blow off valves????

[95_stroker]

Yeah, but have you ever heard them? Sounds b-a-youtiful

B-a-yooty must be in the ear of the beholder.

 

[powerboatr]

i first thought this was a MIL thread

sorry

 

[Hoss 350]

o0o0o a blowoff valve would be suhweet


Erg now I want one...

Blowoff valves in gassers are little more than a large spring-loaded poppet valve that are set to open at a certain psi to bleed off boost. The pressure in the intake spikes when the throttle valves snaps shut, creating air hammer, oscillations, and all sorts of bad things that can and do hurt turbos, pop seals, etc. The pressure spike in a gasser from the throttle snapping shut is what pops open the BOV and causes the Pshsst sound that you are referring to. The BOV is set to a pressure that is just slightly higher than or the same as the maximum boost pressure that the turbo/engine combination can make. That way, when the spike occurs, or an over-pressure situation occurs, the valve pops open, and voila, problem mitigated. (Not eliminated, mind you, because the small BOV cannot IMMEDIATELY bleed off the pressure, but it certainly reduces the problem.)

In a diesel, however, there is no throttle plate. Consequently, there is no pressure spike when you let up off the throttle, and therefore, nothing available to open a BOV. As a result, a traditional BOV will not work on a diesel engine. What is more, the condition creating purpose behind having a BOV does not exist on a diesel engine (no throttle plate) and therefore, beyond making a cool noise, it serves no function whatsoever.

For people that are interested in adding a part to their truck that does nothing but bleed off any accrued boost when they let off the throttle, forcing the truck to start over again building boost when the throttle is crammed back down again, just for the sake of having a cool noise when they let off the throttle, there is a diesel-capable BOV available in the aftermarket. It is electronically controlled off of the trucks MAP sensor, and an electric solenoid actuates it when you let off the throttle. I cannot remember where I saw it, but it is quite expensive (like $400 bucks or something). Keeping in mind that it serves no purpose whatsoever, and functions simply to create a BOV sound at shifts, I would not recommend anybody waste their money on it, unless, to them, the BOV sound is worth $400 bucks, because that is all you get out of it.

What is more, I am not completely convinced that it doesn’t REDUCE performance by blowing off boost that you otherwise could have kept if you shifted quickly enough, forcing the turbo to start all over again building boost.

Anyway, just my .02 on the matter. BOV’s are for ricers. Real trucks don’t need ‘em.

2005diesel, this wasn't directed at you specifically, I just replied to the quote that I saw was most relevant.

 

[CHPMustang]

Yeah, but have you ever heard them? Sounds b-a-youtiful

Yeap in California on every ricer Glad I'm away from all that junk

Gimme Turbo whistlin Diesel power only

 

[ranger boy]

Thanks Hoss, yeah I figured I woulda saw it on a bunch of cummins by now if they had Blowoffs for diesels, cummins seems to be the number one driven by teenager-modded to hell-pickup truck

But thanks for taking the 15 minutes to type that to explain to me

 

[Blane]

whats a wicked wheel.


and i know alot of non ricers with blow off valves. they just so happen to be 700-1300hp mustangs and vipers but thats a different story......


edit: figured it out, thank god for google! lol