Starting and stopping diesel engines.

[jtbo]

Originally Posted by BrianAbington

I agree with what has been said earlier about EGT's being lower. Coking really only occurs in a turbo that has just been run really hard above 1,000 degrees and shut off with no cool down time at all. if your driving like a granny your turbo probably won't ever spool up so you won't have any worries about heat soak.

Pretty much so, also new watercooled ones are so much better in this aspect and modern synthetic oils that starting stopping is much more possible than it used to be.

However especially with longer engines like 6 cylinder ones, there is head warping/cracking issues with sudden temperature changes, so that is another thing to keep on eye when starting/stopping diesel.

I think that efficient P&G will not be very possible with such motor, where you get lot of heat variation, also longer head don't like to be pushed hard when not evenly warmed up, but starting stopping at traffic lights is probably not an issue at all.

Love your engine, care and listen it and it will give plenty of economical mileage

[JanvdW]

Hi,

I am still new at this, but here's my 2c worth...

I have an old diesel turbo, no electronics, no EGR, oil cooled turbo, mechanical Bosch diesel pump etc.
I found that it is not worth switching the engine of at most traffic lights, with the cycles varying from 20 sec to 30 sec. Thus not even a minute.

What I do however do is glide down hills with the engine switched off. HOWEVER, I keep the vehicle in 5th gear with the clutch pedal pressed down, and the ignition switched ON. Starting the engine, while still moving, is a simple matter of releasing the clutch.
If that truck of mine (2 metric tons) is hurtling downhill at 80mph with the engine off, the brakes do very little in terms of stopping the vehicle.
I any emergency situation, I need the engine back on in a split second. No time to fiddle with keys to start, just pop the clutch and it's back on.
Gentle release of the clutch starts the engine quite easily without any jerk, and there is no stress on the starter motor.
Driving like an old woman (or worse) means the turbo is not spinning at 18000 rpm when I cut the engine either.

I plan to install a Volt meter to monitor battery condition, in addition to an alternator cut-out switch. That way I will not be caught off guard without power in the battery.

[jtbo]

Originally Posted by JanvdW

Hi,

I am still new at this, but here's my 2c worth...

I have an old diesel turbo, no electronics, no EGR, oil cooled turbo, mechanical Bosch diesel pump etc.
I found that it is not worth switching the engine of at most traffic lights, with the cycles varying from 20 sec to 30 sec. Thus not even a minute.

What I do however do is glide down hills with the engine switched off. HOWEVER, I keep the vehicle in 5th gear with the clutch pedal pressed down, and the ignition switched ON. Starting the engine, while still moving, is a simple matter of releasing the clutch.
If that truck of mine (2 metric tons) is hurtling downhill at 80mph with the engine off, the brakes do very little in terms of stopping the vehicle.
I any emergency situation, I need the engine back on in a split second. No time to fiddle with keys to start, just pop the clutch and it's back on.
Gentle release of the clutch starts the engine quite easily without any jerk, and there is no stress on the starter motor.
Driving like an old woman (or worse) means the turbo is not spinning at 18000 rpm when I cut the engine either.

I plan to install a Volt meter to monitor battery condition, in addition to an alternator cut-out switch. That way I will not be caught off guard without power in the battery.

If you have vacuum assisted brakes, those should provide three full stops with engine off, that is at least law in here and all cars generally seem to work so. It might be that there is problem with vacuum assist servo if you have poor brakes without engine running, which might be worth to check.

[JanvdW]

I tested the "theory", and got no assistance from the servo, at 400 000km and 14 years of service, the system may need some attention.

[JanvdW]

Another "pro" of re-starting without the keys is that you do not activate the glow-plugs every time.

[kingsway]

My car doesn't have a turbo - I do notice that when stopped and idling at the lights my Ultraguage shows a rapidly dropping short average FC sp, if I have to stop more than a few seconds I do tend to switch off.

[jtbo]

Originally Posted by JanvdW

Another "pro" of re-starting without the keys is that you do not activate the glow-plugs every time.

This would be nice, with my car however, I would need kill switch to get this behavior as shutting engine with keys turns it off, turn key to on position and glow plugs do their cycle, starting itself does not make glow plugs run, turning power to on setting will do that.

With diesel, kill switch should be rather simple to install however, there is shutdown solenoid somewhere and kill power to that and engine shuts off.

[JanvdW]

That old diesel engine of mine has one single electrical wire going to the Bosch diesel pump. If you cut power to that, the diesel is cut off.

If you supply power to it, and turn the engine, it runs. Simple. Also makes the immobilizer easy to override!

[skyking]

similar to my P7100, I'm sure. A big solenoid to pull a fuel cutoff lever.

With my old iron, I will shut down every time I'm out of the rig. Not going to shut down at lights, but do put it in neutral to reduce engine load and fuel consumption. Sitting in the middle of a busy intersection is not the time to find out you need new contactors. There is absolutely no safe braking with the engine off, so besides being hard on the trans I cannot coast.
No warm up time here, either. Once the transmission and brakes have pressure I'm moving, albeit slowly. It warms up just fine on a slow roll out to the faster roads.

[euromodder]

Originally Posted by serialk11r

It's not mainstream at all among American or Japanese manufacturers :/

Hardly anyone buys American vehicles over here - and the Chevrolets they sell here, aren't really American anymore - but the Koreans and Japanese have gone along with stop/start on their newer models.

It results in about 8% less fuel burn on the NEDC, and ever more countries are introducing a NEDC based taxing system, so not having a start/stop system can start costing customers as it make a vehicle less attractive.