1HZ EGTs (1 Viewer)

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Feb 25, 2010
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I’ve got experience with NA 3Bs and 3B-Ts but my HZJ77 is my first experience with a 1HZ.

To get straight to the point - I certainly realize that this engine is “limited“ in its power and that’s fine with me BUT it’s also seems to be rather hard to keep EGTs within reason AND have access to ”high speeds” like 55 and less. At 55 in 83 degree ambient temps on flat to somewhat rolling highways/roads the engine RARELY sees anything under 700 degrees EGT and often times will run to 850 or 900 degrees. If I try and keep the same throttle position she’ll got to 1000 or 1200 degrees EGT. What worries me is this: If the truck was “quick” - it’s an auto by the way - it would be one thing, but it’s slow - which I accept - AND runs high EGTs. Going up a mountain here in VA I kept her at 25mph and slower all the way up for maybe 2 or 3 miles and she hit 1250 degrees AND saw coolant temps pushing 210. On the way down the mtn she quickly came back down to 180 coolant temp and 400 or 500, and less, on EGT coasting.

The engine idles smoother than a new Lexus and starts if you so much as look at the key. She doesn’t burn excessive amounts of oil and the coolant level has NEVER gone down. It also has a larger aluminum radiator and has a total of maybe 90k miles on her. It’s a constant battle to keep EGTs down AND maintain 50-60mph on a relatively flat road. My fear is that turning down the fuel would make the truck wholly incapable of keeping up with a Honda Ruckus or electric skateboard. Any advise?
 

AussieHJCruza

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Is the engine turbocharged? If so, do you know how it was tuned, does it have an intercooler and what have you got in the way of an exhaust?

1250 is about as high as I'd be comfortable with on an IDI diesel but if that's where it stabilises, it's not bad IMHO
 
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80 Series 1HD-FT
EGT on N/A diesels is pretty much a non-issue. You could run it so hot the exhaust headers glow cherry red for most of its life and it'll still last longer than most turbo HZ engines do. I've driven a lot of old n/a diesel engine vehicle and it can be quite a sight seeing them at night with a constant exhaust glow and even a flame coming out the exhaust when on load for hours at a time.
 

mudgudgeon

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Agree you should be able to push it to much higher speeds.
I've had my hzj105 in 46°C ambient temps and pushed it hard up to 60-70mph through hilly country.
Daily driving duties would have it up to 70-80mph on the highway for hours at a time in summer temps of high 30s-low 40s°C
 
Joined
Feb 25, 2010
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I can and have pushed it to higher speeds but the EGT starts seeing 1200 - 1250 degrees and higher.
 

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