Does this look like the right stuff? (EGT)

**dullbird** · 28th September 2009, 09:01 AM

Originally Posted by Bush65

If you want to see what the real EGT at the turbo you need to have the probe extend out of the cast in pocket for the egr and into the gas stream. Also not touching against the side of the manifold - so position and angle in blanking plate is important.

The small diameter probes generally respond quicker, but you need to see the manufactures spec sheets to be sure. 1/8" respond quicker than 1/4" - the one you listed was 3/16" so probably not too bad.

Some people see the numbers in the display changing and assume their probe responds quickly - but this is pie in sky stuff.

Response is measured as the time for the reading to reach the true value when the temperature is changed by a particular step value - not for display reading to change from one incorrect number to another incorrect number.

As you increase the load on the engine the egt will climb. IMHO keep an eye on how rapidly it climbs and if it is approaching say 650C quickly and there is still a good way to the top of a hill, then it is time to ease off with the right foot or grab a lower gear to get engine revs back up.

Had the pump been tweaked for some time and only recently starting to blow smoke. If you are blowing smoke under load, then egt is going to be up.

It is more likely that your not getting as much air as before, than for the pump calibration to have changed.

However, when a pump is tweaked, it needs to be checked with a good load on the engine to be sure that egt will not get out of hand later. Egt will not get anywhere near as high on a steep hill when the vehicle is empty, compared to pulling a trailer or with a big load of camping gear, extra fuel and water, or the like.

Hi John.....the pump has been tweaked for a couple of months.....and it was only tweaked to put the air fuel ratio back in to factory spec because the car was running very very lean...(I have a slightly bigger intercooler)

its hard to say about it blowing smoke as the heavy smoke I'm talking about only ever rears its head climbing up the big hill on the M4 going into the blue mountains in actual fact its only really worse coming out of the mountains as that must be steeper that way.

going up the mountain it puffs a little smoke on a gear change its not until getting towards the top as the car is doing around 80 that it looses enough power to have the car drop to second....and then everyone put your masks on because that is when it bellows smoke!!

My guy at the garage said to bring the car back in and he will check the pump again as before I took it home last time he idd say keep an eye on it as sometimes the adjustment may slip.

I figured the massive smoke cloud would be due to EGT's thats really the only reason why I want to fit one...but like I said bove I dont really get smoke anywhere else.

Now people have said to me smoke with a pump tweak is normal....I dont believe this is normal that's why I want to keep a check on the temps.
I don't want to stress my engine and end its life prematurely.

**steveG** · 28th September 2009, 10:11 AM

Auberins will have the longer probes made in about 10 days. They don't have a part no. as yet, but will email me the info once they have them.

Steve

**Bush65** · 28th September 2009, 01:43 PM

Originally Posted by dullbird

Hi John.....the pump has been tweaked for a couple of months.....and it was only tweaked to put the air fuel ratio back in to factory spec because the car was running very very lean...(I have a slightly bigger intercooler)

...

Diesels run lean, the leaner they are the cooler they will run and the more your engine will love you. Smoke ratio is approx 18:1, so around 22:1 a/f ratio at maximum load is good.

As load decreases air fuel ratio can go well over 100:1 - absolutely nothing to worry about.

Some modern computer controlled diesels do control a/f ratio as part of the emission system.

Originally Posted by dullbird

...
going up the mountain it puffs a little smoke on a gear change its not until getting towards the top as the car is doing around 80 that it looses enough power to have the car drop to second....and then everyone put your masks on because that is when it bellows smoke!!

...

Too much fuel or not enough air!

Altitude/elevation reduces air quantity - turbos increase the atmospheric pressure by a ratio, so as the barometric/atmospheric pressure drops, the boost pressure will also fall. Compressor maps for turbos give pressure ratio on the vertical axis - boost pressure is atmospheric pressure times pressure ratio minus atm pressure.

What are the engine revs after it kicks back to second?

Do you know what your boost pressure is before/after it kicks back?

Hoses have been known restrict air flow due to damage that is not apparent with an external visual examination. Oil accumulation in inter cooler can also restrict air.

Originally Posted by dullbird

...

My guy at the garage said to bring the car back in and he will check the pump again as before I took it home last time he idd say keep an eye on it as sometimes the adjustment may slip.

...

I find that really hard to take seriously!

Originally Posted by dullbird

...

I figured the massive smoke cloud would be due to EGT's thats really the only reason why I want to fit one...but like I said bove I dont really get smoke anywhere else.

Now people have said to me smoke with a pump tweak is normal....I dont believe this is normal that's why I want to keep a check on the temps.
I don't want to stress my engine and end its life prematurely.

Smoke is not due to egt, but egt will be increased if you have black smoke with your right foot down.

