Blow off valve on a diesel?? how does it work

[mrgrumpysleeps]

Was competeing in CQ challenge the other week i watched one of the trucks, Gq diesel gas research truck had a massive blow off valve. How is it so as a diesel doesnt run a butterfly and therfore no vacuum? well i'm just assuming it didnt have a butterfly as its a diesel but didnt get to have a look under the bonnet?

any ideas?

[guerd87]

Could just be the turbo built in wastegate, Get a boosted up diesel with good exahaust and it sort of sounds like a cheap BOV, but different.

Found this on Youtube, have a close listen when he changes out of second, is this the sound you heard?

http://www.youtube.com/watch?v=-jQ2vTG_Gq8

[KiwiBacon]

You'd have to trigger it on accelerator pedal position. A ricer one triggered off pressure differential won't work.

[-Nemesis-]

What engine? I thought I'd heard some Nissan's do run a series of butterflies?

[Z()LTAN]

Most TD42's with high boost make that sound.

The "blow off" your hearing is actually waste gate exhaust hitting the back of the turbine.

The GQ ute i navi in makes that noise on every release of the accelerator pedal making it sound like a "blow off"

Ill see if i can get a movie of it for yas

[lump_a_charcoal]

Even my 100 series Sahara does it a bit...

[guerd87]

All Turbo Diesels do it, but the size of exhaust among other things factor how loud it is usually

[badger]

What engine? I thought I'd heard some Nissan's do run a series of butterflies?

mq's do and i beleive some of the 2.4 surfs did to

[tweak'e]

What engine? I thought I'd heard some Nissan's do run a series of butterflies?

mq's do and i beleive some of the 2.4 surfs did to

quite a lot of makes and models do.

some only use it for engine shut off. makes for a smoother shutdown.
others its all part of the EGR system. it reduces air flow and increase egr flow.
a few vechiles have dual butterflys (eg nissan ZD30) and others have the butterfly directly connected to the throttle just like a petrol (eg toyota 2lte,1kz).

normally the butterfly gets tossed out along with the egr system (otherwise the butterfly causes vacuum in the intake and staves the motor of gas to compress resulting in low effective compression)

for those who still run the butterfly system then a BOV helps just like on a petrol. however because of the egr flow you don't get the vaccum to trigger it so still need to run it by other means.