EGT's in NA 3B

[AJAEbj42]

So, I thought I would track my EGT's and report them for those interested.

I installed an Auber Instruments EGT in my NA 3B, 1981 BJ42, recently.

Automobile Multimeter for EGT, Boost, Red [SYL-1813R] - $48.50 : auberins.com, Temperature control solutions for home and industry

I'm amazed at how much the EGT's fluctuate. Changes of 200 degrees F while simply accelerating or decelerating in a few seconds.

Climbed a short hill (1/4 mile, 400 meters) today. Ambient air temp 10 deg C.

(Sorry, for the mix of F and C temps; I'm Canadian )

Truck at operating temperature. Speed 80km in fourth gear (29's and 411's), not a loaded vehicle.

Climbed past 1000 no problem. Got to the top, same gear and speed, temp dropped 300 degrees in about 10 seconds.

 

[tmarx]

Wow, talk about a De Ja Vu moment: I was about to start the same thread on the same subject matter, so let us hope it is close enough, to not be considered as “chat” and that it may actually help, even if just one, not unlike myself( ignorant), NA 3B owner from killing his/her awesome little 4banger engine.

I turboed my HZJ105 about 5 years ago after stumbling onto MUD and subsequently became an ardent student and believer of the conventional theory regarding EGT's, i.e.:
1. fit an EGT gauge and if possible a boost gauge.
2. Stick to max EGTs of 620 deg C (pre turbo) under full load.
3. In the case of most mechanically powered diesel engines, fuel delivery is throttle controlled as opposed to vacuum controlled(like with most gassers) and therefore
4. Egts will be mostly affected by the indiscriminate (or not) use of the right foot and the actual load on the engine e.g. going uphill or traversing very thick sandy conditions or towing your heavy off -road camping trailers etc
The above I followed (and practiced) until about 3 days ago. Now I am not so sure….

Before, I could almost exclusively control my EGT with my right foot (, with the load permitting it off-coarse but we are not talking extreme exceptions here,) i.e. if I backed off, so would the EGT and if I dropped to a lower gear and therefore upped the revs (assuming the right foot and therefore fuel delivery remained constant) EGT would either drop off or settle in almost the same position as before etc, while flooring it would almost always increase EGT especially if going uphill and towing.

And then for the last 3 days in preparation for my upcoming turbo conversion after I connected my EGT gauge to my NA 3B BJ 42 …..
Suddenly nothing or very little was corresponding to conventional wisdom(or making any sense) which I had previously experienced first hand. i.e.
1. General EGT of the NA 3B was much higher than that of the 1HZT.
2. General EGT is more controlled by the actual increase or decrease in engine revolutions than the actual use of the right foot and or gearing itself! (eg going up a long hill in a higher gear was better than dropping a gear ?)
3. When you reach that “point of no increase in spead” even flooring it, it will not get the revs or EGT up however as soon as the revs start to climb/drop, so does the EGT.


Question: Could all of this be due to the 3B’s IP being an exception to the “fueling rule” relating to all mechanical diesel IP engines being, not throttle controlled only and if so, will this be influenced by the extra air (and revs ? ) being introduced by the upcoming turbo conversion ?

 

[Dieseler]

How bout taking a run up the Coq I would be curious to see what kind of temps you hit and what gears when hitting those numbers not sure which part of the Coq is worse climbing up to the old toll boths or the return climb coming back from Merrit just before the old toll booth

 

[AJAEbj42]

Having done that highway a few time (pre EGT gauge), the run up the toll booths (northbound) is a much tougher hill (my temp gauge climbs more readily). In September, I pushed it too hard I think and put a hole in my exhaust manifold gasket, which started this whole thing.

In my limited observations the EGT responds directly to the right foot. Climb a hill in 4th will raise the EGT's much faster than going up in 3rd. It is really quite a neat instrument.

The 3B really has only two throttle positions going up hill. On or off. Pushing on the accelerator anything past 1/8 does nothing more for extra speed.

Next test will be to try on a longer hill to see how it settles in (if it does). I'll have my son video it because it really changes with shifting, throttle position, gradient, everything it seems.

 

[Kynot62]

I am curious as to all of this as well. What happens to the EGT temp once the engine gets a load on it? Does the temp drop fast when the rpms drop off before you are forced to downshift?

I think the temps are most related to the rpms due to the fact that the IP is controlled only by engine vacuum. Being that there is no mechanical connection to the pump even flooring it won't add any more fuel if you have no vacuum (provided by the rpms). A mechanically controlled IP can continue to add fuel (I do believe) even when the engine doesn't need it or can't use it. Once you load up a 3B it loses RPM and hence less vacuum, cutting back the fuel.

