Any reason for a blowoff valve? - Diesel Forum

Doctorsmack03 · 06-22-2004, 01:15 PM

Or should I say, is there any reason not to put a blow off valve on my truck? I have experienced the barking of the motor when I have had to cut off the accelerator much faster than anticipated. I know why II need one, just don't know if there is a reason I shouldn't.

FamilyRide · 06-22-2004, 05:00 PM

That "burp" is the design of the VGT. That's how it blows off pressure.

Doctorsmack03 · 06-22-2004, 05:17 PM

I have a steep driveway that I pull up daily. The first few times I pulled up it, I would floor it pretty hard and kill the accelerator at the top just before stopping. Twice now, I have blown off the little air filter flow gauge sender on the back of the filter. The dealer said it was due to diesel bark without a place for relief. He says if you run the accelerator too hard and cut it short, all of the pressure that should be run through the motor is forced backwards resulting in broken/bent Turbo shafts.

mikeym · 06-22-2004, 06:38 PM

ford, or well navistar designed this engine to be wastegateless- the vgt doesnt need one. ford wouldnt sell thousands of these 6.0s if they knew all were gonna come back with bent compressor wheels. and most chips seem to raise boost pressure minimally if any at all, so even if youre chipped, you still shouldnt have problems. i get the same response from a lot of people, they think something is broken. its just the way the turbo was designed...

ozhoo · 06-22-2004, 06:43 PM

But it sure would make a man feel better knowing that a wastegate were sitting there set to about 26psi... hhhmmm, you could be onto something there?

O

Doctorsmack03 · 06-22-2004, 07:03 PM

I am looking for reasons not to do it. I think it would be awesome to hear 30 lbs of pressure come out of a blowoff and look up to see a 10,000 pound truck go by. Can anyone think of a reason not to do this?

PSDRob · 06-23-2004, 08:13 AM

[ QUOTE ]
ford, or well navistar designed this engine to be wastegateless- the vgt doesnt need one. ford wouldnt sell thousands of these 6.0s if they knew all were gonna come back with bent compressor wheels. and most chips seem to raise boost pressure minimally if any at all, so even if youre chipped, you still shouldnt have problems. i get the same response from a lot of people, they think something is broken. its just the way the turbo was designed...

[/ QUOTE ]

Ummmmm....a wastegate has nothing to do with a blow-off valve. Everything stated above is corret, but it doesn't exactly mention anything about the thread's questions. The noises you hear from the motor after quickly lifting throttle after being under good amounts of boost pressure, IS from a build up of pressure, not a goofy little turbo noise that's normal. It does cause a decent amount of pressure on the turbo. Think about it....the turbine wheel is still being spun from the exhaust gases, but the compressor side cannot send the pressure into the motor, so it has to get forced back out the turbo and into the intake. This is where in some applications, compressor wheels can get bent. BUT since I'm sure Navistar has tested these motors quite extensively, I wouldn't worry about it unless you find a way to let the stock turbo boost to 35+ psi. If you like to spend money, and you want a cool sound, consider getting the HKS Super Sequential BOV for diesels. Since diesels don't pull vacuum, there's no way to open them when lifting the throttle, so the diesel version uses an electronic solenoid to actuate the BOV. Check it out here... HKS Diesel Photo

daha · 06-23-2004, 09:39 AM

PSDRob,

So, based on their explanation of the part below this would be a benefit to the engine?? I have the "turbo fart" and it varies on its frequency (sometime with just a little pedal) and it is something I have to live with. But, after reading the excerpt below it makes me wonder if this would be a good investment for turbo longevity, performance and getting rid of that irritating noise(I only have minor mods and will NOT chip my truck). I am not a diesel guru and have had NO problems with my truck (only took it in once for speedo recal). What difference in sound is there compared to the "normal" turbo fart? Do you know of anyone who has this mod and their input? Sorry for the novice questions...just trying to increase my knowledge base [img]/ubbthreads/images/graemlins/smile.gif[/img]

