Turbo Diesel Question

[NISMØ]

Hey just a question on Turbo Diesel motors in particular the 4.2L's in Nissan Patrols. I often see offroad modified examples and when they change gear this is sort of a loud blow back noise. Kind of like an loud rush of air. It doesnt sound like a BoV or Compressor Surge and being a diesel it cant do it anyway so what is this noise???

[WARLORD BAS]

Hey just a question on Turbo Diesel motors in particular the 4.2L's in Nissan Patrols. I often see offroad modified examples and when they change gear this is sort of a loud blow back noise. Kind of like an loud rush of air. It doesnt sound like a BoV or Compressor Surge and being a diesel it cant do it anyway so what is this noise???

do you have a clip of this or anything you can show?

as it is possible to get compressor surge, as with the vw diesels you can manege to get it to have a 'dose' or flutter affect.

[Johnny]

diesel engines have turbos just like petrol ones, dont see why it wouldnt flutter or have a bov.

modified examples are comming up now as diesel engine blocks run high compression and are cast iron + i read somewhere that diesel has a high tolerance to detonation so you can run high boost levels e.g. f250 trucks in the U.S. running great quarter mile numbers.

drive next to a truck, you can hear plenty of induction noise/rushes of air off-throttle

[BOZ22N]

diesel engines have turbos just like petrol ones, dont see why it wouldnt flutter or have a bov.

Most diesel engines do not have a throttle body and there will always be a valve open some where for the air to go so back pressure will not build up like a petrol engine. Saying that i have a 3ltr turbo diesel rodeo and it has a throttle body and did sometimes make a tiny little noise when it was new.

[NISMØ]

Yeh I know diesels have same turbos but I was under the impression that due to having no throttle plate there could be no compressor surge. I dont have a sound clip but If u watch some 4.2L patrol videos on youtube some of them make the noise when they change gear. Im sure youve all heard those patrols / landcruisers with the big mud tyres and exhaust before they all make the same noise when they change gear. If any of u know that whistle for a hot chick (cant remember what its called) bird call or sumthin it sounds exactly like that except not 2 stages of whistle just 1... sorry for retarded examples.

[mr-r33]

you will only get a dose or flutter from a diesel if it has a throtlbody on it the motor you are taking about dose not have one

4.2 TD GQ running 18PSI

that is my old HJ60 with a throtlbody running 10PSI

sorry guys i sux at spelling

Edited March 4, 2009 by mr-r33

[nIsMo86]

NISMO...Give roadworia a PM. He should be able to find out the answer to your question as he works on them at nissan.

I know you can get vl style flutter off diesel peugeots when you stall them up lol.

Edited March 5, 2009 by nIsMo86

[T04GTR]

well. as diesels dont have a throttle, they use fuel injection as the throttle. more fuel more revs, they still have the same varieng loads and air consumsion diferances as petrol engines,

so when they get of the throttle the fuel usage drops and so does the amount of air reqired. so surge is not uncommon.

ps.. the im pretty sure direct injection petrol engines dont have a throttle iether..

if im heaps wrong and someone knows please corect me.

[BOZ22N]

Hey dave you are not wrong mate most don't, But some newer DI models mainly the euro and California spec ones do have a throttle body but it is not used as the throttle as you above mentioned. It is only there to control black smoke and emissions etc.

Our large diesel engines don't even run wastegates, They only boost up to how much fuel you give it and how much load is on the engine.

[WARDY32]

As said in earlier posts the only diesels that will give a flutter/dose/compressor surge are the ones that have a throttle butterfly. they work in the same principle as a petrol engine, butterfly position determines the amount of diesel that will be injected and how often etc and as you all kno the pressure has no where to go but out of the air filter..

Most of the new aged japanese diesels run on a common rail system, engine runs a normal engine driven fuel pump which feeds up to the "common rail" it then goes from there to each cylinder through an EUP (electronic unit injectors) which inject the right amount of diesel determined by throttle position via a sensor on the accelerator pedal/rpm/load/speed etc!

The older diesel engines just run the conventional style diesel injection pump, which has a rack inside it, inturn it sends the diesel up the pipes to the injectors detirmined by engine position (its run via the timing gears) so it doesnt need a butterfly

All a bit confusing i kno but it sort of makes sense when u work on them everyday, might not have everything 100% right but it gives you guys a bit of an idea how they work. some of the euro diesels combine all of them together to really stuff us up lol, we have a Merc vito van as a breakdown vehicle and it flutters like mad!!

As stated above ^^ most of the diesels that have butterflys are there for emissions purposes. but i have seen a few engines that actually use themas a throttle body

Edited March 5, 2009 by WARDY32

[rob82]

well. as diesels dont have a throttle, they use fuel injection as the throttle. more fuel more revs, they still have the same varieng loads and air consumsion diferances as petrol engines,

so when they get of the throttle the fuel usage drops and so does the amount of air reqired. so surge is not uncommon.

ps.. the im pretty sure direct injection petrol engines dont have a throttle iether..

if im heaps wrong and someone knows please corect me.

Whaaat - you guys are on drugs. There is no factory realeased DI gasoline engine that doesn't have a throttle plate!!