Remember the only mechanical connection is the throttle plate in the intake manifold, the pump only responds to vacuum.

Surprised by the high temps though but not by how quickly they drop.

Keep us updated Rob I want to see what happens in other situations.

Tony

 

[eleblanc]

I'm amazed at how much the EGT's fluctuate. Changes of 200 degrees F while simply accelerating or decelerating in a few seconds.

Bad ground, you might have lost the ground wire between engine block and frame.

I could easily reach 1350 deg F and even flirted with 1400 on some occasion.

 

[Fantom]

The 3B is a little of a weird beast when it comes to EGTs, granted I did not have an EGT gauge before I installed the turbo but I did notice the common scenario of when you reach the max speed (and RPM) loaded then it doesn't matter what you do with the pedal it will not affect it (unless you back off). It only allows more air into the system not fuel. I did notice that if I tried flooring the truck up a hill it would actually start to slow down a little due to too much air, if I backed off a little on the pedal it seemed happier.
Now after I installed the turbo and the EGT gauge it still proved the same thing, once I max out the output of the engine under load it makes no difference to the EGTs if I apply more on the pedal, they stayed the same. This is because it kept burning the same amount of fuel and maxed out the power output. If I backed off a little and lowered the boost, speed and RPMs the EGTs would quickly lower.
The 3B is a little underpowered so when you reach the max power output that's it, unless you change some other factors like adding a turbo, more fuel or lower the load on the engine.

 

[daboheme]

In between your right foot and the IP is an important little component called a governor. This regulates fuel delivery according to load and speed.

 

[prado t]

The only Non turbo diesel vehicle I have driven were the 1986 pattern CUCV Chev 3/4, 4x4 with the 6.2 boat anchor. Going up a hill to the floor and then backing off the throttle a bit, it will slowly accelerate. Anyhow if your EGTS are going skyhigh say in 4th, then downshift put her in third and back off the throttle till the load on the engine lessens. It may be a bit slower but everything will be happier.

 

[VTCDN]

So let me interject a pre-cup drop !!!

For those of us who didn't have a Exhaust Temp Sensor installed (most drivers of 3B's ) . and we all know that going up hills we never get ready to accelerate in anticipation of the neck straining we could receive,
these unseen temps till now is making you drive differently ?
Trying to keep the muffler bearings from getting damaged ?

Install a Pyro in a sport euro gasser and see some real serious temps . I have seen the temps Via the 4 HO2s . these are after turbo , but still higher than the diesels were on about here.


Another thing to keep in mind is were not boats /generators / water pumps ,always under load pushing currant / water etc. Most of the throttle / fuel load is under 40 % of full . Only some roads are built like that you need over 40% for long periods . The Coke is . You would be amazed of the colour the turbo , exhaust manifold and the downpipe into the CAT's is after the haul up the "Coke" in a euro twin turbo gasser . Orange !! dull glow at night time.. Seen that a few times.

VT


Edit add:
Mine is 1200f - 1400f @ 2000rpm 4th pulling doing 80kms or real close (lots of critters you need to watch out for) No Turbo yet.

 

[crushers]

most people that install a pyro into a diesel are shocked with what comes out.
1400F in a NA 3B with factory settings can be seen.
Bruce has said in the past that this might be the cause of the cracked precup syndromn.

i would say this attests to the strength of a 3B as a whole. i know guys that have abused their 3Bs from new and still have them running at 500K ( of course i have also seen them dead at 150K).

welcome to the world of "eye opening experiences"

 

[tmarx]

What surprised me most was how different it behaved compared to the 1HZ. If I started a hill in 4th at about 95km/h @ about 2850 rpm then it will gradually drop speed and revs and by 2000 rpm I would normally change back to 3rd when doing about 70 km/h. This results in the revs going up to about 3250 rpm and the egts quickly going up to my pre-set alarm of 620 degC (Staying in 4th all the time would see a max of 520 deg C) Before fitting the guage I would just sit there till about 3500 rpm and about 80 km/h before changing to 4th again without realising how high my EGTs were in 3rd. Thankfully those days are over now ...

 

[lostmarbles]

I'm not going to fit an EGT gauge Theo.

I don't want to create any new worries .... And I prefer to stick to my existing driving regime in complete ignorance of that parameter.

 

[tmarx]

LMHO !


How about just a revcounter then ?