this is returning from full boost to clutch in for idle.

I don't need to "reread your post I know what your saying. My point is there is NO way there is residual boost left in the system after your engine has returned to idle. You either have a restriction or a POS gauge that doesn't react fast enough.

It's a mater of simple physics sir. The boost is gone as you discontinued the fuel input..

It takes FUEL to SPOOL....

[vanagonturbo]

Well, if we are talking about physics here. lets talk about inertia. I find it very hard to beleive that as soon as the engine has returned to idle, that the turbo is instantly responsive and returns to 0 boost. Especially when my gauge tells me otherwise. My gauge is a new Autometer and there are no kinks.

I find it very hard to beleive that the turbo (spinning at 30k rpm) returns to idle rpm instantly.

we can use a pinwheel as an example. If you blow on a pinwheel and get it to spin, the pinwheel does not come to an instant stop as soon as you are done blowing on it.

[zukgod1]

Ok I guess you win.

I'm not going to argue with you about it.

[vanagonturbo]

Im not trying to pick a fight, I just dont understand how the turbo returns from 30k rpm to say maybe 10k in the timespan of 1 second (about what it takes for the engine to return to idle).

[Turbinepowered]

Im not trying to pick a fight, I just dont understand how the turbo returns from 30k rpm to say maybe 10k in the timespan of 1 second (about what it takes for the engine to return to idle).

The internal friction of a turbo is high, and in the case of our own turbos the inertia is very low. Very small compressors, very small turbines, combined with journal bearings (which are among the higher friction bearing variety) all combine to bring the speed of that turbo down very, very quickly.

The reason they spool up quickly, in turn, is because they have very low inertia.

Combine the sudden loss of exhaust pressure with the internal friction of the turbo and the bit of back pressure inherent in any compressor, the turbos spin down quite quickly.

Even the huge Holsets on our buses don't take more than a second to go from peak boost to no boost, and they're pushing 45+ PSI with nearly six times our own engines' flow rate.

[saurkraut]

I find it very hard to beleive that the turbo (spinning at 30k rpm) returns to idle rpm instantly.

Try 100K RPM.  That's the ball park RPM they spin at under full boost.

The boost on my TD rabbit drops like a rock when I take my foot off the go pedal.  I specifically watched it yesterday while I was driving all over the state.

To even have a chance of haveing the engine wind down faster than the turbo, Id have to rev the greegree out of it under full load (third gear or higher), then push the clutch in and coast.  But I still think the turbo will decel faster than the engine.

And I can't think of a normal driving scinario where I'd want to do that  on a regular basis.  And I drive 'em like I stole 'em too

The low rotating mass of the turbo will also help it decel faster than the engine, which has humungus rotating mass.

Try cleaning your boost gauge.  There is some bizaar gak that lives in the crank case vent gasses.    They tend to condense out when then have a chance to sit.

I have to clean mine out occasionly.  (its due for a cleaning now)  I stuff the stick nozzle thing that comes taped to the side of brake cleaner aerosole can, right up the kazoo of the boost gauge.  A hoste of black goo cascades out.  I also disconnect the line from the engine and back flush it too.

I like the fart sound the VDO gauges make when they're clean.


Oh, and for the record, I believe my turbine blade failure was a combination of metal fatigue, agrivated by spinnnig it too fast.

[Vincent Waldon]

One other thought... many many "boost gauge install kits" have a tee with a restriction build in... the restriction damps the small pulses in boost around 0 that cause the needle to buzz against the zero stop.

I bought one of these tees on purpose... the buzzing was driving me mad... and now the buzzing is gone, however, the trade-off is that the boost gauge doesn't drop quite as fast as it used to.

[saurkraut]

My VDO gauge makes a buzz (fart) as it exhaustes the boost pressure when everything is clean.

I can tell there is gak in there as it doesn't make a sound.

It doesen't buzz at low boost either, just when the boost is dropping.

I like VDO as it matches whats in the car already.