Black smoke is incomplete combustion of fuel. Nearly always due to enough air to burn the fuel, but could be due to poor atomisation from a faulty injector (but 300Tdi's don't have many injector problems).

Tweaking the pump can involve up to 4 adjustments.

Some smoke can be tolerable, as long as it clears reasonably quickly (when boost pressure increases).

To get boost to build sooner, more fuel is required - the turbine needs the exhaust gasses to drive the compressor.

One adjustment, the torx screw adjustment in the top of the boost compensator adjusts fuel when there is no boost - screwing this down gives more fuel to help get the turbo going.

The screw under the spring below the diaphragm in the boost compensator will increase/decrease fuel quantity as the boost pressure increases.

Rotating the conical fuel pin is used to adjust fuel rate at maximum boost pressure. But will increase/decrease fuel across the full range (zero to max boost).

Most instructions I see give adjustment procedures in the order I have above. But IMHO it is back to front - rotate fuel pin 1st, then adjust spring pressure if required, then the torx screw.

The 4th adjustment is the maximum fuel rate screw on the rear of the pump - unless you have an upgraded turbo you shouldn't normally need to adjust this.

The purpose of the boost compensator is to reduce fuel when the boost pressure drops.

High egt is bad for the engine - piston melting etc.

Increased boost pressure will increase air quantity and lower egt.

The increased performance which comes with boost presure will result in an insignificant increase in stress of engine - this is due to the part of the cycle when it occurs. The majority of stress is due to inertial loads due to reversing the direction of the reciprocating parts. The inertial loads increase with engine revs - power increase from turbo does not increase revs.

**dullbird** · 28th September 2009, 03:02 PM

Originally Posted by Bush65

Diesels run lean, the leaner they are the cooler they will run and the more your engine will love you. Smoke ratio is approx 18:1, so around 22:1 a/f ratio at maximum load is good.

As load decreases air fuel ratio can go well over 100:1 - absolutely nothing to worry about.

Some modern computer controlled diesels do control a/f ratio as part of the emission system.

Too much fuel or not enough air!

Altitude/elevation reduces air quantity - turbos increase the atmospheric pressure by a ratio, so as the barometric/atmospheric pressure drops, the boost pressure will also fall. Compressor maps for turbos give pressure ratio on the vertical axis - boost pressure is atmospheric pressure times pressure ratio minus atm pressure.

What are the engine revs after it kicks back to second?

3000

Do you know what your boost pressure is before/after it kicks back?

No I don't run a boost gauge

Hoses have been known restrict air flow due to damage that is not apparent with an external visual examination.

Oil accumulation in inter cooler can also restrict air.
Hoses are probably 2 year old they are silicone.....and last time we had the hoses off there was only a very very small amount in the end of the hose like a dusty light covering

I find that really hard to take seriously!

Smoke is not due to egt, but egt will be increased if you have black smoke with your right foot down.

Black smoke is incomplete combustion of fuel. Nearly always due to enough air to burn the fuel, but could be due to poor atomisation from a faulty injector (but 300Tdi's don't have many injector problems).

Tweaking the pump can involve up to 4 adjustments.

Some smoke can be tolerable, as long as it clears reasonably quickly (when boost pressure increases).

To get boost to build sooner, more fuel is required - the turbine needs the exhaust gasses to drive the compressor.

One adjustment, the torx screw adjustment in the top of the boost compensator adjusts fuel when there is no boost - screwing this down gives more fuel to help get the turbo going.

The screw under the spring below the diaphragm in the boost compensator will increase/decrease fuel quantity as the boost pressure increases.

Rotating the conical fuel pin is used to adjust fuel rate at maximum boost pressure. But will increase/decrease fuel across the full range (zero to max boost).

Most instructions I see give adjustment procedures in the order I have above. But IMHO it is back to front - rotate fuel pin 1st, then adjust spring pressure if required, then the torx screw.

The 4th adjustment is the maximum fuel rate screw on the rear of the pump - unless you have an upgraded turbo you shouldn't normally need to adjust this.

The purpose of the boost compensator is to reduce fuel when the boost pressure drops.

High egt is bad for the engine - piston melting etc.

Increased boost pressure will increase air quantity and lower egt.

The increased performance which comes with boost presure will result in an insignificant increase in stress of engine - this is due to the part of the cycle when it occurs. The majority of stress is due to inertial loads due to reversing the direction of the reciprocating parts. The inertial loads increase with engine revs - power increase from turbo does not increase revs.

Perhaps I should bring the car to you for adjustment John

**Bush65** · 28th September 2009, 07:38 PM

Ok, if it is blowing a lot of smoke in 2nd at 3000 rpm, then egt is bound to be very high and there is a problem that you need to address.

You need to look at both, the lack of air and the over fuelling.

**dullbird** · 28th September 2009, 07:58 PM

Originally Posted by Bush65

Ok, if it is blowing a lot of smoke in 2nd at 3000 rpm, then egt is bound to be very high and there is a problem that you need to address.