"HKS compressor blowoff and bypass valves play a vital role in any turbo system because they not only improve the performance of your vehicle but they also increase the longevity of the turbocharger as well. The primary function of any blow-off or by-pass valve is to prevent compressor surge by relieving the compressed airflow that reverses direction as the throttle is closed. HKS blowoff and bypass valves reroute the pressurized air, that is normally forced backwards into the turbo compressor, into the intake stream or by venting it to the atmosphere. Subsequently, engine performance is then increased from quicker turbo spool up, as the compressor speed is not reduced by the backward airflow. The longevity of the turbo is also increased, as its bearings will not suffer from the impact that is also produced by compressor surge. Though many vehicles incorporate factory by-pass valves, they are often undersized and quickly are beyond their capable operating range as airflow levels are increased. HKS offers four types of compressor blowoff and bypass valves: Standard, Racing, Super Sequential Blow-Off Valve, and the Racing Blow-Off Valve Type II."

PSDRob · 06-23-2004, 02:31 PM

DaHaHAZMAT,

It's tough to say. On a gas application, I wouldn't run more than about 7 psi without a blow-off valve. The blow-off valve is well worth it on any high boost application, I just don't know how well the HKS diesel model will perform. As long as it opened at the right times to release the compressor surge, I suppose it would work and be worth owning. The problem is that they retail for around $500 for the diesel model, which I couldn't find listed on their site anymore, so they may have stopped selling it. The sound is a high pitched, whistle sounding flutter. It is much different than the turbo fart you are used to. You can get a weld-on flange and mount it on the hot pipe (pipe from turbo to intercooler). The actual HKS SSQV works great on gas applications...I have used them personally with great success.

Again, I doubt that these engines and turbo would be at any risk of damage due to 100k+ miles of compressor surge, unless it was overlooked in engineering. It may lead to turbo failure sooner, but I doubt in most people's normal ownership time frame.

Also to consider...
The 6.0L uses a MAF sensor, which MAY cause a problem with a BOV. The air being released from the BOV has already passed through the MAF sensor, therefore, it will cause a slight rich condition, unless you found a way to vent it back into the intake pipe between the MAF sensor and turbo. The HKS SSQV isn't designed to be vented back in due to the design, but they do have an optional fitting that would allow you to vent back into the intake with a section of hose.

daha · 06-23-2004, 03:01 PM

Thanks for the info! I called HKS to get some more info but, the item is no longer available (no plans for another either).

Thanks for replying!

Take Care,

David

bigmac40 · 06-23-2004, 06:53 PM

I have been told that diesel engines do not have blow off valves because there is not a throttle body. Diesel just simply do not put fuel in when you let of the throttle instead of shutting off the air. Because of this, there is not a excessive pressure to hurt the turbo. I am not a expert just passing along the reason I was told.

UncontrolledCopy · 06-23-2004, 09:09 PM

So... I should worry that my Attitude reads 37+psi once in a while? I have never had a turbo fart. I wonder if a blowoff valve is the same as a popoff valve? Can you help my ignorance since I can't?

Thanks [img]/ubbthreads/images/graemlins/shrug.gif[/img]

soccerstud19 · 06-24-2004, 12:35 AM

I'm not sure totally about this either but won't a BOV cause problems when going from gear to gear? A BOV vents the air everytime you shift also, wouldn't that cause a slight lag or skip in power since a diesel motor does not need to release this pressurized air between shifting?

koolkat812 · 06-24-2004, 08:51 AM

Why would you want a BOV when these turbo's sound cool as hell the way they are stock??

Turbo fart included...

Christian Roth · 08-30-2004, 02:22 PM

At BD Power we make a BOV for diesel trucks its called the turbo guard. Its primary appplication is for the Dodge Cummins but it has been installed on a PSD before.

The bark is actaully compressor surge, and no the turbo/engine was not desinged for it. On gassers this surge is caused by the throttle body cutting the engine flow rate down to zero which in turns casuses all the bosst pressure built up in the intact to stall the compressor wheel. In a desiel applilcation the surge is caused by removing all the driving energy from the turbine side of the turbocharger.

Overtime it will destroy the thrust washers on the turbo and eventially the compressor wheel will clip the housing resulting in major damage.

www.bd-power.com