The end is in sight....just a few loose ends !

[DieselMonkey]

Guys, the end of my 1.9D > TD is almost there (for the engine part anyway). But i have a few questions here.

When i have the exhaust manifold off and the motor is still out, will i drill the manifold right where the gas enters the turbo for my pyrometer, or will it be ok to drop the engine in and simply place the EGT sender in a plate made for the EGR outlet flange. This would be a lot simpler but if the readings will be considerably different, then i will wait until i get the probe (probably 3/8" BSP or somthing).

I had the oil pump off the motor when i dropped the pan and baffle (need to drop the pump to get the baffle off of the block !) and so, it lost prime. I have planned to pour oil down the block, into the pump since the filter housing is off. Will the pump hold prime until i add the rest of the oil in 2 / 3 weeks time ? (still waiting on the delivery of my M14 oil temperature plug which replaces sump plug, so cant pour my Delvac 1 yet).

Lastly, i'm officially on the hunt for a proper 1.9TD pump with immob. (95' -ish +). Has anyone played with the 2 wires that are connected to a plug into the bottom of the pump, supposed to reduce Nox, and i'm told this is what causes the slight delay in acceleration.

If i do get a TD pump, can anyone describe what boost pin would be ideal. I was thinking of turning a pin from 01 tool steel and hardening it. But if this is not worth the hassle please let me know.

Much appreciated. DM

[rackley]

Well EGT readings are very subjective.  Tapping the same model car in the same place will produce different readings based upon the smallest variations.  

What will you be comparing your readings against?  Your own car, or others'?  If others', then you need to tap it in the same place the as the comparing cars.  If you want to compare it against your own pre/post fiddlings, then you can tap it anywhere.  If you want higher readings, tap very close to the exhaust port.  If you want lower readings, tap close to the turbo exhaust housing inlet.  

My own spiel is that I think EGT readings are pretty useless.  I mean they're pretty to look at, but what actionable data do they give you?  That your exhaust gas it hot?  Sure...  but then again you already knew that.  How hot is too hot?  1500?  1600?  1800?  Too hot for what component?  The valves?  The turbo?  The manifold?  The combusion process?  And what makes you think that measuing 1600 in the exhaust manifold means the valves are at 1600?  Or are they at 1800?  Or 1900?  

Plus, almost all thermocouples have a very long lag time.  I have an EGT in my turbo'd 95 Miata.  I can do a WOT run in 2nd gear and it will only register 400*C.  If I do the same WOT run in 4th it will show 600*C.  But obviously the exhaust gasses are the same temperature in both runs.  It's just the thermocouple delay and the heat sink of the exhaust manifold that screws up the readings.

As a further example, I get my hottest EGT's at cruise, about 700*C.  But I can be on the freeway and let in the clutch and coast until my EGT reaches the lowest peg reading, 50*C.  If I then let the clutch back out and cruise, it takes about 20 seconds for the EGT's to reach the 700*C mark again.

So what condition will you be measuing EGT under?  Keep in mind that depending on the reaction time of your thermocouple you may have to hold that exact condition for 10+ seconds minimum to get a REAL reading.  (this is impossible for almost any situation except cruise)

WBO2's on the other hand have nearly instant and accurate readings and tell you a whole lot more.

[watsongs]

Fill your pump with ATF before you start it - it will lubricate the pump and help clean out any junk -

[jackbombay]

it takes about 20 seconds for the EGT's to reach the 700*C mark again.

  That is some slow response, mine is way faster, while shifting mine drops 100* F for example, I have a few seconds lag at most. The times I really wnat the EGT info are when the EGT is way up (1500*F) and in that situation it rises slowly so the lag is minimalised. I have it installed right before the turbo which is widley reported to be able to take 1450 sustained and 1650 for brief periods of time.

[fspGTD]

EGT readings are useful if you're doing fueling and boost modifications.  It can be information you can use to keep your combustion chambers from getting hotter than they should.  One reason for doing this is when increasing the fueling level, avoiding the concern of melting your piston tops.

To really test max EGTs, you should run the engine at WOT until the gauge reading stops climbing.  What I do is floor it in fifth on the freeway up a mountain pass, and drag the brakes as needed to keep the engine from accelerating, until the EGT reading stabilizes.  This is the true "peak" temperature for your engine tune.  Warning: this is also a very stressful test for your motor.  If you think it might exceed what is safe, it might be best not to test it but de-tune your fueling until you think it's safe, then incrementally test and make small increases as long as you are still comfortable with the result.

Not all thermocouples are created equally... some are much more quick-reacting than others by the way.  A useful one should react very quickly after you make a major throttle position change, IE: go from no load to floored, gauge should start climbing very shortly after you floored it.  Sure it may take 10+ seconds before full temps are registered, but also realize that the piston tops and combustion chamber surfaces aren't heating up instantaneously either and until they reach an equilibrium temperature, they will be conducting heat away from the combusted gasses.

The readings should be useful and comparable to other VW Diesel engines.  You can compare readings to what others up on this board have posted theirs to be without incurring engine damage, or if you want more conservative you can use the factory thermal limits.  Either test that yourself on your own pyrometer if your engine is stock before you've done any modifications, or find a published figure if available for your engine and use that.

For pre-turbine EGT installation, you generally want to measure all your cylinders.  Wherever you can find a location to install the probe that gets its tip in the exhaust airstream of all the cylinders before the turbine is fine.  A couple inches variance one way or another is probably not going to make any major change in the reading.

For post-turbine EGT installation, generally you want to get it close to the turbine outlet for the hottest temp.  Pre-turbine measurements are most reflective of what is going on in the combustion chamber.  Post-turbine measurements are dependant on how much pressure drop there is across your turbine.  So, post-turbine EGT readings are less useful than pre (but still, more useful than no reading at all.)