3B NA High Egt (1 Viewer)

[Benz67]

Hey all!
Hoping for some 3B guru input here. New to the forum and new to diesels so any advice is welcome!
My daily is a US-spec ‘91 FJ80 which the PO swapped the drivetrain from a 1983 60 series into, so H55 and NA 3B. It was a stalled conversion and sat for 10+ years unfinished before we got it back on the road last spring. The goal has always been a turbo conversion which I have most of the pieces for, but I’m trying to get it dialed naturally aspirated and understand the mechanics of it before I slap a turbo on it.

Just recently we changed our exhaust from the manifold back to 2 1/4 side exit and installed a pyro just below the manifold. Fuel has not been monkeyed with yet as far as I know(safety wire is still installed). Currently I’m seeing an average of 8-1000F on somewhat level ground at 100-110kph, and the more concerning part, 1350F pulling steep grades in 4th with the throttle buried. I almost never notice any smoke at all from the tailpipe. Temps never climb past halfway on the gauge even crawling around in summer heat.

For reference, again, it’s a stock 3B, factory fuel setting, linear pump, H55, locking hubs, and running 31s.

What I can’t understand is how I can have such high egts with no modifications and no smoke. I live in a very hilly area so it’s working hard for a good majority of the time, and I’m not comfortable driving every day pulling hills above 1300F. I would like to increase the full to have a whisper of smoke under load, but I don’t dare touch it with my current temps.

Any input is appreciated!

 

[KiwiDingo]

EGT on a N/A diesel is pretty much irrelevant. There's no restriction in the exhaust like there is with a turbo which causes high EMP and increases cylinder/head temps so you don't need to stick to the same safe EGT as they do. You can run N/A diesels so hot the headers start to glow and in some cases depending on exhaust length blow flames out the end of the pipe and it's completely safe. Not many people run EGT gauges on N/A diesels due to this but when they do most are shocked by how hot it gets compared to figures spoken about by people running turbo diesels where it's a critical factor. EGT on N/A diesels is pretty much a non-issue

 

[duncanrm]

It seems unlikely that a 3B without a turbo could generate those temps. Can you verify with another gauge/probe?

 

[Hulsty]

As above, NA EGT's will be very high and the engine would have been running like that for 40 years without issue. Boost + EGT is what to worry about.

 

[Benz67]

It seems unlikely that a 3B without a turbo could generate those temps. Can you verify with another gauge/probe?

Unfortunately I don’t have another to cross reference the temps I’m getting.
I’ve heard from other threads that stock NA temps seem to be pretty high especially when you’re used to turbo numbers.

 

[Benz67]

EGT on a N/A diesel is pretty much irrelevant. There's no restriction in the exhaust like there is with a turbo which causes high EMP and increases cylinder/head temps so you don't need to stick to the same safe EGT as they do. You can run N/A diesels so hot the headers start to glow and in some cases depending on exhaust length blow flames out the end of the pipe and it's completely safe. Not many people run EGT gauges on N/A diesels due to this but when they do most are shocked by how hot it gets compared to figures spoken about by people running turbo diesels where it's a critical factor. EGT on N/A diesels is pretty much a non-issue

That’s definitely comforting! I’m pretty unfamiliar with EGTs and what is considered “safe”. I’ve seen a lot of numbers for guys running turbos so that’s why I got concerned with the numbers I’m seeing.

 

[bj70bc]

ive head that a 3b will get to 1400f N/A, which is probably why they almost all have cracked heads between the valves where the greatest temp differential will be,
add a turbo and it will get forced a diet of cold air that will help greatly with the egt's (properly tuned)

 

[Benz67]

ive head that a 3b will get to 1400f N/A, which is probably why they almost all have cracked heads between the valves where the greatest temp differential will be,
add a turbo and it will get forced a diet of cold air that will help greatly with the egt's (properly tuned)

That’s definitely the next item on the to-do list. It’s a different thread but has anyone tried using the stock log-type manifold in a turbo application? I’ve heard that the 4-into-1 manifold is less efficient for running a turbo, but if it’s a negligible gain from shelling out $500+ for a 13BT manifold, than I’d rather just use what I’ve got.

 

[bj70bc]

build one... i did
good little project if you have a welder

 

[dare]

I have an EGT on my BJ73/3B. As stock the highest I could get it was 730c (1350f) and that was towing up a long hill, WOT way longer than I should have just to see how high it could go. Cruising into a head wind it could be high 600s. Later I upped the fueling and changed the governor spring and it could hit over 800c (1500f) but it made quite a difference to the performance, it was much nicer to drive. It will haze the exhaust a bit but certainly not an offensive level of smoke.

Another local bloke had an EGT on his and had very similar temps to me. We're near enough at sea level.

I wouldn't stress about sustained temps under 750c/1400f, it's a non turbo IDI with under piston oil squirters.

 

[Benz67]

I have an EGT on my BJ73/3B. As stock the highest I could get it was 730c (1350f) and that was towing up a long hill, WOT way longer than I should have just to see how high it could go. Cruising into a head wind it could be high 600s. Later I upped the fueling and changed the governor spring and it could hit over 800c (1500f) but it made quite a difference to the performance, it was much nicer to drive. It will haze the exhaust a bit but certainly not an offensive level of smoke.

Another local bloke had an EGT on his and had very similar temps to me. We're near enough at sea level.

I wouldn't stress about sustained temps under 750c/1400f, it's a non turbo IDI with under piston oil squirters.

Since reading up on the input from the forum I played with the fuelling over the last week. Quite a difference at low speeds, and minimal smoke still at this stage. I tried a half turn out which I think is the sweet spot, then I got greedy and did a full turn, but I was belching smoke everywhere and dialled it back down pretty quickly.
With a hair over a half turn out I’ve got much better throttle response and a decent improvement at most speeds, especially around town and accelerating up to about 80 kph. I’ve only seen a minor increase in EGTs, maybe 100°F under load. Normal highway driving is between 800-1000°F and hills push it to 1400°. Overall definitely worth doing, time will tell how the fuel bill will change. Currently getting between 18-20 MPG so hopefully that won’t take too steep a nosedive.

 

[bj70bc]

with around 20psi max, i turned mine up 1.25 turns out with absolutely no smoke at all.
1250f max egt, pre turbo, w/a intercooled, retarded timing

 

[4Ruster]

Retarded timing will also cause high EGTs and reduced smoke