Throttle plates and compressor surge

[monsterer]

Hi guys,

So, i've read the 3.0TD engine still has a throttle dispite being a diesel, so i expected to hear a compressor surge noise (commonly misnamed as wastegate chatter) when changeing gears (as the thottle closes when i come off the accelerator), yet all i hear is the turbo spooling down slowly.

What gives?

Cheers, Paul.

[surfenstein]

if your surf didnt have a throttle you wouldnt get very far. on the other hand its a diesel not a race car engine.i think what your trying to explain is over boost,the surf turbo has an internal waste gate,so you wont hear it.

[monsterer]

if your surf didnt have a throttle you wouldnt get very far. on the other hand its a diesel not a race car engine.i think what your trying to explain is over boost,the surf turbo has an internal waste gate,so you wont hear it.

Not true! The diesel engine was originally conceived to be throttleless! The throttle's function is generally replaced (in a normal diesel) by controlling the amount of fuel injected only, while keeping the air flow constant.

However, i believe the surf has a throttle to enable manifold vacuum to be used for brakes/clutch...

And the noise i refer to is nothing to do with the wastegate, its the noise of the turbine blades being forced to stall and spin backwards by the closing throttle.

Cheers, Paul.

[surfenstein]

ooops sorry i see what your on about now,with concern to the throttle.but ive never heard of the turbine blades being forced to stall,you learn something new every day.

[monsterer]

ooops sorry i see what your on about now,with concern to the throttle.but ive never heard of the turbine blades being forced to stall,you learn something new every day.

Its what a dump-valve is designed to prevent...

[TonyN]

Not true! The diesel engine was originally conceived to be throttleless! The throttle's function is generally replaced (in a normal diesel) by controlling the amount of fuel injected only, while keeping the air flow constant.

However, i believe the surf has a throttle to enable manifold vacuum to be used for brakes/clutch...

And the noise i refer to is nothing to do with the wastegate, its the noise of the turbine blades being forced to stall and spin backwards by the closing throttle.

Cheers, Paul.

hehe, we keep arguing, you need a throttle (just an air flap in reality) to keep the air/fuel mxture correct.

Brake booster vacuum is supplied by a vacuum pump, there isn't enough intake vacuum on a diesel motor.

The Turbo won't spin backwards, there is always airflow over the turbo even if the throttle is closed, the engine is still running.

[BUSHWHACKER]

Two options, get a dump/blow off valve fitted, or buy a Scooby!!

[monsterer]

The Turbo won't spin backwards, there is always airflow over the turbo even if the throttle is closed, the engine is still running.

How does this arrangement differ from a petrol turbo engine - in that case you can hear compressor surge as the throttle closes (if there is no dump-valve) ?

[TonyN]

How does this arrangement differ from a petrol turbo engine - in that case you can hear compressor surge as the throttle closes (if there is no dump-valve) ?

Its the same, a dump valve just saves the turbo from slowing down to much then the throttle is closed, so it spools up quicker reducing turbo lag next time you stomp on the throttle.

A turbo is a turbo, whether its on a oil burner or a petrol car.

[monsterer]

hehe, we keep arguing, you need a throttle (just an air flap in reality) to keep the air/fuel mxture correct.

But a diesel engine is lean-burn, so you don't need a throttle at all. It can run at 200:1 AF ratio and be fine.

[monsterer]

Its the same, a dump valve just saves the turbo from slowing down to much then the throttle is closed, so it spools up quicker reducing turbo lag next time you stomp on the throttle.

A turbo is a turbo, whether its on a oil burner or a petrol car.

Right, so that slowing down you mention is called compressor surge and can is quite a distinctive noise; Jerremy clarkson said it sounds like feeding squirrels into a blender.

The surf doesn't have a dump-valve so i should hear compressor surge but all i hear is a slow spool down, as if the throttle doesn't close *that* much when you lift off...

[monsterer]

Two options, get a dump/blow off valve fitted, or buy a Scooby!!

What for?

[TonyN]

But a diesel engine is lean-burn, so you don't need a throttle at all. It can run at 200:1 AF ratio and be fine.

So why has it got one?

[TonyN]

I don't get what the issue is, you press the throttle, turbo spools up till it reaches max pressure (decided by the wastegate) you back off the throttle, engine speed decreases, turbo slows down. You can keep the turbo spinning a little longer to avoid lag by fitting a BOV, but it doesn't make a lot of difference on a diesel engine.

Its just physics. What are you trying to achieve?

[BUSHWHACKER]

What for?

Reading this thread and your previous posts, it seems to me that you're unhappy with the way your 3.0 turbo diesel engine performs, be it sound, power output or engine aesthetics. As long as it's running O.K. and no leaks or smoke, looks good parked on your driveway and gets admiring glances from inferior 4x4 owners, then whats the problem? If you want M.A.F. sensors and M.A.P, sensors and dump valves and wastegate chatter, then you should have bought a W.R.C. Evo or Scooby!

You've obviously done your research on all things diesel and petrol turbos, and know what they should and shouldn't 'do', but the Toyota 3.0 4Runner is what it is, a handsome looking 4X4 with a turbo diesel engine and a throttle body, which, for some reason you think doesn't need to be there. Take it off and see how the engine runs if you like.
Sheesh!!