You need to look at both,

the lack of air and the over fuelling.

Will get the garage to check the fuel to air ratio again.....

I will check my hoses and I will check my intercooler..

would it have anything to do with my centre muffler being removed?

**Bush65** · 28th September 2009, 08:40 PM

Air/Fuel ratio is going to change wildly as engine revs and accelerator position change.

It would only matter at maximum load and foot flat to floor - need a dyno for that.

**dullbird** · 9th October 2009, 05:24 PM

Any updates on the part number for the new probe that is supposed to fit better?

**Leo109** · 10th October 2009, 08:41 AM

Diesels run lean, the leaner they are the cooler they will run and the more your engine will love you. Smoke ratio is approx 18:1, so around 22:1 a/f ratio at maximum load is good.

As load decreases air fuel ratio can go well over 100:1 - absolutely nothing to worry about.
...

Most instructions I see give adjustment procedures in the order I have above. But IMHO it is back to front - rotate fuel pin 1st, then adjust spring pressure if required, then the torx screw.

The 4th adjustment is the maximum fuel rate screw on the rear of the pump - unless you have an upgraded turbo you shouldn't normally need to adjust this.

The purpose of the boost compensator is to reduce fuel when the boost pressure drops.

High egt is bad for the engine - piston melting etc.

Increased boost pressure will increase air quantity and lower egt.

Hi Dullbird & others,

Wish I'd come across this thread earlier. Bushie is spot on! It's pretty meaningless to talk about air/fuel ratios in diesels. The only time the term has any relevance is at full load & full throttle.

From previous posts, Dullbird, you seem quite mechanically savvy but I suspect like most people who've gained their mechanical knowledge with petrol engines you may not be fully aware of the differences with diesels (no offence intended). Could I suggest you have a look at http://www.thermoguard.com.au/Ttalk1R3.pdf and the others articles on this page?

Regarding the pump adjustment process, again I agree with Bushie about the order of adjustments. Some notes I wrote on this topic are floating around on this site somewhere but I've never been able to find them. Please PM me if you like a copy.

About EGT sensing on the 300Tdi, I've measured EGT simultaneously at both the No.1 cylinder branch and in the EGR 'pocket'. While the No.1 cyl probe responded slightly faster there was little difference in the peak temperatures, so I've concluded that measurement in the EGR pocket is quite adequate. I think it's erroneous the think of the EGR pocket as a spot of 'still, cool gas'. The exhaust manifold is a violently turbulent place and I believe the EGR pocket does give a quite representative sample of the exhaust gas.

You might also like to have a look at ThermoGuard Instruments for some info on using your EGT gauge once installed.

Hope this helps.
Ian

**dullbird** · 10th October 2009, 12:29 PM

Originally Posted by Leo109

Hi Dullbird & others,

Wish I'd come across this thread earlier. Bushie is spot on! It's pretty meaningless to talk about air/fuel ratios in diesels. The only time the term has any relevance is at full load & full throttle.

From previous posts, Dullbird, you seem quite mechanically savvy but I suspect like most people who've gained their mechanical knowledge with petrol engines you may not be fully aware of the differences with diesels (no offence intended)

. Could I suggest you have a look at http://www.thermoguard.com.au/Ttalk1R3.pdf and the others articles on this page?

Regarding the pump adjustment process, again I agree with Bushie about the order of adjustments. Some notes I wrote on this topic are floating around on this site somewhere but I've never been able to find them. Please PM me if you like a copy.

About EGT sensing on the 300Tdi, I've measured EGT simultaneously at both the No.1 cylinder branch and in the EGR 'pocket'. While the No.1 cyl probe responded slightly faster there was little difference in the peak temperatures, so I've concluded that measurement in the EGR pocket is quite adequate. I think it's erroneous the think of the EGR pocket as a spot of 'still, cool gas'. The exhaust manifold is a violently turbulent place and I believe the EGR pocket does give a quite representative sample of the exhaust gas.

You might also like to have a look at ThermoGuard Instruments for some info on using your EGT gauge once installed.

Hope this helps.
Ian

No offence taken

.....I'am still very much learning about all these things. Thats why I ask so many questions.......I ask questions based on my own common sense and what makes sense to me and not always knowledge and experience....so sometimes it does make sense and sometimes its doesn't. but its how I help myself to understand, as sometimes I get lost in a lot of terminology.

Unfortunately people have seen this in the past as me being purely argumentative...which is very far from it. I just sit down with the knowledge that I have acquired (some times its false and sometimes not) and think up of different scenarios and then ask more questions. Again this helps me to learn and understand.

I have learnt an INCREDIBLE amount from this site and from the people I hang out with and talk to......
So thank you everyone!!!!!

Oh and thank you leo for the links

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